pressure loss with spring check valve

Tom Noftle

Hot Rod thanks for responding. I'm using an on demand water heater for DHW and for a loop to a HX to heat my floor. I'm a carpenter not a boilermaker so these cv factors and pump curves make my head spin. I'll see if I can find the info you refer to, but, I'm not sure I'll know what to do with it once I have it.
Tom

Tom Noftle

how much will a spring check valve restrict the flow on a loop going to a flat plate heat exchanger? will a Grundfos UP15-18 pull the water thru it ok?

hot_rod

That data should be available

from the people that make the check valve. it's called the cv factor. The flow rate in GPM with a one psi drop.

Ideally you want the check on the discharge side of the circ. The 15-18 will also have a pump curve and the HX a pressure drop listing at various GPMs.

All these pieces of the puzzle will answer your question.

Is this a small DHW recirc flowing thru an isolation HX by chance?

hot rod

hot rod

hot_rod

The loop thru the on-demand

will need some serious pumping power. They usually have a fairly restrictive heat exchanger. I'd guess more like a 26-99 to move enough flow to get some of the capacity. i doubt that you will get the full capacity out of the heater with a "pumped flow." These units really aren't a good match for hydronic use. The small HX and low 80% efficiency, when firing, work against the initial "good price

Most of the manufacturers of those instantanous heaters have a flow chart available. What brand are you considering?

Glenn Sossin wrote a good post about this with a piping schematic back about 8/8/07 if you search the archives it may turn up.

hot rod