Should we use new steam boiler for hot water heating?

New Hampshire DIYer

We will shortly be replacing a leaking, gas-fired Weil-McLain EG-75 steamer, probably with a SlantFin Intrepid TR-40 (thanks to all the detailed comments and opinions here). The old unit is oversized for our old, 3000 sq ft house due to insulation, storm-windows, and various renovations over time that reduced the space heated by steam to roughly 2300 sq ft. When we replace the boiler, would it be more efficient long-term to also change the DHW setup? We currently have a stand-alone, 40 gal, nat gas fired tank-type hot water heater that sometimes can't keep up with hot water demands, especially because our house also has a separate, 1 bdrm apt over our attached garage, served by the same HW heater. This happens mostly in the winter because the temp of the incoming water from the city pipes is significantly colder (I'm in New Hampshire). Not sure it's relevant, but tenant has separately-metered, gas-fired hot water boiler. Related question: if we put the tenant on her own water heater, would that change our decision? I'm trying to think ahead here. The current unit is fine right now, but when water heaters fail, it's alwys an emergency so we homeowners have to throw in whatever basic unit the local supply house stocks instead of getting of the most efficient for the LT.

SWEI

You might consider two indirects

one for each boiler.  That would separate the two gas bills while providing more hot water for each unit and (if properly installed and maintained) should have several times the lifespan of a typical tank heater.

icesailor

EDR's:

Is the existing radiator load measurement 585 EDR? Or is that what you think you need because of the reduced heat loss in the building due to improvements?

Those old dead guys were usually so tight that they creaked when they walked. They spent someone else's money like it was their own, they didn't.  I'm just wondering why they put a more expensive 750 Sq. Ft boiler where a smaller and cheaper one would have done. It is said that unexpected things can happen when you fire a smaller steam boiler into a system that needs a bigger one.

Just asking.

BobC

It depends

Could you boost the temperature of that tank and stretch the supply of hot water in the winter? Make sure you install a mixing valve on it's output to limit the temperature of the hot water that is delivered to the taps.



While an indirect is more efficient, would it make sense to have one for a single occupancy apartment? My 40 gal stand alone gas hot water heater only uses about 5 therms a month in the non heating months and that costs me about $17 a month, it is going to take a very long time to recoup the cost of an indirect (on energy savings alone).



If you use a lot of hot water I would consider installing an indirect but make sure you know the costs. For the apartment I'd just install a stand alone gas hot water heater (10 year tank) and I'd replace the anode rod every 3 years to extend it's life.



Bob

New Hampshire DIYer

585 EDR is correct

That's the current radiation. Over the years (and before my time), radiators were removed from the kitchen/DR (now heated w gas "woodstove'), large upstairs bath (toekick elec heater), and part of the apartment space (FHW)--a total of over 800 sq ft.



I know it's not particularly relevant, but using the Weil McLain heat loss calculator available on their website, I figured that my actual heat loss for the space still heated by steam is around 80,000 btu/hr. Even if I bump that up by 25% to compensate for old house inefficiencies, my radiation is oversized for the space. 585 EDR x 240 = 140,500 btu/hr right?

New Hampshire DIYer

Thinking ahead

I guess the point of my original question is this: someday the existing HW tank will fail. Would it be better (in terms of life-cycle costs) to replace it with an indirect off the Intrepid steam boiler or get a newer, efficient stand-alone tank heater? I'm thinking of this now because if I'm doing an indirect eventually, wouldn't it make sense to order the pieces now while I'm ordering the boiler?

jumper

segregation forever

Unless you don't have the room go with direct fired DHW. Install water meters and you'll learn why water heater can't keep up. If you flush a tank water heater annually it can last a long time.