help with hissing and slow heating, main vent sizing?

roberts

I moved into a new house this past summer, my first with steam heating. I read Dan's great book and have been learning a bunch, but can definitely use help getting my system to work better. Some of the radiators make a hissing sound as the system warms up and the air leaves the system (of course one in the bedroom does early in the morning!). And, it takes almost an hour for the radiators to get hot from when the system turns on. So, I'm thinking perhaps my main vents are not working properly or are sized too small?

There are two main branches of 2.5 inch pipe coming off the boiler. They each have roughly seven legs connecting to the radiators. Each of these two main branches have vents at the end in the basement.

One branch has a single valve, I'll post a picture below. I don't see markings on it, so I'm not sure what it is. There is roughly 21 feet of 2.5" pipe to the end of this branch.

The second branch ends with a tee with two valves, both are Gorton air eliminator no. 1. I'll post a picture of that below as well. That branch is roughly 42 feet of 2.5" pipe from the boiler to the vents. There are some longer offshoots connecting up to radiators off this branch in particular.

Thanks for any ideas and suggestions!

Jamie Hall

The second one looks like a Hoffman 75. A perfectly respectable main vent -- but you might have better luck with a Gorton #2 there. Problem there is it looks like your clearances are a bit tight, and you may have to get creative with some fittings -- it may be necessary to use a union and a couple of short nipples to get it in there. The other two on the antler look like Gorton #1s. Again, a perfectly respectable main vent, but again, a little small perhaps. And so, again, a pair of #2s.

roberts

Thanks Jamie! Looks like these main vents are not cheap. Any experiments I can do to confirm that this would help things?

I just found this article which suggests removing the main vents and then running the system to see how long it takes for the pipe to get hot by it. Sounds like maybe a good idea, but is that a bit dangerous?

Steamhead

The Hoffman #75 and Gorton #1 vents used to be comparable, but the Hoffmans I've seen lately vent slower than in the past.

Start by replacing the Hoffman with one of the Gorton #1 vents, and put a single Gorton #2 on the long main. The steam should reach the ends of both mains at about the same time.

ethicalpaul

How much are you setting back your thermostat at night?

roberts

Good idea to try replacing the Hoffman with one of the Gorton #1 vents. I'm not so experienced working with these so I'd love some confirmation on how to replace these. Looks like the Hoffman has 1/2" female threads connecting to an adapter that has male threads on both ends and finally connecting to the steam pipe. The Gorton has 1/2" male threads. Is it reasonable to think I could unscrew the current fitting between the Hoffman and the steam pipe and then screw the Gorton directly into the threaded port on the steam pipe (with teflon tape)?

(Sorry if my terminology is wrong, hopefully my description above makes sense!)

Thanks again!

roberts

ethicalpaul said:

How much are you setting back your thermostat at night?

At night we have the thermostat set to 66 degrees compared to 70 during the day. But generally speaking, from a cold state, how long should it take for the radiators to get hot from when the thermostat asks for heat?

Jamie Hall

You need to bring the boiler up to steam first -- you can time that, and venting will do nothing about that. Then the steam needs to make it to the ends of the mains. That will depend a lot on the insulation on the mains and less on the venting, but the venting is important. A well insulated main with adequate venting will, I find, take around 5 minutes for every 20 feet of main. Give or take a lot...

roberts

Thanks Jamie, that's very helpful. I have some experiments/investigations to do!

ethicalpaul

Yeah Jamie hit the reason why I asked. If it's a shoulder time like this it's possible the boiler is off all night during that setback, then you are wanting to heat up a cool boiler full of cool water and yes it takes awhile. As he described, you want to separate the heating up of the boiler time from your main vent filling with steam time.

It's easy to do that by cutting power during a call for heat, leave it off for maybe 5 minutes and then power it back up, make sure it's calling for heat still and then time how long it takes for steam to get to your main vent.

roberts

I finally got a chance to take some measurements.

The longer main went from 69 degrees to 205 degrees in about 26 minutes. At 12 minutes in it was 142 degrees.

The shorter main vent went from 73 degrees to 207 degrees in about 18 minutes. At 12 minutes in it was about 180 degrees.

A couple questions on pipe insulation. How important is it to cover the elbows and connections? Mine are only covered where smooth.

Also, any reason not to insulate all the pipes coming up from the boiler? Mine has none there, see attached photo. It definitely gets hot in the boiler room, but maybe that's a given!

ethicalpaul

You're still not getting the useful times. You are timing how long it takes to heat up a cold main. This is a number that is unrelated to how good your venting is.

Interrupt a call for heat where the mains are already steam hot. Then wait like 5 minutes. Then power the boiler back up start your timer and go to the main vent and stand there until it stops venting air. That's when it will close to the steam and that's how long it takes for your venting to allow the air to escape.

You don't have to insulate the joints, or you can insulate the joints. It won't matter much either way. Yes, you can insulate the "near boiler piping", it will make a difference.

109A_5

Hello @roberts,

One example;
Today about 30 ° outside and a bit windy.
Single 36 foot insulated Main pipe, old T87 thermostat, boiler runs about 3 cycles per hour.
From the boiler firing up it takes about 30 seconds to start steaming.
From the boiler firing up to the Main vent closing is about 2.5 minutes.
The boiler runs for 8.3 to 9 minutes.