[Bonzoso]

Hi all,

I just replaced my thermostat 2 months ago when it was acting erratically. The new Honeywell RTH6450D1009 programmable thermostat has worked perfectly for about 2 months. This morning I got out of the shower and noticed the house felt hot. Sure enough, I checked the thermostat and the room temp was 77 but the program setting was 62. I lowered the temp manually to 55 and pressed the hold button. The boiler continued to cycle on and off. After about 15 min, I turned the thermostat to the off position. After about a minute it stopped showing a set temp in the display but the boiler continued to cycle on and off. I finally waited for the burner to stop and allowed the circulator pump to run about 3 min then turned off the power to the boiler. I'm kinda thinking it may not be the thermostat, that something in the boiler electronics went haywire. Can anyone give me an idea how to troubleshoot this. I can use a VOM. Thanks!

 

[WhatRnsdownhill]

check your connections on the thermostat wire, if is crimped together some place its bypassing the thermostat, if you can find the thermostat wire down at the boiler , disconnect it at the boiler and see if boiler continues to heat,

 

[Bonzoso]

check your connections on the thermostat wire, if is crimped together some place its bypassing the thermostat, if you can find the thermostat wire down at the boiler , disconnect it at the boiler and see if boiler continues to heat,

Boiler heats without tstat connected. No touching wires. Anyone?

 

[WhatRnsdownhill]

did you disconnect the thermostat wires at the boiler or just at the thermostat?

 

[Bonzoso]

did you disconnect the thermostat wires at the boiler or just at the thermostat?

at the aquastat relay

 

[WhatRnsdownhill]

ok, did you hear the relay click on and off as you disconnected the wires? connect 2 short wires back or jump out the screws and see if you hear the relay, if not the relay could be stuck..

 

[WhatRnsdownhill]

what brand boiler is it?

 

[Bonzoso]

what brand boiler is it?

Thanks for the replies

It's a New Yorker boiler with Honeywell L8148A aquastat relay. After I killed the power I did tap the relay itself and it snapped down to the down position as if it was stuck.

 

[WhatRnsdownhill]

can you get in there with some sand paper and clean off the contacts? if not and it keeps happening, replace relay..behind that grey looking tab that moves are the contacts..

 

[Bonzoso]

can you get in there with some sand paper and clean off the contacts? if not and it keeps happening, replace relay..behind that grey looking tab that moves are the contacts..

Thanks again SRD. Yes I'll get in there and clean them off. See if that fixes it. Unit was replaced in 09. Are you suggesting the relay itself can be replaced? Thanks again

 

[beenthere]

Replace the entire aquastat.

 

[WhatRnsdownhill]

on that aquastat the relay is not replaceable unless you want to get into soldering on the circuit board...just make sure no water drips in there causing corrosion on the relay..it should have lasted longer than just 7 or 8 years...

 

[Bonzoso]

on that aquastat the relay is not replaceable unless you want to get into soldering on the circuit board...just make sure no water drips in there causing corrosion on the relay..it should have lasted longer than just 7 or 8 years...

I thought so too, but I got in there with some emory and then contact cleaner. Blew dry with duster. Seems to be working for now. Thanks!

 

[WhatRnsdownhill]

:wink2:.......................................

 

[supers05]

They don't make things the way they used too..... Congrats on the fix. I'd buy another Aquastat, and keep it handy when the current one stops working again.

Cheers!