Aquastat Relay sticking

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Old 11-27-12, 06:41 AM
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Aquastat Relay sticking

Hello everyone, new guy here.

Couple days ago I noticed the house getting cool. Went to my Honeywell RTH6450D (5-1-1) that has been working for months and it said "Heat On". I went to the radiators, and they were cold. Went to the boiler and found the L8124A, C mechanical relay wasn't picking. So I pushed it, and the pump started and heated the house. The next morning, it was freezing again, and same thing. Seems the relay is getting off its axis when it releases and cannot re-make, not all the time, but sometimes. Had a service guy come look at it and he said those boards are about $300, we cycled the power on and off like 6 times and it worked every time when he was there, of course.. So I said I'd wait and see. Well, this morning it was freezing again so I pushed it in and got heat. But I can't keep doing this.

So after some searching I found people here recommend the L7224U1002, and for $135 from Patriot, that seems like a deal.
1) Will that relay work with my current thermostat?
2) Are there any "gotchas" that I will need to know for installation, such as different terminal labels, and lettering/numbering?
3) How easy/hard is it to set the limits and deviation? Are there easy instructions online?

Thank you,
Joe
 
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Old 11-27-12, 04:12 PM
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Seems the relay is getting off its axis when it releases and cannot re-make,
Your problem is much more typical of a cracked solder connection on the pc board that the relay is mounted on.

Do you own and are you skilled at using a soldering iron for electronic work? If so, we can guide you through a possible zero cost fix.

1) Will that relay work with my current thermostat?
The 7224 aquastat will replace your 8124.

2) Are there any "gotchas" that I will need to know for installation, such as different terminal labels, and lettering/numbering?
It's pretty straight forward, read the manual that comes with the new aquastat before you start and before you remove one wire, understand how to fully complete the job.

3) How easy/hard is it to set the limits and deviation? Are there easy instructions online?
Can you work a tv remote control? You can program the 7224. You can find the install manual for the 7224 on-line from various websites.

Here is one:

http://s3.pexsupply.com/manuals/1290..._PROD_FILE.pdf


But check first that a simple solder connection isn't your only trouble.

By the way, the 8124 is also available on-line for about half what your contractor quoted.

PEX - Radiant Heat - Radiant Heating - Plumbing Supplies - PexSupply.com
 
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Old 11-27-12, 09:19 PM
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Thank you. I will look at the solder joints when I get some time. I have solder experience. The unit seems to work well once I push the relay. For example, I have the thermostat set back during the day to 64, when i got home the stat was calling for heat but the relay wasnt picked. I pushed the relay and the unit heated and cycled normally until the next setback.

i will take a look at the solder joints soon. Just wondering, what reading should I have between the T-T terminals when the stat is calling for heat?
 
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Old 11-28-12, 05:24 PM
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what reading should I have between the T-T terminals when the stat is calling for heat?
When there is a heat call, there should be ZERO volts at T-T because they are SHORTED by the zone valve (or thermostat) switches.

When there is NO heat call, you should read the 24V transformer inside the aquastat.
 
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