We're about to replace our radiant heating system. We are trying to decide between using a single Rinnai tankless heater to provide hot water for both the radiant system and also for bathrooms and kitchen vs. using a Rinnai for the bathroom/kitchen and a separate Quietside boiler for the radiant heat. Any opinions?
That sounds interesting, but I think I read somewhere that you don't want to be cooking or drinking with the water that goes through the radiant heat pipes. I don't remember the reasoning, but I think it was something to do with the closed loop system of Eichler's radiant heat system.
What I'm really interested in is the approx. cost for either option and if you see any savings in gas therms used. Thanks!
The radiant heat cannot be in the loop such that water in it comes in contact with the potable water for the house. There are a number of reasons for this.
However it is possible to have one boiler/heating unit that can heat both domestic hot water and the radiant heat. We had a Munchkin unit installed with a "indirectly fired" hot water heater. Basically the hot water heater is "fired" by a heat exchanger that carries water from the boiler.
I am unfamiliar with the brands and models of units you ask about so I can't comment on their suitability.
Tankless waterheaters are 80% efficient, Munchkin boilers are around 95% efficient.
If you want to go the boiler route, you need a hot water storage tank that has a heat exchanger coil inside of it. Munchkin boilers are made by Heat Transfer Products. They have a line of stainless steel tanks named Superstor Ultra.
In a nutshell, the boiler circulates hot water through a closed loop that provides heat to the radiant system and also the heat exchanger coil in hot water storage tank.
If you want to save space, check out the Phoenix water heater (also by Heat Transfer Products). It is basically a Munchkin boiler inside of a Superstor Ultra tank. It is one of the most efficient systems at something like 97%. Other manufacturers have similar products.
If you want to chat about high efficiency heating and/or solar thermal energy some time, give call me (650-327-3200). A couple of solar heat collector panels produce enough energy savings to achieve a 5 or 6 year pay back. Now that is efficient!
I'd like to find out more about your system.
1. What size storage tank did you use?
2. What are your domestic hot water demands? I.e., how many people taking showers. Do you run out of hot water after one shower? Two?
I'd appreciate discussing your choice with you. You can call me if you like at 650-380-4013.