I saw a thread about connecting two thermostats in parallel. I could not add comment to that thread, so I put question here.

My tenants always shut off thermostat or reduce temp when they are not in their unit during winter time. It has caused several pipe to become frozen and cause a flood, though I told them many times. They just want to save money for heating.

Now based on that thread, it seems that we could connect two thermostats in parallel. I am not sure whether it could meet my requirement.

What I want to do is: on the other side of the wall (with one thermostat), I add another one (that the tenants could not see), I connect them in parallel. Once the colder months come (in our state from September to April), legal requirement is to set temp at 64 F or above. In my side, I set heating on and set temp to 64 F, to the tenant's side, even they turn off thermostat or reduce temp below 64 F , their thermostat could not do anything unless they increase temp to 64 F or above. Do the parallel connections for both thermostats work that way? Thanks. rose

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    If you need to heat to 65 to keep your pipes from freezing, your building's broke. Your building should be able to tolerate 50 at the very least. – Harper - Reinstate Monica Feb 28 '19 at 18:23
  • Do they leave for long periods at a time (say for months?) - if so could you not simply enter the apartment (as landlord) and turn the thermostat back up? – mike65535 Feb 28 '19 at 18:29
  • it is very normal for our areas pipe frozen and flood. you could see this happen in many houses, especial old houses, this is why in our state, law require landlords to give heating after middle of sept each year, and have to keep temp above certain degree. – bigfatter Feb 28 '19 at 18:50
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    they leave for a couple of days. but in the extremely cold days, usually plumbers ask keep temp in above certain degree, and also keep all water pipes dripping , this is very normal in the north parts in usa – bigfatter Feb 28 '19 at 18:52
  • So they turn down /off the heat when they are not home to save money on their heating bill. You want to keep the heat on to your liking in their unit and make them pay for the fuel? Yeah that's not right. The minimum temp the landlord is required is if YOU are providing your tenants heat. – Gunner Feb 28 '19 at 19:18

Legal issues aside... if there are any...

The thermostat on your side will be detecting your side's ambient temp, not their side's. So their side will be getting heat whenever (and only when) your side does. If the two sides are more-or-less equal in terms of their thermal properties (heat loss rates, etc.) it should work reasonably well.

  • I put the thermal just next to tenant's thermostat on the other side of wall. It means in the same unit and next to each other. – bigfatter Feb 28 '19 at 18:53

Electrically, there is no problem with it as long as you are using simple thermostats. Smart 'stats like the Nest might have a problem with it.

Operationally, a building that is so sensitive to pipe freeze is a nightmare. Less because of the inevitable tenant squabble (but that too), and more because that also means your house will not last long after a power failure. You should be able to lose power for a day+ before pipe freeze becomes an issue.

Legally you are able to oblige your tenant to heat enough to prevent pipe freeze, but 65 is a pretty high bar. I would not want to try to explain to a judge why my house couldn't handle 50. The way that would end up playing in court is looking like you're just wasting energy because somebody else is paying for it. I think the judge would say that's as wrong as when a tenant does it. The tricky mechanical enforcement would only antagonize and get a harsher judgment. Wouldn't want to be defending that.

  • I got some suggestions that if tenants do that (thought lease told them to follow law), ask tenants to pay the cost, if not, evict them since they do not follow lease. That will be long fight, I just want to avoid this from the begining. Yes, in our state, each winter, some years, there is a couple of days with very low temp. Once the frozen happen, hard to find plumbers since they are all busy to deal with this. – bigfatter Feb 28 '19 at 20:28
  • @bigfatter -- have you considered upgrading the insulation and air sealing building-wide? It sounds like that would be worthwhile... – ThreePhaseEel Mar 1 '19 at 2:56

In 1982 I had a somewhat similar problem while renting an upstairs apartment. Our downstairs neighbors had the thermostat in their apt and used to leave for the weekend and turn the thermostat down when they left. I investigated the furnace in the basement and found the wire to the thermostat, patched into it in parallel with a thermostat mounted on the wall in our upstairs apt. The way it worked was either would turn the furnace on, as long as it was set above the actual room temperature. Once both thermostats have their set temperature met the furnace turned off.


A "freeze protection outlet" will let you plug a small heater (and/or alarm) in, and will only activate if the temperature dips to a dangerous level.

You can also use heat tape around any pipes that are likely to freeze, and insulate any pipes in under-insulated areas.

Finally, not all thermostats have an off setting. Compare this Honeywell thermostat, which has an explicit off setting with this thermostat which only goes down to 40 degrees. While 40 degrees isn't great for a building, it's a lot better than not having heat at all.


I would think you could get a thermostat that you can control remotely - like a Nest or other WiFi-enabled device. That way, the tenants can still control things at the unit itself, but you could override their settings if desired. There maybe some available that also allow settings of general rules like 'temperature setting cannot exceed xx degrees'.

  • You would need a thermostat with "parental controls" type things i.e. specifically made for an authority to override. – Harper - Reinstate Monica Feb 28 '19 at 19:52
  • thanks for your answers . I will try to find this . – bigfatter Feb 28 '19 at 20:31

Simple: Buy an Ecobee and set it up to your account. Disclose to them that you are to have control of the Ecobee remotely via web page or your phone's app. You will need to edit (ammend, and have them sign/initial) your rental contract stating you are in charge of what the minimum temp allowed is, you may have some unhappy tenant(s) and then you are liable for paying a percentage of their heat bill which is not very easy to calculate in these situations, so just a discount in rent that month may be an option.

The Ecobee allows you to set minimum allowable temps, so you could make it so they just can't take the temps below x degrees.

This is much cheaper than having pipes burst. But then again it sounds like you could have things re-piped with Pex-A and have this issue already solved without needing more energy use.

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