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Pool Heat Pump Calibration Explained (Madimack)
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- Опубліковано 7 гру 2023
- Pool heat pump calibration explained. They aren't as simple as you think, and actually have a very narrow operational range in terms of water flow rate. If you don't calibrate it correctly then you are going to be wasting large amounts of power and your COP/efficiency will decrease.
Also, fixed pump vs variable speeds pumps, spherical cows, and the Millenium Falcon.
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You didn't mention *why* it's more efficient! It's more efficient because it's all about the refrigerant loosing too much energy into the large volume of water and thus needing to be heated up even more by the radiator/compressor before the phase change occurs which is just wasted energy, modern high efficiency refrigeration systems (and other industrial processes) are all about optimizing the system to always stay around those phase change regions as pretty much all of the energy transfer in a refrigeration system is from the phase change of the refrigerant hence why heat pipes in heatsinks also have a 'narrow' range of operating temperatures and heat loads for optimal thermal conductivity.
Thank you for this comment 👍 makes sense
Yes this is basically a very specialised AC unit, with the outdoor coil replaced with a small compact heat exchanger. Pressures and flows of the refrigerant are optimised so that the heat exchanger has a section where, with the correct water flow, the phase change is done from hot gas to hot liquid in it. Too high a water flow rate and this occurs near the inlet, and thus the system runs at a lower pressure differential, as there now is hot liquid refrigerant occupying most of the heat exchanger, and thus the overall system runs at a lower pressure, reducing efficiency. Too low a flow rate and this zone moves outside the heat exchanger, and there is likely a temperature sensor on the piping to detect this high temperature exiting refrigerant, and shut off the unit for flow rate.
The air refrigerant side now sits with a small zone of acceptable temperature, the rest of the evaporator not being used to transfer heat to the cold gas, as it is now at ambient temperature, because of the lower volume of refrigerant there. This is because these almost invariably have no accumulator or receiver drier, that holds a larger buffer of ambient temperature refrigerant, so allowing the correct pressures in the various parts, irrespective of ambient temperatures. Small volumes of refrigerant you need to keep inlet and outlet temperatures very constrained to maintain efficiency, though there is likely a small volume of liquid held in the piping to the expansion device, either a few capillary tubes that exit direct into the evaporator, to reduce pressure that way, or a TXV that meters the liquid into the evaporator based on either temperature of the evaporator, or more likely using a small stepper motor to do this via a microcontroller, but basically the same.
@@SeanBZA Can variable speed water pumps work in tandem with the heat pumps to keep the refrigerant at the optimal pressure continuously?
@@dosgos Sure there are systems that integrate the variable flow pumps with the heat pump, but you are then adding a lot of unneeded complexity to the system, and in general with a pool, you can be sure that you will be replacing parts regularly, especially pumps, as they do have a rather high failure rate on them. Pool pumps will either wear out seals, or will cavitate themselves to death, or will wear out the impellor or housing, just from the water and dirt in a pool. Then they will also corrode to nothing motor side, and, as they are all now wound with CCA wire, they are also prone to having motor windings burn out, or go open circuit. Run capacitor also goes low value, and that in turn burns out the main winding as well.
Thanks Tim , you are a wizard. I am pretty highly educated and have worked with heat pumps for a few decades but I couldn't have explained as well as you do.
Lemme tell you the funny story 😁. When I just moved in into my house in Phoenix. I cranked up my natural gas pool heater (~150k kW), cause I wanted to celebrate it and party during Christmas and New Year's holidays. I heated up 15k gal pool almost up to a hot tub levels ~35C, while there was -3C temp outside. I kept it running for a few weeks, and we spent WONDERFUL holidays! Until I received my next gas bill, i realized that our pool party just cost 2k US dollars 🤣. I never ever used my gas pool heater again since then 🤣
Oops!
Have to say, I'm enjoying this new PoolBlog channel. Can't afford my own pool, and I live in England, so I'll watch Dave talk about them. Can't wait until he shows us how to deal with leaves and sand in the bottom of the pool.
You pump some amount of heat at some rate. If you receive it at 60l/min you get 3C difference. If you receive it at 6x 60l/m you get 3C/6 difference, almost linearly. As basic as in Ohm's law. Yet still it's the same amount of heat received by water.
I would say when you're sitting in the pool with 3° warmer water on your back will "feel" substantially warmer than .5° warmer for the whole pool no?
except that 3 degrees is already being mixed with the full flow rate of the cooler water bypassing the unit via the diverter valve....it won't enter the pool at that temperature.@@JyeKelly
@@vintagepc64 I didn't consider that, good point 👍
Problem is that if you higher the flow you will cool the condenser more and lower the coolant pressure in the condenser resulting in a heatpump working outside of its ideal condition -> less efficient.
Efficiency will drop considerably and can even drop to a point where it would be as or even more efficient to use a conventional water heater.
@@ppdan It will drop, but not considerably.
How much could it drop worst case? The differential so 3K.
If the heat pump evaporates at 15°C and condenses at 35°C, it will still work with 33°C condensing.
When the water is colder it will condense even lower and still work fine.
Pipe dream of mine has been to have one massive heat pump that moves heat for everything in the house. Moving the heat out of the house into the pool and hot water tank in the summertime, and then moving the heat back in from the pool/ground in the winter.
There are poeple who have done this DIY style.
@@EEVblog2there are companies that will do it non DIY.
@@EEVblog2 Yes, like Linus from LTT
@@marcellipovsky8222and to not include a room rad at the start was quite an oversight
Yes! This is what I would love too.. I hate sitting on my deck, watching my home unit pump heat into the air, and 30' away watch my pool unit sucking heat from the air trying to heat the pool! If they weren't so far away, I'd try to somehow integrate their heat exchangers! 🙂
Can someone tell me the difference between heating 300l for 0.6 degrees and heating 60l for 3 degrees. I don’t see the it.
COP differences mostly
No difference in theory.
My guess would be that the optimum flow rate is a balance of getting enough water through to keep af low temp delta - but not waste pumping energy by pushing a huge amount of water through the heat exchanger.
The heating efficiency could in fact be a tiny bit better with lower temperature difference/higher flowrate. But the water pump would have more work to do.
And with a couple of degrees temp delta it feels warmer in the pool (right by the inlet).
There wouldn't be if everything was linear with the heat pump, but it's not. There is an optimial efficiency flow rate so the water spends the ideal amount of time inside the heat pump exchanger. Too fast and the peak efficiency drops. And too slow the peak efficiency also drops.
@@MrKruchov I can't really feel the 3C difference at the outlet in the water, will have the try a probe. But in any case it's the average over tiem that matters.
@@EEVblog2 Yes, that could be it. But it would be interesting to see the real world difference between the optimum and the just let it rip. I suspect the difference is there but not that big. I couldn’t find hard facts about that and am really interested because of my own solar water heat exchanger and future heat pump install. It’s about the robustness of the system for me.
It sounds like what you have is the best compromise.
But I would take the sticker off on top of the heat pump. It will not look good in a year and when you remove it then, you will still see the outline of it, because the paint was protected by the sticker from the giant fireball in the sky.
Something personally I want to see is, is how the plants overgrow everything in a couple of years and how it looks. Now it looks a bit bare - obviously.
He hasn't done his electrical work to as3000 standards; I don't trust the bloke when I even offered my services.
@@TradieTrev Chill the unit he has isn't even a hardwired unit, its a 10amp wall plug type unit all he needs to make that work is the normal pool bonding and and a proper GFCI outlet on for the pool area which he should already have for the pool pump.
In the next video, we want to see Dave floating in the pool with an umbrella drink.
Only for Sagan to cannonball and create chaos.
While ice forms.
You can calculate the COP of your heat pump easily if it doesn’t tell you on the display… Take the temperature difference between input and output (3 degrees here) and the water flow in litres/second (1l/s here, ie 60 l/minute) and multiply by 4.2 (specific heat capacity of water in kJ/kg). So your heat pump is making around 1x3x4.2 = 12.6 kW of heat. Now check the power consumption - hopefully much less!!
Just did some experiments in the game stationeers and also had to the same math 😂
Given that's it's only a 10A (2.4kW) mains outlet, yeah, I'd say much less!
At a flow rate of 360l/min (6l/sec) then the result would be 6 x .5 x 4.2 = 12.6 kW of heat, exactly the same efficiency...
@@HarmanRobotics It doesn't scale linearly like that. The COP will drop if you cool the hot side too much, meaning it's no longer 12kW. Heat pumps aren't just like an electric heating element and are very complex and dependent on the temperature difference between the hot and cold side (of the heat pump, not the pool water inlet and outlet)
@@LB-fx1kn Based upon the numbers Dave gave (0.5C at 360l/min and 3C at 60l/min) it is the same amount of heat transferred according to that calculation. What is missing is the power consumption at the different flow rates.
Thanks Dave my Madimack just stopped working.
Luckily it is just a flimsy reed switch connected to a paddle they use as the flow sensor, just inside the outlet. Kept throwing E3 error for no reason. Just superglued the magnet back onto the paddle and it works again.
While trying to find a fix, I found your video and my flow is way to high and have dialled it back 🙌
Hey Dave did you look into running a separate pump for the heater so you don't need to run the filter pump the whole time? You probably only need to run the filter a few hours a day to clean the water, the rest of the time running the 1kw pool pump is just pushing extra water around for no reason. Every little bit helps when going for efficiency. 😃
Dave, what are you doing?
So as far as i understood, dave has decreased his efficiency of the heat pump
Of course the heat exchanger generates fewer temperature rise if you pump 6 times the volume through the heat exchanger, but this increases the efficiency because you need not that high temperatures
You have now a higher temperature(with worse efficency) at the heat pump output and mix it again with the unheated water and get a lower temperature again but you dont see it because theres no sensor
Will the heat exchanger gets a damage from the too high flow - i dont know - thats the only point which would support your voodo "CALIBRATION"
Will your plastic valves will survive this constant switching - i dont believe so
To have a efficient heat pump it must have its coolant pressure at the designed levels. If you pump too little water the condenser will heat too much and the pump will shut down because the coolant pressure in the condenser gets too high. If you pump too much water the coolant pressure in the condenser will drop too much and your heatpump will work outside it's ideal conditions and be less efficient.
No, I'm doing the optimal thing. For the technical explanation see the pinned comment from WizardTim
could you repurpose the cold side for the house cooling?
Yes. Water acts as a great sync for a heat pump. E.g. AC cooling loop goes through the pool.
In the UK big houses with ponds / lakes do this Vs air source or ground sync as it's cheaper and easier.
But obviously we need the heat so that cools the ponds and lakes so we are back to front for what most people would want in Australia
Yes, but often when you really need cooling in the house it's probably so warm outside that your pool doesn't need heating ...
Neat system and explanation. I was wondering if the value the pool has added to your house covers the installation cost?
Likely. That does make me sleep a bit better at night.
Enjoy Saturday's forecast temperature of 44 degrees Celsius for Sydney... I have colleagues who are moving office at Parramatta, so I hope their A/C works in their new building!
You sure picked the PERFECT day to get your Pool installed... 😁👌
So with a 3° temperature difference Air temperature -3°C Will it only put out 0°C @ 40KW
This is just thermodynamics Dave. More flow rate at the same heat input results in lower delta T but the same input in energy to the pool.
Yes, the COP drops if you aren't in the ideal flow rate range.
It is interesting you'd bring this up, since my dad and I have been having a debate on the flow rate we should use for a solar panel pool heater he built using 3/4" copper pipe.
It was my opinion that quantity of heat would remain the same regardless of flow rate. My dad on the other hand was basing his thoughts on temperature differential, which would require a slower flow rate. After all, the goal is increase in heat, which is temp differential times quantity of water heated.
9 hrs? That's an awful lot of time to only rise the temp by 3C. You probably could lose all that overnight when the pool pump is shut off, thus never getting your pool temp to where you want it at the times of the day you'd want to swim, especially on colder days.
I was going to experiment and test how much heat I would actually generate at different flow rates:
Take a 4L (really 1 gallon around here in the US) container, time how long it takes to fill it, and measure its temperature (heater output temp) compared to pool temp (inlet temperature).
Really i don't think his solar panel really does much, just too much pool and not enough heat from the home-made panel.
He used to have a pool solar heating system on the roof, but had to remove it in favor of electric solar. We even used it to cool the pool down when it naturally got too hot by running the pool pump at night.
Which then has me think of how efficient are HVAC heat pumps really? They deal with air as the fluid medium, which I would think has a slower heat transfer rate. Those things have to raise temperatures a heck of a lot faster than just 3C in 9 hours!
FYI, I believe this heatpump is a rebrand of the Mr. Silent, Aqua Forte or AQS. The controller is a standard Tuya jobbie. Advantage is that hooking into the wifi capabilities and controlling/capturing data is easier since it's just a generic-ish controller.
4:20 yeah, right. Where does the energy go then? It doesn't just evaporate into the aether. Of course the measured temperature would be lower, a given quantity of water would have less time to contact the heating element. Doesn't mean that the heat didn't enter the water.
I misspoke. The efficiency (COP) drops. So you get less heat pump action. It's not like I'm putting 11kW into it. But if you want 11kW heat pump action output from your
@@EEVblog2 that makes sense.
Instead of bypassing part of the water flow, I wonder about just choking the output flow of the filtering pump? Because the filtering pump in spite of being fixed speed, is based on an impeller, meaning it can be choked, and the motor instead of pulling more amps, the opposite will happen. There is only so much you can choke however, because at a certain point there is cavitation in the impeller, causing water to boil and damage the pump.
Then you wouldn't be filtering the pool as much. The bypass valves is the better option.
you can use a variable speed pump to achieve a similar result . ie valves can be fully open and pump is running slower , but you need to also factor the water turnover for filtration. We aim for 3x turnover but seldom achieve it domestically , usually somewhere around 2x per day . Of course this all depends on how big the pumps is vs volume of pool , if you put a big arse VS pump on a tiny pool then turnover isn't an issue
Shame they don't have a built in automatic flow control valve, so it can modulate it's self
I don't get it why lower differential of in and out would make any difference. Pump is either making heat exchanger colder or hotter at constant rate, why would the difference matter ?
See the pinned comment.
Learnt something new today, now I know how to tweak the efficiency :) Also, I recommend basic (KISS) G2 zodiac cleaner, they are really good. Oh and... don't forget the deep return valve in the box, it'll also be a little more efficient.
Deep return valve?
@@EEVblog2 maybe he is talking about pulling cold water from the bottom of the pool rather than heating water from the top???
I must be missing something, a 1/2 C temp increase at 360 liters/min is exactly the same amount of heat going into the water as a 3 C increase at 60 liters/min. No difference in efficiency.
Ok I found how they work. Next Q: can the exhaust cold air be used to cool your beer?
Is there an optimum fan speed to do this?
you wait until it’s hot and the heat pump is belching out freezing cold air and you wished you could duct that into the house😂
Most of the heat introduced from the heat will be at the heat pumps saturated tempature for the pressure of the condenser, by slightly lowering the average water temperature. You will lower the heat pump evaporator saturated tempature by having a smaller delta you will make the system more efficient. Being a varible capacity inverter unit it should be able to adjust the compresor to make they system run at peak efficiency. Most likely the flow specs are due to fluid flow through the heat exchager being as small as that unit is. I would recommend running it off a second pump to keep it in the desired range and not restrict your main flow.
No need when you have the valves to adjust the rate.
No coils of pipe on the roof as a solar collector?
Basic question: where does the heat get pumped *from*, and how?
I guess I'm confused. Why would you heat your pool during the summer? Wouldn't you want the water to be as cool as possible (within reason)?
SWMBO. But we may not have too much, as we haven't installed and tested the pool cover yet. That will also absorb and also contain the heat.
@@EEVblog2 Gotcha. :)
@@kjlovescoffee Our first dip in the pool was without the heater and it was 23C. Mrs EEVblog and the kids all said it was "a bit cold" and the youngest didn't want to stay in log, but I thought it was fine. They liked 27C better. Tomorrow will be a 40C+ day!
australian summer is our winter ;)
@@EEVblog2 The pool cover will be a major game changer. Not only does it help heating on sunny days but it also reduces losses during the night.
You will also save lots of water. Look how your water level drops over time without using the cover and compare that to using the cover as much as possible.
Nice demonstration video.
This also true for airconditioning? What's the discharge air temp vs ambient air temp differential?
Aircons are alos heat pumps. This unit can also cool as well.
Is that a ground or air source heat pump?
So now come the debate, which automatic pool cleaner, and remember they are all based on the original Kreepy Krawly, which was invented in South Africa, but saw the most sales in Australia.
Mrs EEVblog wants the expensive automated robot...
@@EEVblog2 What's another couple of grand? Tis but a drop in the pool budget 🥲
Be interesting to see the running costs of this.
From the electrical connection details that we saw on the label, it can use upto 2.3kW of electricity to push upto 11kW of heat into the pool water. It will probably use less electrical energy as the specified electrical connection only allows 10A at 230V (or 2.3kW).
Wouldn't a flow rate gauge on the inlet pipe be helpful?
Yes very interesting Dave about the heat pump
I don't understand the idea behind it ... The water pump runs at full throttle anyway and uses electricity.
If the heat pump gets more water, the temperature delta will decrease, *but the COP will definitely increase*.
btw: The current “calibration” will change as the sand filter becomes clogged.
Is the heat pump always in operation when the filter pump is on? If not, automatically switchable valves would be worth considering to remove this resistance from the filter.
See the pinned comment.
Does the outgoing temperature differential remain the same regardless of the desired set point? That is: if you set it to heat the pool to 27 degrees and the heat pump has a +3 degree differential, will it output water at 29 degrees if the incoming water is 26?
Yes, remains the same. The flow rate essentially determines the temperature differential. The set point temp is just a cutoff point.
How many litres is your pool please
To be fair from all I have read your heat pump is also somewhat undersized.... you wouldn't be that far off with the 12kw version and probably could match the flow rate with an inverter pump, and control it such that during heating it runs at the lower speed and only runs at the higher speed during certain periods for cleaning/water turnover reasons. Just eyeballing it your have around a 40k liter pool which is at the upper end of this unit... thankfully more inverter heat pumps are being sold so you can oversize the unit somewhat and widen the efficiency range significantly. I think its an area where state of the art is definitely moving in the last few years... a few years ago nobody would have even sold anything more than an OFF/ON heat pump even though though and oversized unit running at 25% is a lot more efficient than a unit running at 100% outupt this is also in part because in addition to matching your coolant flow, the available heat or heat capacity in the air also varies with climate, and the inverter unit can match that better also... I don't think any of them actively try to hit an optimal efficiency point yet though.
Are those valves really mixing valves, or ball valves with two outputs? Whats the actual flow in the system after setting the valves?
Those are 3-way valves (works both way : converging and diverging).
I guess you have to set the valves symmetrically to avoid chocking the pump.
Kiwis would use it in winter without a heat pump. :)
To all those nerding with the math details and trying to finesse the best energy transfer rate: The heat pump is just too small. Why? Because Dave wants to run it off his solar panels' excess power when the house / car is not using it to the their full capacity. Not taken into account is the cooling of the water from conduction (through the pool's concrete body to earth), radiation from the surface to the ambient air (cool in winter) and evaporative cooling to the air (due to breeze / wind). Essentially of those heat losses exceed the capacity of the small heat pump (regardless of how efficient it may be) the pool water will cool and not be comfortable in the cooler months. I doubt anyone will bee using the pool in those cooler months.
Also note that this heat pump uses about the same amount of electric power as the pool pump which looks like between 1 - HP (i.e. 750 - 1500 Watts)
You are forgetting the pool cover. Also, the heat pump was sized with the idea that the pool wouldn't be used in the dead of winter.
@@EEVblog2 Oh Yeah, the pool cover. Well knowing you, there will be a lot of data gathered which can be evaluated in 6 months or a year to see the temperature of the pool.
Too complicated, just wear a jumper and some socks if it's cold.
It doesn't matter how much water is passing through the pool heater. If you are running the 60l flow or 100l flow the unit is still putting the exact same amount of heat into the water. If you goal is to have a 3* temperature rise on the outlet then you need to have the lower flow rate. At higher flow rates the temp difference will drop but you are putting the same amount of BTUs into the water but spread out over more volume of water.
Your argument is like the car guys saying that having a highflow water pump doesn't cool as well because the water doesn't stay in the radiator long enough to cool the water....
Course here in TX we are wanting pool coolers as they get too hot to use in the summer. Usually people will have an ice company deliver a load of ice to dump in it if they are having friends over.
Nope, there is an optimial flow rate point, that's why it's in the datasheet with a +/-20% figure and spelled out very clearly in the claibration process
That is true for heaters like electric and gas, where you just have a bunch of energy to dump into the water.
Heat pumps are not just brute energy sources but are heat engines, which operate on a temperature delta between the condenser and evaporator. The size of this delta affects the performance of the heat pump greatly, so you can absolutely cool it too much with excessive water flow and ruin the efficiency.
Does weather impact the 3* differential calibration?
So when it's being ineficent, where is the 11kw going?
Sorry, I mispoke. There is never 11kW of electricla energy going into the heat pump. The COP just lowers.
Is a heat pump running on solar more or less efficient than a traditional rooftop pool solar system?
Had this discussion with a friend that installs both types of solar systems and EV combined with a heatpump is a clear winner.
Not only can you compensate the less efficient EV by using a heatpump but you will also produce electricity that you can use for other purposes when not needing heat.
He has both systems on his house and his EV is currently oversized but with new regulations comming soon he might want to expand his EV system and might replace the water solar with more EV.
My friends recently bought a new bosch tumble dryer fitted with a heat pump, it's absolute wankery! It takes about 4 hours to dry a few pairs of trousers.
Then that one might be defective/just sucks :D The cheap Beko A+++ ones will do a full 8KG load of towels in 3h5min on the driest setting and thats worst case.
@@tschuuuls486 Possibly, but a regular 3Kw dryer would do it in about 40 mins.
someone mentioned that you should do a couple shake/snap with the clothes as you remove them from the machine the airflow will remove the last moisture.
@@MattyEngland I know. But usually I don't babysit my drier. I never thought, oh wow I wish this would dry faster. If it's about the same speed as my washing machine, who cares :D
And since that 3h is absolute worst case this never has been an issue.
But power is pretty pricey here, so the trade off is worth it. Also the vented drier pumps already warm air out, which the heat pump one doesn't.
what do you do with the heatpump cold side? house AC?
Vented to atmosphere.
Is the NSW heat wave heading your way Dave? Pool will be handy
yep!
How did you establish the flow rate? Just thought it might be nice to have a flow rate meter there on the back of the pump 😊
I don't think he knows the precise flow rate into the heat pump. He's using the temperature differential as a way to estimate the flow rate, based on the specs in the datasheet.
I don't know the precise flow rate, I'm just guessing based on the data from Madimack. i.e. 60L/min should result in that 2-3degC temp differential.
@@EEVblog2fair enough!
Dave, is your pool chlorinated? Brominated? Salt?
When are you going to send out a channel notice about the grand opening? 😂🥳
Salt
2:00 how many already claimed Dave's madmack QR code offer?
Me, but they wouldn't ship the free kangaroo sex doll internationally 😢
almost correct dave, but you (and/or your pool guy) is wrong on the reason whay this unit need 65L/min. the problem is that a heat pump will only work better the more water you give it but at some point the relativly small heat extchanger in the unit is simply too restrictive to deal with the full pump capacity of your circulation pump. with a delta T of 3 you are already walking the line of getting the maximum out of the heat exachnger you can reasonly expect. increasing the flow rate would have no meaningful efficiency gains. if you give it 6x the water rate it would still move 11kW into the water regardless but the (water) pump losses are quite large. the heat pump itself LOVES it, but everything else in your system would not.
We’ve had heat pumps for decades. My fridge/freezer has a heat pump in it. No one ever thinks twice over those.
They are relatively new for pool applications though I think.
I think it is better to move 360 it helps with cleaning the water.
9:28 1/6 of the flow heated up by 3 degrees is exactly the fucking same as heating the whole flow by half a degree!
x - initial water temperature
5x/6 (the water bypassing the heat pump) + 1/6(x + 3) (the water being heated up) = 5x/6 + x/6 + 0,5 = x + 0,5
It doesn't matter, the water is heated up the same.
You spend so much time reiterating the same over and over and don't ACTUALLY explain why the heat pump is so capricious and wants such a low flow rate.
Yes, the efficiency/COP decreases with the higher flow rate.
Apparently Sydney is due for a 42C heatwave this Saturday, so you might want to run your heat pump in reverse! 😂
It can cool as well as heat.
@@EEVblog2oh that’s cool! Bonus over resistive heating or burning dinosaurs!heatwave and you can have a nice cool pool. I do see from the specs tho that it can handle up to 43c outdoor temps
The difference in efficiency outside of the optimum flow rate is minimal, you've just proved that yourself if you think about it..... You can raise all the water by 0.5c or 1/6 of the water by 3c. Then you blend that 1/6 back with the other 5/6 that hasn't been heated at all and guess what, you've raised all the water by 0.5c.... The biggest factor is the difference between air and water temperature rather than water temperature differential across the heat pump. Probably less of a problem in Sydney than here in the UK where the air is pretty much always colder than the water!
No, the effiency of the heat pump is very much determinted the flow rate and hence temperature differential.
@@EEVblog2 Sorry Dave but your own video shows otherwise! You’re putting the same amount of energy into 1/6 of the water so it gets 6 times hotter. Unless you can show that it’s using significantly more electricity at higher flow rates then the difference in efficiency is minimal. I’m not saying there is no difference, but you’re certainly not pissing away power.
@@arharman the efficiency of the heat pump is affected by the temperature difference between the condenser and evaporator. It won't use more power but the output will drop (lower COP). It's nothing to do with what happens in the pool water heat exchanger (you're right there about 3 degrees at 60lpm vs 0.5 degrees at 360lpm), the difference is with the heat pump itself and the difference in temperature between the two sides of the reverse Carnot cycle heat engine.
@@LB-fx1kn Exactly. The difference between the condenser and evaporator temperatures - I.E between water and air temperature. The higher flow rate can only cool the condenser to the water temperature. It’s no different to running the pool a couple of degrees cooler, yes it will have a small effect but it’s not really significant. Dave’s figure of 1/6 is obviously approximate, and 0.1c resolution on 3c is also not perfect, but within those limitations he’s shown that it’s giving pretty much the same output power regardless of flow. I believe he said it was running at 100% both times so presumably using the same input power in which case it’s roughly the same efficiency. Variation in air temp will be much more significant. My own heat pumps (Proteam I x7) quote maximum COP of 16 and 27c air 27c water, but only 8 at air 15c water 26c.
I need a heat pump to cool the pool.
i don't agree with the logic presented .. if the heat pump adds 4kw @60l/hr with a 3 degree rise, or 4kw @600 l/hr with a .3 degree rise.. is the same amount of heat added to the pool's fixed volume 30,000 l.
just like wattage for resistors 100 v @ 1 amp is 100 watts, just like 10 v @ 10 amps is 100 wats
The COP of the heat pump changes.
@@EEVblog2 how about a testing video where the flow rate changes and temperature differential across the pump is measured
From that output btu can be determined
it doesn't matter loss in == loss out unless the casing gets hot .. this all makes no sense to an aquarium owner ...
Uh, these aren’t Australian made?
Earlier and some of todays cheaper pool heatpumps show the coolant pressure of the condenser (high pressure side) and you are supposed to regulate the waterflow to obtain the ideal condition for the heatpump.
The higher the waterflow the more heat you will draw (you'll cool the condenser too much) which will lower the pressure on the condenser side. If the pressure is too low or to high your heatpump will work outside of its ideal conditions and be less efficient.
Most bypass setups I have seen or used consist of 3 normal valves (one input, one output and a bypass) or a single 3 way valve (sometimes a output valve is added on the pump to be able to completely isolate the pump for servicing). In your case there are two 3 way valves which can be interesting but also "tricky" to use since you probably have to set both valves symmetrically to avoid "chocking" your pump.
PS : if you max the flow to your heatpump you will think that it's not working anymore at all but in fact it is still working only it is heating a huge amount of water less efficiently and the temperature delta is very low and might not be "visible".
That would be an interesting project for Dave!
@@dosgosWas thinking the same thing after seeing all the responses on this video. Looks like people are not aware that a higher flow would negatively influence the effeciency of the pump.
What you describe will only be a problem if the water is very cold, like below ambient temperature.
With a too low pressure differential in the refrigeration cycle the evaporator might starve of refrigerant because the expansion valve can not supply enough refrigerant.
What do you think how much the high pressure will vary between 3K delta and 0.5K? Not much!
The mean temperature difference between refrigerant and water will go down and the efficiency will go up.
More of a problem is the excessive water pressure drop when trying to push that amount of water through the heat exchanger.
@@Alexander470815 Then how you explain the COP falling considerably? (talking from experience : 18000L pool with 5kW heat pump)
Never seen a heat exchanger fail because of the water pressure generated by a pool pump. Those a circulation pumps and will not create very high pressure, also they are placed after the filter where the pressure is MUCH lower.
When I change the water flow thru my heat pump the high pressure side of the refrigeant can easily vary 30% in pressure pushing the heat pump outside of its ideal working condition which can easily have your COP fall from 5 to 3.
That how it's given by the manufacturer and that is exactly what I have experienced.
@@ppdan The heat exchanger won't fail. Its just the (water side)pressure drop getting pretty high limiting the water flow.
When working with low temperature differences it gets pretty hard to measure the cop reliable.
Temperature measurement must be highly accurate or the measuring error will be very high.
0.1K Error for 3K delta? Not great but does work.
0.1K Error for 0.5K delta? Not usable.
How do they calculate the efficiency?
1. If you have a 750 Watt water pump and the heatpump is using 490 Watt for heating, then the efficiency is very low, but it is cooling the heat exchanger very fast, so that you have nearly no heat difference.
2. But if you would reduce now the power of the water pump to 200 Watt, then the heat difference is a bit higher, but the used value used energy per kWh of heat is higher.
There is a optimum point somewhere between water-pump-energy + heatpump-energy compared to generated heat.
So there is a way to reduce the power of the water pump and this increase the efficiency. To reduce the flow rate with this valves, this is doing nothing.
Dave, you can set this valves to fully open, so that the flow rate is the maximum.
If you do not change the power consumption of the pump, the efficiency does not change ... or better say, if you waste the water flow with this valves, then you reduce the efficiency.
I would add a energy monitoring to the heatpump. I think it tries to create a heat difference of the input and output water.
I think the installation company had created a own system to use a unregulated pump and deal somehow with the waterflow-efficiency-thing what they had found in the documents. But it does not work this way. Possibly they have explained to you very convincing, but it is not right in the way they have realized it. Possibly they do not know how to realize it, because they have no electronic expert in their team, only plumber.
If you higher the flow you will draw more heat which will lower the temperature of the heatpumps condenser followed by a pressure drop of the refrigeant in the condenser. This lowers the efficiency of your heatpump because it's now working outside of its ideal conditions.
Efficiency can really drop a lot.
@@ppdan - My heatpump has a wide spectrum of the working-area, a problem is only the very cold or very hot temperature.
If it is now 20 or 30°C is not a real problem for the heat pump, the best is a low difference between source and sink, then the device need less energy for the heat transfer.
And the concrete base under the heatpump has a broken corner already. tss tss tss 😀
When you need to put out a minimum number of videos so you can declare your new pool a business expense eligible for a tax rebate. :D
JK, it's all good, we share something and maybe learn a thing or three.
er, tell me you know nothing about thermodynamics without telling me you know nothing about thermo-dynamics ;-)
Heat transfer by a fluid is governed by three factors:
1) the fluids specific heat capacity, which for pure water is around 4.2 kJ per Kelvin per kg ie it 1 kg of water will be warmed up by exactly 1 kelvin if you put into it 4.2 kJ
2) The mass flow of the fluid (mDot) this should be obvious from 1), ie the more kg of fluid you flow in any given time period, the more heat you move
3) The temperature difference, again, this should be obvious from 1) that a fixed mass of fluid up by 2degC takes twice as much energy as warming it up by 1 degC
If we assume for a second you heat pump has a fixed heat output (it doesn't, but we'll come to that in a bit) then as you increase the secondary flow rate the temperature difference MUST reduce. This DOES NOT mean less heat is being carried, simply you are trading deltaT with mass flow. More mass, less deltaT, less massflow, more deltaT
Now, like for all heat engines, for a heat pump which uses a phase change method to move heat the "wrong way" ie against a thermal gradient, we have a fundamental physical characteristic that governs how efficiently it can do that (The carnot efficiency). The efficiency with which it can move heat is INVERSELY PROPORTIONALl to the magnitude of the thermal gradient across which it is moving that heat. What this means is a heat pump has max efficiency at min deltaT, effectively in laypersons terms this is because it is "pushing the heat against the smallest temperature gradient". The practical embodyment of this characteristic is that your heat pump will move the most heat with the least input power at the lowest deltaT achievable
So, in reality, you really want your mass flow to be infinite, ie there to be NO deltaT, ie your heat pump output temperature is the same as its input temperature. This is obviously not practical, and in a real system the thermal gradient across the interface boundary (ie across the plates of the heat exchanger that keep the differing fluids apart) is clearly none zero as well.
To work out what the best secondary mass flow actually is, and it's almost certainly a significantly higher than the recomended flow range, you actually have to measure the total system energy consumption including the pumping elements!
If we consider a pool in a 25degC ambient, were we want a 30degC average pool temperature, and with two secondary mass flow rates for the pool water, a "low flow" which gives a heat exchanger output temp of say 35degC and a "high flow" option that results in a 32degC output temperature in order to keep the pool at our average.
The theoretical CoP is set by the absolute temperature difference between the heat pumps input and output fluids and we must work in Kelvin (0 degC = 273 kelvin)
Case 1, low flow CoP = (35+273) / ((35+273)-(25+273)) = 31
Case 2, high flow CoP = (33+273) / ((33+273)-(25+273)) = 38
Here, because the deltaT's are so small, we are into a range where the inverse nature of the division inherent in the Carnot efficiency calculation makes large differences to the CoP for small differences in the deltaT. In a real system we will not be quite as "high gain" as this, because we have those temperature gradients intrinsic to the heat exchanger itself, ie we actually have to push the heat across the boundary between the two fluids. Add in a practical 3degC heat exchanger boundary graident and those CoPs fall to 19 and 22 respectively.
You heat pumps maximum CoP (claimed to be around 14) will be developed at the lowest possible secondary deltaT, and probably at it's lowest rated power. This claimed max CoP obviously includes all the other "in-efficencies" and losses" ie driving the cooling fan etc
So why, you ask, do heat pumps have a recomended "flow rate range"? Well this is because in a practical system, moving the secondary fluid ie the pool water is not free, ie it takes energy to move, and as the dynamic loses in a flowing system go up with the square of the velocity, trying to ram too much water through the heat exchanger becomes counter productive. In a practical heat pump, the size of the heat exchanger is set by limits, a larger exchanger costs more, takes up more space, is harder to seal and harder to make work evenly.
It's insane that the "baby" heat pump draws almost 50 amps.
Where do you get it from?
@@wiktorm5839 11kw @ 240 volts
@@homersimpson6985 divide that by the heater's COP to reach the current draw. So it will be between 3A and 8A depending on conditions.
17% Heat Pump flow rate, but 100% Filtration flow rate...
Correct.
Destination F’d!!!
Not happy with your electricity work Dave! Unprotected corro that powers it fails as3000 standards.
Huh? If you are talking about the ribbed corro it's for the earth wire to the fence, not the power. Power is in the 25mm orange conduits
@@EEVblog2 I could make a whole video how your setup is wrong electrically. Like WTF doing a solder joint wrapped in tape then cemented?! Moisture will leak down and deteriorate.
You're an EE FFS I expected better from you and I even offered to help on the project.
8:06 That's not a real shark.