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Multi apartment one-pipe hot water system - better temperature control

Lev77Lev77 Member Posts: 50
Hi all,

We have an older building with hot water heating (gas), where one pipe heating loop passes through all the apartments.

In each apartment there's a valve and remote actuator (non-electric). These are the closest examples I could find for what's there:

However effective in getting the heat working, these don't provide adequate control of temperature to prevent waste.
People turn on the heat "full blast" then open a window if it gets too hot.

I'm considering replacing these with motorized valves (or just motorized actuators) and thermostats.
Getting all zone loops to start in the basement is not feasible.

Maybe use each apartment's electricity and look for a 120V zone valve?
Or if possible, reuse the existing valve and find a compatible 120V actuator.
Then install a thermostat to work with it that would have some internal limits and anti-tamper?

Any thoughts or suggestions on these?


  • JohnNYJohnNY Member Posts: 2,541
    Are the apartments' radiators on one continuous loop of piping? If not, you'd have to install multiple zone valves. Another way of dealing with your problem might be to lower your system's water temperature. That would send fewer BTUs to the apartments even with their TRVs wide open and will eliminate the desire to open windows. It's a bit of a balancing act but it will save you lots of money on both operating costs and retro-fitting new expensive zoning devices.
    For troubleshooting and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F Mechanical, LLC"
    Or email John at [email protected]
    John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
    For residential service and installations in New Jersey, please see Toro Plumbing & Mechanical and fill out our contacts page, upload pics, and submit, or call (973-672-1000).
  • Lev77Lev77 Member Posts: 50
    One long pipe goes through all apartments, and at each apartment there's a valve and actuator with remote sensor similar to what I've mentioned before, and from the valve there's a pipe that goes through that apartment, and that pipe does not appear to be a loop.

    I'm not opposed to investing in an effective and efficient solution per apartment. Trying to learn about solution options that people have used and ideas.
  • jumperjumper Member Posts: 1,530
    Set TRVs and then remove adjusting dials?
  • Lev77Lev77 Member Posts: 50
    Thanks @jumper , that's a low upfront cost idea, just buy TRV or actuator if I can reuse the same valve, for each apartment and basically it'll be in the baseboard.

    Assuming I'll block access to the TRV so it's not played with (otherwise it's no different from the current setup if the tenant just turns the head on the TRV, is that right?), there are 3 disadvantages: 1. it can't be just manually turned off/on by the tenants 2. the temperature setting will be fixed whether day or night 3. temperature sensing will be inside the baseboard, and may be skewed and not measure the ambient temperature in the apartment or room.

    What about an option where I install a motorized zone valve in the apartment? Either instead of the current TRV or use a motorized actuator if I can get one to match the current valve?
    And attach to a thermostat? Any reason not to do that?
  • HVACNUTHVACNUT Member Posts: 3,554
    I've seen a similar setup at a Friary.
    Constant circulation.
    The branches for each bedroom was simply a 120v x 24v transformer, 24v zone valve and a T87F.
    It was original, or at least done during a renovation because there was no exposed wiring other than the ZV connection at the baseboard.
    And there are thermostats that can be programmed for minimum and maximum temp and are password protected.
  • jumperjumper Member Posts: 1,530
    A smart (knows outdoor temp) water temperature high limit is easier to live with than zone valves in my experience.
  • Lev77Lev77 Member Posts: 50
    @jumper the boiler does have outside temp sensor, but here in the winters the temperature is low enough that the boiler is constantly on for most of the winter.

    @HVACNUT Thanks, I just can't think of anything else I can do with this type of setup.
    At least I can work on each apartment separately so I don't have to do all of them at the same time.

    In some apartments there's drop ceiling so I should be able to snake wire in the wall and put a transformer in the ceiling or something.

    Any recommended parts to work with or details I should not skip?
  • EastmanEastman Member Posts: 927
    Heatlink's wireless thermostat can interface with one or more of their wireless valve actuators:
  • Lev77Lev77 Member Posts: 50
    Thanks @Eastman! I'm checking if there's a tamper proof version of the thermostat.

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