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Plumbing cast iron radiators.

lincolnmaniac Member Posts: 6
i'm a regular at coalpail
installing a 1967 efm 350 coal boiler to heat my house and garage.
recently picked up nine cast iron radiators that just came out of service. they were very inexpensive. the house they came from was built in 1938.

how do i plumb these? each has a valve but if the valve was closed to the first radiator all the flow there would be is thru a pencil lead sized hole in the valve assembly.

should i tee the radiators to the supply line for the zone? will the water go into the radiators or just flow past the tee?

i have searched for diagrams and not come up with much, i got two of dans books too on primary secondary systems. most people on coalpail think i'm nuts for doing a primary loop.

any help would be appreciated



    JUGHNE Member Posts: 10,898
    Sounds like your rads came from an old gravity flow system.
    The small hole was to insure some flow thru the rad to prevent freezing. Most I have seen only rotate one full turn...fully open or down to the small hole. In between you could control the flow to a certain degree.
    These were connected with tees to the supply and return mains.

    Some could be on full flow and some shut almost down.
  • Jamie Hall
    Jamie Hall Member Posts: 22,085
    Or to say what @JUGHNE said in a slightly different way, the radiators need to be connected in parallel. That is, you have a supply main and a return main, and each radiator has a supply line connected to the supply main and a return line connected to the return main. Rather like a ladder, perhaps, with the radiators on the rungs and the two mains being the sides.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • jumper
    jumper Member Posts: 2,139
    I'd consider manifolds. Partial to soft copper.
  • lincolnmaniac
    lincolnmaniac Member Posts: 6
    i was going to use new slant fin baseboard but i came across these radiators for 30 dollars each. so i had already purchased the pipe and some of the pumps, etc.
    this is my first boiler install ever, i am also trying to install it with primary secondary pumping. getting people on the other forum telling me it's too complicated.

    would there be any problem running the radiators in series without valves? the manifold idea sounds great but i don't got a lot of space for all that 1/2" pex piping. i have 1" pex and fittings, it would cost too much to send the pipe back and exchange for smaller. was worried about inner size and flow (was going to use baseboard) gotta use what i got. it's getting cold in pennsylvania.

    there will be several zones in the house.
    the first zone getting installed is over the basement, 5 rooms and about 750 square foot, 5 radiators. walls well insulated, new windows and doors, it's a 1930's bungalow, dad and i insulated it well. all walls at least r-13 and there is 3/8" foam on the exterior under the siding that was taped, i'm heating the house at the moment with a reading coal stove in the basement with a 6" duct hooked to the cold air return on the furnace.

    second zone will be 3 radiators one large two small about 450 sq foot over a crawl space. crawl space is going to get insulated when i run the piping for the radiators, walls are well insulated, brand new windows, windows are not large.

    third zone is second floor room, approx 450 sq foot, 2 radiators, ceiling only r19 walls r13.

    fourth zone one large radiator in the basement.

    the 5th zone is radiant heat in the garage slab, installed when the garage was built last year. there is insulated pex going to the basement from the garage.

    might have a 6th zone, either radiant under the kitchen floor or a kickspace heater under the sink. Doubt the kickspace heater could be in zone 2 with the 3 radiators.
  • Jamie Hall
    Jamie Hall Member Posts: 22,085
    The biggest problem with running radiators in series is that the last radiator in line will get cooler -- possibly much cooler -- water. You can reduce that, but you can't eliminate it. Further, there is no way to control the balance between the radiators. It is what it is.

    However, let's consider for a moment. You have some 1 inch PEX (hopefully oxygen barrier? I hope...). What you can do -- and get very good balance and control -- if you have enough of the stuff -- is to run a 1 inch line from your pump or control valve or whatever past all the radiators in the zone. Take off from that with 1/2 inch or whatever to the inlet of each radiator. Now take some more of that 1 inch PEX and run that from the first radiator reached by your supply line all the way to the last radiator in the zone and then back to the manifold or whatever. Take off from that line and connect to the return fitting on each radiator. Yes, it uses more PEX. However, if you do that, each radiator is fed separately from the supply line and returns separately to the return line, and, because you ran the lines so that the first supplied radiator is the farthest one out on the return line, each will get the same temperature water and they can be controlled independently. This is called reverse return piping, if you need a name for it.

    Note that there are only two connections at the manifold -- one supply and one return -- so space there shouldn't be a problem.

    Now you have a total of 5 zones. So... you will need two manifolds, one supply and one return, each with five connections for the five zones. Then, to create primary/secondary pumping, those two manifolds are connected, in turn, to the boiler loop through closely spaced Ts.

    The radiant floor zone will need very different temperatures from the other zones -- so it will need its own circulator and a mixing valve to recycle some of its return flow. The other zones could be powered by a single pump and zone valves, or they could be powered by individual pumps. Either way works. The boiler loop, of course, has its own pump.

    Thumbnail description. Check Caleffi's excellent web site for more detailed descriptions!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • lincolnmaniac
    lincolnmaniac Member Posts: 6
    yes it's oxygen barrier pex. i have 300 foot of it.

    i have new circulator pumps and a new taco 6 zone switching relay three are taco 007e and one is a Wilo ECO 16RFC. got them on ebay auctions. last yr when i started buying parts, the circulator pumps were cheaper than zone valves.

    a supply header and a return header i could run down the center of the basement. then hook to the radiators with smaller pex. would i use regular tees then? thanks for clearing it up some for me, hard to visualise something that has not been built yet.

    here is a video of the boiler when i got the domestic coil plumbed in. i got the heat exchanger before i found the cast iron radiators.
  • Jamie Hall
    Jamie Hall Member Posts: 22,085
    Yes, regular plain vanilla Ts will work just fine. Not only hard to visualise, hard to describe, too, if you've never set one up!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • lincolnmaniac
    lincolnmaniac Member Posts: 6
    can i use these boiler headers on the primary loop for the closely spaced tees or do they need to be closer together?

    i need 10" minimum between sets of closely spaced tees correct?

  • lincolnmaniac
    lincolnmaniac Member Posts: 6
    ordered the fittings to install the boiler and the radiators. got what i could in american made fittings. anyone interested in my progress? should i start a new thread on the boiler install?