Circulators and system pressure

Marty_11

For a standard low head circ, at what point in system pressure drop will it stop being able to circulate water.
I have been in many basic homes where the water feeder has malfunctioned, there is maby 5lb of boiler pressure and the zones are circulating fine. I was told that if the pressure drops to zero, the circs will not move any water. Can someone verify this and explain why.

Thanks,
Marty... 4yr rookie and trying to learn.

Geo_22

pressure

0 would mean theres no water above the circulator(no water no circulation) and 5psi what say theres about 11 1/2 feet of water above that boiler and probly why theres heat in a basic residential app.

Marty_11

Circs and pressure

Geo
So are you saying that if a 2 story home has a zone filled with water that the circ will move water even if the boiler pressure is at 0 due to pressure from gravity??

Marty

brucewo1b

Marty thibk of it as a staw

with your finger over the end the water is in the tube. Now put that tube flat fill with water and put it in a circle with a circ where the ends meet stand on end. The water is in a syphon but will circulate do to pressure difference at both ends of the pump. the same theory that allows you to heat a zone off of a steam boler with water.

Marty_11

circs and system pressure

> For a standard low head circ, at what point in

> system pressure drop will it stop being able to

> circulate water. I have been in many basic homes

> where the water feeder has malfunctioned, there

> is maby 5lb of boiler pressure and the zones are

> circulating fine. I was told that if the pressure

> drops to zero, the circs will not move any water.

> Can someone verify this and explain

> why.

>

> Thanks, Marty... 4yr rookie and trying

> to learn.



I think your lesson, i got it with steam boier, is that
the circ will move water even if the system pressure is 0 or near 0.?? Is that correct? I have never read, and I have many books, that if the system pressure is dropped to zero, that a circulator can not induce a pressure dif, and still circulate water. Whats the final answer???

Marty

Marty_11

circs and system pressure

I think your lesson, i got it with steam boier, is that
the circ will move water even if the system pressure is 0 or near 0.?? Is that correct? I have never read, and I have many books, that if the system pressure is dropped to zero, that a circulator can not induce a pressure dif, and still circulate water. Whats the final answer???

Marty

brucewo1b

Steam boiler is at zero pressure basically

and what goes up one side is cancelled out by the collum coming down the other side so it is still basicly zero in the loop at the circ unless its an openloop gravity system then the head preasure is related to the total height of the water. Most times by the time we get a call air has gotten into the system so then circulation stops.

EBEBRATT-Ed

Marty-

With any hot water system the fill pressure should be set to maintain 4 psi at the highest point in the system. This is the minimum pressure at the top of the system for any job residential or commercial. Most homes are set at 12 psi at the fill connection (usualy in the basement) which is determined by the setting of the city water pressure reducing valve. Expansion tanks are also pressureized to the same pressure.

This can be altered if necessary depending on the height of the building but the pressure setting of the feed valve and the pressure in the expansion tank should match. 12 psi is good for a buildin about 24 feet high (roughly 1psi=2' of head or height)


ED