Recent Heating & Cooling Thermostat FAQs set 4, questions and answers on installing, using, or fixing heating or cooling thermostats.

This article series answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs.

Room Thermostat Diagnostic FAQs set #3

These questions and answers were posted originally

at THERMOSTAT DIAGNOSTIC GUIDE - be sure to see that article as it's the starting point for diagnosing and fixing problems with heating and cooling thermostats in buildings.

Our photograph illustrates an antique room thermostat still in use at the FDR Estate in Hyde Park, NY.

[Click to enlarge any image]

On 2018-11-25 by (mod) - When heating starts in zone 2 the zone 2 thermostat (this is connected directly to power) goes blank

Andre,

Thank you for asking interesting question. That's a condition that I have not encountered. Normally when a thermostat display goes blank it's because there's a loss of power to the device. I would start by checking the electrical connections on both ends of the thermostat circuit.

As a very speculative guess, it's also possible that a low voltage Transformer on your system is overloaded, that is being asked to power too many devices.

On 2018-11-22 by Andre

I have a 2 zones heating/cooling. Evrytime the heating srart in zone 2 the zone 2 thermostat (this is connected directly to power) goes blank.

When the heating stop the zone 2 thermostat turn back on.
My zone 1 work fine.
What can cause my zone 2 thermostat to go blank?
Thank you

On 2018-11-19 by (mod) - thermostat 155.00 error code

I would like to help Brian, but unfortunately error codes are not Universal across all brands and models of thermostats.

You need to identify the brand and the model and then get ahold of the owners manual or we can look up the error code.

For example here is just one manufacturer's error code translatoor:

TRANE ComfortLink™ II SYstem Heat Pump Service Facts and ERROR CODES [PDF], (2011) Trane Corporation, Website: www.trane.com

Our free HVAC downloads of service and operating manuals for all brands can be found at MANUALS & PARTS GUIDES - HVAC - home - Master Index to All Brand Names & HVAC manuals, wiring diagrams, installation and repair guides

On 2018-11-18 by Brian

I have a 155.00 error code on my thermostat and my outside unit will not communicate with the air handler. Anyone know what the code 155.00 is?

On 2018-11-11 by (mod) - thermostat doesn't turn on the heat

Sounds as if power is off to the system

On 2018-11-11 00:26:57.952418 by Anonymous

I don't hear the thermostat click and heater doesn't turn on at all. I didn't see the light on at all in the heater

On 2018-10-13 15:31:37.941879 by (mod) -

Jeremy

A frustrating problem indeed.
I'm not sure what's wrong but I'd start the diagnosis by disconnecting the thermostat, first, at the thermostat, and second, disconnect the thermostat wires at the heater.

See if either of those steps stops the short cycling. That will be diagnostic.

Let me know.

On 2018-10-13 08:56:04.240455 by Jeremy

I have an electric heat pump. It is on heat mode and it seems to be short cycling. The temp is set at 66 and the thermostat is stating its 70 degrees inside the house. Still, it continues to turn on for 5-10 seconds, then shuts off for 30 seconds. This cycle is continually happening.

On 2018-06-14 00:59:15.618525 by (mod) -

Christian

When a breaker keeps tripping it could be the breaker but usually it's a short or a failing component.

If your electrician simply swaps wires between two breakers of the same amperage rating in the panel, and if the thermostat circuit trips the new breaker that's a pretty good diagnostic.

On 2018-06-13 18:02:58.067553 by Christian

The circuit breaker is tripping even though the fan motor sounds fine, and works fine. The connections all seem good. It is a Lennox 80HUF gas furnace and blower. Could it be the circuit breaker?

On 2018-06-13 16:17:18.644348 by Christian

The 120V 20A circuit breaker that powers my thermostat, and I believe the 120V side of the HVAC keeps tripping. This causes the A/C to not work because the thermostat has no power. I can reset the circuit breaker and everything works fine, and 2-3 days later it trips again. Where should I start looking, in the HVAC contactor?

On 2018-05-21 22:39:08.859563 by (mod) -

I'd look for an overcurrent tripping a breaker first. Is there a separate blower or zone damper motor or other motor that could be giving trouble>?

On 2018-05-21 22:26:36.367820 by Mooneydriver

I have a hydro air system with Trane air handlers and slow-close Taco zone valves. On one of the zones, the cooling side and the fan work OK. When the thermostat (Ecobee 4) calls for heat, I hear the blower come on for a second and then the entire system shuts down and resets (including the thermostat which is powered by the air handler). Any ideas? I'm pretty sure the thermostat is operating normally.

On 2018-05-21 21:43:43.043066 by (mod) -

Depending on the sensitivity of your thermostat it may not turn on your AC before temp reaches 80

On 2018-05-21 01:20:47.857501 by Anonymous

House is 79degrees inside shouldn't it kick on when thermostat at 79 too

On 2018-05-11 02:28:13.784764 by Teri

We have a westinghouse furnace heat pump and AC the thermostat says LOW PRESSURE SWITCH

On 2018-01-28 00:36:09.820821 by (mod) -

Chris

What you describes sounds like a wiring error or shorted thermostat wires.

Beutler is not a brand I recognize, though there is a service company with that name. If this is close to you I'd give them a call:

Beutler Air Conditioning and Plumbing
855 National Drive, Suite 109
Sacramento, CA 95834
Tel: (916) 696-8711

On 2018-01-27 by Chris Morrow I have a Beutler Heating and A/C.

Ok, I did not see my issue listed above. I have a Beutler Heating and A/C. I live in a two story house and have a stat (TS40B) both upstairs and downstairs.

There are supposed to be two working zones. One for upstairs and the other for the downstairs.

The upstairs stat will not allow me to turn on the heat or A/C.

The digital display is working, but there are not a few options missing from the stat that used to be there, and can be found on the stat downstairs.

The upstairs stat says "Econ Sys Off", and there is no longer a "hold" selection. I swapped the stat control on the wall, and the problem still appears to be the same upstairs (no change).

The downstairs stat turns on both the A/C and the heater, but here is the catch.

The downstairs stat turns on the A/C and heater upstairs. The heater will run continuously since it is not changing the temperature downstairs. Any ideas?

On 2018-01-18 18:08:45.411877 by (mod) -

Anon

Assuming that your AC unit is also a heat pump that is supposed to be giving you heat, it may be that outdoor temperatures are too low for your heat pump to work and your backup heat is not working.

Start at HEAT WON'T TURN ON https://inspectapedia.com/heat/No-Heat-Diagnosis.php as you've already said your thermostat is set to 90 degrees (not %) and it sounds as if you're not getting heat.

On 2018-01-18 15:33:08.902423 by Anonymous

My Ac unit is set at 90% but my house temperature is only 64 what could be the problem i need more heat its cold

On 2018-01-14 by (mod) - Honeywell RTH2400 and a Honeywell RTH2300

Shawn

It does not sound to me as if this is a thermostat problem. If the heat continues to run but room temperature never reaches the thermostat set point then the thermostat is doing its job - asking for heat.

More likely there is a boiler temperature problem, a circulator flow problem, or the combination of an unusually high (80 degF) thermostat setting combined with very low outdoor temperatures and the rate of heat loss from your building exceeds the heating system's capability.

On 2018-01-14 by Shawn the room temps never seem to climb

Hi All,

I have a natural gas hot water boiler heat system, an Utica PGB125, and do not have an air system in house, just heat only system.

I recently replaced my old round honeywell thermostats with new digital Honeywell thermostats.

I have a Honeywell RTH2400 in my living room that controls one side of my house (living room, sunroom, kitchen, & laundry room) and a Honeywell RTH2300 in the bedroom that controls (2 bedrooms and the bathroom).

I have programmed the thermostats to 80 degrees, but I can’t get the living room above 73 and the bedrooms above 69 degrees.

The boiler does kick on and circulate and heat comes out of registers, but the room temps never seem to climb. Thermostats only had a two wire hook up

...

Continue reading at THERMOSTAT DIAGNOSTIC GUIDE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see THERMOSTATS, DIAGNOSTIC FAQs-4 - more-recent thermostat troubleshooting questions and answers

Or see these

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• THERMOSTAT SETTING INSTRUCTIONS - Separate article - How to Set the Thermostat
• THERMOSTAT OPERATION - how digital thermostats & their displays work
• THERMOSTAT SETBACK ADVICE
• THERMOSTAT TROUBLESHOOTING - Separate article: What to check if a thermostat is just not working
  • HEAT ANTICIPATOR ADJUSTMENT
  • HEAT ANTICIPATOR ADJUSTMENT - T87
  • THERMOSTAT ERROR CODES - How to Translate the error codes on digital thermostats
• THERMOSTAT WIRE CONNECTIONS - how to wire up all types and brands of heating & cooling thermostats

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THERMOSTATS, DIAGNOSTIC FAQs-3 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HVAC THERMOSTATS

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