Using a Rinnai Water Heater for Radiant

Waylon Lowery

I have a customer that is requesting that we use a Rinnai Water Heater instead of Boiler. I have done a bit of research and it seems like a viable option, but my gut instincts say that something just isn't right. My biggest concern and question is how long will these units last and are they really suitable for a heating system? Anyone have any history Rinnai and Radiant or Snowmelt?

Alan(CaliforniaRadiant)Forbes

Rinnai

We used one on a Berkeley hydronic system; radiators upstairs, radiant downstairs. The owners were attracted to the price for the Rinnai even though I explained that the running costs would be greater than if they used a high efficiency boiler, like the Munchkin.

You also have to use a high head pump to overcome the pressure drop of the heat exchanger; expensive to run that monster of a circulator.

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lchmb

ok....

I have used a Rinnia in one instance for a strickly radiant floor system. I had no problem overcoming the head pressure using a taco 008. The system was designed by an engineer who went through all spec's and has had no problem to my knowledge. It was conveniant in the fact you can set your water temp and did not need a mixing valve to accomplish this. Alan question for you sir? Was the large circulator needed for the radiant side or the radiator's upstairs?

Alan(CaliforniaRadiant)Forbes

Rinnai

We piped primary-secondary and used a 0013 pump because if you look at Rinnai's published "Hydronic Heating Pump Selection", they say:

"Rinnai recommends a circulator that can handle 6 gpm @ 30 foot of head".

That's one mondo pump.

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Jack_21

P/S & GPM x delta T X 500=BTU

What I have done with them is use a p/s system. Taht way you can use the 008 or equiv fro the Rinnaiand take the pressure drop off the main system. Then run what you want for your dist loops. For low btu they are fine...but I still like them best as a water heater. Have been doing a lot of commercial hw with them too

Unknown

Rinnai Continuum Training

Jack Frederick from Frederick Geraghty Inc will be on HVACTV.com on Tuesday night August 31 at 8:00 PM. Tune in and ask the man who knows any questions regarding this unit.

Jack_21

6gpm

You are correct in your flow curve info. Go to the tech info section of Rinnai.us for the actual curves. However, the mid-range on the flow curve will give you 4-5 gpm with a pump in the 008-009 range. I will not design a system using those very highest pump rates (6gpm). To damned big a pump. Also, Alan, be aware that you can read the actual GPM thru the unit on the key-pad. Push and hold the red button and then hit the green button. Release both and the unit will display the flow thru the Rinnai. Very nice feature. Every time I do this I think back to all the years I stood holding onto a pipe, feeling like a dope, wondereing what was going thru it.

Alan(CaliforniaRadiant)Forbes

Flow

Thanks, Jack; it may be a good idea for me to go back and change that pump.

Alan

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