'vacuum' in a circuit

[Deleted User]

so, i get the question/call as to the reason why a customer is having to bleed a circuit 2-3x per week. my answer - leak/s. great! now go find it/them. so, it's off to the customer's boiler room

older, pumping 'to' operation. system/pumps off of course, and sure enough, mineral deposits from various
'dry' leaks, and one wet leak. boiler gauge says 12psi, tank water-logged/near full sight glass, and one supervent has it's cap loose. things seem obvious, but here's what threw me; the problem circuit/room 216. for the heck of it, i open the finned baseboard bleeder and hear hissing but it goes on for too long with no water coming out. so i grab a piece of handy floor lint, put it near the hole, and it gets sucked in. twice. vacuum?!

so, when i opened the vent/'took my finger off of the top of the straw', where would enough water be going in order to create a vacuum? full tank, full system?, 12psi. the wet leak that i found wasn't leaking THAT bad. defective flow check/s? 'large' area of empty section of system?

spoke with customer, and next week is wire brush all the obvious leaks clean, up the pressure/bleed all circuits, and wait and see if leak/s appear

Steamhead (in transit)

First of all

how many stories in that building? If more than two, you need more than 12 PSI.

Second- you mentioned a Supervent with a loose cap and an expansion tank with a sight glass in the same sentence. This is wrong. Your tank is a plain steel one without a diaphragm, which in itself isn't bad, but it needs some method of routing system air into the tank. If the Supervent is the automatic vent I think it is, it routes the air out of the system rather than back to the tank. So the tank waterlogs.

Does the system have an air separator? If not, install one, and either run the line to the tank off of the separator or replace the tank with a diaphragm type that will keep the tank's air cushion from working its way back into the system.

Some of us like to replace all non-diaphragm tanks with diaphragm types, but I find that a properly-piped plain tank won't waterlog or create air accumulations in the system.

And Pumping Away is a must!

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jimmac

tank with a sight glass, you sure it is a closed system ?
how many pipes come out of the tank? just asking

[Deleted User]

hey steam

2 stories, and the supers are honeywell products and they're out in the system/not routing it back to the tank. and yes, the tank may be misplaced and without a separator. but i don't think i'll be able to talk them into a diaphragm. but if so, i'll work it into pumping away

[Deleted User]

one pipe, if i'm remembering it correctly

and yes, closed, unless i missed it's vent up in the rafters. pics will be taken and posted

Steamhead (in transit)

Don't need a new tank

replace the supervents with manual vents, install an air separator with a 3/4" (preferable) or 1/2" tapping in the top that can be piped up to the tank, and an Airtrol fitting on the tank. Then Pump Away and watch your troubles disappear.

B&G makes a microbubble-type separator with a 3/4" tapping on the top. Not cheap, but it works great!

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jimmac

the tank is in the rafters?meaning the attic ?

[Deleted User]

no attic

i meant floor joists

[Deleted User]

yeah, the b&g

there's one on another system that we maintain. and since this tank is reletively new, they probably will want us to make it work instead of replacing it