Inside Heat-timer Varivalve Radiator Vents
Ever wonder what's inside a Varivalve vent? Or what makes them spit water or why they fail?
I looked inside. I really wanted to love these. Beautifully machined American made brass gems that emit a bodacious amount of air - faster than many main vents. An adjustable slide varies the output. Good if you have a clean, dry steam system and bad if you have anything else.
Advantages are a self cleaning valve seat, an o-ring valve that seals against the seat and a bronze sylphon, just like a little steam trap. Disadvantages are no float to keep squiring water off your floors, and the fatal one to most of these vents - a plunger that falls out from the sylphon bellows sealing its seat permanently.
In the cut-away below, you'll see the brass "plunger" that the bellows presses against the seat when the valve closes. Unfortunately this plunger is retained in the bellows with a press-fit. After the bellows expand and contract over and over again, the bellows swell and distort, finally ejecting the plunger out of the bellows and onto the seat. Gravity then keeps it there - plugging the seat forever.
And that's the end of the valve. About a third of the ones we've installed have failed this way in the first two years.
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Below is the original 1950's "temperature adjustable" Heat-timer adjustable vent. "The radiator vent with a built-in thermostat" also spat water but was constructed differently and didn't fail closed like the present design. The "factory calibrated thermostat" knob on top simply raised or lowered the sylphon bellows lifting the plunger from the seat:
Comments
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Thanks for that. I too want to love these vents, they are apparently made (or at least the HQ is located) about 10 minutes from my house.
Side note: Gorton and Maid O Mist "floats" don't float
NJ Steam Homeowner.
Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
See my sight glass boiler videos: https://bit.ly/3sZW1el1 -
I wanted these vents to work also, but most of them failed in this exact manner. They also vent too aggressively even on a low setting which tends to throw the balance off…. Also annoys me that Heat Timer will not acknowledge that there is a defect in the design that causes failures in a high percentage of vents. Many people complain about this problem. All you have to do is give it a gentle shake and you can hear the separated valve seat shake. The vent is then toast…. My system also consistently ran at the proper very low pressure with dry steam when I tried these vents, for those who say its a system problem…
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Can you explain that? I've had several 'system flood' events, the most recent when chimney guys dropped debris on the ball valve handle, opening the fill! (I've since removed that handle) The MoM and Hoffman valves closed, I had a Varivalve that spewed water.
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The MoM have a plastic "float" that is solid and more dense than water.
As for gorton, I have the video below.
So why didn't they leak in your case? Maybe they were failed closed, or ?? I wasn't there.
NJ Steam Homeowner.
Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
Ok, for arguments sake, if that bimetal arc is what closes the valve when it gets hot, it's probably supporting part of weight at all times. so to close in a system flood, the 'float' doesn't need to lift the entire weight, just add enough 'lift' to the bimetal support to close the valve. Can I assume you haven't bench tested just flooding a vent under tap pressure?
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It can't provide lift if it sinks in water, but feel free to make your own experiment to disprove mine!
NJ Steam Homeowner.
Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
Obviously the bimetal is capable of supporting 100% of the floats weight when hot, If the bimetal supports 50% of the weight when cold, and the air inside supports 60% of the weight, it will float even if it sinks in your beaker.
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If the strip is adding lift, then it's adding weight as well, so the "float" would actually need more buoyancy to float. If it didn't have to float the weight of the strip, then it's lifting off the strip and only needs to float it's own weight, which Paul's experiment proved it's incapable of.
As he said, please provide the results of your own experiment to show us, many of us like learning new things. If it does float, I'd like to see how it's floating since Paul's experiment shows it sinking.
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"If the strip is adding lift, then it's adding weight as well". This is false logic. The bimetal is essentially a spring whose tension varies due to temp. It's not adding weight. Picture it being a coil spring under the float, would that be adding weight?
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Strip is in the open position not moving. If the float is lifting off of it, how is it providing lift?
If it was attached rigid to the float, at some point the weight of it comes into play, because again it's cold and in the open position, it will not move to closed without steam heat. So it's weight absolutely would come into play.
It's NOT a spring, it's a bimetalic strip that moves with heat, they are very different things.
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In Joseph Gorton’s patent for their vent he refers to the “float” as the Bell Valve. I would think that when water enters the vent it would trap air in the bell causing it to rise and seal the vent. In Edward Jacobus’s patent he refers to the “float” as the bell or float. I think the older Jacobus vents had a bell and not the solid plastic float like their current product. I have not done an experiment to prove or disprove if they do in fact seal against water that enters the vent housing.
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Also, I had heat timer vents on my rads for like 10 years before I replaced them with Gorton’s 15 years ago and never had any issues with them.
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As said above....Extremely nice dry steam...no.problem..Wet Steam? They will gush like a tub spout. They are a chunky little piece of brass. They do add some heft to the scrap bucket. Mad Dog
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perhaps the needle used to be soldered to the bellows and they decided they didn't need to do that anymore.
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If that needle was soldered on, I would love these for certain applications where huge venting was needed and steam quality was good. Alas, as they are they fall apart.
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Continued….
They can be disassembled and "repaired".
You pluck out the aluminum nameplate either prying with a small screw driver or by punching a screw through the top and pulling it off. It's glued on.
The top of the sylphon is brass and it's pressed (or glued) into the body. It has a hole in the top that is used to fill it with its alcohol mixture. You can thread a steel 5mm machine screw a few turns into the soft brass and use it as a grip to pull the sylphon out.
I pulled on it with a small slide hammer made to remove faucet handles. It pops right out and the disconnected plunger, pin or button flies across the room. It disappears like magic.
If you find it, you'll see it was attached to the bellows with glue. It wasn't even pressed in. It's a lose fit without the glue.
I assume Heat-timer used a high temperature adhesive like Loctite 603. The problem is that the bellows is thin bronze and flexes. That flexing causes the glue to fail and the plunger disconnects from the bellows. Then it falls down onto the seat.
So I'll glue it back and see what happens.
Can it be soldered? I tried but just couldn't heat the sylphon face while keeping the rest cool. The heat would probably cause it to over-extend and explode. It has to be soldered before the sylphon's charged and sealed.
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Designing and controlling tolerances on the press fit on the bellows side I can see being difficult. More robust design would have snapped the bellows onto the syphon but that too would have required incredibly tight tolerances on some small bend radii.
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When all else fails, use glue. They should just solder them on, but that would be a lot of work.
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