Boiler keeps running

DK27

I have a single zone heating system controlled by a white rodgers 1f80-361 thermostat. The thermostat is currently set in the SL mode for steam heat systems(assuming this controls cycles per hour and temp variation?). I am having two issues. First when I have the thermostat set in "heat" mode at 68 degrees on a mild day, the temp inside the home never dips to 68 degrees before the heating cycle starts again and pumps the heat to ~ 71.  Second issue, if i turn the thermostat mode to "off",  the boiler still turns over from time to time providing heat to the radiators.  Has anyone encountered this before? Is this a thermostat issue or something related to the boiler?

Rod

Most probably the Thermostat

Hi- I would say it is most likely the thermostat that is causing the problem. You can check this easily by removing the thermostat module from its mount. The boiler's burner should then not start at any time. If it does start, with the thermostat disconnected, then  the burner needs to be checked out by a pro.  Also check the wiring attached to the terminals on the mount. The manual has diagrams for the different wiring configurations.  (Attached is a manual in case you don't have one) 



What the SL mode accomplishes isn't exactly clear. What you really want is a thermostat that has a definite settable cycles per hour. (1,2 ,3 etc. these usually go up to 5)  Steam systems with cast irons radiators are usually set to 1 cycle per hour.

- Rod

DK27

Thermostat

Thank you for the quick response and the manual.  Forgive my ignorance but when you say remove the thermostat module, does this mean disconnect the wires?  Thanks again.

Rod

Thermostat

Good Question! Sorry, I guess I was thinking Honeywell where the whole thermostat module

comes off the base. With this model look on page 4 in the manual under "Operation"

on how to remove the cover and then you just need to disconnect the wires. Be careful

that they don't fall back into the wall when you disconnect them.

- Rod

DK27

Thanks for the info

Thanks again for the info.  I'll give this a shot tonight to see if that does the trick.  Hopefully it's just the thermostat.  If that's the case, any recommendations on which thermostat to buy. I also have a single stage central A/C system that runs off it.

-Dave

Rod

Thermostats

Hi Dave- I was assuming that the thermostat just controlled the boiler. Since you have air conditioning on the same thermostat, I would check over the wiring and carefully compare it to the appropriate diagram in the manual. It's more likely that there is a misplaced wire causing the problem.

I'm not sure what thermostat would work best for you as to turn on the air conditioner here in Maine, we just open the windows!  Having air and steam,  I would look at the one of the Honeywell thermostats like the 8000 series. I've attached the I&O manual so you can look it over. On any thermostat I always look up the I&O manual first to check it out and see if it has the features I want.  Notice too that on the 8000 (and most other Honeywell thermostats) there are different models for different configurations.

- Rod

DK27

wiring setup

This is the wiring setup as it currently stands. I am not expert but I believe it is setup correctly. From what I can tell it's wired like figure 5 from the manual.  What do you guys think? One thing I did notice, the switch was in the "Electric" mode, this may have been part of the problem as the system doesn't have to control a fan for heat.

Rod

Wiring

Hi Dave-  I'm not quite sure what to tell you. I can't really tell from the picture but is there a jumper wire going off the RC terminal?  If so where does it go?   If there is a jumper -  Figure 5 doesn't have a jumper.  Figure 5 is the setup for system having a transformer on both the heat and cooling side (two transformers -one for cooling and one for heat)  First question-  Do you have these transformers?  

- Rod

DK27

wiring

Thanks again Rod.

There currently is no jumper on the thermostat.  I assume that means there are two transformers, but how can I confirm this for sure?

-Dave

nicholas bonham-carter

runaway boiler

have you disconnected the thermostat from the boiler to see if that stops the runaway condition?

it would be easier to do so at the boiler, as you have the complication of the a/c wiring at the thermostat to contend with.

if the boiler stops, then it must be in the thermostat, and it continues to run, then the boiler control [fan center?] must be the problem.--nbc

Rod

Jumper Wire

Hi Dave - See attached photo. When I looked at your original photo, I  saw this as a shadow across the "B", but on blowing it up there appears to be something definite that looks like a jumper. Could you check this out and see if there actually is a jumper and if so, where does it lead?

   As NBC says you can disconnect the thermostat from the boiler wires and this should tell you if you have a boiler or a thermostat problem.

    As for the transformer (s) (if there are two transformers) one is most likely in the vicinity or on the boiler and the cooling transformer is most likely in the vicinity or on the AC evaporator/fan inside the house.

-Rod

DK27

Jumper wire

Thanks again for the great info and quick responses. I will try disconnecting the wires at the boiler later today to see if it stops the cycling problem. Also I'll take a closer look to see if there is a jumper wire connecting the RC and RH posts. I'm hoping this is just a thermostat issue and I can look into maybe getting the honeywell vision pro 8000 as you suggested

-Dave

DK27

wiring

Rod, turns out what looked like a wire in that pic was part of the wire insulation. With that said, I believe my configuration is what's shown in figure 5,  3 wires for the cooling and 2 for heat.  I disconnected the wiring from the boiler and it shut right down.  My next project is to get a new thermostat.  I think I will give that honeywell thermostat you suggested a try.  Thanks again guys for all the help and great information.