Question about Heating & Cooling

2 Answers

Honeywell T8400B Thermostat Display Intermittently Blank

Two of the 4 thermostats in our house (for water circulating radiant heat) have on occasion had blank screens for several hours, then spontaneously came back on. Turning them off and on or changing the temperature had no effect. Is this a known problem> Should they be replaced?

Posted by on

2 Answers

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 1 Answer

I have the same problem. It's because your domestic hot water (dhw) is on the same system as your radiant heat. In these systems, dhw is given priority over floor heating. That is, when your dhw needs heat, power to your Tstats are shut off until your dhw is satisfied. (Makes sense: cold showers no fun) Your T8400B's have no battery, so they are dead unitl power to them is restored by your zone control. It's really stupid that they use these Tstats, because you can't even SEE your room temp or settings let alone change them. I will be replacing my Tstats with battery powered soon; hopefully that will allow me to see and adjust during dhw cycles.

Posted on Nov 07, 2009

  • Level 1:

    An expert who has achieved level 1.

    Hot-Shot:

    An expert who has answered 20 questions.

    Corporal:

    An expert that hasĀ over 10 points.

    Mayor:

    An expert whose answer gotĀ voted for 2 times.

  • Contributor
  • 52 Answers

Most likely a bad tstat i would replace I recommend honeywell focus pro 6000

Posted on Aug 29, 2009

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
goodluck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

Tip

Underfloor Radiant Heating for Your New Sunroom


You want to add a brand new sunroom onto your existing house. The problem is that you are not sure how to heat it. Electric heating with baseboard heaters will spoil the look that you want from your new room. Hot water baseboard is going to present all types of problems getting hooked in to the existing system and piping it. And, if you have hot air heating system then you will have the problem of getting ductwork to the room. There is another way to heat this room easily and efficiently.

Radiant heating has been one of the most comfortable and efficient ways for heating for many years. The problem has been in the past to find a good heating source for small radiant floors that will be affordable, effective and efficient.

This problem has been solved now, with the availability of small new electric combination heater- circulator units. These units use small electric heating elements together with a small circulator pump to give you a all in one heating source and circulator pump.

Now you just have to lay your tubing in the floor of the room you are adding on to your house. Then you run that tubing into your existing basement or other room in your house. The tubing and the electric are attached to the heating unit. Then, wire a thermostat to the unit, and you are now ready to make heat. This really makes heating a new addition room very inexpensive and easy to do.

The greatest thing about using this type of heating system is that most average do-it-yourself types can do this. All that is needed is a basic knowledge of plumbing and electric.
If you are thinking of building that little add-on and are worried about how you will heat it, think about using radiant floor heat and a small electric heater-circulator to do your project.

on Dec 05, 2009 | Heating & Cooling

1 Answer

My Honeywell programmable thermostat's display is blank and I do not have any heat?


The thermostat, depending on the model, normally does not get powered by batteries, they are for backup power. You might be losing 24 volt from the furnace, causing the thermostat to run on batteries.

Apr 09, 2014 | Honeywell Programmable Thermostat Heater

1 Answer

St6400c thermostat wont run the central heating independantly


This does not sound like a thermostat problem. I would be looking for a zone valve or circulator pump problem.

Nov 05, 2009 | Honeywell Programmable Thermostat Heater

1 Answer

Honeywell thermostat t8400c intermittent blank screen


It actually sounds like the batteries are going dead if the 24v from the furnace are not providing the power to the thermostat.

Sep 28, 2009 | Honeywell Electronic Programmable...

2 Answers

A/C not turning on - Digital screen is blank


Your honeywell should have battery back up but the primary power for this is a 24 volt transformer located in the air handler probably in your attic. All these controls run on 24 volts

Jul 11, 2009 | Honeywell Programmable Thermostat Heater

1 Answer

3 year old Lennox system stops intermittently 2-3times past 24hrs


i would have the thermostat receiving 24 volts all the time by running the c terminal from the air handler to the thermostat and go from there

Jun 21, 2009 | Honeywell Heating & Cooling

1 Answer

Chronotherm III Thermostat Completely Blank Screen, No Heat


One of two things either the disply has gone out which is likely as it is a common failure for that thermostat or your heating unit is not sending control power. the older chronotherms were system (24volt ac) powered the new hardware/box store units are battery powered. Either way display should not be blank with fresh batteries. to get heat on remove the thermostat jumper or twist together the wire from the R terminal with the wire from the W terminal. note the color of each wire for later reference, heat up house disconnect wires from each other and go purchase a new thermostat

Dec 17, 2008 | Honeywell Programmable Thermostat Heater

2 Answers

T8411r1028 honeywell thermostat


Check in the heating unit itself for an automotive style fuse.

Dec 17, 2008 | Honeywell Programmable Thermostat Heater

Not finding what you are looking for?
Heating & Cooling Logo

Related Topics:

513 people viewed this question

Ask a Question

Usually answered in minutes!

Top Heating & Cooling Experts

paulcarew

Level 3 Expert

2398 Answers

Dan Webster
Dan Webster

Level 3 Expert

8205 Answers

Donni Steen

Level 3 Expert

659 Answers

Are you a Heating and Cooling Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...