Noritz NCC199 for Radiant heat/ DHW

Sol Hydronics

I have a client that wants to use the noritz heater on his house. I know they make 2 models that are heating specific but the min btu is 55,000 and his house need less like 30,000. He also likes the stainless steel look and this is why I would like to use this product. I will use a flat plate heat exchange to seperate the 2 systems. I don't know why this would not work, do you? Thanks for any imfo you would like to share, Mike

meplumber

Short cycling might be a problem.

There are other manufacturers that make models with higher turn down ratios. With that big of a gap between minimum output and structural needs, you could have short cycling issues. Especially above design conditions.



A buffer tank is one solution.



Good Luck

Turbo Dave

NCC199 vs. NH150-DV

It sounds like what you would be installing would be a NH150-DV which is radiant heat specific. Some thoughts:



1) The NH150 is not stainless steel like the NCC199, it looks to only be available in white.

2) The NH150 must use Class B 4" venting.

3) It only has an 83% thermal efficiency rating and 55,000 BTU minimum firing rate as you said.

4) I just installed a combo  condensing unit for a radiant floor application. It has a minimum  fire rate of 17,000 BTUs, has a thermal efficiency of 90%, and as a condensing unit, can be vented with 3" PVC. Since it is a combo unit, it already has separation from domestic water to heating loop. It also has an outdoor reset and sensor, which combined with the lower firing rate should eliminate the possibility of short cycling. There are a few manufacturers of these type of units that would use less fuel and last longer due to less cycling.

5) Yes, I think your idea would also work.

Turbo Dave

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Jean-David Beyer

Short cycling. It depends.

I have a different brand mod-con from what you are considering. 80,000 BTU/hr max input, 16,000 BTU/hr min input. Smallest one available in the product line. I have a small house with double pane double hung windows, pretty good insulation, not too much leakage. 1150 square feet Cape Cod house in New Jersey. Design temp 14F.



Two zones; one about 6,500 BTU/hr heat loss. The other about 24,000 BTU/hr.  Until I diddled the control settings, I did get short cycling when only the small zone called for heat. Now I do not get too much short cycling when only the small zone is calling for heat, except in warmer weather. I would have been better off with a boiler half that size, but not available then.



What I had to do is increase the minimum water temperature to the zone up to 110F, change the gap between turn-on turn-off from +|- 5F default to +7|-8F, and reduce the maximum firing rate for that zone from 94% to 55%. For my boiler, the homeowner (me) can do this with buttons on the front of the boiler. If I needed tools, I would also have needed a combustion analyzer and training. YMMV.

RobG

Eternal Water Heater

What about an "Eternal" brand water heater. It's stainless steel and modulates down to 31,000 btu's. I've head good thing about them and since your planning on a flat plate HX you won't have any problems using it for space heat. It also has an internal storage to prevent the "cold sandwich" effect on domestic apps.

Just a thought

Rob