I think it's a flow issue

Mark Eatherton

It could be MANY things, but if you have a static fill of 16 and a running pressure of zero, it indicates that your pumps are pumping towards the expansion tank, which is probably connected to the boiler. Move the pumps so they are pumping away from the expansion tank and the boiler and the pumps will generate POSITIVE pressure instead of negative pressure.

You could also have parallel pumps which are staged, and if there is no check valve on the outlets of the pumps, the water is short circuiting. If both pumps run at the same time, then checks are not needed.

Got pictures?

ME

John Pipkorn

help with a flow issue

I need some help. I was called in to look at a problem in an apartment building with hydronic heat. They have consistently had problems with two apartments on the end of the building. The system consists of one boiler with two circulators on the return. The supplies split off just outside the boiler room and basically handle each half of the building. The system is fin-tube with motorized zone valves for each apartment. They had someone from a local supply house come out and tell them that the pumps were too small and got them to buy two new B&G circulators, no word from them when that didn't work. The building is two floors with parking in the basement. All the valves are in the basement and the two apartments they are having problems with are on the first floor. I ran water through the two apartment baseboards to make sure there were no restrictions. When I put a pressure gauge on several places in the building, I read static pressure, around 16#, when we turn on the circulator that pressure drops to 0#. If I check the other half of the system the pressure only varies a little when the circulator starts up. I think I have a flow issue, but I am not sure where to look from here. Sorry for the long post, but this one really has me stumped.

Thanks, John

John_56

Thanks

I understand that the pumps should be on the supply, but the thing that confusing me is that on the one half of the system I don't see the drop to 0# and everything is working fine on that side. The pumps are for each half the building. No I don't have any pictures at this time, sorry.
John

World Plumber

Direction

Are all your pumps pumping in the same direction? I have seen that cause a problem. Had a zone that would get warm but not keep up with the rest of the building. Found that pump pumping back to the manifold while all the others were pumping away.

John_56

Only two circulators

There are only two circulators, one for each half of the building, both on the return. I know that's not the best, but it is what it is and the other half of the building is working fine.
John