Proper Tankless Coil Setup

Hilly · February 2017

1. Are Multi-Orifice Flow Control Valves (ie. Watts P3) required?
2. Should they be piped with 2 Shut-offs, 2 Tee's and 2 Dran-taps for future flushing?

I ask this question because I got a picture e-mailed to me stating they need the domestic copper on 'their furnance' replaced because they both leaked on the oil company doesn't service domestic side of boiler under service contract. They say there is pex at the ceiling and they'd like to tie back to that point.

So code around here - Canada, although nobody looks at heating in my province - says 3' of copper of the boiler. So I was going to put in the 2 Shut-offs, 2 Tee's and 2 Dran-taps and bring copper up to horizontal transition.

Question comes down to, do I put the P3 back in. Do I move it to the cold line, if so, where the manufacturer says it belongs. If I can omit it, there where exactly are these meant to be use, it is on really old coils that maybe had a different make-up and the flow needed to be controlled to keep up with the heat transfer? I just know if I leave it out, I will be asked why and I like to have answers. Also I e-mail NYI and they responded leave it out but with no explanation.

EBEBRATT-Ed · February 2017

Flow control is used so that you don't overdraw the coil. As far as I know it is not code required. (could be in your area??)

for instance most tankless coils are rated at 200 deg. F boiler water temp. Most of the time the boiler water isn't that hot.

so if we had a tankless rated at say 5gpm with 200 deg boiler water we would sometimes put a 3 gpm flow restrictor on it to make sure they didn't run out of HW.

Jamie Hall · February 2017

The question really is -- what is the temperature rise capability of the tankless coil at various flow rates? The purpose of the P3 is to limit the flow through the coil to something which will produce hot enough water. So you really need to know what the tankless coil can do.

Proper Tankless Coil Setup

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