System Venting Problem

David Nadle

That's not a Hartford loop, it's a main.

Does the main vent on the bad main get hot around the same time as the main vent on the first main? Can you hear it venting soon after the boiler starts steaming?

Bob Hoff

System Venting Problem

Background:
I have an early 1900's 4-square home with single pipe steam heat. I recently had my 1951 vintage American Standard boiler with a new Burnham. It appears that sometime in the intervening years the system was modified to have 2 Hartford loops (an enclosed porch was added and a radiator was installed in the kitchen). I know that a radiator was removed from the small bedroom over the foyer and the supply pipe was capped. A second loop was added to supply the porch and kitchen.

The Problem:
When the new boiler was installed, the main vent valves were replaced with the same #1 GORTON Air Eliminator. Not sure what vents were there to begin with but I am sure that they were different. The thermostat is in a room on the first loop. The first loop gets hot fast. The second, not so much (the thermostat shuts down long before they heat up).

The Solution:
I am guessing that the old system was vented in such a way as to bias in favor of the second Hartford loop...do I need to find a combination of vent valves to replicate this bias? If so, does anyone have vent valve comparison information related to ther vent rates? Or am I barking up the wrong tree?

Bob Hoff

Thanks for the clarification.

No, it gets hot about 2/3 through the cycle. Yes, about the same time as the other one.

David Nadle

So it's venting, but verrry slowly.

Could there be something about the way the two mains are connected to the header that favors one over the other? Can you post a pic of the near boiler piping?

Bob Hoff

Near Bolier Piping

See the attached pix!

David Nadle

Hmm

Is that header 24 inches or more above the waterline?

Bob Hoff

Hmmm

I make it about 19" from the water level in the sight glass to the centerline of the header. I will check the pix I have of the old installation.

David Nadle

Also

Do you have a tapping on top for a second riser that's not being used?

Try to find the installation manual for that model boiler online and compare the recommended piping to what you've got.

Bob Hoff

reply

Yes, there is a cap on top of the boiler.

I've attached the manual page marked up and provided a diagram of my system to this message.

Unknown

The "It might be easier to do this" is by far the better one as it uses swing joints and a drop header. With the second steam pipe coming from the boiler your steam will have less velocity and therefore be dryer.

I don't know why the boiler manufacturers even show the steam pipe setup other than to get the minimum bid. If they want to do that they should label the one pipe version "Minimum Bid" and the other as "Optimal".

David Nadle

Both diagrams have swing joints.

Unknown

My understanding of a swing joint is that both ends need to allow movement (swing). In the case of the boiler risers this needs to be in the same plane. The left diagram uses a tee and an elbow which do not allow movement of the piping (in the same plane). A "real" swing joint is totally universal like a car drive shaft universal. (See attached drawing)

David Nadle

The purpose of the swing joint is so that when the heated header pipe increses in length an accomodation can be made by at least one fitting rotating slightly on its threads, instead of pushing apart the sections of the boiler.

If you look carefully at the left diagram you'll see that the header is not in the same plane as the risers, and the elbows perform the swing function.

Steamhead (in transit)

But

the tee at the other end of the offset in the left diagram does not allow the offset to swing in relation to the header, so its allowance for expansion on the riser end of the offset is minimal.

The drop header in the "might be easier" diagram is DEFINITELY easier to put together, gives dryer steam, and allows for expansion. That's why we use a drop header on every job with two or more risers to the header.

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Unknown

In the drawing at the right you have free movement (swing) where as in the drawing at the left the tee and the elbow "locks" any movement on the header end. While swing joints help with the expansion problem, they are probably more important in the fact that they adjust for discrepancies in the pipe and fittings. Example: If the header length between the elbow and tee isn't exactly right either by length or by the number of turns that it is tightened it can sets up a tension situation at the boiler end. Thermal expansion will then put further tension on the system.

If nothing else doing them as full swing joints (as in the diagram on the right) makes the pipe fittings much easier to assemble.

Edit: LOL...Steamhead being the pro he is, said it better and faster than I did.

David Nadle

Thanks.

I stand corrected.