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Plotting my downfall; or, help me with control options for the future

R2.0 Member Posts: 99
This year I completed (almost) Stage 1 of the Fisher's Forest Mechanical Plan: I replaced the oil burning Burnham V7 with a gas fired Weil McClane CGt (chronicled elsewhere on this site). The basics are as follows:
  • Structure
    • Built 1944, expanded twice soon thereafter
    • Cape Cod with basement; roof raised and 2 BR built on upper level
    • Walls are 12" thick with brick facing, brick and clay tile core, plaster interior covered with 1/4" Masonite paneling
    • Windows were replaced with vinyl replacement
  • Heating System
    • Gas Boiler with Tankless Coil
    • Direct Return
    • Split Heaters, 1 1/4" Black, insulated
    • Risers 1/2" black, uninsulated
    • No zoning - programmable stat connected directly to boiler controls
    • No radiation in basement, one room, and a radiator was removed from the upstairs hallway
    • Radiators
      • Contemporary to construction
      • National Art thin tube
      • Metal radiator covers over most
      • Radiator valves turn 180 degrees only, do not appear to be shutoffs
  • Occupant schedule
    • Owner (me): Out of the house 0700-1900, sleeps 2200-0630, occupies main floor bedroom and living space
    • Pumpkin/V (aka daughter): College student, only lives there summer and winter break, sleeps in upstairs BR
    • Monkeyboy/R3.0 (aka son): HS student. Occupies the house every other week (split custody). Sleeps in other upstairs BR.
  • Capabilities/Resources
    • Project Management and design of large HVAC stystems (mechanical engineer)
    • Gearhead
    • Can sweat pipe, run 120v & low volt wiring
  • Goals
    • Fuel Savings
    • DIY as much as possible
    • Low installed costs
    • As automated as possible
So now that I've made everyone's eyes glaze over, here's my next steps:
  1. Implement IceSailor's DHW tank. I have the original 50 gal electric HW heater, bought a bronze taco 006 off CL for $10
  2. Implement Outdoor reset: Bought a Tekmar 275 off Amazon ($120 shipped :)) and he threw in a Tekmar 260 and 032 Timer.
Those are pretty definite - probably after Thanksgiving as a matter of fact.

But after that things get more indefinite. Controlling the main floor seems pretty straightforward; I could live with just keeping that one zone. But the bedrooms upstairs are only occupied half the time or less. In addition, the basement presents it's own challenges. More and more I see the need to install radiation down there, and there are plenty of old radiators available, but I'm concerned with breaking into the headers. Ideally I would install threadolets, but welding is one of the things I would need to shop out. Running loops in pex seems an option, but it just seems...wrong somehow. And I don't have the tools.

I have some ideas on zoning and controls, but I'd like to hear what others think first. If you were called to my house, what would you recommend? there's about 30 different ways to skin this cat, but I can't afford to do it all at once.



  • SWEI
    SWEI Member Posts: 7,356
    edited November 2014
    With that much mass in both the walls and your radiators, you will really benefit from constant circulation driven by ODR. The Tekmar 260 will handle the boiler reset, but lower temps in the emitters will maximize both comfort and efficiency. I would add a Taco iSeries-R mixing valve to the system and probably stop there. The other option would be to sell your existing Tekmar bits and buy either a 360 or one of its predecessors. I have good pricing on both 3-way and 4-way motorized valves if you need one of those to go with.

    At some point, you might consider a TRV or two if there are rooms which overheat due to solar gain, a wood stove, cook heat, etc.
  • R2.0
    R2.0 Member Posts: 99
    You've hit on one of the peculiarities of this boiler. The pump is controlled by the boiler control, and there's no option to make it run full time.

    One idea I had was to do a primary/secondary system with the primary being the boiler and a HW heater, plumbed through the holes for the elements and with an air vent at the top. The secondary loop would either come from closely spaced tees or plumbed through the top as well. I have a spare Taco 007 from the previous boiler.

    OR, use the body of the 3 way valve that came with the boiler (Honeywell VC) and replace the cartridge and operator to convert it to a floating mixing valve. The only issue with that is that the boiler controller relies on end switches in the existing operator. So I would have to bypass/jumper some stuff in the boiler controls. I am working on a ladder diagram of the whole boiler control system (because the manual leaves out some stuff) so I can see what's safe to bypass or not.
  • SWEI
    SWEI Member Posts: 7,356
    edited November 2014
    With all due respect, you appear to be overthinking this. First off, do NOT bypass anything in the boiler safety string. Moving the primary circulator from the boiler's internal controls to an external control would not be considered bypassing, just abandoning an internal feature.

    You will need two circulators, one on the primary (boiler) loop and one on the secondary (system) loop. The boiler can generally control its own circulator sanely in this kind of arrangement. The secondary circulator is generally managed by the ODR mix/injection controller and typically stays on as long as the outdoor temp is below WWSD.
  • R2.0
    R2.0 Member Posts: 99
    I should have clarified that I would only be messing with controls in the DHW loop. That's what the 3 way valve is for. The high limit, rollout, boiler room temp safeties, etc are all sacrosanct. I was even adding an LWCO.

    The CGt comes with a 3 way diverter valve. It is normally closed, bypassing the system. On a call for heat the pump starts and the valve opens. When valve is open fully an end switch fires off the burners. When the demand is satisfied, pump shuts off and valve is de-energized. The other mode of operation is when the water temp in the boiler drops. When it hits the low limit, the pump turns on and the burners light off, but the valve stays put. The pump just recirculate the water until the low limit opens again.
  • SWEI
    SWEI Member Posts: 7,356
    Constant circulation with ODR control is the key. Given that you already installed a conventional boiler, this means you will need to add either valve or injection mixing to the system.
  • R2.0
    R2.0 Member Posts: 99
    OK, that gives me my control scheme: constant circ with odr. Not quite sure how I'll implement it yet. Initially I'll just balance all the radiators, but at some point I'll zone off the rooms upstairs.
  • SWEI
    SWEI Member Posts: 7,356
    You seem to be comparing apples with oranges on this. Balancing, zoning, and control schemes are all important, but you can not really compare them with one another.
  • R2.0
    R2.0 Member Posts: 99
    That was more of a side observation - I still need to rebalance the system from the install. But I wish I could find some info on the valves.
  • SWEI
    SWEI Member Posts: 7,356
    Unless you can find a way to wrangle something like a Tekmar 356, 360 or similar control, I would just buy a Taco iSeries-R valve and call it done.