steam boiler-programmable thermostat-gas furnace vs electric setting

rhodebump

Our steam boiler sometimes does not stop heating. While it works often, sometimes the thermostat reads 85 degrees and we have it set for 70. Our steam guy told us that he thinks it's the thermostat, and next time the boiler does not stop heating, to pull the thermostat from the wall, and if it's shutdowns, that the problem is with the thermostat (and not the boiler).

Well, it happened again, and we pulled the thermostat. Boiler immediately quit heating. Thermostat is a Honeywell RTHL2310/RTHL221

In reviewing the thermostat, there is a switch that needs to be set on the back. The switch is to toggle between "Gas or oil" and "Electric or Heat Pump"

We currently have it set to "Gas" , but I am wondering if it should be set to "Electric or Heat Pump"

Appreciate any troubleshooting.

ratio

That switch has to do with who controls the fan (thermostat or furnace) in heating mode. Not likely to be your problem.

How old is the thermostat? An intermittent stuck-on failure isn't the first thing I would think of, but fits what you've told us of the symptoms. Any reason not to replace it with a new stat?

unclejohn

This thermostat is compatible with the following systems:
• Gas, oil or electric furnace
• Central air conditioner
• Hot water system with or without pump
• Millivolt system
• Central heating and cooling system
• Heat pump without auxiliary/backup heat

No where do I see BOILER. Get a new stat, one that works with boilers.

rhodebump

Thanks, there are so many stats out there. Any recommendations?

TIA

EBEBRATT-Ed

any low voltage thermostat will work with a steam boiler. It may have features like a fan switch or air conditioning which you don't need

Jamie Hall

I like Honeywell VisionPro, the simpler the better -- check your local big box store.

PinkTavo

I have been using the digital version of the old Honeywell Round (Honeywell T8775A1009 - Round Non-Programmable, Heat Only, Digital Thermostat) since my original one with mercury failed. Had one go bad after about a year, but the replacement has been working fine for over 9 years since. The only odd thing is that when the boiler cycles off on pressure the power to it goes off...no display. I haven't bothered to change the wiring so it goes to the thermostat first. Doesn't really bother me. They are pretty cheap at HD or Lowes.

mikeg2015

PinkTavo said:

I have been using the digital version of the old Honeywell Round (Honeywell T8775A1009 - Round Non-Programmable, Heat Only, Digital Thermostat) since my original one with mercury failed. Had one go bad after about a year, but the replacement has been working fine for over 9 years since. The only odd thing is that when the boiler cycles off on pressure the power to it goes off...no display. I haven't bothered to change the wiring so it goes to the thermostat first. Doesn't really bother me. They are pretty cheap at HD or Lowes.

That's because the pressuretrol is a safety device, not really a control. If it's turning off power to the transformer.

2 options:
1) Many of us add a vaporstat on the 24VAC side and leave a pressuretrol as a safety backup on the 120VAC circuit.
2) Use batteries on the thermostat only and don't wire up the "Common" (C) terminal.
3) Use a relay. (I like adding a small LED light and a bypass toggle switch too so you know it's calling and can trigger it when at the boiler)

rhodebump

All,
Wanted to report that in the advanced settings for this thermostat, there was a setting for a gas boiler. Once I set the configuration to use that, my problem was fixed.

This stat was a Honeywell RTHL2310/RTHL221