steam/HX question

Bob Bona_4

I'm a little stumped on this one. Just finished an Everhot RH8 tankless running off a steam boiler for a HX to radiant.

On the boiler side: bronze 007 below the water line pumping into the RH8. Return comes out of the RH8 and goes right into the lowest point of the boiler. The simplest loop going, and the supply and return piping is only 4 feet of 3/4" copper.

Problem is, the 007 sounds like a can of marbles unless I gate down the inlet or the outlet side of the pump and restrict the flow. There is a temperature gage on the outlet side of the pump and it hasn't gone over 200 degrees.
I was thinking maybe the condensate is flashing to steam inside the pump from the volute's drop in pressure, but it is really stretching my imagination, since the condensate doesn't get near boiling. Pump seems hotter than normal, but then again, all the piping near it is darn hot too.

Client just called about a high pitched squeal. Gee, I wonder what it could be?:)

Any ideas?

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=167&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"</A>

Unknown

yup

All of the pump differential shows up negative at the inlet, because the PONPC is the boiler, at almost no pressure.

If you can build a boiler bypass, and throttle both the bypass, and the return to the boiler (provide some head on the outlet side of the pump) you can bring the inlet pressure up and the inlet temperature down to a point where the inlet pressure becomes positive again.

It's a pretty fine balancing act, with a low head loop.

Noel

Bob Bona_4

can you

sketch it for me Noel? I have Dan's stuff on doing a bypass for a straight heating loop off the condensate, and I did think bypass here too, but not sure how to pipe it..Thanks!

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"

Unknown

Use this sketch

http://www.heatinghelp.com/newsletter.cfm?Id=29

Use the bypass valve (mostly open) and the return-to-the boiler valve(mostly closed) to get a quiet circulation while steaming the other zone. Only open the valve through the boiler enough to get what heat you need for the Delta-T that you expect. The head on the pump outlet side becomes high enough that the inlet stays (barely) positive.

It takes some playing to get enough temperature and small enough Delta-T to heat the zone properly, quietly.

The 100 series had a flatter curve, so it made less difference as you adjusted the valves.

Noel