Mono-flo system - no heat to the 2nd floor radiators

gb98501_2

I have a single loop hot water system with mono-flo tees and baseboard radiators. The boiler is new in 2011, but the piping and radiators are from the 1950s. When I fired up the system this year, there was no heat from the radiators on the second floor. The boiler is in the basement of a two-story house. The radiators are spaced around the loop with 1st floor and 2nd floor units alternating, so it's not that the radiators at one end of the loop are cold. When I open the air bleeders on the 2nd floor units, I get nothing -- no spitting, no air sound. The boiler was serviced last week, and the boiler guy assured me the boiler and circulator are operating well and that the system is showing the right pressure. He opened the air valves and rattled the pipes like I do and then said I would need to get a plumber to look at the pipes and radiators. When the boiler was replaced they added a backflow prevention device, and that was tested a couple of months ago.

With all the 2nd floor units cold and no response from the bleeders, I wondered if the system is actually full of water, but I guess that could not be true if the system is showing the correct pressure. Any other suggestions would be much appreciated.

delta T

Can you tank a picture of the cirulator and near boiler piping? When you say you get nothing out of the upstairs radiator vents, I assume you mean that you do in fact get water out, but that no air is present, correct?

What is the boiler pressure at?

Ironman

Don't assume that your pressure gauge is accurate. Make sure the shut off valve on the fill line is open.

Monoflo systems are notoriously hard to purge of air. Once you know that you have at least 15 psi static on the system, try bleeding again with the pump off. You may get some air or just water out, but still be air bound. If that happens, try adding about 1/3 cup of Dawn dish washing liquid to the system. Of course, that will involve depressurizing it and removing the relief valve or the like to be able to pour the dawn into the boiler. Then repressurize it, bleed what air you can, and let it run.

gb98501_2

To clarify, when I open the bleeders on the upstairs radiators I get neither air nor water. The pressure gauge reads 6psi.

The fill line is open.

One other item: the backflow prevention device has been dripping more than usual since it was inspected in September.

Thanks.

Tinman

Your pressure is way too low.

Why did they install two backflow preventers?

Tinman

Unrelated to your current issue but the plastic pipe on the discharge of the relief is not a good idea. It should be steel or copper.

gb98501_2

An ill-informed question: how do I adjust the pressure?

As for backflow preventers, the fancy one on the left was added at the behest of the city inspector. I had assumed that replaced another one and didn't realize there are two.

Tinman

From the picture, it doesn't look like you have a fast fill feature. Looks like it's a Watts brand? There's a nut on top of the pressure reducing valve that you would loosen up a bit so the screw on top can be adjusted. Turning it CW will increase pressure, CCW will decrease. Adjust in very small increments and wait until the system comes up to it final pressure. 15# like Ironman suggested should do the trick and then some.

delta T

So, assuming your pressure gauge is right, you can only fill to 13' 10" above the fill valve, which would explain why you get absolutely nothing out of the upstairs vents, the water is just not that high yet. I am leery of a 'boiler tech' who did not see 6 psi pressure as a problem or seem to know how to deal with pipes? That throws a flag up that he said to get a plumber for that part. If you are uncomfortable changing the pressure, we can walk you through it, Stephen Minnich has laid out the process above. Or you can go to the 'find a contractor' link here and see if you can find someone near you who knows what they are doing.

And FWIW, your backflow preventers should not drip at all...(referring to your comment about how they are dripping 'more than usual')

gb98501_2

Well, you guys are just awesome. I easily bleed the air after raising the pressure to 15 psi. My second floor radiators are warming up nicely. Thank you so much for the guidance.

Solid_Fuel_Man

Not directly related to OP, but anyone know what type of grey vent that is? Gray like poly, but glued together like pvc.

Taylor

SWEI

That's CPVC pipe.

Solid_Fuel_Man

Wow, no suppliers carry that around here I always assumed cpvc vent was off-white like the smaller sizes for potable water.

Here in N Maine they are pretty lax on gas venting, everyone uses pvc or polypropylene around here, unless a specific manufacturer forbids it.

Taylor

SWEI

The off-white is FlowGuard Gold (or a clone) and comes in CTS sizes. Schedule 40/80 CPVC comes in IPS sizes and is usually gray.

Ironman

It also costs more than PPL around here and has a lower temperature rating. The only advantage being that you can cut a 10' length multiple times without loosing the socket.

SWEI

CPVC has some big disadvantages in my book. Solvent glue being the biggest, and thanks to that, no real ability to rework (without sacrificing fittings and making ugly.)

billtwocase

In regards to your relief valve, the drop should be copper or brass, and 12" off the floor. Steel can rust closed. It is to be non-ferrous, here in Mass anyway

SWEI

That's the one place where we do use FlowGuard Gold.