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jamegail1 09-15-2010 12:21 PM

Boiler still runs even when thermostat is off
:help:I have a two zone Smith GB100W gas boiler that still runs after the thermostat has reached the desired temp. Even when you shut off the heat at the programmable thermostat the boiler keeps running. I replaced the thermostat to no avail. I am wondering whether it is the Honeywell aquastat controller.I have model L4080b on the boiler. Any help would be appreciated. Thanks again , jamegail1

beenthere 09-15-2010 05:21 PM

Is the second zone, an indirect water heater?

jamegail1 09-15-2010 07:27 PM

boiler still runs even when thermostat is off
The second zone is not for a water heater. It is for the second floor of my house.

beenthere 09-15-2010 07:40 PM

Are you sure that thermostat isn't calling of heat?

Is there only one aquastat on the boiler?

jamegail1 09-16-2010 07:28 AM

Boiler still runs when thermostat is off
Thanks for replying to my post beenthere.There is only one aquastat controller on the boiler. Both thermostats are turned to the off position. The boiler turns on even when it is shut off at the thermostats.

AllanJ 09-16-2010 01:26 PM

The boiler itself may have an internal control to keep itself at a certain minimum temperature so when the thermostats call for heat, the rooms will get heat faster.

In a typical system the aquastat controls the burner independently of the thermostats and circulator pumps controlled by the thermostats send the heated water to each zone.

If there is a domestic hot water coil then the aquastat will maintain the boiler temperature for the hot water and the act of doing so will keep the boiler ready to supply heat for the rooms.

beenthere 09-16-2010 04:56 PM

I don't recall Smith having a gas boiler with a tankless coil.

Its probably the R8225D relay stuck closed.

jamegail1 09-16-2010 07:34 PM

boiler still runs even when thermostat is off
Thanks for posting. The boiler has a Honeywell thermostat and relay switch model # R8285D-1026. I don't know if this will help or not. Both thermostats are turned off. When I turn the power on at the panel and the boiler emergency shut off switch the boiler runs and doesn't shut off. This just happened all of a sudden. Any help would be appreciated.

beenthere 09-16-2010 07:51 PM

Sounds like the relay is stuck closed.

Needs replaced. Just the relay though.

jamegail1 09-16-2010 08:24 PM

Boiler still runs when thermostat is off
Thanks beenthere !!! I will try that first and hope that it works. What part of Pa. are you located in ? My Dad lives out by Johnstown. Just curious. Again thanks. I will post after I install the relay.:thumbup:

beenthere 09-16-2010 08:28 PM

Lancaster county.

jamegail1 09-22-2010 11:14 AM

boiler still runs even when thermostat is off
I just received the new R8285 control center yesterday. I went and tried to replace only the relay switch and that didn't work. I then installed the transformer part of the control center and that failed also. Any other suggestion out there ? Thanks in advance, jamegail1

beenthere 09-22-2010 04:44 PM

Do you have a multimeter, and know how to use it.

jamegail1 09-22-2010 06:40 PM

boiler still runs even when thermostat is off
Yes I have a multimeter.

beenthere 09-22-2010 06:43 PM

With thermostat turned off, or set to lowest temp setting.

See if you are getting 24 volts between the W and C terminal on the relay.

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