external control of Vent Right #1 air vent on steam radiator

DavidLaidlaw · February 2019

I am trying to put microprocessor controls onto steam radiators in order to zone them. I would like to be able to cap the vent on my radiators to prevent them from heating. I installed a cap on one, but it still warms up. I have Vent Right #1 adjustable vents. I am wondering if anyone has an internal diagram for that vent so that I can determine how it might be venting even after capping. I am guessing that my cap could be leaky, but it's also possible that the adjustment knob on the bottom is not airtight, and that it is how the vent is still letting air out.

Thanks in advance!

KC_Jones · February 2019

Before you go down that road (and i won't suggest not doing it) have you fully and completely balanced the system and it's still not working correctly?

Many people use TRV's on the rads, but anything you add should be to improve a properly functioning system, not fix a problematic system.

Fast main venting, balanced radiator venting, then start getting "fancy".

Jamie Hall · February 2019

A somewhat more general approach would be to look for a small powered valve which could be installed between the vent and the radiator and controlled by your gadget. That way you could have the vent set correctly for optimum balancing (at least when it was open...) and use any vent you liked.

I might point out, however, that in single pipe steam changing the venting of any one radiator will affect the entire system, and throw it off balance to a greater or lesser extent (assuming it was balanced in the first place), as well as effectively oversizing the boiler. Not saying to not give it a try -- but beware of unintended side effects.

PMJ · February 2019

Like @Jamie Hall said maybe one of these between rad and existing vent?

https://ussolid.com/compare/717/712/711/710

nicholas bonham-carter · February 2019

Yes, balance the system with good main venting, and maybe you won’t need any more complexity.
What is your pressure in ounces, and what main vents do you have?—NBC

Fred · February 2019

@DavidLaidlaw , when you say the radiator still gets warm. Do you mean all the way across or just the first section and by "warm" do you mean warm or hot? I have to believe that even if you were to put a plug in that radiator the steam would still compress the air in the rad to allow a little steam into one or two sections. What pressure does your boiler build to during the end of a heating cycle?
@nicholas bonham-carter , sometimes people do things because they can. That may be the case here. OP really hasn't said he has a problem (yet). May be living out a desire to come up with an elegant steam zoning solution. I hope he understands that with each radiator that is shut off during a heating cycle, the boiler becomes bigger, relative to its connected radiation and at some point will start short cycling unless he implements some type of timed cycle solution.

DavidLaidlaw · February 2019

Thanks for all of the suggestions! I don't have a malfunctioning system. I am aiming for more control than my single-zone steam system provides. The system is working fine and is balanced, but I can't make the downstairs cooler at night or compensate for a rainy day, when the upstairs is colder than the downstairs. That's just how a single-zone system works.

My pressuretrol is set at the lowest setting, and I think that's somewhere between 0.5 and 1 PSI. I don't think it is calibrated to ounces.

The radiator I mentioned getting warm is getting warm across 3 or 4 of the 8 sections, and the first 2 are hot. I'm pretty sure that I was not sealing the opening in the vent sufficiently, so I have some more experimentation to do with that. I do think that air is getting out the vent. At 1 psi or less, I don't think that more than a few percent of the volume would get steam based on the air being compressed.

The pointer to actuated valves is great. They are a little pricey to put on lots of radiators, but they would very likely work for what I want to do. I would need to make sure that they were open at the end of every heating cycle let air back in. The valve I'm imagining on the vent would function as a vacuum breaker as well as preventing air from escaping when closed, which seems somewhat safer.

Short cycling is definitely a consideration. It will probably happen when there is a scheduled change in the desired temperature in one part of the house but not another, especially on the coldest days. That will require heat to just one of the parts, and so present a load to the boiler that does not match its size. Once the different regions have reached their new temperature points, though, I believe that changes in the load will be masked at the start of each cycle, as the system gets to its full radiating capacity over 45 minutes to an hour. In southern New England, we have a lot of heating cycles that never completely warm all the radiators, and in those cases, I don't think short cycling will happen. But I am speculating here somewhat, and I think that I'll need to see how things work out. There would be lots of control over the system using actuated vents, so tweaking the control strategy should make it possible to keep the boiler from short cycling.

I don't think that this concept is much different from the thermostatic vents that Danfoss makes, and I have not heard of short cycling with those.

Any other info about capping those vents welcome or thoughts more generally would be welcome!

external control of Vent Right #1 air vent on steam radiator

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