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

This article series 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.

Line Voltage Thermostat Q&A

These questions & answers about line voltage room thermostats (120VAC or 240VAC thermostats) were posted originally

at LINE VOLTAGE THERMOSTATS - you'll want to read that article too.

On 2018-04-29 by (mod) -

There is a way to use a low voltage thermostat to control both. Basically the low voltage heating system will have to talk to a separate switching relay that turns your heat on and off. We've written about this solution here.

On 2018-04-29 by carmen

i have a line voltage thermostat for my heat and 24v thermostat for my a/c unit do they make a thermostat to control both ?

On 2017-11-23 by (mod) -

I'm really sorry that it took a day to get to your question David we've been swamped with heating requests. I'm not sure that I can understand the question either. How do you turn what on? Your heat?

Check that the power is on in the electrical panel. If it is and you set the thermostat above room temperature and the heat does not go on then you need to leave that circuit off and ask for repair help from an electrician since most likely there is an open connection or bad relay or switch.

On 2017-11-21 by David González

Please I'm freezing

How do I turn it on

On 2016-10-23 by (mod) -

Clarice:

1. confirm that electrical power has been turned on to the electric heating circuit(s) - at the electrical panel

2. Turn the heater thermostat to a setting above room temperature or until you hear the thermostat's relay click

On 2016-10-23 by Clarice Nathaniel

How do u turn the heater on

On 2016-09-08 by (mod) -

For other readers, the Stelpro is a line-voltage 120/240V thermostat handling 16Amp loads, suitable for electric baseboard heaters or convectors and specifically not suited for central heating nor forced air heating systems.

The user's manual discusses set point temperatures:
Temperature set points
The set point may be edited by the user using the UP and DOWN buttons located on the thermostat.
The set point may also be modified through the Z-Wave network.
The minimum set point is 5°C (41°F) and the maximum set point is 30°C (86°F).
NOTE: if the set point is set at 7°C (45°F) or below, the frost-free warning icon will be displayed to warn the user that water pipes might be subject to freezing.
...
This product can be included and operated in any Z-Wave network with other Z-Wave certified devices from other manufacturers and/or other applications.

Reading through the product user's manual I agree that it looks as if the heat is always ON at low temperatures, and specifically at temperatures below freezing the thermostat is always "ON". If, for example, this thermostat were installed to control electric heat in a building that was to be "shut down" with heat "off" in a winterized condition, you cannot turn off the heat compeltely at the thermostat.

However you can turn off your heat at the circuit breaker - just as you proposed. I imagine that this would be the company's response to a direct question about the absence of an "off" position on the thermostat itself. Functionally this is probably fine, but technically, since circuit breakers in an electrical panel are not designed nor intended to function as a standard, frequently-operated "ON/OFF" switch, it may be a questionable design.

Unless a circuit breaker is labelled as "SWD"-rated, it is NOT intended for regular use as an on-off switch. (SWD-labelled circuit breakers are in fact designed and rated for use as control switches.) Even SWD-rated switches are not intended for very frequent on-off cycling (thousands of times vs. tens of times).

MIke Holt's Electrical Forum discusses the NEC and provides this helpful description of circuit breakers and SWD ratings:

Brittian, L.W., "Circuit Breakers", [web article], L. W. Brittian, Mechanical-Electrical Instructor, lwbrittian@hot1.net retrieved 2016/09/08, original source: https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/ElectricalCircuitBreakers~20020419.htm

Stelpro can be contacted at
E-mail: contact@stelpro.com
Website: www.stelpro.com

On 2016-09-08 by (mod) -

re-posting

Les F said:
Looking at a Z-Wave line voltage thermostat Stelpro STZW402+ (It's the only Z-Wave line voltage model I have found). The only thing that bothers me is that it has a low setting of like 40 degrees F and no actual 'OFF' mode. I would think that the inability to turn heat off at the thermostat would be some kind of code violation.

I understand the idea of freeze guard, but it just doesn't sit well that a 240v thermostat can't be fully turned off without turning it off at the circuit breaker. Any thoughts?

On 2016-02-09 by (mod) -

Typically an electric baseboard is controlled by a line voltage thermostat such as the one you name. Wiring instructions included with your thermostat must be followed lest you burn up the house or get electrocuted. An electrician will determine the status of wires at an unknown wall box using a VOM or DMM. You may have two live wires providing the line voltage or "power" side of 240V for the heater.

On 2016-02-01 by Travis

I am installing a 240V, line voltage thermostat. I have 2 black wires coming out of my wall box. I do not know which one is Power and which one is Heater

On 2015-02-25 by Fan Coil Question

I live in a NYC apartment and have a 2 pipe Fan Coil unit. Recently installed the Honeywell E-connect Heat Only thermostat to control the Fan and it works great. My concern is what I do when the building cetrally switches over to cool and I need the thermostat to work in reverse. Are there any options to use a different thermostat with the existing Honeywell EIM? Thanks!

On 2014-08-21 by (mod) -

Duckly

I don't know details about the specific installation you describe but it's a fair guess that it's not a unique design and that among the huge number of thermostats for sale (Grainger lists more than 100) there is either a suitable model or a pair of models that would suffice.

Honeywell lists at least 6 line voltage thermostats that are in the right "ballpark" for your application.

The Honeywell T4159A is for electric inductive/resistive heating.

Possibly more appropriate for your application:

The Honeywell T4051 and the Honeywell T6051 "Heavy Duty Line Voltage Thermostats are used to control fan coils, fans, motor starters, valves, contactors, and circulator motors in heating and/or cooling systems."

The company also provides a Honeywell Q651 used for manual switching between two T6051 units.

It may help to point out that basically a wall thermostat is an "on-off" switch that calls for heat or calls for cooling based on room temperature.

On 2014-08-21 by Duckly

I want to replace my current line voltage theromostat but our building is unique and the manager says they arent exactly replaceable with new programmable models. We have radiant heating/cooling where our boiler and chiller feed into the same loop system where fans force air accross the radiators.

There is a sensor on the piping leading to the main unit of the condo that feeds the thermostat to tell it what mode to be in, heating or cooling. Apparently it is this summer/winter changeover that makes finding a replacement tough. The thermostat also controls 3 seperate fan units off 1 thermo pipe sensor. My email is blueduck3285@gmail.com

Question: plug in themostat for a 220V AC unit

(June 13, 2014) Ray said:

I am looking for a plug in thermostat for a 220VAC wall A/C unit. do you have any or can recommend a location to get one?

e-mail info@kevlau.com

Reply:

Ray

Take a look at room thermostats used to control electric baseboard heaters for 220/240V rated models. They are available at your heating supplier as well as at most building supply stores such as Home Depot. Several models are described in the article above including the plug in thermostat you asked about.

Question:

8/21/2014 Duckly said:

I want to replace my current line voltage theromostat but our building is unique and the manager says they arent exactly replaceable with new programmable models. We have radiant heating/cooling where our boiler and chiller feed into the same loop system where fans force air accross the radiators.

There is a sensor on the piping leading to the main unit of the condo that feeds the thermostat to tell it what mode to be in, heating or cooling. Apparently it is this summer/winter changeover that makes finding a replacement tough. The thermostat also controls 3 seperate fan units off 1 thermo pipe sensor. My email is blueduck3285@gmail.com

Reply:

Duckly

I don't know details about the specific installation you describe but it's a fair guess that it's not a unique design and that among the huge number of thermostats for sale (Grainger lists more than 100) there is either a suitable model or a pair of models that would suffice.

Honeywell lists at least 6 line voltage thermostats that are in the right "ballpark" for your application.

The Honeywell T4159A is for electric inductive/resistive heating.

Possibly more appropriate for your application:

The Honeywell T4051 and the Honeywell T6051 "Heavy Duty Line Voltage Thermostats are used to control fan coils, fans, motor starters, valves, contactors, and circulator motors in heating and/or cooling systems."

The Honeywell T4051 line voltage wall thermostat is shown at left.

The company also provides a Honeywell Q651 used for manual switching between two T6051 units.

It may help to point out that basically a wall thermostat is an "on-off" switch that calls for heat or calls for cooling based on room temperature.

...

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• THERMOSTAT POWER & VOLTAGE

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