water flow stops,when bleeding system

frimi

Recently i replaced few items in my hydronic finned baseboard system,(as expansion tank, air vent valve, pressure relieve valve and rebuilt all inline valves),so system was drained out. Now I fill system with water and start to bleed air out of it.As usual I closed return valve to boiler,opened line drain valve and set water feeder to manual(full street pressure).In the beginning water goes down well,with air,then flow is slowing down and stops almost completely.I have to close drain valve,open returned water valve to boiler and set feed valve to auto .When pressure rises again,everything's repeating. No constant water flow. I have 2 loops upstairs,but only 1 circulating pump. There are no bleeders on baseboards.
Any suggestions ?
Thank You.

HVACNUT

Well water? If so it might take time to pressurize the wells expansion tank. At times I've bypassed the PRV and hooked up a hose directly from a cold water valve to the boiler drain valve.

frimi

No,not well water,just regular street main.

JUGHNE

PRV have a filter screen inside....could be plugged.

Are you watching the pressure gauge on the boiler while you do this?

frimi

the PRV i installed brand new.Yes,I'm watching pressure on the boiler.When it reaches 20-25 psi,I close return valve and open drain valve.Water goes down nice and almost stops,till next drainage.

CTOilHeat

"I have 2 loops upstairs,but only 1 circulating pump. There are no bleeders on baseboards."

Is it a zone valve system? If so are you opening each zone manually to allow flow to each of the 2 loops?

frimi

yes,exactly.

Solid_Fuel_Man

Sounds like you have a restriction somewhere in the fill system. Back check, PRV etc.

frimi

looks like water flow is limited by something in system after boiler.

HVACNUT

Just a thought. Did you flush out the water feed line before connecting to the BFP and PRV? There's often a nice wad of crust jammed in there if the domestic isn't filtered. Mmmm.
When you wrote "rebuilt all inline valves", explain please. Can you post some pics of the work?

frimi

I mean rebuilt,that's returned valves,drain valves,boiler drain valve: replaced packing and washers.Replaced boiler PRV,air vent,ET.

Jamie Hall

frimi said:

the PRV i installed brand new.Yes,I'm watching pressure on the boiler.When it reaches 20-25 psi,I close return valve and open drain valve.Water goes down nice and almost stops,till next drainage.

Ah... hold the phone here. Water will only flow if there is a pressure difference. So I'm a little confused. If the drain is open and the feed is open, water should flow -- even if there is a restriction, at least some flow should take place. How is pressurized water getting into your system when the drain is open? How is it finding its way to the drain?

frimi

That's what problem is.Drain valve is opened, feed valve is opened on manual (full pressure from street),but just a little bit of water 's coming out (i've been waiting for 10+ minutes)

neilc

maybe post some pictures,
one wide shot of the whole boiler area,
where you're draining,
the fill,
and the control valves to each zone,

Jamie Hall

frimi said:

That's what problem is.Drain valve is opened, feed valve is opened on manual (full pressure from street),but just a little bit of water 's coming out (i've been waiting for 10+ minutes)

OK. Something -- somewhere in your system -- is closed or nearly so. If it's not a stray valve somewhere, or a faulty pressure regulating valve on the feed line, first look for an overlooked valve. Don't assume anything!

And don't try to run the boiler or circulator until you find and fix the problem.

JUGHNE

Do you have any flow-check valves? They should open with full pressure. They have some sort of manual bypass.
One could be stuck shut.....just about never happens though.
Just some other component to consider.

Or you could be pushing water in the wrong way against them?

frimi

I can't push water in a wrong way,as I didn't change anything in piping,just serviced some valves.Before that everything worked as supposed to.

neilc

can you break a union after the feeder and confirm it does fast fill, or feed at all?

frimi

I have a pressure gauge installed in system,by the ET.When feeding valve is set on auto,the pressure stops at about 15 psi (my base boards on 3rd floor,boiler in the basement).When feeding valve is on manual(full street pressure),the gauge slowly goes up,and I start bleeding,when it reaches 25psi(less than 30psi,not to trigger PRV).That's why I assume the feeding valve works properly.

mattmia2

Did the innards of one of the valve you took apart and rebuilt stay inside and plug it up or maybe the new washer came loose and wedged in the seat?

Jamie Hall

frimi said:

I can't push water in a wrong way,as I didn't change anything in piping,just serviced some valves.Before that everything worked as supposed to.

Take them all apart and service them again. Something went wrong with one of them. General rule: if it worked before you worked on it, and doesn't work now, the problem is something you did when you worked on it.

frimi

i understand that,but why when I start bleeding water goes nice,full stream,after few seconds's slowing down and stops,almost. If that's something wrong with valves,then it would be right away,when start bleeding,not after say 30-40 seconds.

frimi

there are some pics I took from my system

mattmia2

Could be pressurizing air somewhere that is pushing out water that accumulated slowly or debris is flowing up against something and blocking it then settling somewhere when the pressure equalizes then it gets picked up and blocks something when the water flows again.

mattmia2

Might be a check that is integral to the circulator as well, so it might only pass in the direction of normal flow.

neilc

how about one picture showing all the parts in one shot

neilc

when your draining,
you have the fast fill engaged? full street pressure, correct?

HVACNUT

Are you purging one loop at a time? I'm asking because of the wye hose adapter.
Its possible the PRV is not set to 12 psi so even with the lever up, its still feeds slow. Have you tried adjusting the PRV?

frimi

Yes,full street pressure, one at a time.

neilc

well then what Jaimie said,
take it back apart and see where you did what wrong,
there's a valve blocked or closed there somewhere.

Alan Welch

When you said you replaced the prv, did you mean pressure reducing or relief valve? Also, when you purge, close both red handles on the return piping, and using a single hose , individually open the drains above , and see if the flow is good from either with 20 to 25 lbs pressure. If it isn't, open the red handle below and see if it improves.

HVACNUT

Like @Jamie Hall said, the problem lies in the work that was done. I would start with the "rebuilt all inline valves" part. Occam's Razor.

frimi

going away from home for 2 weeks; will continue,when back.

Intplm.

frimi said:

i understand that,but why when I start bleeding water goes nice,full stream,after few seconds's slowing down and stops,almost. If that's something wrong with valves,then it would be right away,when start bleeding,not after say 30-40 seconds.

Some debris is probably caught in the piping. When you bleed the system water "goes nice" as you say. Then after a few seconds it slows down and stops.

Possible debris is floating in the piping causing a obstruction while bleeding. It's time to take things apart and look.

frimi

I'm back and finally found the culprit. The pressure reducing valve,the only one I didn't touch had debris in inlet and let very little water to flow,even when on manual(street pressure).Still system shown high pressure,but when accumulating water was drained it stopped water flow almost completely(had to wait 5-10 minutes to fill system again).
Now I have another question : I bought new pressure reducing valve Watts model 1156F,which preset to 15 psi. Should I now precharge my expansion tank to 15 psi also,or to leave it to factory charge 12 psi ? Thanks everybody for help.

Intplm.

The pre charge and factory charge are nominal. In your case you can leave the two set pressures as they are.

neilc

Intplm. said:

. . . In your case you can leave the two set pressures as they are.

um,
you sure about this?
pretty sure the expansion tank should be set to match the 15# fill valve setting,
or we use up all that expansion on first fill,
pros chime in please, , ,

Intplm.

Um ? Thanks @neilc . Don't know where my head was.
For best performance, @frimi have the pressures match.

mattmia2

But you have to know how much water is in the tank when you set the charge pressure, right?

neilc

the tank must be either taken off the system, or isolated and drained to zero water pressure,
, , , so no water in the tank.

Intplm.

In other words. Set the pressure before you install the tank.