Shoulder Season Issues (Increased Pressure, Rattling Radiator)

NY2024 · April 9

Hi everyone,

During this year’s heating season (January & February 2025), I got the one-pipe steam system working pretty well on our newly purchased house in New York's suburbs (with a lot of help from the members here). The system was operating at pretty low pressure (generally just a few ounces of pressure to 1 PSI max) and heating the house relatively evenly. During Jan/Feb, I insulated all of the near-boiler piping and the 40 ft. main in the basement with 1 inch fiberglass insulation. I replaced all the valves on the radiators with new Maid-o-Mist valves and adjusted them using extra orifices I bought till the system was relatively balanced. I also swapped out the very small Gorton No. 4 which was on the main when we bought the house for a much, much larger Gorton No. 2.

This shoulder season (and particularly very recently), the system hasn’t been working as well. Although it doesn’t cut out on pressure (set at 1.5 PSI) the system operates at a near constant 1.25 - 1.4 PSI. I can tell that the radiators/boiler don't like this. One radiator in particular, on the 1st floor, sounds kind of like a dishwasher when it's running, with condensate swishing around in there. It rattles and bangs too. During the heating season I had a #6 orifice on this one. I just swapped it for a #4. This has helped slightly, slowing the steam uptake on that radiator and I believe helping to redistribute some of the steam more evenly up to other radiators along a nearby riser. However, I can still hear the condensate swishing around, the radiator rattling and the radiator valve hissing too much (though the banging stopped).

The valves on certain other radiators are hissing and whooshing much louder too, whereas when the system was operating at lower pressure it was a very pleasant, steady venting sound coming from them.

The boiler itself is definitely oversized for the EDR of the house. Is it possible that this is showing itself more now during the shoulder season than during the prime heating season?

The EDR of the 10 radiators in the house is 302 sq. ft. (i.e., 72,480 BTU/HR). The Burnham steam boiler (model number SIN6LNC-LE2) has a net EDR of 450 sq. ft. (i.e., 108,000 BTU/HR). So, the boiler is appx. 49% oversized by my estimation.

Any ideas about how to solve this so that the system operates at lower pressure again for the shoulder season and can get rid of the whooshing, hissing valves and rattling in that one particular radiator.

Should I decrease the orifice sizes of the radiators closest to the boiler and increase the orifice sizes in the radiators higher up in the house to draw more steam to the higher floors quicker to relieve pressure on those radiators closest to the boiler (which are the ones hissing and rattling)? Is this likely related to the boiler being oversized? Perhaps having insulated all the near boiler piping and the full main (as well as the exposed portions of all the risers) in the basement has made the oversized boiler even more prominent an issue.

Please let me know your thoughts. Thank you very much!!

Hap_Hazzard · April 9

How much temperature swing is your thermostat allowing? Try setting it to the minimum possible and see if things improve.

dabrakeman · April 9

The only real difference between the colder months and shoulder season is that likely cycles are spaced out significantly farther apart so piping would be generally completely cold at start of cycle as opposed to warm. This requires more steam and thus more condensate production to get steam out to the radiators. Given your described symptoms you obviously want to make sure your new Gorton #2 is still functioning but more likely the higher amount of condensate is causing problem. It would seem it would only cause problems if the condensate is building up in the supply piping somewhere restricting steam flow so I would reexamine your mains and takeoffs for problems with pitch or sags. I too live with a similarly oversized boiler. First cycle of my recovery is the only time I ever really hear any occasional light hammer so probably for the same reason. Others here will probably be able to provide more insight.

ethicalpaul · April 9

If you hear sloshing in a radiator, regardless of the main vent, regardless of the radiator vent, then either your boiler is surging, or there is a sag in the supply pipe to some radiator that is collecting water. Is the sound only at a single radiator? What happens to your water level during a call for heat?

How much temperature swing is your thermostat allowing? Try setting it to the minimum possible and see if things improve.

Respectfully, I don't see the relevance of the thermostat here.

This requires more steam and thus more condensate production to get steam out to the radiators.

Respectfully, this is mistaken thinking. The boiler produces X amount of steam, and Y amount of condensate regardless of whether it's the shoulder season, and regardless of the size of the main vent.

I would reexamine your mains and takeoffs for problems with pitch or sags.

^^^^ this I can get behind

dabrakeman · April 9

@ethicalpaul perhaps you misread my point as I think you know a cold system does indeed run longer to get x amount of heat to the radiators than a warm one even after producing steam and thus it does indeed produce more condensate. This is just due to the delta T of the piping.

Jamie Hall · April 9

@ethicalpaul and @dabrakeman — you're both right. Starting from cold will produce more condensate — in the mains and runouts — than starting from warm. Not, however, in the radiators (usually — although very long off periods will result in the radiators being cold, too). After all that, the difference isn't that much — but it's enough that you may get pooling or even slight water hammer on a cold start which you wouldn't get on a warm start.

Hap_Hazzard · April 9

I think @dabrakeman and I are looking at the same issue. In the spring and fall, the off cycles are longer; thus, issues relating to temperature swing become more apparent. The greater the swing, the longer the off cycles, and the pipes and radiators don't retain much heat between cycles. It's perfectly easy to test this hypothesis. Adjusting the swing doesn't cost you anything.

NY2024 · April 9

Thank you guys. By adjusting the swing, do you mean changing the 'heating cycle rate' on my White & Rodgers Series 80 Thermostat from SL (Slow) (which I currently have it set to) to FA (Fast)? See excerpt from the thermostat manual below:

"Select FA or SL (Fast or Slow) Heating Cycle Rate - The FA setting is frequently used for gas, oil or electric heat. The SL setting produces a longer heating cycle which is normally for hot water or steam (hydronic) systems. Both settings produce very accurate temperature control and can be set to your personal preference. FA cycles the system just under 1°F and the SL setting cycles at approximately 1.5°F."

In response to some of your other questions: (i) Yes, the Gorton # 2 on the main is still working; and (ii) I believe the condensate is building up somewhere in the system as generally at the start of the cycle now, the boiler cuts off on low water one time (which wasn't happening during the prime heating season). I think the condensate is getting stuck out in the system during the early part of the cycle.

Hap_Hazzard · April 9

@NY2024 Yes. Set it as fast as possible. I've found this works best for steam. If it doesn't help you can always change it back.

delcrossv · April 9

https://forum.heatinghelp.com/discussion/comment/1851711#Comment_1851711

By adjusting the swing, do you mean changing the 'heating cycle rate' on my White & Rodgers Series 80 Thermostat from SL (Slow) (which I currently have it set to) to FA (Fast)?

Yes. If your stat had cycles per hour, I'd recommend going from 1 cph to 2.

in your case, I'd try switching from slow to fast . You'll get more firings but things won't cool down as much.

FWIW, one of the one pipe systems I service is happiest at 2 cph.

ethicalpaul · April 9

I think if changing the swing affects anything during the shoulder seasons (if), that's not really a solution of anything

delcrossv · April 9

https://forum.heatinghelp.com/discussion/comment/1851718#Comment_1851718

Depends on what your solving. This is "treating symptoms ", where a major repitching job would be "treating causes".

A running all winter coal fire was a lot more forgiving of dubious piping than gas or oil is.

NY2024 · April 9

Thank you! I'll let you know how things turn out after I adjust the swing later this afternoon. My guess is that it will help some. Right now, in the shoulder season, if I set the temp at 68, the thermostat often overshoots 2 degrees to 70. Hopefully adjusting the swing will run the system for less time, avoiding some of the pressure build towards the end of the cycle and the temp overshoot.

Also, to be clear, this was not an issue at all during the heating season. This is purely something that cropped up just recently. I'm hesitant to believe that there is a major pitch issue, as this problem wasn't occurring during the heating season.

Will keep you posted!

dennis53 · April 9

On the problem radiator, could the valve disc have fallen off the stem, allowing steam in but trapping water?

Any new piping installed lately? A good skim might reduce your higher-than-normal pressure.

Good luck,

Dennis

ethicalpaul · April 9

This is purely something that cropped up just recently. I'm hesitant to believe that there is a major pitch issue, as this problem wasn't occurring during the heating season.

I hear you but I reiterate that if you are hearing sloshing in a radiator, SOMETHING is wrong other than it being Spring.

Steamhead · April 9

https://forum.heatinghelp.com/discussion/comment/1851732#Comment_1851732

I'll bet the valve disc came off- this is not uncommon. If you disconnect the radiator you should be able to see this- if the disc is lying on the seat, replace the valve.

Hap_Hazzard · April 9

https://forum.heatinghelp.com/discussion/comment/1851749#Comment_1851749

I'll take that bet. What are we playing for? 😉

mattmia2 · April 10

https://forum.heatinghelp.com/discussion/comment/1851749#Comment_1851749

or the vale just isn't fully open or closed

Shoulder Season Issues (Increased Pressure, Rattling Radiator)

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