On-demand water heaters for small heating loads-pros and cons?

Marc K.

Looking for some feedback about using on-demand water heaters for small heating loads.  This one is under 20,000 btu/hr (at design load). It seems like small, wall-hung, gas boilers are quite a bit pricier, and although I've heard of folks using on-demands, I'd like to hear from contractors' experiences. thanks

Ironman

Very Bad Idea

This subject comes regularly here and you can find several threads dealing with it that will give more particulars.



I'm not following your reasoning that because it's a smaller load (20K) how that would make it a better candidate for an on demand. On demand's are 100K and up. Mod/cons start at 50K with modulation down to 10K.



The simple answer is that they are not designed, built, controlled or approved for space heating. An on demand is designed with a high head H.X. and it's looking to have a 70* + delta T. It's designed and controlled that way.



A typical hydronic system is low head and usually designed for a 10 or 20* Delta T depending on application.



Gotta use the right tool for the job or you'll wind up paying for it the second time around when it could have been done right the first time.



Navien, Bosch, T.T. and others have combi units or heating only boilers that are low end priced that would be a much wiser choice. But either way, you get what you pay for.