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Using EK1 Boiler Transformer for C-Wire, Sketchy or ok?

NEMatt
NEMatt Member Posts: 56
I am looking to replace two older heat-only thermostats in my house with smart thermostats.

Energy Kinetics' wiring diagram for power-borrowing tstats says I can utilize the existing 24V transformer wired into the A2 port on the energy manager for the common.

Is this a wise choice or do I risk frying expensive parts of the boiler... specifically the energy manager itself if something gets wonky? Boiler is 11 years old.

Comments

  • NEMatt
    NEMatt Member Posts: 56
    The followup being, would it be worthwhile to wire in an additional transformer to "help out", since I think a factory 24V 50VA transformer is only good to like 2-odd amps. I'm sure 2 smart tstats+opening/closing zone valves will exceed that.
  • Jamie Hall
    Jamie Hall Member Posts: 23,176
    If the total amp draw is close to the rating of the EK, you will need a relay or relays to switch a more powerful transformer. Do NOT try to wire an additional transformer in the "help out" -- unless you are very fortunate indeed, that is almost guaranteed to fry the energy manager..
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SuperTech
    SuperTech Member Posts: 2,140
    I think the EK energy manager is about as "smart" as any component of the system should be, I don't see any benefit to using a smart thermostat with that boiler.  
    If you really want a new thermostat I would use a separate transformer to power the thermostats. You might be okay with the boilers transformer depending on how many zone valves you have. 
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    If you do it right you'll be fine.
    steve
  • NEMatt
    NEMatt Member Posts: 56
    Jamie, EK's own tech manual shows secondary transformers wired in should you wish to add additional zones to their large energy manager. Granted I believe they have to be the exact same one or else it could get let the smoke out.

    SuperTech, I want to have one with a larger temp differential or cycles per hour. Right now our upstairs and downstairs tstats are in the first room into which heat flows so it winds up short cycling the boiler.

    Steve, yeah I have seen that wiring diagram. I am just thinking that it will be at the limit of the factory transformer.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,455
    @NEMatt

    A thermostat is only a switch to turn things off and on. Thermostats don't "use" any measurable power
  • NEMatt
    NEMatt Member Posts: 56
    So if I put my clamp meter around the c wire on a Nest or Ecobee or pick-a-wifi-tstat, what would I be reading?
  • HVACNUT
    HVACNUT Member Posts: 5,804
    edited October 2020
    NEMatt said:
    So if I put my clamp meter around the c wire on a Nest or Ecobee or pick-a-wifi-tstat, what would I be reading?
    Like Bluto's GPA, 0.0

    There is no problem adding 2, 24v powered thermostats using A2 as the common to the Energy Manager. 
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Maybe your piping is the fault here. Hot water should be flowing to all parts of the system equally. Maybe you can throttle down The flow to the hotter areas, if they are over radiated.
    Certainly a thermostat is a switch, but some are broadcasting stations, using more power.—NBC
  • NEMatt
    NEMatt Member Posts: 56
    Each floor has two loops, one for the front side of the house and one for the rear. They run lengthwise down it so our MBr sees hot water first, and two guest bedrooms last. So if the tstat in our bedroom is only trying to raise temp by a degree or whatever, the rads in that room see heat first and suck it out of the system. Tstat sees that temp increase before the rads at the other end of the house really heat soak properly.

    Now, if I raise the temp by 3 degrees, all of the system gets smokin hot for long enough that the every rad in each room has a chance to arrive at a higher temp.

    I don't see any getting around that by messing with valves since both loops start in the MBr and end at the other side of the house. Kinda stuck with that design choice from 1977 :)
  • Roger
    Roger Member Posts: 329
    Thank your for your post, @NEMatt .

    It sounds like you have cast iron radiation. For your system, we recommend primary/secondary piping. It will greatly improve your heat distribution and comfort in your home. It does require adding a circulator and SR501 type relay to each zone and some piping changes, but it is the right way to go to make your system work as well as possible. This will be a nice upgrade from 1977 tech.

    Regarding NEST thermostats, we’ve run 4 on a single 50 VA transformer without issue. The wiring diagrams on our site are all time tested and proven in the lab and field (including the C-wire). Sometimes, if it is a new installation and the NEST batteries need charging, it could take a half or more before they “spring to life” and start functioning so you can see the display.

    Best,
    Roger
    President
    Energy Kinetics, Inc.
  • NEMatt
    NEMatt Member Posts: 56
    Hey Roger, thanks for the reply as always. It's an all copper system.  It would be lovely if the loops on each floor somehow ran in opposing directions.  At this point rerouting piping is slightly outside scope. I'll try with temp differential first, or perhaps one of the tstats that utilize a remote sensor.
  • JoeHNJ
    JoeHNJ Member Posts: 18
    Not sure if you mentioned above - are you heating with baseboard loop, convectors, or radiators?
    Joe Harazim
    Technical Support
    ENERGY KINETICS
  • NEMatt
    NEMatt Member Posts: 56
    Standard finned baseboard with the exception of the bathrooms that have the thin vertical Runtal ones.
  • Roger
    Roger Member Posts: 329
    You're welcome, @NEMatt . I'm interested in your reply to @JoeHNJ to help better identify your heating system.

    If your return temperature from each zone is nearly the same as the supply temperature, the baseboard/convectors/radiators are outputting all the heat they can. Look for reasons why that is not adequate. If the returns are coming back colder (30°F to 40°F or greater temperature drop from supply to return in steady state), there may be a flow problem - depending on system design.

    Alternately, as I recall you had some flow restrictions/blockage from prior posts, your zone valves may be bypassing and gravity heating the first part of the zone when the thermostat is not calling. This could cause overheating as you describe.

    Roger
    President
    Energy Kinetics, Inc.
  • NEMatt
    NEMatt Member Posts: 56
    Roger, I think the problem is it never reaches steady state unless I turn the heat up by a few degrees.  If the tstat is just trying to maintain like 65, the first room reaches that temp and the tstat cancels the call before the return reaches steady state.  Might change when it's actually cold out and the heating calls are more frequent.

    When there is no heat call nothing above any zone valve is hot.
  • Roger
    Roger Member Posts: 329
    Thank you, @NEMatt . It sounds like you have to find out why so much more heat is coming out of the first part of the zone. 3/4" tubing/baseboard has about 40 feet per gallon, so the return on a 100 ft loop should come back in about 30 seconds if it is flowing at 5 GPM.

    Thermostat placement is also a consideration. If your thermostat is directly above the baseboard instead of on an inside wall (or in some other location where it does not accurately represent the room temperature) it can satisfy quickly and then call again soon afterwards.

    Roger
    President
    Energy Kinetics, Inc.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,455
    @NEMatt

    Wrap some tinfoil around the fins on the baseboard in the rooms that are overheating. Just cover a couple of feet and see what happens
  • NEMatt
    NEMatt Member Posts: 56
    Yeah this is 1/2" copper for each loop. 

    One theory I have with a minor 1 degree heat call might be the zone valve comes on and off a few times as the cold return water trips off the manager.  Then reheat to 140, open the valve, etc.  So maybe that super hot water is sitting in the MBr rads for longer than the others in general until the return gets hot enough to keep the valve open full time.  
  • Roger
    Roger Member Posts: 329
    @NEMatt , how long is the entire loop? How long does it take before there is a temperature rise in the return?
    @EBEBRATT-Ed 's idea is a good one that can help correct if the first part of your baseboard is greatly over-radiated vs the other parts of the zone, too.
    President
    Energy Kinetics, Inc.
  • NEMatt
    NEMatt Member Posts: 56
    Hmm, from dead cold I'd have to time it.  And also measure each loop. 

    However from dead cold the zone valve does probably 4x cycles before the return temp remains high enough to stay open.  Maybe 5. 
  • NEMatt
    NEMatt Member Posts: 56
    2nd floor measurements:

    Each individual loop in the zone is ~45 ft down a given side of the house longitudinally. Plus up 2 floors and down 2 floors, so ~24ft (?) vertically. Plus over 12ft and back 12ft since the boiler is equidistant from both walls and the basement return is in the center of the house, so 24ft laterally. The return in the basement is centrally located and is 1" pipe into which all 5 loops in the house dump, and also ~45ft.

    Therefore, rough estimate, the second floor full zone totals something like 186ft of 1/2" copper split into 2 loops, and an additional 45ft of 1" copper common to all zones.
  • NEMatt
    NEMatt Member Posts: 56
    edited November 2020
    @Roger or @JoeHNJ it seems, at least for the downstairs tstat I tried to wire today, the existing cable goes up and over one stud and must be stapled or something.

    I soldered the new 3 wire cable onto it and tried to pull it through the wall using the existing cable but it wasn't budging. Definitely something beyond a "pull harder" type deal.

    So... talk to me about wiring in the 280-CR15-200-RC resistor between A2 and Tx. Should it be on a small wire that goes from screw terminal on A2 to screw terminal on the specific Tx, or should it go from screw terminal on A2 then soldered directly into the white wire departing the specific Tx?
  • Roger
    Roger Member Posts: 329
    No soldering is necessary, @NEMatt . You can wire to the terminals you described with A2 and Tx on the quick connector where Tx represents the zone requiring the resistor for the power stealing thermostat (T2 if its zone2). Bend the resistor wires so it stands away from the quick connector and other wires.
    Roger
    President
    Energy Kinetics, Inc.
  • NEMatt
    NEMatt Member Posts: 56
    @Roger sounds good.  I did manage to just run a full new 3 conductor cable after some redrilling and about an hour with a borescope with a hook, so the downstairs is running using A2 as the common.  Might have to go the resistor route if the upstairs doesn't play along when the time comes.