Why would a 240v line voltage thermostat have a blank display?


In a bathroom I have a single 500w 240v electric baseboard heater, and AUBE/Honeywell TH305 digital line voltage single pole thermostat.

I noticed yesterday, that the display had gone blank. A quick check showed there was still power to the stat. I tried switching it with another one from another room with no luck.

I checked for power at the heater (which there was), and then tried switching the heater in case a faulty thermo sensor was the problem. Still no luck.

So now I have power at both the stat, and heater, but still a blank display...

All the other heaters in other rooms on the same circuit work fine.

So now what?? Could it be a voltage problem? If so, how was it working before? How would the voltage change??

Any help or input would be much...

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Makes perfect sense, 12/2 cable is a fine choice for a 240V heater. They don't need neutral, so white is re-tasked to be another hot, and should be wrapped with tape to mark it.

I cannot understand what you mean by two 12/2 wires. A 12/2 Cable contains two Wires (other than ground), colored black and white. You probably do have two cables. One goes back to the service panel and is the supply cable, both its wires will be Hot compared to ground. That is the "line" side.

In the other cable, both wires should have low or no voltage until the thermostat is wired and turned on. That is the "load" side.

Hook up the line side, complete, to the line terminals as marked on the thermostat. Pay no attention to the physical position of the terminals on the old thermostat, they are all different. Once the line side is hooked up, test if it practical. Then hook up the load side. Do them separately like this to keep things simple and...

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Electric baseboard heaters are good for "spot-heating" areas of your house that central HVAC does not reach.

If you are going to put in a baseboard heater, make the thermostat set-up the best you can.

On The Wall or On The Baseboard?

You can install a thermostat on the heater itself, but this means bending down every time you want to adjust the heat. Plus, a thermostat situated in the lower 6 inches of your room isn't accurately measuring temperature, since cold air sinks.

Wall... thermostats allow you to situate your heater's "brain" near the middle of the strata of heat layers, or about 48" high. This position is closer to where you are and reflects your comfort. The simplest thermostat is called a line-voltage thermostat.

On-Off Switch: What Could Be Easier?

If you have your walls open and drywall down, install a wall thermostat. Line voltage thermostats are extremely simple mechanical devices. All they do is connect and disconnect the...

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Looking for something that would cut down your energy bills? An investment in thermostats would be a wise idea. Now if you still wonder what kind of a device this is, a thermostat basically controls the temperature of a system (this could be your air conditioner, baseboard heater, heat pump, room heater etc). This device not only helps in cutting down your energy bills, it also ensures proper cooling/heating of your home appliances. However, there are different types of thermostats to serve unique functions. You have to buy the right thermostat that serves your purpose. A little research before buying would help you choose the right thermostat model and save you a lot of extra expenses. In this article, we review line voltage thermostat models (aka line volt thermostat) which are thermostats that uses direct line voltage to function (say 110 volts). Line volt thermostats are usually used to control heating equipment like baseboard heater, room heater etc.

When we speak of...

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Just bought my first home and this is my first time posting, so please forgive me if my terminology is incorrect.

I currently have bedrooms upstairs each with 1 baseboard heater and thermostat for each. The circuit breaker is off and I've undone most of the wiring to it.

The thermostat is an analog, single pole line voltage.

It looks like there is 3 wires (really groups of wires, I don't know the term for this), possibly 10-3 or 12-3 coming into the junction box. I didn't specifically look that the gauge. It might actually be 10-2 or 12-2.

Do I simply need to connect 2 hots and 2 neutrals to the thermostat and I am set?

OK, quick terminology issue: Single-pole and double-pole. The poles are channels, which could have any purpose. A single-pole switches one channel; a double-pole switches two. (ignore the "st"). (source)

For a thermostat, one pole is sufficient to turn the heaters on and off. For the other pole, you'd simply bind the...

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A line voltage thermostat is commonly used to control electric baseboard heaters or a direct-wired electric furnace. It works by turning on the power to the heating and cooling system when the thermostat detects the room temperature is no longer within a few degrees of the desired setting. The power supply, measured in volts, is switched directly on and off by the thermostat.

Thicker power wires are an identifying characteristic of a line voltage thermostat. It operates using a direct current of power and is typically seen in older buildings. Programmable, digital and non-digital thermostats are compatible with a line voltage system.

Some types of thermostats are designed for use with a particular range of line voltage systems. For example, a certain thermostat model may not be designed to work with a central heating and cooling system. Instead, it may be designed to work exclusively with electric baseboards or a floor heating system.

A programmable line...

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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Guide to line voltage thermostats 120V or 240V room thermostats for electric heat, fan heaters, radiant floor heat, convector heaters.

This article describes types of line voltage wall or floor thermostats used to control heating or heating & cooling equipment where switching of 120V or 240V devices is required.

Green links show where you are. © Copyright 2017 InspectApedia.com, All Rights Reserved.

Line Voltage Thermostats: choices, wiring, repair, replacement

I have a two wire honey well thermostat T451A - I want to replace this thermostat with a programmable. Presently
there is a two wire ( black and White ) 120 volt line;

Any suggestions ? Thank you - M.S. 3/15/2013


The Honeywell T451A room thermostat (illustration at left) is a line-voltage (120V) wall thermostat, a...

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For wall thermostats, please go to the thermostat section and choose your model to find the owner's guides with complete installation instructions.

For step-by-step instructions on wiring a Cadet Electric Baseboard to a wall thermostat, view our How-To Video


After you have disconnected factory connector A (left side) or factory connector B (right side), proceed to the next step. Route supply wires to the thermostat wiring box. Connect one supply wire to one thermostat wire (typically marked L1). Connect remaining thermostat wire (typically marked T1) to one heater wire. Connect remaining supply wire to remaining heater wire. Connect supply ground to grounding pigtail provided.


After you have disconnected splice A (left side) or splice B (right side), proceed to the next step. ...
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[HVAC] 24v / Contactor / No Heating or Cooling

Hey guys/gals. Figured i'd try picking some brains on this new issue that cropped up with my (older) Heat-pump Unit. It's been working fine all winter long after having it's compressor changed last year (the switch from heating to cooling last year is when it stopped working and was replaced).

Basically the system is a split heat-pump and the indoor unit comes on as expected but not getting any cold or heated air from the system. Checked the condenser outside and that doesn't run at all.

So here's a few things I've tested to get to where I am now:

- Tested new and old thermostat and both behave the same way.
- Checked breakers to make sure not tripped (none of them are).
- Multimeter to test contactor inputs and it has 240 volts
- Pushing down on the contactor starts the compressor and condenser fan.
- when calling for cooling/heating - no 24v across the CONTACTOR.

I tested at the...

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Each Honeywell thermostat model has a unique number that can help you get support for your product faster and easier . Depending on your model, this number is preceded by the letters TH, T, RTH, CT, TL or RLV.

Please watch this video for a quick visual guide on how to find your thermostat model number:

The fastest way to see your thermostat model number is to look for it on your thermostat ID card. If you do not have a product ID card, the fastest way to find the model number is by removing the thermostat from the wall-plate. Depending on your model, the thermostat will separate from the wall-plate with moderate pressure or there might be small screws holding the device in place. After removing the thermostat, flip it over and look for the model number, which is printed on the back of the case, starting with the group of letters mentioned above.

If the thermostat is battery operated and the batteries are accessed from the front of the...

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