Furnace keeps coming on... help please.

[Jaugust124]

Got up this morning and it was unusually warm downstairs, felt like the heat was on.
Checked the radiators and the heat was on in one zone. Odd, so I checked the thermostat and everything seemed fine, but I lowered it down to 50 anyway, thinking maybe I bumped it...whatever.

Got home around 4:00ish this afternoon and it was about 90 in that section of the house and the baseboards were warm. Changed the thermostat thinking that was the problem because the heat was not being called for in any other part of the house. As soon as I tuned the system on, immediately that zone called for heat.

So, can someone give me some idea where to look next before I call the repair man?
And, can I just turn off that one zone so that I can still get my hot water without having to turn the boiler off and on when I need it?
There is a valve going to that particular zone, can I just shut that off so that the system can do its normal thing without the heat running?

Thanks in advance for the help.

 

[heat seeker]

On my 3 zone system, a given thermostat will call for heat. When it does, it completes the circuit to its own zone valve. That zone valve then calls for the furnace to fire up. Thus, the thermostat does not directly control the furnace as in a one-zone system. Removing the wires from that zone valve will prevent the valve from calling for heat. Mark them carefully for future reconnection.
It sounds like either a wiring short in the thermostat line, or a defective zone valve switch. There are contacts in the zone valve itself. One of mine has leaf contacts, the other two have tiny microswitches.
Your system may differ, but the basic idea is probably the same.
Let us know what happens.

Edit: not a good idea to shut the furnace off and on repeatedly. On most units, that will make it leak between the sections. It's okay for an emergency, but not as normal practice. My parents tried that some years ago to save oil. Ended up costing them a furnace, since it would have been so expensive to repair the old one's leaks. They just can't take the expansion and contraction repeatedly.

 

[Jaugust124]

heat seeker,
Thanks for the help. I did what you said and after a few minor missteps and speaking to the owner of my oil delivery company I managed to get the job done. Defective zone valve switch. Now we at least have hot water and the downstairs is no longer 90*. I will get it fixed for good when I have the company do the cleaning.

Your help in this is greatly appreciated.

 

[heat seeker]

Glad to help!
Monitor the radiators for a short while. If the zone valve itself is stuck open (unlikely, but possible) the heating water will move by convection up and around the loop. My circulator pump died, and the only way I knew it was that it started humming louder and louder. The house was being heated just fine with the water circulating itself when the zone valves opened. Makes me wonder why I spend almost $400 getting it fixed!
If the radiators still get warm, let me know, and we'll proceed to Plan B. Nothing to it, really.
And, thanks for the update - I so much like to hear the end of a story.

 

[Don2222]

Hello

You could change the zone valves to circulators and sweat check valves for each zone. Then you will never have that problem again!

 

[raybonz]

Hello

You could change the zone valves to circulators and sweat check valves for each zone. Then you will never have that problem again!

Sounds like a sweat check valve is hung up.. This happened on my upstairs zone and it got over 80 up there due to a natural flow.. I have 2 circulators and no zone valves on my system.. I replaced the upstairs zone sweat check to fix the problem and also added 2 ball valves on either side of the sweat check valve so I can replace it without draining the system.. Temporarily you can rap on the sweat check to seat the weight and stop the flow until you have time to repair it.. Personally I think zone valves are a more positive way to stop flow as the sweat checks rely on gravity to stop the flow..

Ray

 

[Don2222]

Hello

You could change the zone valves to circulators and sweat check valves for each zone. Then you will never have that problem again!

Sounds like a sweat check valve is hung up.. This happened on my upstairs zone and it got over 80 up there due to a natural flow.. I have 2 circulators and no zone valves on my system.. I replaced the upstairs zone sweat check to fix the problem and also added 2 ball valves on either side of the sweat check valve so I can replace it without draining the system.. Temporarily you can rap on the sweat check to seat the weight and stop the flow until you have time to repair it.. Personally I think zone valves are a more positive way to stop flow as the sweat checks rely on gravity to stop the flow..

Ray

Interesting, I have two sweat check valves running for 25 years on nice clean town water with zero problems!
Do u have
well water?

 

[raybonz]

Hello

You could change the zone valves to circulators and sweat check valves for each zone. Then you will never have that problem again!

Sounds like a sweat check valve is hung up.. This happened on my upstairs zone and it got over 80 up there due to a natural flow.. I have 2 circulators and no zone valves on my system.. I replaced the upstairs zone sweat check to fix the problem and also added 2 ball valves on either side of the sweat check valve so I can replace it without draining the system.. Temporarily you can rap on the sweat check to seat the weight and stop the flow until you have time to repair it.. Personally I think zone valves are a more positive way to stop flow as the sweat checks rely on gravity to stop the flow..

Ray

Interesting, I have two sweat check valves running for 25 years on nice clean town water with zero problems!
Do u have
well water?

Yup well water but I have been here around 25 yrs.. For many years the water was untreated but a hot water system is a closed loop system only adding via boiler makeup valve if needed which is rare..

Ray