Gas and Oil Home Heating Furnaces - Two Thermostats controlling 1 furnace

Hi,

I own a house with tenants in the main floor and I live up top. The thermostat for my new Lennox 2 stage gas furnace is in their suite. The furnace supplies heat to both suites and I have baseboard heaters to augment the heat in my suite. The issue I have is high gas bills and tenants who won't implement the night setback on their programmable thermostat. Everytime I am in their suite, I see that the night setback temp is only 1 degree below the daytime temp. My gas bills went up by about 10% despite buying a high efficiency furnace, after these gals moved in. (Heat included in the rent).

I want to place another programmable thermostat in my suite to override their thermostat at night time and during working hours. The thermostat is battery powered with 2 18 guage wires leading to the furnace. There is no A/C in the house. What type of signal is sent to the furnace through those wires? I have access to the wall cavity. Can I wire a new thermostat in series or in parrallel?

Thanks,

If you wire the two t-stats in series with one another should achieve what you are looking to do.

Since a t-stat is nothing more than a switch that completes a circuit, (sending 24 volts back to the board) both t-stats will need to be calling for heat for the furnace to run. If their's is set for 75 and yours only 70, 70 it is.

A two-stage furnace really should have a two-stage thermostat but it is possible that your furnace is actuating the second stage by means of an internal timer.

If the thermostat in the tenant's suite has only two wires then they should be colored red and white and connected to the R (or RH or Rh) terminal and the W (or W1) terminal respectively.

To have your own night setback thermostat you would have to cut the white lead and connect the ends to the R and W terminals in a new battery-operated thermostat. Program this new thermostat with the times and setback temperature you desire but set the "home" temperature to a much higher than normal setting.

The result will be the tenant's thermostat will control anytime the new (your) thermostat is in one of the "home" time periods and your thermostat will control during the "away" time periods as long as the tenant's do not turn down their thermostat below the setting of yours.


I want to warn you, subject to whatever landlord-tenant laws may be in effect in your area what you propose doing may be grounds for breaking the lease and possibly even legal action against you. Having a situation were heat is included in the property and yet removing control from the tenant is a dicey proposition.

I think that you can technically do what you want but I will also comment that in a rental situation what you want is not right.

I think you need to find a solution that does not take away what you promised to provide.

That will work out great! I'll wire a second thermostat in series and set its "home" temperature to 90F and the away temp to 50F.

FYI - I'll leave it on "home" throughout Dec and Jan, but I just found that here in July they had the furnace running with 2 windows and their back door open! They were informed of the night setback requirement before they were given an application form as one of the reasons why their rent is lower than market rate. My June gas bill was as high as it was in February!

Brian

You should give them another warning before making any changes. Maybe something else is wrong and they just haven't told you(I.E. a zone valve not closing).

Out of the box here. Id run the R wirefrom the furnace up to the tstat you put in. The run the W off yours down to the R on theirs. That way as long as yours calls for heat they can control it. But like said You cant do this if you rent it out with heat. Also any code I know of .No way can you have a hot air furnace heat two units. Or like one furnace for two rential units that way

I want to warn you, subject to whatever landlord-tenant laws may be in effect in your area what you propose doing may be grounds for breaking the lease and possibly even legal action against you. Having a situation were heat is included in the property and yet removing control from the tenant is a dicey proposition.

As long as you pay for the heat... you have to set it so their apartment gets no cooler then 65 degrees(depending on locality) Fahrenheit... thats how it works where I'm from.

Since you rent with heat included, you have the right to control the heat with reguards to the federal standards for heat and A/C thermostat settings. Goto Lowes, Home Depot, or your local building supply center and buy a thermostat lock box, it is a box that will allow air flow to get to the thermostat so it will read correctly, but it till prevent the tenant from tampering with the settings. Set the A/C temp to 78' and the heat temp to 68', lock it up and leave it alone. If you want to set up the night time settings and lower it a bit, then I would not go any lower than 65'. You are still providing heat to your tenants, and you are still under federal guidlines.