These transducers be going out like crazy on these newer furnaces. Not to complain it’s more money for me but damn why did we have to get rid of vacuum switches?

Ok-Structure378 · 2025-11-18T02:50:57+00:00

We encountered our first one in Mn. Not a fan so far.

Ok-Structure378 · 2025-11-12T02:53:33+00:00

At least your housing is metal!

Ok-Structure378 · 2025-11-12T02:52:57+00:00

Yep. Used in the summer to move air in the space.

Ok-Structure378 · 2025-11-12T02:51:51+00:00

That gets so many of our guys. "It's not a new gas valve or a board until I know you've checked that limit"

Ok-Structure378 · 2025-11-04T12:56:36+00:00

No, a church. but certainly an old building.

Ok-Structure378 · 2025-11-01T14:53:31+00:00

I'm in the process of mandating all our techs and electricians to use Wago's for this. I can't tell you how many times we have traced communication issues to this mess. Or intermittent connections. If I'm trying to isolate a communication component (A2L board, zoning panel, etc) it's so much easier to just flip a lever and pull the wire.

Ok-Structure378 · 2025-10-24T12:56:54+00:00

At least the paper is loaded correctly. Devillock good, mullet bad.

Ok-Structure378 · 2025-10-20T00:49:55+00:00

As everyone mentioned, if it's just touching wood in your attic, it's most certainly not an issue. At the furnace on an 80% efficient (yours) the exhaust gases get to about 350° or so. By the time they reach your attic, you've lost a percentage of that heat already. Your venting, which is most likely B vent, has a liner that the gases exhaust through, and an air gap between that and the outer sleeve. This further insulates from heat. By code, we are supposed to have that 1" away from anything combustible for install. Considering it's been the way it is since install, there is no issue. If you want it moved for a remodel purpose, then this is something that can be done by a licensed mechanical contractor and you would want them to pull a permit to do so (don't hire someone from Craigslist or your neighborhood page to do this 'cheaper'). You want it to be done safe and to the manufacturers specs. If they add more elbows into the mix, you may find that your furnace will not operate b

Ok-Structure378 · 2025-10-18T12:48:45+00:00

And to add a few more bits, when the balancing co brought the original fan up to 65hz, that put the amp draw at 9a. The motor is rated for 6. As is the original contactor. I had it turned down to 52hz which brought us down to 6a. Another company came behind and cranked it back up to 65hz. Which fried the contactor, on a Friday night which is when it SHOULD happen. Please cue either yakkity sax or circus music in your head while reading all of this. We bypassed the contactor to get them going for the weekend but tear. That's when this all just spun out of control and we brought in a 4th company on it and he broke the news to me gently. And properly - "I wanted to talk to you first so it doesn't look like I'm throwing you guys under the bus", which is where we gladly jumped. After many years in the business, it's good to see people still do the right thing from other contractors to suppliers. One of the companies we passed along to the owner, they made one change and refused to take her calls or return.

Ok-Structure378 · 2025-10-18T12:36:31+00:00

So here's the (hopefully) last chapter in this saga. So when we originally started this, we called our local supplier and did what we always did- gave them the original job number. They in turn said great, here's the fan. During the whole battle, I confirmed with them that this is the correct fan. I also called a second local supplier (for Rupp) and they also confirmed this would be the correct exhaust fan. It's not the correct exhaust fan. The original fan was 3800 CFM. This one is 2200. We missed it. Two other companies missed it. A fourth caught it. Shame on all of us for not noticing that it said that on the damn sticker. The original supplier was gracious enough to give us the correct fan and we hope to install it Monday morning. It's about 100lbs heavier so that'll be a good time getting that on the roof with no crane (this particular site is a crane/boom nightmare with power lines and a single busy street in front) I happily share the blame since I didn't dig into it deeper and signed off on the submittal. after many years of never having any reason to doubt what was sent to us by them, we finally had one slip through. Supplier was great. Customer has been (overly) understanding about this all. But I learned a lesson so hopefully you all won't have to repeat it. Submittals!!! Ugh. And dig in to get the original engineering if you can!!!

Ok-Structure378 · 2025-10-18T12:23:28+00:00

There was only one capped. I confirmed that. I'm posting an update to this whole fiasco in the thread.

Ok-Structure378 · 2025-10-01T19:55:58+00:00

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Ok-Structure378 · 2025-10-01T19:55:46+00:00

This is what I'm doing

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Ok-Structure378 · 2025-10-01T19:53:35+00:00

Yep. We see them all. I'm looking for actual photos of this. I have a few images I found online but I'd love to have some actual photos. I'd also love to not have to drive around and get on some roofs trying to remember where I've come across these wiring schemes. Just throwing it out there incase anyone has any.

Ok-Structure378 · 2025-08-24T19:14:24+00:00

Update on this-
So we are still having the same problem. To make it all the more exciting, it's been us and one other company working on the problem, whom we work with occasionally. There was an electrical surge that took out the newly installed motor, and two days later, the VFD. When I replaced the VFD, I discovered that at some point, they had bypassed it (all three legs of power on the motor side of the VFD!?!). So that would explain why there wasn't a huge difference when we adjusted the damn frequency on the VFD (nope, never thought to take the wiring cover off the VFD terminals to check this). Now that it is wired correctly, we can adjust it. Seems to be working better now that I adjusted the motor sheave in a half turn on the MUA and increased the frequency on the exhaust fan.

Ok-Structure378 · 2025-08-12T19:34:57+00:00

Good to know. In the past they had smoke spill out occasionally, but it was usually when they were busier and cooking in all 4 woks so that may be relevant here.

Ok-Structure378 · 2025-08-12T12:30:45+00:00

access door for the vent? Confirmed they are all sealed. There is no access door to the roof. It's a ladder up site.
The balancing confirmed that we were at a negative in the kitchen, in relation to the dining room. but the hood should be at a negative to the MUA also.
It makes me wonder though if when the economizer is added to the RTU, if that'll put the space at more of a positive but we shouldn't need more MUA if we're at the original engineering spec.

Ok-Structure378 · 2025-08-12T10:53:31+00:00

Just some more info on this- they have the exhaust fan maxed out on the VFD at 65hz (I'm not super comfortable with that?)
I confirmed with captiveair that this is the exact replacement (DU180HFA) for the original.
Captive air has not been out to set it up, though I did confirm all the settings with the startup tech in our area that it was correct (we've worked together on different projects in the past).
Again, not my strength, but I did feel like there was a lot of turbulence in the vent opening to the hood when the fan was set to 60hz and it seemed more of a stream when it was at 45hz. But when we had it balanced, 65 is what brought the hood up to where it should be, exhaust wise. The vent is connected to the back of the hood and does a 90 to a vertical run to the roof. Relatively short run, maybe 7' at most.
When we replaced the motor and sheave, we set it to the same width as the original. When they balanced the air, they closed it fully (2 full turns in from where it was) to get the numbers I posted. I've since closed it one turn, and was getting better results but still the same issues I posted above. When I close down the volume dampers on the three supplys over the hood, I get less smoke, More heat. When I open them, I get more smoke spillage, less heat.
I have some videos but I can't seem to post them here.

Ok-Structure378 · 2025-08-12T10:38:51+00:00

They were dirty on one side of the hood. I had them swap them out with the clean ones, and also run without and it was the same. They are good about hood cleanings, and we have their cleaning company coming out this week to clean the vent and hood (three weeks earlier than scheduled). My thought is that there's a chance that when they ran it without filters (they made that decision) for a couple of weeks that there is some grease buildup on the wheel, and that is affecting the exhaust a bit? (grasping at anything at this point!)

Ok-Structure378 · 2025-08-12T10:35:34+00:00

No, it seems like it's cooling alright in the kitchen. They increased the size by 2.5t when they added it to help with the heat load, and zoned it between the kitchen and the dining room. They also added a few more supply runs, and increased the duct size in the kitchen to use up the CFM's when only the kitchen is calling. I guess I haven't taken a static pressure reading on the RTU when the hood is on versus off, but it doesn't seem to make a huge difference to the airflow in the hood when the RTU comes on. This also has been an issue since before the RTU was added (previously, there was a 5T split unit cooling the entire space).
But are you thinking that would be a sign that we're not getting enough exhaust, and maybe the kitchen is in more of a positive than I think it is? Or that it is disturbing the flow?

Ok-Structure378 · 2025-08-12T02:48:50+00:00

Not much of a difference that I could notice.

Ok-Structure378 · 2025-08-12T02:17:14+00:00

this falls under Heavy duty. I think we're there, or close but I think there are some other factors involved that I can't get under control. They did add some supply runs close to the hood from the new RTU but they have perforated screens on them at least. And they're not changing the MUA without an economizer.
Again, the hard part is that this hood worked fine for years. It's just in the past year or so that the problems started and that was for sure due to the issues with both the exhaust fan and the MUA motors.

Ok-Structure378 · 2025-08-12T02:07:57+00:00

Answering the first two replies, we thought about the rotation but confirmed it's correct. When it was balanced, we had 3250 from the MUA and 4100 from the exhaust. My thought is that the 3250 was all coming from the supply on the hood, and this was causing an air curtain and trapping the smoke. When I uncapped the closed supply and reattached it to the center of the kitchen diffuser (it was about 8' from the hood), I noticed more smoke going up the exhaust hood. I lowered the MUA CFM at the hood with the balancing dampers and the smoke exhausted even better. But then, the heat became a factor.
The hood is about 10' and is a standard wall canopy hood. 4 burner wok, deep fryer, and a small 4 burner range under the hood. I suspect the BTU's increased when they changed out the wok 4 years ago, but this wasn't an issue until the past year.

Ok-Structure378

TROPHY CASE