Mitsubishi Electric / Fan Replacement on a PUHZ-YKM & Static Pressure Measurements
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- Опубліковано 13 чер 2024
- Returned to site to carry out static pressure measurements and adjust the dip switch settings accordingly. Then, returned with the outdoor fan to replace. Trying to make the best of a bad situation with this install.
I think generally to get a reasonable static pressure reading it has to be taken 5 (unsure of exact number) duct diameters downstream from elbows or anything that would cause turbulence.
Hard to get that sometimes in real scenarios.
Thanks for the tip mate, appreciate it. I’ve also come to realise that my static pressure readings will be wrong without the cowls present. I’ll need to go back once the cowls and duct reworks have happened to remeasure.
Awesome video!
With regards to the updates, would you be able to do a video to share what they do?
Next time I do an update I’ll film the entire process and explain what the updates achieve. Sometimes it’s countermeasures to problems they seem in the field and other times it’s new features.
@@hvacraustralia That’s awesome! I’m part of the facilities committee for my church, and we have 3 AE-200s that are on slightly older firmware. I downloaded a copy of the 7.99 firmware and I’m keen to know what it does and what I need to take note of before I upgrade them.
While I’m not trained to access the compressors, it’s really neat to know that their firmware can be upgraded. Never knew that before!
I appreciate that you originally thought the static would be wicked high, but actually came back to test it to confirm and was lower than you thought. Some people would just say "it's cooked" without testing.
Question for you - why have the fan static setpoints there at all, rather than just letting the fan go flat stick if it ever needs to? Figure it'd be smart enough to know what speed it needs without needing manual adjustment.
Also, have you looked at the manuals for those outdoor units to see if they mention anything about ducting like that? Most fans typically have a circular shroud around the blade, looked like those were missing/removed, which would allow air to recirculate around the edges of the blade, lowering their efficiency, requiring them to run at a higher speed to compensate.
Edit: looking at those outdoor units, they're missing a pretty substantial shroud around the fan, which I suspect impacts their efficiency quite a bit.
It’s a good point. Give the fan the ability to ramp up to 100% if it needs to. I guess it probably just comes down to wear and tear. If it doesn’t need to ramp up to X RMP’s then why let it.
I looked in both the installation manuals and service manuals for these units and it only mentions that you can increase the static if required. Nothing about guidelines on how to install condenser ductwork. I guess they know people do it so they will give you an option to increase static pressure but they don’t really want to give specifications. Maybe a liability thing?
I’ve been doing a lot of reading and talking to people about this situation since filming this (filmed this a few weeks ago) and I completely agree with you about the shroud. I believe this is why my static was lower than I thought it would be. The air isn’t being drawn over the fan as designed meaning a lot more turbulence around the fan, resulting in lower airflow across the coil and low suction pressure that I’m seeing. I underestimated its impact. Only issue is, unless they rip off the roof, the only way I see to make it better is to design a makeshift low profile shroud and install it on the ductwork forcing the air over the fan as intended and remeasure the static. The height of the room really messes with any other solution I’ve thought of. It’s a real shit show.
@hvacraustralia Curious to see what they end up doing with it! Shrouds will definitely help that a lot, but you're right, bit of a prick to do it after the fact.
Here's a random question for you, have you ever seen one of those outdoor units freeze up outside in free air when it's 20c?
Just saw one on the roof of a random building, solid block of ice in direct sunlight. Just defrosted as I'm typing this. Figured they'd defrost waaaaaaay earlier than that.
I changed my recommendations and said we need to make alterations based on getting the shrouds back on. Once they’re back on I’ll remeasure the static pressure and adjust accordingly. Thanks for the feedback. Promoted me to read further into it and get a better understanding.
I haven’t seen one, but Ive heard about it happening. I think it was a bypassing valve. Was it a YNW? The look for certain parameters before it goes into defrost. TH3 temp below -5 for X amount of time, compressor durations time from memory.
@hvacraustralia No worries! I always learn a lot digging into stuff like that. It's nice chatting to techs that actually give a shit about getting to the root of the problem. Looking forward to the follow up vid! Seems like it's something that's hard to quantify without actually trying it, but most papers I can see online directly correlate the fan blade tip clearance with static pressure, so in theory shrouds should help a lot!
Unfortunately, I have no idea what the units actually were, mainly a refrig apprentice now, don't have much to do with AC. They were just on the top of a random building we don't service. Same circular shroud as all the mitsi's I see on google but more of a square top edge.
WTAF were they thinking with the ducting....is it some stupid attempt at beauty at the expense of working A/C units....
Pretty much this. Originally the roof wasn’t meant to be there. The installing company also went a bit rogue with the unit locations and ductwork. It’s a real shit show.
Let's just say hypothetically they replaced those acoustic louvre wall grilles for just mesh fencing, pretty much see through - would the increased airflow lead to a reduction in noise, and would the noise levels from outside the compound be about the same as they were with the acoustic walls and units running balls out? food for thought :)
If the end result is more airflow then absolutely. More airflow across the coil means it won’t need to run as hard to maintain the suction pressure on this instance. This is a few issues I’m working through with this one. Yet to land on the next course of action.
What a balls up of a job that was!. Probably starving the condensers of air aswell that many condenser in one spit and shitty fresh air flow
Also the fan shroud should've be left on and then duct over the top.
It’s a shit show of a job. I have don’t more reading into this and changed my mind on what should be our next step. I underestimated the impact of the missing shrouds. I’ve now recommended we replace them, adjust the ductwork and remeasure the static pressure.
@@hvacraustralia I'm no engineer but I think spiral duct the size of the shroud opening essentially fan blade width would be the go for these. Either way your more switched on cookie than the guys that slap these in the first place 🫡
I ended up recommending a fair few reworks to these units. First choice is getting the manufactures shrouds back on and getting new ductwork, then remeasure the static pressure and go from there. Hopefully they go ahead with it. We’ll see though 😂
The exit point for the added ducts looks heavily restricted by the slats going across. They should have cut them and put a grill in place.
Absolutely. This entire install is a shit show.
that looks like the worlds biggest shit show
It is. Still ongoing too.
@@hvacraustralia I wouldn't have any hair left after an hour working on that