water heater

Discussion in 'HVAC Heating & Cooling' started by netmouse, Oct 4, 2013.

  1. netmouse

    netmouse Member

    Aug 7, 2012
    Along with prior post on converting a residential boiler from oil to natural gas, this is about the water heater - a standard 40 gal gas tank or indirect.

    I am trying to decide on a gas steam boiler and I'm down to Burnham's INS4 (or 5) or Peerless 63-03. I live alone and don't use much hot water.

    Are these lower efficiency boilers (about 82 to 83%) nowadays cold start for these specific brands? Meaning I would not heat the boiler water at all during summer if I choose a standard tank? Some say cold start risks problems in Fall start-up. But the KEEA energy website says: "Typically, the controls that reduce off-cycle losses function best with condensing boilers. But any boiler can benefit by being wired for “cold” starts, where no heat is maintained in the boiler unless there is a need for heat in the house. Ask an installer or technician about these options."

    Would it be true that the standard tank's lesser efficiency with some energy going up the chimney is not really an issue in my case as there is not a lot of cold water pouring in to heat up given that I don't use much hot water?

    Not sure how to compare fuel use comparing a std tank versus an indirect that heats and uses the boiler water to warm domestic water. Given I use so little hot water. I don't like the thought of firing up the boiler once or twice a day in summer, but I also don't like a rupturing std tank risk.

    If the gas standard tank costs about $1000 installed and is $1000 less than an indirect, I'm assuming I could buy two standard tanks instead of 1 indirect and get 12 years maybe, maybe it "evens out".

    This is the new Peerless Indirect (steam only).

    Thoughts appreciated on helping me sort this out - std tank or indirect.
  2. Dana

    Dana In the trades

    Jan 14, 2009
    For low volume use even cold-starting a 3-4 plate steam boiler isn't going to be any more efficient than a standalone tank during the summer months, but the net heating + hot water efficiency will be higher during the winter. Every time you fire up the boiler in summer you heat up it's entire thermal mass to well above domestic hot water temps, heat that then gets "abandoned" in the boiler, slowly dissipating into the basement. Just the ~400lbs of cast iron has the same amount of thermal mass as 40 gallons of water, and if you're only doing 1-2 burns per day your summertime efficiency will be under 30%: 18% of the source fuel energy goes up the flue during the burn, then 2/3 of the rest of the heat of the burn stays in the boiler rather than the indirect, and the boiler has a much higher standby loss than the indirect itself- it'll be pretty close to room temp after 10 hours. With heat purge control you might get it up to 35%, net efficiency by ending the burn early, and parking the boiler at about the same temp as the indirect rather than 20-40F hotter, but the thermal mass of the boiler is a drag on hot water heating efficiency when there isn't a heat load.

    At very low hot water use an electric tank water heater might have a lower overall annual operating cost. It's a more expensive heat source per BTU, but much lower standby loss than either the standalone gas fired tank or an indirect on a small cast iron steam boiler. The installed cost of the electric tank is comparatively low too- half to 2/3 that of a gas-fired tank, and WAY below that of an indirect. If you're a 25 gallons a day kind of user that's probably the right way to go.
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  4. netmouse

    netmouse Member

    Aug 7, 2012
    Thank you, Dana!

    So aside from the domestic hot water, are the two gas boilers INS4 or Peerless 63-03 considered cold start in the summer, my interpretation is that the water is room temperature unless there is a call for heat. Is that true? Or like my current oil boiler Weil McLean oil gold series, the boiler must be set to keep a temperature around 100 or, because it is a non-condensing boiler, and can have leak issues or problems when started in Fall heating? Someone said that with today's boilers there are steel fittings/nipples keeping the sections together so cold start is OK, but you still risk leaks.
    Last edited: Oct 4, 2013
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