T-stat issues - advice needed

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Old 02-11-03, 06:43 AM
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T-stat issues - advice needed

Hi all.

Recently had 2K in HVAC work done - new ducting, central humidifier and 7-day digital T-stat.

All work was complete and everything has been great. I have had a pleasant experience with the techs, but we had one problem with the t-stat.

They installed a Honeywell Chronotherm IV, and I noticed that when the buttons were pressed, and the back lighting came on, the backlighting was "flashy/flickering". I thought it might just be a loose connection, so I called them and they came to check it out. They agreed that something was up, so this morning they replaced it with a new one.

Problem is still there -- it isn't flickering quite as bad maybe, but it is still definitely noticeable. They could see it as well.

They think that it is from a voltage difference between the central A/C outside and the furnace inside. To correct they would need to rewire from the outside back in.

So, my question is, has anyone heard of this before? And is it reasonable for me to expect them to fix it, considering I spent $270 for the unit.

Thanks!
 
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Old 02-11-03, 10:05 AM
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tstat

IF they put it in they should fix it ED
 
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Old 02-11-03, 03:03 PM
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comgenboy:

If you are referring to the back-light flickering then it is not likely any interconnecting wiring.

Is this a back light that you have to press and hold, or does it stay on continuosly?

Ed is right, it's their headache.
 
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Old 02-12-03, 05:36 AM
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Yeah, just the backlighting is flickering. It is the kind of backlight that comes on when a button is pushed, and then turns off after buttons haven't been pushed for 10-20 seconds.

I guess I will give them another call.
 
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Old 06-13-03, 07:26 AM
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Update - A/C Clicking?

Well, I figured I would post here rather than start a new topic.

Anyhow, I had the work done months ago, they replaced T-stat, still flickers. I really don't care much at this point, but I now that it is hotter than sh*t here, we now have the A/C unit on...

Question - is it normal to hear a "clicking noise" at the t-stat when it cycles the A/C on?

Also, when the unit comes on, there is a slight dimming of lights - even though I have 200A service. Is 30A normal for a 5 ton sears unit? It seems to cool very well.

Thanks!
 
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Old 06-13-03, 07:43 AM
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most digital electronic tstats will "click" when a call for heat or cool is made. 30 amps on 5 tons? sounds low, check the rating plate on the outdoor unit for "minimum circuit ampacity"
 
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Old 06-13-03, 07:58 AM
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Thanks. I will check the unit when I get home.
 
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Old 06-13-03, 01:40 PM
Thomas W.
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30 amps is way to low, also look into how many other breakers 2 pole are close to that one.
The t-stat is normal to click.

If the lights on it still flicker they should put in a isolation relay as you are getting back feed from the low voltage circuit. It is common because that stat does use the batteries to operate only for back up it uses the low votage circuit as it's operating source.

I know A/C companies who have stopped using those just for that reason.
 
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Old 06-13-03, 03:23 PM
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comgenboy:

The stats that click have a mechanical relay but some use an SCR to switch the load. These type are silent.
 
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Old 06-15-03, 04:04 AM
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The label on the outside unit says "max breaker 35 amps".

The wiring to the outside disconnect is 10/3. Like I said, it is working fine. I might move a few breakers that are near the a/c one to try that.

I have to have the hvac company back out to balance the system once I finish the rooms in a few weeks, so I will revisit the flickering T-stat with them. Maybe I will get them to go to a different model.

Thanks again.
 
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