Replace main or radiator vent?

notch

The last radiator in my house is only giving heat sporadically. I am wondering if I should change that radiotors vent or the main vent on the 2 pipe sytem first? Is there a way to trouble shoot to find out which if one of those vents are the issue? Thanks in advance for any help.
FYI my boiler cuts out around 1 1/4 lb

Abracadabra

There should be no vent on a 2-pipe radiator.
Pic of the main vent?

notch

I apoligize. I meant one pipe. I will send a pic of the main vent in a few hours right when i get home from work.

Koan

1) wondering if the pressure is a bit high

" keep the Pressuretrol® or Vaporstat® set as low as possible, because:
Low-pressure steam moves faster than high-pressure steam. If you want steam to reach the end of the main quickly, lower the pressure and make sure you install a large-capacity main air vent.
All radiator vents have a “drop-away” pressure rating. This is the maximum pressure at which the float inside the vent can fall down without stopping the vent from re-opening. lf the pressuretrol setting is too high, the vent closes and stays closed, and any air remaining in the radiator can’t vent.
One-pipe steam radiators were sized to heat the house on the coldest day of the year with less than 1 psi of steam. For every square foot of EDR, the radiator will emit 240 BTU/H when the room temperature is 70°F and the steam temperature is 215°F."

unitedstates.xylemappliedwater.com/2015/07/14/dos-and-donts-for-one-pipe-steam-systems/

2) I would replace the radiator vent first. It is easier and less expensive.

notch

Here is a pic of the main vent.
Makes sense to change the radiator vent first. I have a Gorton C valve as well as 1-5lb psi gauge ordered. Be interesting to see if I can calibrate my pressuretrol better with the Gaige branched off that pigtail and solve the problem. If so I can just return the vent. If not I'll give the new a vent a try

Fred

That main vent is no where near what you probably need for the main. You always want to vent the mains fast and first before you try to balance radiator venting. The more air you can get out of the mains, the less air left for tiny radiator vents to try and push out. How long is each main and what diameter pipe? That will tell us how much venting you need. While it is not necessary to vent dry returns, if your vents are at the end of the dry returns, we need to know the length of the pipe from the boiler header to the vent location. Air need to be pushed out of all the pipe, to the vent before it will start to push steam out to the radiator run-outs evenly.

notch

Thanks everyone. I finally got a gauge that reads 1-3psi. From there I discovered my pressuretrol was actually cutting out at around 3 lb and not cutting back in for a while after it hit 0psi. I was unable to get it working with less pressure so I replaced it with a vaporstat. I got it to cut out at around 1 1/4 and kicks back in at 1/4 and walla the radiator at the end of my run is working great! Just as you guys and every other post I've read through said.
The only problem I now have is that I'm getting extremely short cycles. The pressure raises up to the 1 1/4 within 45 seconds (not on initial cycle) then drops back to 1/4 after only 30 seconds or so. The first thing that comes to mind is to change the main vent. In answer to Fred's question in the last post I have roughly 90' of 2" pipe running the diameter of my basement with 40' of 1.25" branching off for 7 radiators.
I am leaning toward the Gorton #2 air eliminator. If anyone has advice on another main vent that would be better please feel free to add it. Thanks again and I'll keep ya posted on how that changes the cycle.

Fred

On that 90 ft. main, you need two Barnes and Jones Bigmouths. They are a little less costly than the Gorton #2's and each one is about double the capacity of a Gorton 2, not to mention much, much better quality.
https://www.amazon.com/Barnes-Jones-Big-Mouth-Vent/dp/B01F26P13C/ref=sr_1_fkmr1_1?ie=UTF8&qid=1483750656&sr=8-1-fkmr1&keywords=Barnes+and+Jones+Bigmouth+vent

notch

Thanks. I'm assuming I should tap threads into the pipe around 6" I front of the other vent? Could I have them both branch out in a manifold to avoid tapping into the pipe?

notch

I figured it can't hurt to include other pics as well

Fred

Yes, That's a 3/4" tapping there. Put both of them on an antler and install it where that old vent is.

Jamie Hall

You can indeed have them both hooked up to a pipe arrangement and have just the one tapping into the main. You could probably put them both where that one vent is now, although that's not ideal.

Abracadabra

your boiler is rated for 358 sq. ft. EDR. what's the total radiation?
measure the radiators.