RV.Net Open Roads Forum: Tech Issues: Will a household thermostat work?

RV Blog

  |  

RV Sales

  |  

Campgrounds

  |  

RV Parks

  |  

RV Club

  |  

RV Buyers Guide

  |  

Roadside Assistance

  |  

Extended Service Plan

  |  

RV Travel Assistance

  |  

RV Credit Card

  |  

RV Loans

Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Help and Support  |  Contact

Search:   Advanced Search

Search only in Tech Issues

Open Roads Forum  >  Tech Issues

 > Will a household thermostat work?

This Topic Is Closed  |  Print Topic  |  Post New Topic  | 
Page of 2  
Next
Sponsored By:
cybervanner

Richmond, VA

Senior Member

Joined: 09/25/2007

View Profile


Offline
Posted: 03/12/08 02:48pm Link  |  Print  |  Notify Moderator

On an RV furnace? My current furnace thermostat is one of the mechanical ones, and the problem is that the temperature swing is too dramatic between off an on. I want something that will cycle the furnace quicker.

I have a regular "5-wire" electronic heating and air thermostat that came out of my house when I upgraded to a heat pump. Will this connect up to the furnace? I don't have thermostat wiring for the AC side, but if it will work just off the heat side, that will be perfect. It doesn't need to be level because it is electronic, but I didn't know if the wiring is any different between a home thermo, and an RV thermo.

Here's the pinouts for the home thermo:

Hot
Ground
Burner on
Fan on
Compressor on

When the unit is in heat mode, the thermo only switches on the burner on line when heat is called for. The fan unit in the furnace is activated by a heat sensor inside the furnace...when the heat exchanger is warm enough, the fans come on. RV furnaces seem to work the exact opposite...the fan is started, and then when the furnace sees that the fan is OK, then it lights the burner.

When in AC mode, when cooling is called for, both the compressor on, and the fan on leads are switched at the same time, activating both.

Home thermostats are designed to switch only a few hundred milliamperes at 24 volts. Do RV thermostats carry the full 12 volt load of the furnace through the thermostat? I imagine running the thermostat at 12 instead of 24 will be fine since the actual temperature sensing electronics operate off a battery, but if it's carrying too much current, it could damage the relay switches inside.

whisler6

Traveling

Full Member

Joined: 04/19/2006

View Profile


Offline
Posted: 03/12/08 03:02pm Link  |  Print  |  Notify Moderator

Yes, you can use certain house thermostats in your rv.


I RV to Live and Live to RV. When I'm not relaxing I'm posting on Forums . When I'm not here I'm over there, Where RvLivin.com and when I'm not there I am posting here at RV.net. Confused Yet?
Games

DeadeyeLefty

Sunshine Coast, BC

Senior Member

Joined: 03/28/2007

View Profile


Offline
Posted: 03/12/08 03:12pm Link  |  Print  |  Notify Moderator

Mine has a Honeywell home thermostat coupled to a Suburban furnace. I'm not sure of the model #'s(moho's in storage)but it's certainly doable.


Project Glacier trailer build.

PaulJ2

Northwest Oregon

Senior Member

Joined: 12/23/2005

View Profile


Offline
Posted: 03/12/08 03:20pm Link  |  Print  |  Notify Moderator

Take a look at your old one. Many have what is called an anticipater. Has a small scale and a movable pointer with something like .2-3 or something like that. Moving the pointer toward a lower number sets the on-off temperature closer.

Chris Bryant

DeLand, Florida, USA

Senior Member

Joined: 03/26/2003

View Profile



Posted: 03/12/08 03:24pm Link  |  Print  |  Notify Moderator

The furnace draw will be just about 1 amp, which should be fine for most thermostats.
Coleman air conditioners send +12 volts to the control circuits, DuoTherm units ground out the relays, so the hookup will be different.
If you search the forum for "hunter thermostat" you will find lots of info, along with a link to Les Adams article and diagrams.


-- Chris Bryant
My RV Service Blog
The RV.net Blog

hwybnb

Southern California

Senior Member

Joined: 05/02/2001

View Profile



Posted: 03/12/08 03:30pm Link  |  Print  |  Notify Moderator

Good grief. I thought this subject had been covered so often everybody knew.

No you cannot use a typical residential thermostat in an RV. The reason is that most of them are designed to use 24 volt AC power, and RVs have no such power source.

You can use a thermostat that is battery-powered and that is designed for "millivolt" control systems. The one that a lot of RVers use is the Hunter 42999B, available at Walmart for about $20.

Hunter Thermostat Upgrade

javaseuf

California's Gold Coast

Senior Member

Joined: 03/30/2005

View Profile



Posted: 03/12/08 04:38pm Link  |  Print  |  Notify Moderator

hwybnb wrote:

Good grief. I thought this subject had been covered so often everybody knew.

No you cannot use a typical residential thermostat in an RV. The reason is that most of them are designed to use 24 volt AC power, and RVs have no such power source.

You can use a thermostat that is battery-powered and that is designed for "millivolt" control systems. The one that a lot of RVers use is the Hunter 42999B, available at Walmart for about $20.

Hunter Thermostat Upgrade


Not quite as far as millivolts go.
First of all, a millivolt thermostat is designed for gas valves that are self-powered using a pilot generator, which the new RV furnaces do not have. They will not work on a 12-volt furnace.
The mechanical thermostats used on a RV furnace are rated for 12-volts DC.

Second, even though residential thermostats operate with 24 volts AC, you CAN use them in a RV as long as the thermostat uses power from the internal thermostat batteries. The Hunter does this.
Most residential digital thermostats do this but some do not, these taking power for operation from the 24-volt transformer in the heater. The latter will NOT work in a RV.

BTW, a millivolt thermostat is used for heating only, not air-conditioning and most will NOT work on a 12-volt RV system due to the current limitation of the heat anticipator.





javaseuf

California's Gold Coast

Senior Member

Joined: 03/30/2005

View Profile



Posted: 03/12/08 04:50pm Link  |  Print  |  Notify Moderator

Also, my spec-sheet states that my Suburban 30K BTU funace draws 5.5 amps during operation.

ScottG

Bothell Wa.

Senior Member

Joined: 02/25/2005

View Profile


Offline
Posted: 03/12/08 04:50pm Link  |  Print  |  Notify Moderator

Sorry Steve but your last comment is incorrect. A millivolt Tstat will work for AC and it will work with a 12V RV system. You simply dont connect the 12v feed wire to anything when you wire it up. As for the AC part, they are indeed designed to run them and even have seperate programming for both heat and AC if they are of the programable type. A common residential millivot Tstat works great in both my TT and my house, which also has AC.

Cheers.


Scott, Grace and Wesly
2003 Dodge 3500 4x4, 6 speed Cummins (lightly bombed),
2004 Forest River 25RKS many, many mods.
POS H0NDA eu2000i

ScottG

Bothell Wa.

Senior Member

Joined: 02/25/2005

View Profile


Offline
Posted: 03/12/08 04:52pm Link  |  Print  |  Notify Moderator

javaseuf wrote:

Also, my spec-sheet states that my Suburban 30K BTU funace draws 5.5 amps during operation.


But it doesnt pull this 5.5 amps through the Tstat.
The stat trips a relay that carries the load.

This Topic Is Closed  |  Print Topic  |  Post New Topic  | 
Page of 2  
Next

Open Roads Forum  >  Tech Issues

 > Will a household thermostat work?
Search:   Advanced Search

Search only in Tech Issues


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:

© 2014 RV.Net | Terms & Conditions | PRIVACY POLICY | YOUR PRIVACY RIGHTS