Radiator vents “breathing,” other oddities. Service plumber needs help!

Ambivalence_83

I’m a service plumber in an area with lots of steam heat and I can’t figure out what’s going on in my own house. 

House was oil with a cracked boiler *surprise!* I converted to gas. No idea if these issues were here previously. 

1. One first floor rad stays quiet during heating, then suddenly releases a huge loud rush of air out of the vent. 

2. One second floor rad vent “breathes” loudly. Blowing air, sucking air, and sometimes the huge hiss like above. Lasts a long time too. 

During all this, checked the boiler and saw the gauge at 4psi. 

The facts:

House built in 1922. 

An addition was added with a piece of steam baseboard. Has a steam trap on it. 

Properly sized brand new gas steam boiler (sized based on square feet of steam). 

All brand new vari-vents on all rads. 

Brand new Gorton #1 on the end of the main. 

All rads have pitch toward the valve. 

All valves fully open. 

Supplies to rads have proper pitch. 

Honeywell Pressuretrol set to .5psi with 1psi differential. 

Pigtail is not clogged. 

Return is not clogged. 

I’ve tried throttling the gas to reduce the firing rate, but it did not change anything. 

I’m stumped. 

Jamie Hall

irst comment would be -- is that pressure reading from the code 30 psi gauge? If so, it's dubious. If it's from a low pressure gauge -- there's a problem with the pressuretrol. Pigtail clogged? But you say you checked that. Or something amiss with the pressuretrol?

Panting vents are almost always due to water pooled somewhere in a pipe. I know you've checked that all the pipes have proper pitch, but is that end to end, or every inch? An older house may have had sags developed in the pipes which can trap a pool -- which may not hammer, but may give that panting behaviour.

One note -- don't fiddle with the firing rate unless you have, and know how to use, the test instruments for draught, excess air, oxygen, carbon dioxide, and carbon monoxide.

Ambivalence_83

I checked every bit of the line feeding the most troublesome of the radiators, which is the 2nd floor bedroom one. 

After more research, I’m beginning to think the 1” supply/return pipe (single pipe system) is too small for the size of this radiator, which is large for a room of its size. 

Based on other recommendations, I’m going to try a smaller vent to slow down the process and see if that helps. 

And adjusting the gas flow was just an experiment to see if it made any difference in the interest of narrowing down the possibilities. 

Jamie Hall

1"? One pipe steam? That is probably too small. The maximum EDR for a horizontal 1" pipe is 28.

If you don't have it, you really should have your own copy of "The Lost Art" (from this site) and make yourself into the local expert!

ChrisJ

Most of my radiators are piped using 1" vertical runs that go down into 1 1/4 horizontal.

We need pictures of the piping around the boiler as well as the gauge glass clearly showing the water.

Bonus points for pictures of the radiators and vents.

Jamie Hall

1" vertical will take, I think something like 48 without problems -- and now, I'm not going to find the table in Lost Art at this time of night.

DanHolohan

Why is that trap there?

Ambivalence_83

I’ll get photos tonight. 

And I’m not sure Dan. I didn’t alter any of the existing piping. 

Thanks all!

DanHolohan

If it's one-pipe steam and there's no boiler-feed pump that vent shouldn't be there. Check to see if the trap discharges into a wet return or the steam main.

Ambivalence_83

Another development is that there is a main vent at the end of the supply run. It was just hidden in a wall. 

I replaced it with a Gorton #1 and raised it up with a nip and coupling. 

It hasn’t made a huge difference in the problem radiators. 

The baseboard install looks sloppy and I’m betting it wasn’t done properly. The baseboard does have it’s own return line though. 

Gsmith

If you are sure you have adequate main vents, consider changing the radiator vents, which you said are vari-vents, and replacing them with slower vents or adjustable vents like vent-rite or Hoffman. The varivents are almost always too fast for radiators and can seriously unbalance the system

lowballj

I had panting, hissing, train whistle issues with one radiator myself. Hypothesis was the valve wasn't open all the way and was causing water + steam collision and pooling.
Had the valve replaced. No more issues

Ambivalence_83

Ok. Pictures of what’s going on. 

The radiator in question.

The boiler (forgive the Pro Press, I’ll be replacing it with black pipe).
The supplies for the first floor rad (quiet, then huge rush of air, 1 1/4”), 1” black pipe going to 2nd floor rad that “pants” and the 3/4” copper return for the baseboard with steam trap.
Supply to baseboard is 1 1/4”

Ambivalence_83

The picture of the three pipes is the first floor rad, second floor rad, and the return for the baseboard.
The pipes are pitched properly. Both break the bubble all the way to the main. 

The main vent is in the wall at the end of the main (pic with all the model airplanes). 

Ambivalence_83

Going to replace the vent and valve on the 2nd floor rad and see if that helps. 

JUGHNE

In the airplane room, the main on the left looks pretty flat.
Does it slope down away from the boiler draining towards the section of the main on the right?

DanHolohan

Why is the trap in that radiator?

Ambivalence_83

JUGHNE said:

In the airplane room, the main on the left looks pretty flat. Does it slope down away from the boiler draining towards the section of the main on the right?

It’s basically dead level. 

Ambivalence_83

DanHolohan said:

Why is the trap in that radiator?

Don’t know. I didn’t put it there. It’s on the return line of a 10’ piece of 1 1/4” steam baseboard. 

Should it not be there?

Jamie Hall

Ambivalence_83 said:

DanHolohan said:

Why is the trap in that radiator?

Don’t know. I didn’t put it there. It’s on the return line of a 10’ piece of 1 1/4” steam baseboard. 

Should it not be there?

If it's on a return line, and if that return goes, in fact, to a return, you do need it -- unless the return at that location is wet. In which case, you don't. However, there must be a way for air to get out, too. What is it?

DanHolohan

And if this is one-pipe steam and the trap is connected to a pipe above the waterline, it’s connect to the steam main. That can’t work. The there’s steam on both sides of the trap. 

Ambivalence_83

Jamie Hall said:

DanHolohan said:

Why is the trap in that radiator?

Don’t know. I didn’t put it there. It’s on the return line of a 10’ piece of 1 1/4” steam baseboard. 

Should it not be there?

If it's on a return line, and if that return goes, in fact, to a return, you do need it -- unless the return at that location is wet. In which case, you don't. However, there must be a way for air to get out, too. What is it?

It has a vent on the end of the baseboard, where the 3/4” copper line returns to the boiler. 

The baseboard isn’t the issue here though, as it does heat. It’s mildly noisy but not overly so. 

Ambivalence_83

DanHolohan said:

And if this is one-pipe steam and the trap is connected to a pipe above the waterline, it’s connect to the steam main. That can’t work. The there’s steam on both sides of the trap. 

I’ll try to take more pictures and label them. 

Every radiator in the house is single pipe. 

The baseboard supply comes off the supply right above the boiler (picture 3, first tee after the new copper).
The baseboard runs along this wall over an unconditioned crawl space.
It returns back into the basement in 3/4” copper, into the trap (picture 1) and returns to the boiler return at the lowest point (picture 3, 3/4” copper line with bend in it. Far left).