Radiator vent valves for single pipe steam: Venting capacity range of fixed vs. adjustable types.

2wheelinfool

Bought a house with gas powered single pipe steam last year and learned a lot so far reading on the forum, but now I have a specific question. The second floor is heating faster with all MaidoMist Jacobus type with "D" orifices. I am thinking of replacing these with Vent-rite #1 so I can dial in each room.

When a ventrite is wide-open does it have the air flow capacity of a "D" orifice? When it is dialed down, can the air flow capacity be reduced to that of a "4" orifice, or lower?

Also, I know I need more venting on the main: I know it's the wrong valve because it's a 1/8" valve inlet. Don't want to risk changing it during heating season because it looks to be rusted in place for many years. Another advantage of the adjustable radiator valves is I can re-tune the system more easily after I upgrade the main line vent.

As an aside, when I replace the main vent, are MaidOMist or Vent-Rite better?

SteamingatMohawk

A Vent Rite #1 can go from completely shut off to about a #5 (maximum 0.083 cuft/min at 10z.) at an 8 setting on the scale. A "D" has a capacity of 0.330 cuft/min at 10z...4 times as much.

The report at this link has lots of information about vents, it's in the resources on HH. Look at the table on pages 11 and 12 for the numbers I quote.

https://heatinghelp.com/systems-help-center/balancing-steam-systems-using-a-vent-capacity-chart/

Also, I built the chart below from data in the report to try to show the differences and similarities among several manufacturers' radiator vents. I only included the ones with which I am familiar.

Make sure you read and understand the notes at the top, they are important for your overall understanding.

If you have any questions, post them or message me.

Clance

@SteamingatMohawk Thanks for posting the chart, its helpful as I too am about to balance my system.

ethicalpaul

A D is a massive, massive vent to put on any radiator. I would say with all Ds on your upstairs radiators, balancing the system would be very difficult or impossible.

What is your main venting situation?

ethicalpaul

Here’s a D and a 6 (which is a largish vent in its own right)

Note that this D orifice came from a #1 MAIN vent!

2wheelinfool

Thanks for the useful data. I will post some pics of the system components in the basement for feedback.

Big Ed_4

You are on the wrong path on balancing . Less is more up stairs. You first want to charge the mains with large vents . You want air resistance up on the radiator so steam would fill the mains first .. You then size the radiator vent to the size of the radiator .. You also want to use float type vents just incase your boiler is over filled and to prevent water damage .. I prefer good adjustable float vents . I can fine turn if need be .

I would first size the smallest radiator to lowest setting , medium radiator to second setting and the largest to number three ... Then throw the thermostat up ... Follow the steam across the main , Then go upstairs . Walk around follow the steam across the radiators until the vents pop close . The idea is heat up the radiators at the same time . Adjust slowly if need be . I would keep in mind where heat may not wanted.. , Like when the thermostat was added later in the main foyer with the biggest beast of a radiator .. I would let it lag for now and can adjust later. When they all close on the first floor , forget about the beast then go upstairs .... If some of the vents already shut down move on to the ones that did not .. Bring up a notch on the radiators that did not fill , if you like or down if you do not ...

2wheelinfool

Thanks for the balancing procedure explanation, Ed.

2wheelinfool

There is about 670" of 3" main in my system. How much vent capacity should be specified? Pictured is the only vent valve, which I don't think is enough based on the small hole size. I think I need to remove that bushing and install one with a bigger ID to install a proper vent valve. Will the bushing come out if I heat with a propane torch?

2wheelinfool

Here are some more pics of the near-boiler piping, if that also figures into the venting requirement.

Does everything look copacetic?

nicholas bonham-carter

Insulate those pipes, and add main venting, until you are under 2 ounces of back pressure on a low pressure gauge. Then you are ready to tackle the radiator vent sizing. Start with small, and go larger as needed, following Ed’s instructions.
Remember that you are balancing the resistance of the mains against the aggregate of radiator venting.—NBC

dabrakeman

Looks like you only have one main that loops all the way around and comes back to the boiler where your current vent is? How long is the entire loop? I don't know how big your system is but do what NBC says. I can't imagine that you would need less than a Gorton #2 or a BigMouth, maybe more if one main is feeding a two story house. Is there a plate on the boiler listing the EDR or BTU?

HarryL

As you say, you could probably help things a bit by replacing that vent in the picture. Danger is breaking something in the process and how much to tackle before spring. If the vent comes off intact you could put a D on there. If you feel more confident you could usa a 1/4 to 3/4 or 1/4 to 1/2 fitting with other nipples and fittings to take on a bigger vent. It isn’t ideal but you can get a pro in after the heating season to get that bushing out and fix it correctly. My worry would be though that things might go wrong just getting that old vent off, but 1/4” fitting are a lot easier to free up and you can probably remedy the situation yourself. Just wait for a warm spell early in the week so pros won’t all be out on other no-heat calls if you end up needing one. Whenever the pro comes in have them install a drain and plan a good flush. I doubt it has been done in a long time if ever from the looks of the sight glass.

Fizz

How long does it take for steam to reach main vent? If it's quick and no steam is coming out, you may not need new vent, then just try balancing rads.

2wheelinfool

@dabrakeman, the main is a loop. I measured and there is 670" of 3" pipe in the main. It's a 2 story house. 7 rads on the 1st and 4 on the 2nd. On the boiler spec plate, it says INPUT: 140000 BTU/HR. There is an OUTPUT field, which is left blank (what's up with that?).

2wheelinfool

@HarryL, my thought is wait till heating season is over, than attempt to remove the bushing. Any tips? What are the risks related to attempting that myself?

HarryL

@2wheelinfool I'm just a homeowner, but agree that waiting on the bushing makes sense. From other comments it doesn't sound like your main issue.

I had a similar bushing and couldn't get it out (heat, PB blaster, big wrench, etc) and had a pro do it when I had them in for some other work. I was able to get a bigger vent on it which helped. Mine was also was also not closing so maybe I saved a few bucks for the rest of the winter. I suppose the risk of doing it yourself after the winter is causing more work for the pro, though likely not a lot more. When I first started tackling some of my own work I tried to fix the packing on a leaky valve. It was in an awkward position and I cross up the threads on the packing nut. Doh! It was an old valve so I was just as happy to get it replaced.

dabrakeman

I think it is safe to say you are under vented. You can run the test @Fizz mentioned. After starting the boiler place your hand on that elbow on the riser coming out of the boiler. When it gets steam hot (meaning you have to remove your hand...) time how long it takes for the pipe entering your main vent to get steam hot. I think you would be way over the couple minutes or so many shoot for. You are likely doing most of your venting through the radiators. A couple Gorton #2's are 1/2" fittings and could antler off that 1/2" pipe. Am I correct that the pipe below the elbow is 1/2"?
You could probably use two people and two pipe wrenches, one on the elbow and the other on the riser into the elbow for back torque and see if you can get it to budge. Could let some PB Blaster work for a couple days and give it a try and if that not enough add some torch heat to the elbow and try again. You could also cut the riser pipe below the elbow and get or rent a pipe threader.