Boiler wont circulate without pump on[cavitation] Use too?

[ozzie88]

Here a old systom with one pump that use to circulate with pump off, now I add the dhw. tank and he says it wont circulate?/ I have 4 tanksin my systom and the water will move threw them all with pump off and check valve open I dont understand unless there is still air in the systom? With air this would stop it from moveing the water right?? There are no check valves or controles just the pump is on the inlet side of the boiler,hot comes out the top copper pipe in photo.
He has about 4 zones on this one pump but it did move water before?If i incress the presure in the systom to say 25lb, will this help get air out the bleeders? And run the pump one zone at a time.

 

[maple1]

Air can stop water from circulating, yes - even with the pump running. So could a heat trap (too much up & down too quick). Is it circulating anywhere without pump on (the other zones?), or not circulating anywhere at all?

 

[BoilerMan]

I think Maple hit it, air or heat traps as long as there are no flow checks in the system.

TS

 

[ozzie88]

Air can stop water from circulating, yes - even with the pump running. So could a heat trap (too much up & down too quick). Is it circulating anywhere without pump on (the other zones?), or not circulating anywhere at all?

Well, he says it is not circulating water anywhere? Said it did before,but he has no way to get rid of air in basement pipes,just upstairs on radiators. I thought of useing a saddle valve to put on pipe,poke hole in it,let air out then close up and cap, should work be alot easier than cutting thing apart to put air valve in,I knoe it not right but this is low budget operation. Like i said I have 4 tanks in loop and it moves water threw them?

 

[maple1]

If he has a way to get rid of the air upstairs on the rads (highest points in system?), he should be able to get things moving by bleeding there. Unless there is an up & down point somewere else in the system for an air pocket to get stuck at. Putting an air valve in should be cheap cheap to do, they don't cost that much - as long as there's a place to get at to put it in at. It'll pay for itself many times over if you can get it in the right place.

Has to be an air pocket if nothing is circulating - sounds like an air pocket in a main supply line if it's affecting everything. They can be real hard to get out without a decent low place to screw a garden hose on & decent high place to let the air out.

 

[ozzie88]

If he has a way to get rid of the air upstairs on the rads (highest points in system?), he should be able to get things moving by bleeding there. Unless there is an up & down point somewere else in the system for an air pocket to get stuck at. Putting an air valve in should be cheap cheap to do, they don't cost that much - as long as there's a place to get at to put it in at. It'll pay for itself many times over if you can get it in the right place.

Has to be an air pocket if nothing is circulating - sounds like an air pocket in a main supply line if it's affecting everything. They can be real hard to get out without a decent low place to screw a garden hose on & decent high place to let the air out.

There is one spot thats up&down where air will stay. that pipe that goes into the tank goes 30inch. down into it which is good spot for air to stay,,I got this brainstorm and it workd,I got a saddle valve [like on ref. ice line] clamped it on the 1 1/4inch pipe,screwed down poked hole into pipe and air came out,ran pump did this several times cleared it up. Water seems to be moveing now and I just caped off valve for future use, Not like a boiler man may have done it but it worked and wont hurt anything,