Hissing Post Cycle

TroubleinNY

Hi. I’m having issues balancing my one pipe system. I’ve pretty much got every radiator to heat at the same time. That said the radiators are hissing immediately after the boiler finishes the heat cycle. Could the issue be not enough venting on the main? Could it be a nozzle sizing issue? The nozzle size was just increased b/c I wasn’t getting steam to an old extension that was don’t in the house. On the main going to that room I have 3 Hoffman 75’s which seems to have cured that issue. But I dropped the other two mains down to 1 Gorton #1 on each. Pressure set to .5 cut in and 1.5 cut out. Should I vent the mains with the gortons more and/or have the nozzle returned to the original size?

TroubleinNY

Sorry forgot to mention the only rads hissing post cycle are the ones upstairs at the end of the 2 mains I downgraded to the Gorton #1’s. 

JUGHNE

The hissing is probably air going back into the system.
The more venting in the basement would put the hissing down there, IMO.

TroubleinNY

Thank you. So should I leave the nozzle increase alone? 

Jamie Hall

TroubleinNY said:

Thank you. So should I leave the nozzle increase alone? 

Yes. If you've got the radiators balanced, leave them be! Also, since you've got it balanced, leave the end of main main vents be.

However, to control the hissing at the end of the cycle, if you have a handy spot very near the boiler try putting a vent there on a longish nipple (to keep it cooler). That may open faster, and break the vacuum rom the slower opening vents in the rest of the system.

May not, too.

JUGHNE

I would increase the venting on the main with the hissing rads.
Most of the cases here have overfired boilers, causing short cycling of the burners. You have increased your firing rate. Shorter cycles may cause increased air venting and hissing of air reentering the system.

Without an EDR study of radiation and boiler EDR comparison it hard to judge the nozzle size.

TroubleinNY

JUGHNE said:

I would increase the venting on the main with the hissing rads. Most of the cases here have overfired boilers, causing short cycling of the burners. You have increased your firing rate. Shorter cycles may cause increased air venting and hissing of air reentering the system. Without an EDR study of radiation and boiler EDR comparison it hard to judge the nozzle size.

Thank you! I’ll try the main vents first since that would seem the path of least resistance.  As for the EDR, I’m embarrassed to say I don’t know how to calculate. It’s a new boiler recently installed which threw off my balancing. What I do know is that it’s a peerless EC-3 with 446 sqft of steam. The radiators were calculated to 416 sqft. I was considering putting a radiator back where the prior owner removed it so we went with the 446. The installer was well qualified and is on this forum often. He said his posting name is RonJr. Can you tell me what nozzle size it should be or so you need more specifics?

JUGHNE

IDK much about oil.....plenty here do though.

TroubleinNY

I also just noticed that during the heat cycle when the heat reaches upstairs there sounds like what is water sloshing / gurgling in the rads. No banging of any kind. This started when the balancing adjustments were made. Could that be a main venting issue? 

TroubleinNY

Ps I checked and all rads are pitched towards the pipe not the vent. Single pipe system. 

neilc

TroubleinNY said:

said the radiators are hissing immediately after the boiler finishes the heat cycle.

like Jamie said, a large vent next to the boiler that can let air back in, or a vacuum breaker there,
don't change your nozzle size or you go back to not making enough heat for those far reaches

TroubleinNY

neilc said:

said the radiators are hissing immediately after the boiler finishes the heat cycle.

like Jamie said, a large vent next to the boiler that can let air back in, or a vacuum breaker there, don't change your nozzle size or you go back to not making enough heat for those far reaches

Thank you. So would that be on one of the mains close to the boiler? Or on the wet return? 

Ps44

Just wondering if it the hissing are the vents or the radiator. I ask because one of my radiators was hissing and noticed that the vent was closed so suspect that the radiator has a small leak somewhere (possibly confirmed by a small amount of water below), thus the continued hissing. Radiator is very beautiful, just restored but old.

Jamie Hall

TroubleinNY said:

neilc said:

TroubleinNY said:

said the radiators are hissing immediately after the boiler finishes the heat cycle.

like Jamie said, a large vent next to the boiler that can let air back in, or a vacuum breaker there,
don't change your nozzle size or you go back to not making enough heat for those far reaches

Thank you. So would that be on one of the mains close to the boiler? Or on the wet return? 

On the main. If the wet return is really wet, the vent will never open (unless it is a BigMouth, in which case you will lose all your water...) since it has a float.

JUGHNE

(Has no float)

Jamie Hall

JUGHNE said:

(Has no float)

Yeah. My English was confusing. The BigMouth has no float. Most other vents do have a float.

TroubleinNY

Jamie Hall said:

(Has no float)

Yeah. My English was confusing. The BigMouth has no float. Most other vents do have a float.

Thank you!! I appreciate it. Do you think this will help with the gurgling in the 2 upstairs rads? They’re pitched using a level. Ever since I dropped the main vents they gurgle. Very odd. 

neilc

what do you mean by "Ever since I dropped the main vents " ?

gurgleing sounds more like a supply valve not completely open, or its disc dropped and is holding back condensation,
or could be supply piping level or sagging under the floor?
can the supply side of the rad(s) lift up at all?

post a picture of the rad

TroubleinNY

neilc said:

what do you mean by "Ever since I dropped the main vents " ? gurgleing sounds more like a supply valve not completely open, or its disc dropped and is holding back condensation, or could be supply piping level or sagging under the floor? can the supply side of the rad(s) lift up at all? post a picture of the rad

I meant I used slower vents on 2 of 3 mains to balance out the system so I could get heat over to the third. I also used slower vents in the upstairs rads. If you reference the earlier post, this is a new boiler (peerless ec-3 446 sqft of steam). The nozzle size was also bumped up to aid in resolving the main not getting heat. As a result, I’m fairly balanced now. 

That said, the rads upstairs started hissing post cycle. And at the same time, during the heat cycle a gurgling/sloshing sound can be heard. No change in supply pipe pitch. The only change were the vents on the mains feeding the upstairs rads, the vents on the upstairs rads and the nozzle. 

I’m hoping that increasing the venting on the 2 mains that I previously reduced will help resolve the issues. 

TroubleinNY

So I installed the additional main vents and the hissing issue is resolved. However due to space limitations in the basement, the main vents, while high enough off the main, run back towards the main not behind it. 

Will the vents running nearly parallel to the main they are venting cause issues? 

Gary Smith

Not as long as the pipes from maim to vents are sloped to drain back to the main with no low spots

TroubleinNY

Gary Smith said:

Not as long as the pipes from maim to vents are sloped to drain back to the main with no low spots

Ok so I need to make sure there’s no sagging in the 3/4” pipe with the vents installed?