Sad story: Neither heat nor AC working

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  #1  
Old 06-15-19, 05:15 PM
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Sad story: Neither heat nor AC working

Hi,

I'm new here with a new house. We moved in a few weeks ago and all was well with A/C anyway. I turned on the central AC and nothing happened. I tried the heat, same thing. Quite new Amana gas furnace. Quite old AC unit.

Back story: One of the first things I wanted to do was to install smart thermostats. I purchased Ecobee thermostats which I have installed in the past without trouble. I started the installation and immediately was advised to call their help line. Long story short: Ecobee was not compatible with our zone control board. I put everything back as it was and ordered a new zone control board. Fast forward to today: No A/C (and no heat which I also tried). I have a new zone control board but have not attempted to install it.

I checked the breakers and the emergency switch. New Amana furnace control board LED says "0n". I checked the transformer and its putting out about 21V A/C which seems a little low. Not sure about that.

Possible causes that I have checked:
1. When I took the thermostats off to check the wires I might have loosened the wires. All checked and good.
2. Zone control board fuse checked and good.
3. When I took the cover off of the zone control board I might have loosened a wire. All checked and good.The new zone control board has some diagnostic LEDs that I thought would be helpful but when I started looking at transferring all of the stuff, I find that the old one has some unlabeled connections that I don't know where to put on the new one.

So, I'm kinda stumped. I'd really appreciate some diagnostic help here. Like is there something I can jumper on the zone control board to tell AC to come on?

I have attached pics of the old and new zone control boards. Not sure if that helps.

Here is a link to a higher resolution pic: http://dkrasmussen.com/zcb.jpg

Thanks,
Dan

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Last edited by PJmax; 06-15-19 at 06:51 PM. Reason: added two full size pics
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  #2  
Old 06-15-19, 05:25 PM
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Welcome to the forums.

Can't help you much with that tiny picture. Can't see anything in it. Most zone control boards use their own transformer..... not 24vAC from the furnace. Have you checked the R - C "24v IN" connections for power ?
 
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Old 06-15-19, 06:07 PM
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Hi Pete,

Thanks for the input. I just measured the power at the zone control board and at the transformer (which is for zone control board only). It's measuring just a bit below 17V which does not seem right. Transformer has audible hum if I put my ear near it. Could this be my problem?

Because I have just moved, I don't have all my gear. I have a nice variac which I could test with but not here yet.

Note: I added a link to a high res pic. Here it is again: http://dkrasmussen.com/zcb.jpg

Thanks,
Dan
 
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Old 06-15-19, 06:43 PM
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Excellent picture. I split it and posted them in your first post.

The T'former input needs to be a minimum of 24vAC. Not sure why there is only 17v but that's not going to work. Maybe that's not a 24v transformer.

I just had a member that had an A/C float in the transformer line and that caused troubles.
 
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Old 06-15-19, 08:34 PM
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Transformer is marked 24V/40V. Assume the selection is done when wiring it up because I don't see separate taps. I'm going to try a new tranny in the morning. Keeping fingers crossed.

Next I'm going to need help wiring up the new zone controller. Will do that in a separate post.

Thanks again,
Dan
 
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Old 06-16-19, 08:42 AM
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You can actually keep the thread going here. The preliminaries are already out of the way.
I'll change the title.
 
  #7  
Old 06-16-19, 07:42 PM
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Fixed!

Fixed!

OK. It turns out that the 17V reading from the transformer was not the problem. I got a new one at Lowes and installed it. When attached to the board my Fluke 77 reads 17V AC plus or minus. I went back to the old transformer and decided to install the new zone control board. The main reason was that the new board had some status lights on it so that I could at least get an idea of what was going on but... When I got the new board installed and powered up, I was back in business!

Thanks for the suggestions.
Dan

PS Here's my new zone control board in action. It's nice to be cool again.
 
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Old 06-16-19, 09:52 PM
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Interesting. If you were drawing enough current so that the transformer only measured 17v...... it should have been very warm..... almost smoking.

Good to see you back in business.
 
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Old 06-19-19, 07:42 PM
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I spoke to some electrical engineers at work and they said they were pretty sure I was seeing that because I was using an RMS meter.
 
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