Buderus GB142/24 for DHW + Heat

[Friolator]

We've had a Buderus GB142/24 installed for about 7-8 years now, strictly for heat. The apartment it heats is about 1200 sq. feet. The house has older blown-in insulation, and our windows are the original double hungs with aging storm windows (that is, drafty, but will eventually be replaced).

Our DHW heater is dying and we need to replace this. I'm wondering if it makes more sense for us to simply tap into the Buderus instead of buying a new freestanding heater, since it was designed for this. My question though, is whether the model we have, which was not purchased with hot water in mind, can deal with the additional load. There are two adults and one infant in the house, with one bathroom. We're not planning on any any more kids, and while we will eventually add a second bathroom on the third floor, that will get its own tankless hot water heater so it's not a factor.

I feel like it probably won't be a big deal to do this, because despite the draftiness of the house, we keep it at 68 when we're around and 60 when we're not. The heat isn't running constantly, even in the winter, so also heating up the water for a 40 or 50 gallon tank should be ok, right?

If it would work, which of their tank models would you recommend and why? We're looking for a long lifespan here, so if the indirect tank costs a bit more than a typical hot water heater but will last longer, we're willing to spend the extra. I've been here 12 years and this is already the second hot water heater we've replaced (third if you count our rental unit downstairs!).

Also, is it possible to use the GB142 for tankless hot water? If so, how does that work? Would we need to add anything to the system to make that happen?

Thanks!

 

[Jadnashua]

While an indirect is more expensive to buy, it is much more efficient to run than a stand-alone tank and will recover faster in most all cases unless you buy a commercial gas-fired one. Unless you have a commercial situation where you need monstrous amounts of hot water constantly during the day, you'll have no issues using the boiler to heat the tank. The normal way to hook it up is as a priority zone which means, when it needs hot water, it temporarily restricts all of the heat to the tank. I've had mine for over 10-years, and never noticed the house cooling off because it was heating the tank. This generally happens fairly quickly, and everything else then returns to 'normal'. Many of the indirects available have a lifetime warranty, so you'll probably never need to buy a new one. Verses electric or gas-fired, they don't tend to develop large buildups of mineral deposits either since the heating water isn't as hot as a burner or electric heating element.

Setting things up to use it as a tankless is not a good idea, and as far as I have seen, not supported in that model.