3/8" radiator vents?
It's a strange Honeywell 3/8" adjustable model with a separate removable air vent. (I only vinegar'ed the removable vent part).
Since that hasn't resulted in success, I figured I'd replace the whole thing. So I started researching and found that 3/8" isn't really a common size at all, and I can't even find this Honeywell model at all. I removed it and measured the radiator's opening for the vent and confirmed it is 3/8"
You can see on the vent itself, it's labeled 3/8"
Looking to see if anyone can offer a bit of guidance here on how to proceed
Thanks
Comments
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What you have is a TRV...."Thermostatic Radiator Valve"
A TRV acts as a thermostat to prevent a room from overheating.......they will not give you more heat if the boiler is off. They are usually used in the rooms that tend to overheat.
If your getting banging try turning the thermostat knob to a lower setting....venting too fast may cause banging.
If that doesn't work, put a level on the radiator and make sure the end with the TRV is higher than the end with the pipe. A 2x4 and some blocks to pry with and some shims of wood or metal to raise the trv end may help1 -
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re: knob setting; I've got it set quite low
re: level; it seems tipped towards the pipe sufficiently
re: venting/letting air in...part of why I chose to clean it out with a vinegar soak was because I never actually heard any of (in my experience) the typical "hiss" of air being pushed out as the radiator heated up. any thoughts on that?
re: supply valve - yep, fully open
By the way, the other steam system elements in this room are a vertical pipe coming out of the floor + into the ceiling without a vent; and what looks like a capped-off outlet for presumably a second radiator that is no longer here:
thank you!0 -
That is a Honeywell TRV, no vacuum breaker. That might be part of your problem as @mattmia2 was suggesting.1
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Judging by the break in the trim and shadow line there was a wall removed next to the steam pipe. The capped off pipe would have been for a radiator in the other room.
If the system is dialed in correctly, doubtful, you shouldn't really hear hissing. Does the radiator provide enough heat? I know you mentioned banging, do you also hear gurgling or boiling sounds?1 -
Nope, no other sounds and the heating does seem sufficient.
So regarding what you say about a vacuum breaker, and my search finding limited 3/8" air vents, how do you think I should proceed?
Thank you0 -
Can you post a pic of the radiator?0
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Here you go (hit send too fast, next post has photo)0
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Replace the TRV with a Gorton 5 and send the landlord the bill.
https://www.supplyhouse.com/Gorton-G5A-Gorton-No-5-Angle-Vapor-Equalizing-Valve-3528000-p
The TRV is making your radiator retain water since it lacks a vacuum breaker which is likely causing your knocking sound. Steam is coming up and hitting the condensed steam and they are fighting one another.2 -
I'd happily do that, but it says 1/8" and the hole (and current TRV) is 3/8". Wouldn't that be incompatible?0
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If you look closely you will see a 3/8 nut attached to a 1/8 nipple going into the radiator. Loosen the nut, detach the TRV and it will reveal the nipple. You will need an allen wrench to get the nipple out of the radiator. I don't remember the size of the wrench required.
That is a small radiator, you might want a Ventrite No. 1 vent so you can adjust it slightly.1 -
These are the two states of disassembly I seem to be able to manage easily. Are either of these what you're describing or have I missed the mark? Thanks0
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Thank you! And just so I fully understand before purchasing the Vent-Rite #1...I should install the 1/8" conventional sized vent directly into the 3/8" hole in the radiator like in the 2nd photo - and essentially toss the nipple/TRV that I fully removed?gfrbrookline said:You got this one, now replace it with a conventional properly sized vent and you should be good to go.
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The hole in the radiator is 1/8", the nut adapter assembly to put it in english was a 3/8" union. You can now use any conventional vent on the radiator.0
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The first time I removed one of these I was scratching my head because I thought it was a simple twist and play like every other device. Honeywell over thought the connection but forgot the vacuum breaker to make it work correctly.0
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gfrbrookline said:The hole in the radiator is 1/8", the nut adapter assembly to put it in english was a 3/8" union. You can now use any conventional vent on the radiator.
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gfrbrookline said:The TRV is making your radiator retain water since it lacks a vacuum breaker which is likely causing your knocking sound.
The function of the vacuum breaker is so that when the TRV closes the vacuum can be broken to prevent additional steam from entering and the radiator continuing to heat when one does not want it to.
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KC_Jones said:gfrbrookline said:The TRV is making your radiator retain water since it lacks a vacuum breaker which is likely causing your knocking sound.
The function of the vacuum breaker is so that when the TRV closes the vacuum can be broken to prevent additional steam from entering and the radiator continuing to heat when one does not want it to.0 -
So someone over tapped your hole. You need a 3/8 to 1/8 bushing.
https://www.supplyhouse.com/Bluefin-BLB038-018-3-8-x-1-8-Black-Bushing
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@snootyusher
I don't know what size the radiator hole is but it's a standard pipe thread.
But a new vent which is 1/8" pipe thread. Then buy a 1/4" x 1/8 bushing and a 3/8 x 1/8 bushing which ever one matches the thread on the TRV to put between the rad and the vent.
Put the TRV back in before you leave for the store or you might have a mess if the heat comes on
For identification
1/8" pipe is .405 OD that's a little over 3/8" OD
1/4" pipe is .540 OD a little over 1/2" OD
3/8" pipe is .675 OD a little over 5/8" OD
Pipe is measured by the ID normally
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@KC_Jones The way vacuum was described to me is that once a radiator vent closes the steam will condense creating a low pressure differential which will suck more steam into the radiator, high pressure goes to low, the suction of the vacuum created interferes with the radiators ability to drain the condensate, it sucks it back in like a syphon. The vacuum breaker releases that back pressure by letting ambient air into the radiator, not more steam, lets the radiator breath and the condensate to drain freely. An old MIT Professor put it in simpler terms to me a long time ago, poke a hole in a straw and you can't drink your soda since you don't have a vacuum.
This is why we have improved TRV's like the Danfoss and Macon which have a vacuum breaker built in prior to the thermostat and shuts the radiator off when it hits the set point but still lets it breath/drain.
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@EBEBRATT-Ed good call, I was confusing ID vs OD, long day cleaning out the basement, too much coal dust.0
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Even with the vacuum breaker TRV's do not work well on 1 pipe steam systems.0
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based on my tape measure, it's definitely looking like the hole in the radiator is 3/8" wide, from one end across to the otherEBEBRATT-Ed said:@snootyusher
I don't know what size the radiator hole is but it's a standard pipe thread.
But a new vent which is 1/8" pipe thread. Then buy a 1/4" x 1/8 bushing and a 3/8 x 1/8 bushing which ever one matches the thread on the TRV to put between the rad and the vent.
Put the TRV back in before you leave for the store or you might have a mess if the heat comes on
For identification
1/8" pipe is .405 OD that's a little over 3/8" OD
1/4" pipe is .540 OD a little over 1/2" OD
3/8" pipe is .675 OD a little over 5/8" OD
Pipe is measured by the ID normally
the "OD" references are over my head...but if I know the hole is 3/8" then that's the only bushing I'd need to buy, right?0 -
Having a harder time sourcing Vent-Rite #1, seems like the Hoffman 1A is a good substitute. Any thoughts on that? thanks again for all of the great help here.0
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Oh, this makes sense now! So my 3/8" hole will fit a 1/8" vent (because the hole in the center of the vent thread will be 1/8" and all the way around it'll be 3/8"). Thank you! I just found a Vent-Rite #1 online so hopefully it'll come quickly. You guys are awesome. I hope this works and I'll report back. Thank you!gfrbrookline said:Basically you need a conventions vent. A 1/8 vent means the opening on the inside of the hole is 1/8" and the threaded outside diameter is 3/8". Sorry for the confusion.
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Where are you located?0
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Really appreciate that offer but I'm not nearby. Thank you!0
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gfrbrookline said:@KC_Jones The way vacuum was described to me is that once a radiator vent closes the steam will condense creating a low pressure differential which will suck more steam into the radiator, high pressure goes to low, the suction of the vacuum created interferes with the radiators ability to drain the condensate, it sucks it back in like a syphon. The vacuum breaker releases that back pressure by letting ambient air into the radiator, not more steam, lets the radiator breath and the condensate to drain freely. An old MIT Professor put it in simpler terms to me a long time ago, poke a hole in a straw and you can't drink your soda since you don't have a vacuum. This is why we have improved TRV's like the Danfoss and Macon which have a vacuum breaker built in prior to the thermostat and shuts the radiator off when it hits the set point but still lets it breath/drain.
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@KC_Jones I think we can agree to disagree, given my first hand experience with these Honeywell TRV's I think real world experience tells a truer story. What you are saying might be correct in a 2 pipe vapor system. As soon as I removed them from my buildings 1 pipe system the banging went away and the heat evened out.0
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Just to keep the record straight I have TRVs on 5 out if my 10 single pipe radiators and they work fantastic. So I disagree with the statement that they do not work well.
All 5 do have vacuum breakers but I don't think they actually do anything at least not in my situation. I'd have no problem removing them.
I guess according to that theory no single pipe radiators can drain condensate when the vents are closed and the radiators are essentially at full output? That seems a bit silly. 99% of single pipe radiators do not have any kind of vacuum breaker when the vents are shut and yet they drain fine.
All you need to replace that is a normal right angle vent like a Gorton #5. It's a normal 1/8" NPT.
Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.
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As long as the boiler is firing and steam is entering the radiator, the condensate can leave. It is when the boiler is no longer firing and pushing steam in to the radiator that i'm not sure what happens and probably is dependent on the exact configuration of the piping. Wet steam and unusually high condensate load may be a factor too.0
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I think you're looking at it backwards in this case.mattmia2 said:As long as the boiler is firing and steam is entering the radiator, the condensate can leave. It is when the boiler is no longer firing and pushing steam in to the radiator that i'm not sure what happens and probably is dependent on the exact configuration of the piping. Wet steam and unusually high condensate load may be a factor too.
Pressure is what would be holding the water in the radiator, not vacuum.
Without a seal, there's no pressure differential to cause it to happen. When you hold your finger over the end of a straw and pull water up, it's the atmospheric pressure holding the water in the straw.
At least, this is how I understand it to work.
Look at mercury switches as an example. I believe more often than not those had a vacuum pulled on them.Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.
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Agree to disagree about physics, got it.gfrbrookline said:@KC_Jones I think we can agree to disagree, given my first hand experience with these Honeywell TRV's I think real world experience tells a truer story. What you are saying might be correct in a 2 pipe vapor system. As soon as I removed them from my buildings 1 pipe system the banging went away and the heat evened out.
In the absence of a water seal between the 2 different pressures, there is no pressure differential for the water to "see". To have a pressure differential move water, requires the water to have those 2 different pressure separated. That is the actual physics of the situation. The water draining from a radiator is a trickle sitting on the bottom of the pipe, it can not create a water seal, and the velocity in that rad is so low it won't act on the water in a meaningful way to create a water seal.
Remember vacuum doesn't suck, the higher pressure pushes. So to prove your point, I am more than happy to listen to any explanation you have on how a high pressure pushes water laying on the bottom of the pipe, the pipe being mostly full of air/steam. So explain how that works, and I'm not asking about your thoughts on TRV's, I'm asking you to explain how that would work.
Your straw analogy actually proves my point, the straw is full of water. Lay the straw horizontal and see what happens. It will drain because the atmospheric pressure will push across the top and equalize allowing the water to drain, eliminating any vacuum the water was "seeing".
You have clearly stated that you put smaller vents on in addition to removing the TRV, and yet you persist in thinking it had to be the TRV. The smaller vent reduced the steam intake, reducing the condensate volume, which had the effect of eliminating your water hammer issue. It's that simple.
The TRV is not the problem, slope, too fast of a vent, pipe sag, those are your problems, one or all, but absolutely not the TRV. Basic mechanics and trouble shooting, never ever change more than one thing at a time when trying to diagnose a problem. You change 2 things, yet ignored one of the changes in your diagnosis.
To the OP, please don't give credence to the statements about vacuum holding up water, they are absolutely incorrect and will mislead you and others coming to this board.
One thing I will say, TRV's should not be added to a system until that system has been balanced and vented to the best it can be, only then should one consider a TRV to help with an isolated overheating problem.
I have 2 Danfoss installed, they work perfectly.0 -
Without wading into who is right on this point - because it's over my head - would that mean swapping out this TRV for the Vent Rite 1 wouldn't be the best course?snootyusher said:
This statement is factually incorrect. The only way it can prevent water from leaving the radiator is if the supply pipe/valve are completely full of water. Since the condensing steam is just a trickle at the bottom of the pipe it will freely drain regardless of the presence of a vacuum breaker.KC_Jones said:gfrbrookline said:The TRV is making your radiator retain water since it lacks a vacuum breaker which is likely causing your knocking sound.
The function of the vacuum breaker is so that when the TRV closes the vacuum can be broken to prevent additional steam from entering and the radiator continuing to heat when one does not want it to.
Since you are in an apartment, it's honestly tough to say. Venting is a system, not just your radiators in your unit. It starts with main venting in the basement, then balance throughout the system.
That said, banging is either too aggressive of steam distribution, pipe slope, pipe sag, radiator slope, or most likely a combination of those. If you put a slow enough vent on that radiator it might, let me emphasize, might fix it. If the slope or sag is bad enough, you might not be able to get rid of it. The aggressive steam distribution typically is bringing to light a piping issue, but slowing it down enough, again, may fix it. The end result may be no banging, but remember you are also cutting down on the heat production of that radiator, so you could get cold, but, in an apartment, I would be doubtful of that being a problem.1 -
Interesting discussion
If I am not mistaken they used to have vacuum air vents for one pipe steam which in my understanding could only be used for coal (continuous) firing, and that they had to be removed when firing gas or oil and standard air vents which will break a vacuum had to be installed0
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