Furnace Issue or Thermostat ?

[bigdog]

I have another furnace issue.... last week issue was at Mass house, bad gaskets around circulator pump causing leaks, that issue was corrected and all good now !

This week, came to NH home to check things, b/c of the sub-zero temps.
All seemed ok inside house, heat on and warm, Honeywell programmable digital thermostat was set at 55 degrees and holding.....

I bumped up the temp to 68, furnace kicked on and all seemed OK. Temp however continued to climb and couldn't seem to be controlled by thermostat.

I noticed low battery display flashing, so replaced with 2 AAA, and flashing display stopped ! The temp reverted back to climbing, I set thermostat down to 62, but display is now registering 71.

FYI, I did not replace with fresh batteries, b/c I didn't have at the time, could this still be the issue? Going to Wal-Mart today to get fresh alkaline batteries and replace to see if it makes a difference, TBD ? Could it be the thermostat itself or do you think the issue is at the furnace end ? Up until now, all have been fine !

Thoughts ?

[Slickcraft]

When you changed the batteries you probably had to remove the front section from the wall plate. The front section has all of the switching electronics that close or open connections between the incoming wires. With the front section removed all connections should be open and the furnace should shut down. It may take a few min for the furnace to shut down when the front section is pulled. If it shuts down with the front removed but not when the front is in place, the problem is with the thermostat.

When you put the front section back on there are a number of pins that get inserted into specific sockets on the wall plate. If pins are misaligned or bent operation will not be correct.

[Kamper]

First... Try fresh batteries.


Next (if you are a handy person), shut off furnace at breaker or 'emergency' switch and inspect the connections.

Carefully remove the thermostat from the wall to expose the wire connections. It's possible that something wasn't tightened and an end fell out or broke due to normal household vibration. A loose or detached end might also be short-circuiting another connector causing a continuous 'on' situation. The dip switches could have been disturbed when you changed the batteries but those are usually covered. Definitely worth checking as suggested above.

If that doesn't resolve the situation, check the connections on the furnace. Follow the T-Stat wire to find them. Note: Many newer furnaces are digitally controlled. If you have any doubts here you should leave it to a pro.

Thermostats are relatively cheap. Replacing them is not that difficult so, except for the time, it's not a terrible idea to replace that component if everything else looks good.

I've only once tried to help someone with a situation like yours. It was an older boiler and the issue ended up being further into the guts than I was willing to dig so we called a tech to resolve it.

You can probably mickey-mouse an attic thermostat into the emergency switch but a better idea will be to winterize the place until you can get a qualified tech to look at it of these simple checks don't work. I don't think it's worth any risks for a place you don't have to live in.

Good luck!

[ITD]

I would give it a little time to see if the new batteries fixed it.

[bigdog]

Thanks all for the feedback much appreciated !

Yes, I am aware of the electronic pins on back of thermostat display and how they all connect to female connectors on back-plate attached to wall.
I have to assume that all is good, but have no way of knowing for sure?
But you all know what 'A-S-S-U-M-E' means ! :)
Thermostat is about 5 yrs old.

Slickcraft.... you said that if thermostat front panel is pulled out, the furnace would shut down ? I have a 2-zone system with another thermostat upstairs. That said, would pulling one thermostat out offline, necessarily shut off the entire furnace system ?

I've always believed "keep it simple', so will start by replacing batteries in thermostat, and go forward from there.....

Will report back with results.

Thanks,
BD

[Slickcraft]

BD. pulling the front from one thermostat only eliminates any call for heat for that zone. The other zone should continue to work provided that thermostat is good and there in no fault in the furnace itself.

[Biggd]

I believe you mentioned in your other thread that the replaced the expansion tank. An Issue I had in the past when the diaphram inside the expansion tank came apart, the rubber pieces from the inside of the expansion tank kept getting stuck in the check valves causing them to stick open. The water would keep circulating even though the circulator pump wasn't on. I use to have to take the top of the check valve off and pull out the piece of rubber from the expansion tank. I had to do that multiple times until I got all the pieces out. Either that or you have to have the system flushed.

[FlyingScot]

Regardless of solution to thermostat vs furnace, you might take this opportunity to replace Honeywell with a Nest or similar internet-connected thermostat. You can monitor and control heat from Massachusetts, including calling you when furnace fails, preheating house for arrival, and lowering temp after you return to Mass and realize you left heat on. ;)

Only weakness of Nest (assuming your system is compatible) is that it will not warn you of a power failure. We supplement ours with a separate temperature alarm that requires only a working phone line.

Stay warm!

[Lakeboater]

Regardless of solution to thermostat vs furnace, you might take this opportunity to replace Honeywell with a Nest or similar internet-connected thermostat. You can monitor and control heat from Massachusetts, including calling you when furnace fails, preheating house for arrival, and lowering temp after you return to Mass and realize you left heat on. ;)
The Nest thermostat will call you if heat doesn't come on when it should? How do you activate this feature?
Only weakness of Nest (assuming your system is compatible) is that it will not warn you of a power failure. We supplement ours with a separate temperature alarm that requires only a working phone line.

Stay warm!
The Nest thermostat will call you if heat doesn't come on when it is supposed to? How do you activate this feature?

[Denis D]

We have had a Honeywell Wi-Fi thermostat at home for a few years. Any time it loses connectivity to Wi-Fi, it sends us an Email advising it lost connection. It sends another Email when it reconnects. It has the same remote ability to change any setting from a smart phone.

It cost $100.00 when we bought it compared to $250.00 for the Nest. The only function it doesn't have compared to the Nest is the ability to sense when someone is or isn't home and adjust the temp setting accordingly. Since we would never use that function anyway, the Honeywell was a no brainer.

Denis D

[Slickcraft]

Our mini-split heat pumps at home and on Welch use wireless thermostats that use Honeywell Red Link technology. The in home internet gateway is a Honeywell product logged into a Honeywell server. You can control the thermostats from a PC or mobile phone.

As Denis noted you can set email notifications for loss of connection. There is an ambiguity as the loss could be only the internet being down (but the heat is still on) or it could be a power outage. You can also set notifications based on temperature being either above or below selected points.

For a residence that depends on heat that is left vacant for periods of time in the winter I would either 1. have the wireless system plus a separate low temp phone alert or 2. winterize and shut down.

[Biggd]

I installed a Sensi wifi T-stat this year. Very basic but works great. It will send me an Email if temp falls below 45. I keep the heat at 50 and when we are on our way up I can turn it up to 65 so it's toasty when we get there. I have a programmable at my house in Mass and I'm going to toss it. I just ordered another Sensi from Amazon for $125.

[dpg]

Is the home forced hot water? If so the zone valve may have been stuck open continually moving hot water through the pipes...Ask me how I know.....:rolleye2:

[FlyingScot]

The Nest thermostat will call you if heat doesn't come on when it is supposed to? How do you activate this feature?

No quite, but close. The Nest will send an alert to your cell phone when the temperature in the house falls below your preset "Safety Temperature". Check the Nest website or play with your thermostat or phone app for specific instructions.

[BroadHopper]

I have the old round Honeywell thermostat. I finally bite the bullet and bought a wireless thermostat. Home Depot had a one day sale for $149 (online). There is a form you fill out the receive $100 credit from the state. So I can swallow that.

A call to Nest support and they did a fantastic job of answering all questions so I should be good to go! You can use two wires instead of three and the span is .5 instead of one. My boiler request for a .1 span (Rinnai). They will be glad to remotely program the Nest to .1.

[Lakeboater]

I have the old round Honeywell thermostat. I finally bite the bullet and bought a wireless thermostat. Home Depot had a one day sale for $149 (online). There is a form you fill out the receive $100 credit from the state. So I can swallow that.

A call to Nest support and they did a fantastic job of answering all questions so I should be good to go! You can use two wires instead of three and the span is .5 instead of one. My boiler request for a .1 span (Rinnai). They will be glad to remotely program the Nest to .1.
I thought that the third wire, the C wire, was to give constant power to the Nest so that it charges it's battery all the time versus just when the heat is running with only 2 wires.

[BroadHopper]

According to this article there may be sufficient voltage to keep the battery charged. If not, I can send it back.

https://nest.com/support/article/When-Nest-needs-a-common-C-wire