What alternatives are there to a Hot Water Tank?

John Shea

Come springtime, I am planning to replace my current Weil-McLain steam boiler.

We have added an addition to the house and our current boiler doesn't have enough output, not to mention it's not getting any younger.

We will most likely be replacing our old (8 years) gas hot water heater as well.

Are there any combination-type solutions? Tankless-coil? what is it? any other alternatives?

Thanks

Ken_8

We really like...

The replacement W/M EG with tankless coil.

With the coil you can drive a separate HWBB zone, and indirect - and with adequate storage, you can fire the only 82% boiler on a timer - once a day (you figure out the time and length to make it happen for maybe two times on a day?

Three inch riser tappings, two of 'em! Talk about dry steam! Or do you have oil? If # 2 fuel, take everything I just said and chuck it.

Perhaps an extreme condensing boiler for the new addition - radiant maybe - and indirect at the best level of economy/efficiency short of solar!

Whattaya thinkin' now John?

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John Shea

Sounds great to me.

I'm pretty unfamiliar with tankless coils, but If it works the way I envision, it sounds like a good solution.

You couldn't ask for big riser tappings! They sound like they'd make GREAT steam!

The addition has already been piped for direct and is in operation. Old-fashion (ARCO) rads and all. If I'd have known there were so many options with steam I might have considered indirect.

Oh well, I'm very pleased with the way the addition heats (other than needing 30,000 or so more btus).

Currently running gas-fired W/M EG-45 (120,000 output).

Extreme condensing boiler?

I know just enough to be dangerous.

Thanks for the ideas, Ken. I've got a lot of reading & research to do now.

Constantin

Interesting Project...

Since you have the benefit of time, you could consider a number of options.

I am not a fan of tankless coils. Yes, they get the water hot quick but depending on the local water conditions, they may also scale quickly and require TRV's to prevent them from scalding you. If your water hardness is high, consider installing a water softener upstream of the coil.

Furthermore, in order for high-mass boilers like the EG to provide you with any sort of hot water in the summer time, the boiler has to remain "hot" all summer long. This is pretty inefficient and I doubt that even an EG (82% AFUE) will come out even when compared to a standard-efficiency gas water heater (60% EF) under such circumstances. Hence, I would consider the following:

Could your current steam system be converted to hot water? I know that the Steamheads of the world will howl in protest, but many steam systems have been successfully converted to hot water because the emitters in the rooms were sized for conditions where there was no insulation in the walls and weatherstripping consisted of pushing oakum into the largest gaps. In other words, your existing radiators may be big enough to still heat the rooms with just hot water instead of steam.

Of course, conversions are a lot easier with 2-pipe systems than 1-pipe systems... If you have a 1-pipe system, the additional trouble is probably not worth it and you simply live with it. Or, you could use the tankless coil on a loop into a indirect water heater and hence allow the steamer to cool down in periods of low-activity (i.e. summer).

So, the efficiency advocate in me would push for a hot water conversion to a modulating, condensing gas system. Such low mass boilers (Munchkin, Trinity, Ultra, Vitodens, etc.) will produce lots of domestic hot water via an indirect tank heater, achieve at least 20% annual fuel consumption reduction over any steam system with a tankless coil, etc. However, such solutions may be financially out of reach and perhaps will not pay back the investment with the rate of return that you expect.

I guess all I want to do is expand the universe of solutions that you are considering to include systems beside a boiler upgrade/swap.