What's this doing?

Ironman

Looked at a job with 1920 gas boiler and 2 pipe Dunham traps and packless radiator valves. No Dunham vacuum components.

Can someone tell what this is doing. It looks like a bucket trap, but the way it's piped, I can't see its function. It's high above the boiler on return lines from the 2nd & 3rd floor.

gerry gill

a main vent i bet

EBEBRATT-Ed

that looks like a float vent. you usually see them with a boiler return trap which may have already been removed. was probably a vapor system at one time

nicholas bonham-carter

I believe there would usually be a check valve on the horizontal below that Dunham air eliminator.--NBC

Danny Scully

It's part of the Dunham Home Heating System actually. It has this float inside and an air vent on top.

Ironman

It appears that this is what I have:


I couldn't find an air eliminator that looks like the one we've got, but the piping and system description match up.

Ironman

Another question: can TRVs be installed in place of the Dunham packless valves?

Steamhead

That's right, it's an air vent. There's probably a vacuum check in the top, which you should remove.

Tunstall may be able to supply inserts for those packless valves that would turn them into TRVs.

Ironman

Steamhead said:

That's right, it's an air vent. There's probably a vacuum check in the top, which you should remove.

Tunstall may be able to supply inserts for those packless valves that would turn them into TRVs.

How about replacing it with a BigMouth or Gorton #2?

Steamhead

Ironman said:

Steamhead said:

That's right, it's an air vent. There's probably a vacuum check in the top, which you should remove.

Tunstall may be able to supply inserts for those packless valves that would turn them into TRVs.

How about replacing it with a BigMouth or Gorton #2?

That's doable. Most of these have 1/2" threads where the vacuum check screws in, so it's a simple matter to put a vent there.

I'd use the Gorton. The Dunham unit does have a float in it which is supposed to close against water, but after all this time we don't know if it still works. The Gorton has its own float, whereas the Big Mouth does not.

Sailah

Doesn't look like the Dunham Air Eliminator I have their old catalogs. Looks like their DB Type OB inverted bucket trap someone has converted into a poor mans air eliminator.

You could check that the float works pretty easily by opening a union downstream and filling it with water.

Or you could make an new float trap with air vent by buying a H pattern F&T trap. You'd remove the air vent and plug it in the head. We make those as float traps. Then take a street elbow from the other inlet, add whatever riser you want and add a Big Mouth. That way you'd have the fastest venting and be sure that the float mechanism works.

It could very well be a Sarco or Hoffman Air eliminator. I have some NOS if you want one

Ironman

That's what it looked to me too.

I'm headed back over there and maybe I can get a better look at it and a number. Its hard to reach: down in narrow pit behind the boiler and about 14' up.

Steamhead

Take a look at what's cast into the unit. It should say it's an air eliminator. I've seen this type in the field- IIRC this is an earlier version than the one we usually see.

Ironman

This is the best pic I could get today standing on top of the boiler:


I'm gonna have take a small extension ladder back with me next time to be able to get up to it.

With it being 8' above the boiler's water line, is it even necessary?

Sailah

Def an air eliminator, I bet it works almost the same as a bucket.

Danny Scully

I told you what it is @Ironman! The vent connection is 3/8". You have a Dunham Home Heating System and it's listed in The Lost Art. There is just a simple float inside which I attached in my first post. If the pressure rose too high the water would raise the float and seal the vent.

Ironman

Danny Scully said:

I told you what it is @Ironman! The vent connection is 3/8". You have a Dunham Home Heating System and it's listed in The Lost Art. There is just a simple float inside which I attached in my first post. If the pressure rose too high the water would raise the float and seal the vent.

Never doubted you or Steamhead. I just never saw one shaped like that (even in old books) and I thought that Peter may have been on to something about it being converted into an air eliminator.

So, with it being mounted 8' above the boiler is it really necessary? Could I just replace it with a main vent?

Danny Scully

I would remove it in favor of upgraded main venting, however, a vaporstat must be added and set to cut out somewhere in the 8oz range.