Heil Communicating 2 stage Furnace with Observer Always Fires Second Stage

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Old 03-07-18, 07:06 PM
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Heil Communicating 2 stage Furnace with Observer Always Fires Second Stage

Hi Forum,

I recently had a Heil Communicating Two stage furnace and variable speed A/C installed in my home, with the Observer thermostat. Each time heat is called, the first stage heats for 3 minutes and 30s and then the second stage fires no matter the combination of current inside temperate and set target temperature. In some cases, the second stage fires for only seconds before the target temp is realized. This mode of operation is not comforting: the heating cycles tend to be short because the second stage throws more heat than needed and causes tangible temp swings and (more) temp imbalance throughout the house.

I've been in touch with the installer and he openly admits he's not familiar with troubleshooting communicating systems and forwarded my complaint to his distributor. The distributor advised the thermostat uses complex algorithms to determine when second stage should fire. I did not accept this answer stating the furnace behavior is as if the thermostat is a single stage unit and that this mode of heating was flat out not comforting in the house.

In an effort to help facilitate more troubleshooting, I took to the internet DIY and contractor forums searching for similar problems and I have not found much info related to this--overall info on communicating systems on the web is scarce. The best I could find was a furnace control board that had firmware incompatibilities with the Tstat and/or the gas pressure setting per the different stages was incorrect. Not sure if either finding is relevant in my case....

So, I'm curious if anyone has had a similar issue and how it was remedied. I'll post back what is learned from ongoing troubleshooting.

Also below, I'm adding information that may facilitate commentary. There have been other findings that suggest improper operation:

-The communicating furnace was installed first and the A/C and Observer installation occurred a few days later. The furnace was first wired to a Nest as a single stage thermostat since that was what my wiring accommodated. When the other equipment was installed, it was wired has a communicating system.

-The A/C serial number reads slightly wrong in the thermostat. The numbers are all correct in sequence but the preceding letter is transposed to the middle. I find that strange.

-I've tried locking on first stage heating via thermostat stage lockout options but that has not worked. The second stage still fires on a 3min 30s timer. The thermostat allows me options to lock up to stage 5. I'm surprised this option is allowed seeing that the T/C knows my furnace is 2 stage...but may be nothing.

-There has been 1-off instance where the Tstat will be set at 62, and when heat is called, it heats to 65!

-Outdoor temperature readings are off by 15degF on sunny days. Probably an unrelated finding and an easy fix.

-I flipped the #2 DIP switch on the furnace board but this did not change the operation. Per the Observer manual, the DIP switches are stored on the Tstat but all furnace control board settings can be modified through the Tstat.

-I reside in northern IL, it has been in the 20s-30s at night this time of year.

Any feedback will be greatly appreciated, and I'll share anything I learn.
 
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Old 03-07-18, 07:53 PM
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Welcome to the forums.

You need someone that specifically knows that system. I don't.
My forum partner may.

Posting the furnace model number as well as the thermostat model would be helpful.
 
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Old 03-08-18, 04:59 AM
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Hi PJMax,

Thanks for the response. My equipment model numbers:

TStat: TSTAT0201CW
Furnace: G9MVE1202422A

-Eric
 
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Old 03-09-18, 02:20 PM
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The stat may have an upstage timer that should be disabled.

It should only be running on second stage when the temp is much lower than the setting or first stage can't keep up.
 
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Old 03-09-18, 06:11 PM
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I checked the manual again and don't see an option for stage timers. So if this option does exist for the Observer, it's not given to the homeowner that I can tell.

Link to manual: http://www.utcccs-cdn.com/hvac/docs/..._ICP_24732.pdf
 
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Old 04-10-18, 10:36 AM
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Update:

Short story version: Combinations of new and current T-stats and furnace control boards did not solve the problem of the timed 2nd stage, and any combination of new control boards introduced a new problem of not recognizing the furnace. Troubleshooting still on-going.

The installer showed up with a new T-Stat and furnace control board. First level of troubleshooting started with the installer on speaker phone with Heil tech support. They unplugged the Stat and jumper-wired the control board. They basically did some air temp checks and verified heat rise between stages. That was about 30 minutes of work, and at that time the over-the-phone tech basically said to wire it back up and monitor the situation. He did make the point that the first heat call after cycling power should would make the furnace run for 16 minutes on 1st stage the very first time. So the very first cycle after power up, the second stage kicked in at 3min and 30s. So the problem is still there, even after the power cycle, with the installer there to witness.

We then did a sequence of part swapping, listed in chronological order below, followed by the result:

Old furnace control board, new stat: 2nd stage still fires on timer.
new board, old stat: 2nd stage still fires on timer and tstat could not read model number and S/N of furnace
new board, new stat: 2nd stage still fires on timer and tstat could not read model number and S/N of furnace
Old board, new stat: 2nd stage still fires on timer, Tstat recognizes furnace M/N and S/N

So troubleshooting is still ongoing. I agreed to monitor the situation but some further troubleshooting is needed. The only (easily removable) part not replaced on the furnace is the little model number chip. I'm curious to know if the problem is with that small chip.

P.S. this is mostly me ranting, but I was very off-put by the tech support guy over the phone constantly trying to pawn off issues as "stupid homeowner". There were numerous times I had to defend my position. And if he wasn't so impatient, he could have heard the problem replicated in real time.
 
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Old 04-10-18, 07:47 PM
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are the upstage timers disabled on the board?

these furnaces should be able to used with conventional stats -> can try removing the observer, disabling upstage timer via dip switch and jumpering R and W1.

Should stay on low.

jumpering R to w1 and w2, it should run on high and if u remove jumper to w2, should drop back to low.

The best solution right now may be to use a conventional 2-stage thermostat. Comfort is the same in heating mode but configuration is done on the board instead of stat.
 
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Old 04-12-18, 07:11 PM
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Hi user 10,

Thanks for the response, it's appreciated!

Per the furnace and communicating thermostat manuals, all of the DIP switches on the control board are overridden and then controlled by the thermostat itself through its various menus. There is sw2 on the control board that controls the stage timer, but it's overridden by the stat. I've switched this switch on my own but it yielded no difference in operation.

The troubleshooting performed did utilize jumpers to the extent that the installer and the tech concluded the furnace was working correctly. Though I can't remember the full sequence of jumpering.

I do recognize that a two stage stat would work (I'd have to add a wire but not a big deal). My beef is that I got a 5 stage AC that will only utilize all stages with the communicating stat. I also spend a good chunk of dough on this system and it should work as intended.
 
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Old 04-13-18, 08:29 AM
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So the furnace stages fine in non-communicating mode with w1/w2 inputs?

At the end of the day your distributor or contractor needs to get in touch with the manufacturer's tech support request that they can send someone (a rep if they don't have their own guys) who's intimately familiar with the products.

Something's obviously wrong when the stat is bringing on second stage right away most or all of the time. You should only see the second stage come on when it's trying to raise the temperature or when it's brutally cold.

If no one can get it to work, you should be looking for a full refund on the stat, remove of it and a partial refund on the 5-stage a/c -< then use a conventional 2-stage stat.

I think the super high end communicating/variable capacity stuff can be more trouble than it's worth and the sweet spot is a 2-stage furnace with variable speed blower and a single speed a/c. Offers a good balance between comfort and complexity. Can get good dehumidification out of a 1-stage a/c when properly sized and especially when a humidistat is cooked up to slow the fan down when it's too humid.

If the board on your a/c goes after warranty you won't like the bill.
 
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Old 04-14-18, 09:59 AM
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I recognize there being pros and cons to communicating equipment. High repair costs are paralleled to a lot of things these days so I'm indifferent to this at least for the next 10 years.

The service from the contractor and distributor has been lousy. But these are details I don't care to get into in this post (yet).

I do have some answers to my original questions, documented below for future reference for others.

-The A/C serial number reads slightly wrong in the thermostat. The numbers are all correct in sequence but the preceding letter is transposed to the middle. I find that strange.

Heil Observer formats the S/Ns on-screen similar to Carrier S/N formats...per the tech.

-I've tried locking on first stage heating via thermostat stage lockout options but that has not worked. The second stage still fires on a 3min 30s timer. The thermostat allows me options to lock up to stage 5. I'm surprised this option is allowed seeing that the T/C knows my furnace is 2 stage...but may be nothing.

The heat stage lockout menu is for heat pumps and does nothing with furnace operation.

-There has been 1-off instance where the Tstat will be set at 62, and when heat is called, it heats to 65!

When there is a temperature profile programmed, the stat will start the cycle in advance of the timed temp. Ex: if current temp is 62F at 5:30 and I have it set at 70F at 6:00, the stat will call for heat well before 6:00 such that the temp is actually 70F right at 6:00. I'm thinking my original complaint was me just witnessing the instantaneous call for heat and not a real finding. The old Nest may have worked this way too though just never noticed.

-new board, new stat: 2nd stage still fires on timer and tstat could not read model number and S/N of furnace

Per the tech, the original control board stores M/N and S/N info. So if my control board is swapped with a replacement, the stat won't see a model or serial number. Though the replacement board had a note on the box that said, "Model chip not included, install old model chip with this board" (verbiage not exact). I'm not necessarily challenging this feedback, but seems hand-wavy at face value.
 
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