Tour of discovery

David Taylor

I have a 20 story building with a water circuit cooling tower/boiler set up for heat pumps through out the building the boilers,tower and pumps are on the penthouse.The system has a steel expansion tank with a sight glass.The top of the expansion tank is pipe to a floor drain thus the system is an open type.The building is 30 years old and has had flow problems for day one.My question is why would the expansion tank be vented to atmoshere?And what is lost if anything on pumping capability on an open system.

JimGPE_3

Clarifications?

Are you sure the pipe doesn't connect to a pressure relief valve which would make it a closed system?
What kind of cooling tower - closed circuit evaporator type?

I have never seen an open loop wshp system, so I don't know why this one would be open. Can't think of any good that could come of it.

Can't think of why an open system would pump any differently than a closed one. You still have the city water pressure doing the lifting to the roof, and since the flow is the same and the dynamic pressure loss (pressure drop due to flow) would be the same whether open or closed, it should pump the same.

That's a new one on me.

David Taylor

Yes the expansion tank is open,no a releif. The tower is a closed loop style.

Betz

not a pro but

it seems to me that if city water system is piped into this building it would run constantly since it's open and cannot build pressure, I'm probably missing something though.

David Taylor

water feed is a manual fill

Einsiedler_2

open vs closed - pumping

I believe the biggest diff in pumping an open vs closed system is...

on an open system, the STATIC PRESSURE must also be overcome by pump (in addition to frictional losses which must be considered in a closed system)

for a 20 story building, the pump has to be a monster.

please indicate; Boiler Size, Main Supply/Return Size & PUMP INFO.

correct me if I'm wrong, but if it's an open system, would it not be very corroded (sounds like a ferrous tank on an open system)

??

EIN

Einsiedler_2

open vs closed - pumping

opps

JimGPE_3

Nope.

Even if it is an open system, if it is a looped piping system the pump is only a circulator. If you are pumping to a cooling tower on the roof and the return line drains down when the pump is off THEN the pump has to lift the water. But in a loop the same static pressure exists on both sides of the pump. It is only a circulator, and the city water pressure actually lifts the water to the top of the loop during system fill.