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Indirect off Steam Boiler

This spring we are installing a new steam boiler Burnham MST396 and I have 388 sq. ft. of radiation without taking into account the steam piping. We already have the boiler in place and are doing as much pre-piping as possible before the change over. An after thought lead us to wanting to install a 40 gallon Phase 3 indirect domestic water heater. We a family of 3 and maybe 4 down the road.

The MegaSteam has provisions for the indirect tapping's built into the casting:

<strong>My questions are 1:</strong> Is the sizing big enough to keep up with the domestic hot water demand while heating the home? and if it is workable <strong>2:</strong> Should we run 3/4" 1" or 1.25" supply/ return lines to the indirect?

Thanks So Much for all the help and guidance you pros have provided me~! Joe


  • billtwocase
    billtwocase Member Posts: 2,385
    it has been a while

    since I installed a Phase, and it may be the 36 gallon tank, unless that has changed, but they were 1" supply and return if my memory serves me well. 
  • Steamhead
    Steamhead Member Posts: 16,893
    The Phase 3 doesn't work well with steam

    but the SuperStor does. See your other thread for details and a link.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • billtwocase
    billtwocase Member Posts: 2,385
    i was also

    thinking height issue here. I was going to suggest a separate direct fired heater be it gas, oil, or electric. 
  • Halfbreed
    Halfbreed Member Posts: 4
    Different way to Indirect off of steam

    I use an external plate exchanger and a storage tank, like an electric water heater, instead of an indirect with a coil inside. It overall is cheaper in materials and more efficient. If there is a problem with an indirect with a coil inside, as in a tank leaking or the coil leaking inside the tank, it is costly for the customer to have the whole thing replaced. With the plate exchange and storage tank method, if the tank springs a leak, then you are only replacing an inexpensive electric water heater. If the plate exchanger has a problem, then if you use a type that is installed with unions, you disconnect it and replace it with either a new one or a refurbished one and it is still much cheaper than using an indirect with a coil inside. Whateven you use as a storage tank you will need 3 ports to do so. With an electric water heater, the drain port on the bottom is where you will send the cold water supply to the tank and a tee off of that to feed the plate exchanger. The cold port on the top is where the heated water from the domestic side of the plate exchange will dump into. Either remove the elements and plug off with brass plugs or disconnect the wires and remove and bypass the top thermostat. Use the lower thermostat to control the temperature of the tank. You can remove the top element and bushing it down to install a well for an aquastat or a sensor to control the temperature instead. It is basically an Energy Kinetics' System 2000 design. I use it in all of my heating systems, hydronic or steam, for domestic hot water. As I stated, it is a couple of hundred dollars cheaper overall and saves time and money if service is needed, and is also a little more efficient. Keep in mind that if the boiler takes more than 5 minutes to reach 120 degrees from a cold start, then you will need to install an aquastat to delay the domestic circulator from coming on right away and prematurely cooling down the water in the storage tank before the boiler produces hot water.
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