steamhead; that mysterious? circuit vacuum

Paul Fredricks_9

Yeah, I was looking at that pump too. I'd think it was over sized for that size loop. You'd have to calc out the loop to be sure and I can't quite tell what's hooked to it from the pics.

[Deleted User]

steamhead; that mysterious? circuit vacuum

finally, here are the pics of the system that i mentioned a month or so ago. two stories + basement and at 15psi when i came upon it/off season. and, after explaining the open supervents, tank logging, and repeated air in the system, esp the center circuit, i may have the customer convinced on a bladder tank. but here's the mystery, and the customer knew about it bec he's dealt with it; when that center circuit has it's pump on, and i try to bleed the baseboards of air, it sucks/vacuums air into the circuit. with the pump off and i bleed it, i get the typical air/water spurts. but i haven't tried bleeding that circuit in relation to the other pumps being on or off yet. the customer thinks that the piping for that circuit is backwards/vents on wrong side of baseboards. but as far as anyone knows, none of that has been changed over the years. only the boiler and pumps are new, and the center pump has had it's seals 'recently' replaced already

Steamhead (in transit)

I see the problem

you're not "Pumping Away"! Forget the hoary excuse that it's been like that for years. It's still wrong.

A circ pump moves the water by creating a difference in pressure- what engineers call delta-P and is generally written as ∆P. If the pump's ∆P is greater than the system's fill pressure at the vent location, it will go negative there and suck air when the vent is opened. Put a pressure/vacuum gauge there and you'll see what I mean.

I've actually seen this happen on my own system. One radiator used to get air-bound frequently. I was bleeding it once when the circ started, and the pressure behind the escaping air dropped sharply. No one could explain that until I found Dan's book "Pumping Away", which made it all crystal-clear. When I moved the circ to Pump Away, it solved the air problem. From that point, unless there was a serious obstacle to doing so, I have always Pumped Away.

Also, it looks like the air separators are just looped together, and the system takeoff is coming up from the boiler's built-in air separator. That needs to be fixed.

Here's what you need to do:

1. Repipe the supply lines from the boiler so one full-size tapping is used, unless that would seriously restrict the outgoing flow rate (doesn't look like that's the case though, if that's a Weil-McLain 80-series boiler it should have a 4-inch outlet tapping).

2. Run all outgoing water thru one full-size air separator, and make the connection to the expansion tank at the separator. This becomes the point we "Pump Away" from.

3. What I would do next, is create a simple "Primary Loop" with its own pump, that loops back into the boiler's return. All the zones (secondary loops) would be fed from this loop. If the primary pump is sized to move at least 1-1/2 times the flow in all the zones put together, some warmed water will return to the boiler and help prevent flue gas condensation (you could augment this with a boiler-protection setting in an outdoor-reset control). The primary pump would pump away from the air separator, out toward the system, and would run whenever any zone called for heat.

4. Each zone pump would be mounted on the supply side of the zone, pumping away from the boiler.

5. Watch how much better it works!

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

[Deleted User]

yeah, if i had my druthers,

i'druther re-do it all and pump away, but i don't think they'll go that far

yes, it's an 80, and the separators are looped together in 2" with the 3 circuits coming off of the loop, but i'm missing a pic that would clearly show it. the returns are 4". and that 'parallel' circuit on the front is the supply/tank loop, with for now, the tank is shut off from the system via the b-valve. but why does it 'vacuum' only on that one circuit? and it's not very clear, but the other two circuits have 'double' returns to tees into their respective pumps, while the center circuit has one return, and i'm clueless about that. the center circuit may have had a double return, and barely visible in the pic is what may have been it's other return. i'll see about getting more/detailed pics this week. thanks

Steamhead (in transit)

Which circulator

handles the zone you're having trouble with? If it's the big 2-inch one, that circ can produce a ΔP of about 4 PSI. If the fill pressure at the vents is marginal, that can be enough. Try my gauge suggestion to be sure.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

[Deleted User]

jpeg.5

the center 3/4-1"

Steamhead (in transit)

Depending on which PL pump that is

it might produce a ∆P of as much as 14 PSI. See how this could cause a problem?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

[Deleted User]

14?!

sure do see how. i'll get the model/serial #s

[Deleted User]

more pics and pump info

i found 2 more leaks after letting the pumps run for approx a week, and i've lost 8psi

#2 pump is a PL36/1BL001/K99. the 1-1/2" is an HUL40,the 2" is an H40

calculate that circuit's specs? wooo, that wouldn't be easy. but a ballpark might be doable

and i'm wondering if there's a simple?, 'creative' way to re-pipe the tank so that the pumps is pumping away

and according to another in the know, with the old boiler, they bled yearly at the beginning of the heating season. and since the install, circuit #2 is being bled 2-3 times a week. but so far, only one of the two new leaks is in C2, and it's very small/ant spit. whereas, C3/2", has two decent leaks. the front supply, top of the section/ reducer/union has a very bad leak and very poor access

and, if i can locate them, i may be able to quiz the installer/s about their piping decisions

looking forward to your comments. i want to raise the pressure to 28psi, leave #2 on, and see if it causes vac when bled

Steamhead (in transit)

That would be interesting

but if the boiler has the usual 30-pound safety valve, you'd be pretty close to making it blow......I'd do this with the boiler and system COLD for safety.

The simplest way would be to check the zone piping sizes and see if only one riser from the boiler is enough to feed them. If so, you can take out the second riser and cap its connections. Then the air separator on the remaining one would be your Point of No Pressure Change that you Pump Away from. Connect your tank to this point.

Locate your circs in the horizontals where the flow-checks are. If you can find wet-rotor circs that will pump the needed amounts, use them as they don't need to be oiled.

This won't provide any control over returning water temperature at the boiler though.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

[Deleted User]

paul and steamy - 30# safety

yeah, that's what it has, and i had run the pressure up to 25ish last week. and this week, it dropped 8#. i'll run down there today for a few minutes in-between jobs to get an idea about the piping size and run for that circuit. and i don't know if you can make it out, but behind that center pump, there's another same size line that's teed off but capped, and i don't know it's history

but as a 'simple' fix for simplicity's sake; without installing wet circs, if i were to leave the supervents in place, take advantage of their 1/2" bottom taps, tie them together and run that line into the current tank, or preferably a new bladder tank, wouldn't that equate to pumping away from the ponpc?

Steamhead (in transit)

No

because then you would have two PONPC locations in the system piping. There needs to be only one for it to work right.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

[Deleted User]

ah

i ran out of time yesterday and today, so i didn't get to roll by there to get a better 'picture'/total feets on the piping for that center circuit. but i'll be driving right by there tomorrow so........

i was guessing that parallel teed together would count as one. and, i found out who did the install on the boiler, and i might give him a call tonight, of course without being critical, as to his reasons. esp for that mystery pipe to nowhere under the center pump

but 1st and formost, we have to fix the 4 leaks and keep those vents closed, if not removed