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Is Nest Learning Thermostat good for steam?

Brycewvu Member Posts: 27
I have a one pipe steam system and I installed a standard nest thermostat when we moved in a few years ago. It was free through the  power company so I though, sure why not.  We have had pretty good success with it so far, but I recently found the nest learning thermostat on a significant discount at a local store. I've heard that the learning thermostat provides significantly better controls and will adjust to your heating rates (i guess thats why they call it learning haha).  My question is in all of your experiences, is the learning thermostat a good match for steam heat? What are the drawbacks?


  • Ironman
    Ironman Member Posts: 7,376
    edited March 30
    No, it’s designed for force air which has a faster response than steam or hot water.

    The best thing for steam is to set the thermostat on one temperature and leave it there.

    If you’re looking for the best efficiency, make sure all the vents are sized properly and functional. If it’s a 2 pipe system, make sure all traps are operating. Insulate the steam mains. Tighten up the house envelope. Boiler pressure should be 2psi or less if it’s a vapor system.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,844
    edited March 30
    If you want to control a steamer remotely over a WiFi network connected thermostat, then you are going to give up some of the accuracy that is built into those old mercury switch thermostats that have a heat anticipator circuit. The old T87F (Not the new T87K, T87N or any other electronic switching action thermostat) was one of the best choices for steam heat.

    Some new mechanical or electronic thermostats have a setting for 1 or 2 cycles per hour. Others have a choice for Heat Pump, Electric, gas/oil furnace, and hot water boiler. They can get close but you will never get the comfort accuracy of the old analogue bi-metal coil thermostat.

    That said, if you are using the remote notification and operation for a vacation property, then you will need to go with something WiFi. I believe that Honeywell has something that will work for you, Ecobee has also been known to work on Steam Boilers. If you want Nest because you are already using the Nest App for other devices, then you can also connect a Nest thermostat to your steamer.

    However, if you are choosing the Nest so it can learn your schedule and reduce your operating cost by lowering the temperature daily, when you are away or asleep, I would not waste your money. I you still want to set back the thermostat back after hearing the same advice from several experts, Then only set back about2 to 3 degrees 4°F MAX. Any more than that and you will be asking for other problems that you do not currently experience.

    For confirmation ask @pecmsg, our resident Nest Pro Advocate.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    Long Beach Ed
  • Jamie Hall
    Jamie Hall Member Posts: 23,322
    I'm not quite as eloquent as my friend @pecmsg ... I'd be more inclined to say that first, it's learning and so on capabilities are overkill. Second, they must be disabled to have the thermostat and the system work together. Which leads to the question of why bother. Spend the money on something else.

    Now there are situations where you might want a home monitoring device of some kind, but there are other thermostats which do that for less money and are less intrusive. However, it is worth remembering when going for something of that sort that if you can monitor it, so can others if they are so minded...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Waher
    Waher Member Posts: 251
    If the Nest model doesn’t have a “true radiant” setting it won’t play well with steam systems. You don’t want deep temperature setbacks.

    Nest/Ecobee work best with steam when used as fancy anticipators to sense how long they need to run the burner and let the thermal momentum/lag of cast iron radiators to finish warming up to the degree set point.

    if your boiler doesn’t have a (C)common wire they get tricky to install.
  • RTW
    RTW Member Posts: 60
    "Analog" refers to the continuous nature of a signal, as opposed to a "digital" signal which is discrete. An analog mercury thermometer, for example, can display a continuum of temperature values, while a digital thermometer can only display discrete temperature values (perhaps in 0.1 degree increments).

    Follow the advice of "ED" above. My Mercury T87F was installed a long time ago as they were phasing out mercury thermostats ( due to environmental waste concerns and should Not be disposed of in general trash) I set it and forget it on a seasonal basis, Fall / Winter / Spring There is something to be said about the analog world that's worth keeping. Regards, RTW
    Alan (California Radiant) Forbes
  • Jack M
    Jack M Member Posts: 229
    edited April 4
    The "heat-only" version of the T87F is the Honeywell T86A. I do wish that I could have my boiler shut down when the radiators are full regardless of the room temperature.
  • Jamie Hall
    Jamie Hall Member Posts: 23,322
    Jack M said:

    The "heat-only" version of the T87F is the Honeywell T86A. I do wish that I could have my boiler shut down when the radiators are full regardless of the room temperature.

    eh? It certainly should -- the pressuretrol should cut it off when the radiators are full. What's the pressuretrol set at?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Jackp2
    Jackp2 Member Posts: 4
    Don’t do it. 
    NEST represents that their thermostat can pick up power from the boiler. The steam boiler manufacturers will tell you it doesn’t work. I have seen this. The voltage available to the T-stat varies depending on what the boiler is doing. When it drops, the NEST stops working. 
    The other “smart” feature that will drive you crazy is that if the NEST doesn’t see movement it will set back. Not good for steam as the first post said. This can be disabled. 
    If you still want a smart T-stat, I did install the Honeywell but connected it to a stand alone transformer.  
  • Controlsgirl
    Controlsgirl Member Posts: 13
    I have a nest eco and it has been working just fine.
  • SuperTech
    SuperTech Member Posts: 2,166
    My opinion is that the NEST learning thermostat is not a good choice for any system. I can't see anything but disadvantages to using it on a steam boiler. 
  • clammy
    clammy Member Posts: 3,111
    The issue w nests and smart stats is that they require 24 volts and most low cut off cycle guard included are wired to break line voltage which cuts power to the smart stat which then when power is restored causing it to re boot . To ease the issue and dummy it down for those who follow you instead of a additional transformer and isolation relay its far easier to add a taco sr501 relay and be done nice little all in one package ,easier for anybody to figure out on a service call . i used to do it all the time and lately kinda put it to the back burner being im not a fan of smart stats but people want them and i ve found just adding a sr501 to be the easiest less complicated and quickest way to constant power them w no interference from cycle guards or lwco cutting 110 to the transformer .peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • Robert_T
    Robert_T Member Posts: 9
    In sixty years of owning and working on steam systems, I have found the only good way to control steam is by using thermostats with adjustable anticipators like the old Honeywell in the round. This has been brought up before as people have lamented its passing but White Rodgers still makes a couple of models with adjustable anticipators. This is critical to effectively control the length of the heating cycle, especially with one-pipe steam. In extremely cold weather without the proper length of a heating cycle you end up with flooded systems. This only happens if you have an automated water adder which most systems do these days. Even with forced air length of cycle is crucial for good comfort. All of the new hi-tech stats come with dip switches that don't necessarily provide good control with their one-size-fits-all all mentality.
    Long Beach Ed
  • Dave_61
    Dave_61 Member Posts: 309
    I have the Ecobee on our 1 pipe steam and think it works great. Got it mostly for remote wifi monitoring. It does a great job of anticipating when the house will be up to temperature and shuts off the boiler a little early so that the temp does not overshoot. It also will start the boiler earlier to allow house to get up to the desired temp for the given set time in the morning. I also like the remote sensors that allow me to use the bedroom temp as the setpoint at night and then switch to main thermostat during the day.
  • Lance
    Lance Member Posts: 270
    My experience showed me all heating systems have their unique lead lag heat/cool control. Just ask anyone who has hot flashes. :o
    I have seen a 1 psi rise when a burner shuts off by steam valve closure on a header. Residual heat generation does not stop instantly when the flame goes out. I learned that as a kid when I blew out a match and touched the match head. Ouch! Thermostat droop I am told on average is least noticed by people when the temp changes less than 3F. Honeywell has studied this for years, new digital techs are just learning about it. Imagine how the coal fire which never went out was controlled. Some controls do not adapt well to systems which can have up to six degrees F droop. But the real challenge is most systems are not balanced or properly built. These require fixing before fine tune balancing can succeed.