How do I install a vacuum breaker to reduce whistling rads at end of cycle?

ccordero

I’m just a dumb homeowner, not a plumber so forgive me if this is a dumb question. I didn’t find any good YouTube videos so here I am.

At the end of the call for heat, when air is coming back into the system, the air seems to come in through the smaller rad vents for some time before my main vents reopen up. When it does this, it whistles. Seems to only happen for the first rad on the line.

I’ve looked at my main venting setup and bumped up my venting from 1 Gorton #1 to 3 Gorton #1s in like an antler or menorah lookin setup.  This reduced the whistling a bit. It doesn’t sound like a gosh darn train whistle anymore but it’s still fairly loud to me.

I also insulated my steam pipes in every accessible location I can find too, but it didn’t solve the issue either.

The next thing I want to try is adding a vacuum breaker, as recommended by others on some other posts here on the forum.

What kind of vacuum breaker do I need? Is this the kind of thing I should buy? https://www.supplyhouse.com/Watts-0556030-1-2-LFN36M1-Lead-Free-Water-Service-Vacuum-Relief-Valve

How many of these would I need?

Where exactly do I need to install this? On the same antler configuration as my main vents? At the rads themselves?

Does it install like a cap pipe fitting?

Instructions indicate that I should be using a pigtail but I can only find 1/4” pigtails online, whereas my antler is all 1/2” fittings. Is it okay to use adapters to go from 1/2” to 1/4” for the pigtail and then back again from 1/4” to 1/2” for the breaker above? Any concerns with that?

Thanks for any advice, feel free to talk down to me like a child or like an apprentice on his first day on the job.

EBEBRATT-Ed

You can put it on the same antler as your vents or you can put it on the boiler high above the water line. Use a steam rated vacuum breaker (Tunstall Assoc. Chicopee, Ma) or you can use a good quality Y pattern check valve mounted horizontal. The highest vacuum is at the boiler so that would be my choice. No pigtail needed all they will do is hold water which you don't want it will make things spit water. You can use 1/2" pipe size or 3/4". 1/2" should do it.

EBEBRATT-Ed

like this

clammy

Usually one a one pipe system if it’s going into a vacuume on off cycle it s usually in my experience due to zero insulation behind the radiators . The few cases I have ran into where always sun rads that where recessed and there’s was no insulation behind the radiator . The only cure I ve found to re pipe the radiator and get it out a little bit so that you can get some insulation behind the radiators and make sure there are no outside drafts which is also a issue . In some cases vacuume breaker at the end of the mains won’t help being the vacuumed is forming at the radiators more so then in the mains . The best advice is a simple suggested seal and insulated behind the radiators ,try to elimate any draft behind the radiators, cold air infiltration behind rads is always a issue and will cause your air vents to whistle . Usually in the worse cases as mentioned above is to repipe that radiator out of the recess . Every body wants everything hidden well w steam in cases it not worth the few inches you gain due to the issues you are dealing with . In just about every case it was never some thing new it usually stays w a home forever from home owner to the next until some one re pipes are moves on to a different type of heating system.
I always feel when I see these systems that either a general contractor or a helper did the job being most half brained heating guys would know there will be a issue in the future due to zero insulation behind a radiator or basically there’s just following orders,get a pay check and let it be some one else problem in the future .
What can be said is you only need heat what 4 or 5 months of the years so either live w it or pay to have some take a look and repipe your offending rads to correct a issue which has most likely always been a issue . You can add vacuum breakers any where u want but as stated above if it forming due to lack of insulation on the back side of your rads you shall be adding them to every radiator and it will still not correct the issue only mask it . The reason I know is I have been there done that and seen it first hand as described .
Peace and good luck clammy

ccordero

@clammy, what kind of insulation do you recommend putting behind the rad? Fiberglass batt? Or something else?

ccordero

EBEBRATT-Ed said:

like this

Thanks for the response! Don’t know if it’s just me but neither of those pdfs explain how to install. The Tunstall pdf just says “installation is easy” and the check valve pdf is empty.

it sounds like from your message about installing on the antlers that I just twist it on, I assume with some PTFE tape and pipe dope

clammy

Personally I would try to get in a piece of as thick as you can of a hi density blue board and then have some one make a sheet metal piece to cover it w it really depends on how much room you have behind the radiator . Also is there any insulation in your out side walls and are these radiator below very drafty windows that may not be helping . Usually whistling radiator vents are not something that just started unless all of the radiator vents are very old and non functioning usually which makes a few that are working very noisy.peace and good luck clammy

dabrakeman

How many originally installed steam systems had insulation behind the radiators??? Most are under windows and don't even have insulation in the walls.

dabrakeman

No disrespect @Clammy intended. I fully understand the physics of what you are saying (the cold daft will hasten steam collapse in the radiator) but it just really surprised me that this would be the only or primary solution. Then again a rapid boiler shutdown and steam collapse likely was not a issue with originally installed systems with slow simmering boilers. I have noticed that the whistling is usually at the fasted venting radiator/s.

nde

What are the vents? I have noticed over the years Hoffman 1as can whistle slightly on long burns e.g. running a swing setting. In the last 2 years I converted to set and forget on the thermostat with no swings. Since then I never hear whistling, just soft exhale breaths on the Hoffmans. I never hear the Gortons make noise since set/forget conversion. (50/50 split on hoffman/gorton rad vents).

I run Gorton #2 on each of the 2x mains fwiw. These Gorton 2 replaced original 90 yo main vacuum vents which were designed for coal. The poor system had run for decades on over pressurized, loud, leaking rad vents before we moved in. Before figuring out steam I would hear all kinds of loud whistles, hisses, clicks, etc. After 14 years of steam heat I would say good main venting and set/forget is where it is at for the quietest most efficient cycles.

ccordero

@nde The main vent has 3x gorton #1s on it in an antler arrangement. On the whistling radiator it's got one of those Varivalve vents set all the way open.

I thought about getting Gorton #2s but it didn't fit where I was installing.

mattmia2

I don't think that the vacuum breaker will help, the cracking pressure is too high, it will prefer to suck air in through the open hole in the vent than to move the diaphragm in the vacuum breaker.

I would look at a zone valve rated for steam that is controlled by either a very low pressure vacuum switch or a timer that opens it some small amount of time after the boiler shuts off. It could be mounted somewhere near the main vents.

Waher

Castrads sells vacuum breakers for radiators that are normally used to allow for thermostatic steam valves to function properly. They are 1/2" NPT, so you'd need a 1" to 1/2" NPT reducing bushing installed where the usual 1" plug is installed at the top of a steam radiator.
https://www.castrads.com/us/product/half-inch-npt-vacuum-breaker/?doing_wp_cron=1674841837.1469409465789794921875

ethicalpaul

But clammy, won't every steam system in existence go into vacuum (and by that I mean pressure lower than atmosphere in that locale) every single time the burners stop firing?

I guess I'm just lucky my main vent Gorton #1 seems to open before any of my radiator vents

clammy

No offense taken this has just been my experiences that I have ran into that have had this issue of vacuum being produced was intense enough to easily be heard to the point of annoyance . This is in single pipe systems and notably I ve only encountered one that was in this category and vacuum breaker at the main vents and at the boiler where of no help . The outside of the home had like 3/8 plywood and tar paper the recessed radiators backside where like ice just about direct contract , the issue only got worse as the weather got colder . Again this is my experience and not all jobs and situations are the same . All other minor issues the system had where straighten out but the whistle remained . As you I believe stated that it’s seems to be the quickest vent that usually a issue it because the biggest vent at a rads will also admit the largest amount of air back into the system on the off cycle cycle this is even more true when the radiator is exposed to extreme temp differences . As for replacing radiator vents it comes to my attention that a lot of people no matter how you explain think radiator air vents last forever they don’t and as they get old they not only start to lose there’s air vent capacity but also the ability to allow air back into the system . So if you have 10 old crappy air vents that barely vent and do not open completely at the end of a cycle and 1 new vent if there’s any air being sucked into the system it will surely whistle louder through the one newer vent and add out side air influences to that radiator and there’s the recipe for noise .
I also see tons of recess rads on outside walls that don’t have this issue but in a few rare cases you run into a issue like yours ,a thermal image camera may help especially when compare to radiators on the same system without such issue . A thermal image of before the heat is ;one while heated and one on the off cycle before and while it’s starts whistling a thermal image would show temp differences which would influence what’s happening especially when compared to non issue radiators just food for thought .Theres also nothing wrong w human sense like using your hand to feel backside of the recess . Never discount wind and cold drafts effects on things especially when it comes to either hydronic or steam heating ,it all goes back to the laws of thermal dynamics high to low either pressure or temp or vacuum
Again this is just my opinion and I’m not there .
Peace and good luck clammy

SteamingatMohawk

@ccordero You said, “On the whistling radiator it's got one of those Varivalve vents set all the way open.” According to the Gill/Pajek article, a Gorton#1 has a capacity of 0.700CFM at 3oz., while a fully open Varivalve has a capacity of 1.130CFM at the same pressure. See the chart.




Bottom line that vent is about 1-1/2 times the Gorton capacity. That sounds like a lot. Is there a specific reason you have that much venting at that location?

dabrakeman

Questions to the OP, 1) do you have to vent this radiator so fast? 2) Is the whistling occuring after every cycle or just after particularly long ones (i.e. when this radiator actually completely fills?

Varivalve wide open is extremely fast for any radiator and you say this one is the first on the line. Even the min setting on that particular vent is pretty fast. Also, if you have one radiator that is venting faster than all the others then in general that is where the air is going to want to go back in after a cycle. I have this issue as well (although extremely fast vent rate in my case is a MoM #6) and I can move it around the house by adjusting my venting. Problem I have is my kitchen is simply under radiated so until I can either insulate the walls or get a larger radiator I am a bit stuck venting this one faster than the others. The second fastest venting radiator is our family room where we spend most of our time so of course that is where the whistling goes if I slow the kitchen radiator down to a MoM #4 (and also my kitchen does not get warm enough).

The other consideration I see that @mattmia2 somewhat hit upon is that unless you are in a long cycle that closes the radiator vent (from steam reaching it) the radiator vent remains open throughout the cycle whereas the main vents have always closed, assuming they are working. That gives quite a head start for sucking air in to the radiator vent over the main vents.:) A relief valve with a diaphram and associated cracking pressure (vacuum) would also I think be at a disadvantage relative to that open radiator vent although I am always looking to see if someone has tried it to help this issue. I am a homeowner like you, not one of the expert professionals here, but my gut feel is the best you could do is try slowing down your radiator venting in general and this radiator in particular.

mattmia2

dabrakeman said:

The other consideration I see that @mattmia2 somewhat hit upon is that unless you are in a long cycle that closes the radiator vent (from steam reaching it) the radiator vent remains open throughout the cycle whereas the main vents have always closed, assuming they are working.

I think what happens is that the radiator vent cools and opens after a cycle ends before the main vents cool and open. Some vents open under vacuum as well and perhaps the radiator vents open under less vacuum than then main vents.

dabrakeman

mattmia2 said:
I think what happens is that the radiator vent cools and opens after a cycle ends before the main vents cool and open. Some vents open under vacuum as well and perhaps the radiator vents open under less vacuum than then main vents.

I don't know about the OP's situation but I can attest that the intake whistling can occur after a cycle that does not close any of the radiator vents on the system. However, also true the longer the cycle and higher the amount of average radiator fill the more the whistling occurs. This with very adequate main venting and pressures that stay less than 0.5psi. I think there was an earlier discussion about the need or wish for something like a vacuum check valve with less than 0.5psi cracking pressure.

rcrit

A few of my vents of various makers whistle at the end of the cycle as well. My rad vents NEVER close, and have never in 14 years. I have the thermostat set to 2 cycles/hr to avoid huge temperature swings and the boiler satisfies the thermostat well before any vent even considers closing. The only time I heard my vents close is when my steam guys were validating the new boiler install and had the thermostat cranked to 11. I flipped out because the radiators were making a new sound.

So yes, I'd also like some way to break the vacuum so the pipes aren't refilled with air through tiny, less than1/8th inch openings.

And no the boiler doesn't cycle on pressure and is sized properly. I live near Baltimore and was lucky enough to have a couple of real pros install and balance my system.

mattmia2

An open vent is definitely going to be less resistance to air than a check valve. You could make a manometer out of a piece of plastic tubing filled with water and in a loop and tee it in before one of the vents after the boiler shuts off but I suspect that the vacuum is going to be so low that it won't open a check valve.

mattmia2

The break point of the Tunstall vacuum breaker is "Horizontal Break Point 0.36 psi" which is about 10 inches of water.

ksd99

This is great information but being a non mechanical person - not sure how to fix.the air issue.

dabrakeman

This one from Spirax appears to have a 0.15inhg opening vacuum vs the 2.5inhg of the Tunstall.

dabrakeman

https://content.spiraxsarco.com/-/media/spiraxsarco/international/documents/us/ti/vb14_vb21-ti-4-103-us.ashx?rev=1a327acb1d7c449db95a20638dcbe101

SteamingatMohawk

@ccordero You haven't answered my question,

"Is there a specific reason you have that much venting at that location? "

ChrisJ

dabrakeman said:

No disrespect @Clammy intended. I fully understand the physics of what you are saying (the cold daft will hasten steam collapse in the radiator) but it just really surprised me that this would be the only or primary solution. Then again a rapid boiler shutdown and steam collapse likely was not a issue with originally installed systems with slow simmering boilers. I have noticed that the whistling is usually at the fasted venting radiator/s.

How's your main venting, and what vents are you using?
I've found Gorton's don't seem to hold back against a vacuum and end up letting air in.  That's a good thing in this case.

I also only develop a decent vacuum if most of the radiator vents are shut, which is only on extremely cold days.  Otherwise, most of the radiator vents are still open when the boiler shuts off.   This makes me curious what thermostat you're using and how it's setup.  I.E. a Honeywell set to 1 CPH seems to stink in my opinion, but 2 or 3 CPH will allow it to run much shorter cycles more often, assuming your main venting and piping insulation is up to the task.

dabrakeman

@ChrisJ Not sure if your question was for the OP or myself? My mains have Gorton 2's. 2 Gorton 2's + a Ventrite on one main and one Gorton 2 plus a Ventrite on the shorter main. I control thermostat cycles such that I virtually never close any radiator vents although fastest venting rad will typically get to about 75-80%. Boiler is about 30% oversized.

ChrisJ

dabrakeman said:

@ChrisJ Not sure if your question was for the OP or myself? My mains have Gorton 2's. 2 Gorton 2's + a Ventrite on one main and one Gorton 2 plus a Ventrite on the shorter main. I control thermostat cycles such that I virtually never close any radiator vents although fastest venting rad will typically get to about 75-80%. Boiler is about 30% oversized.

I had confused you with the OP, I'm sorry.