One pipe runout under an obstruction?

Chuck_17

One pipe system (in a church).
In the wing in question the main (~2") (serving two large radiators) slopes down in the direction of flow. At the end it rises to the two radiators and also drops down (untrapped) to a low "return" (~1"). I did not have access to the steam room (where the campus steam comes in and presumably the condensate is pumped back). So I am not sure if the return is wet or dry. (Piping is in the basement below the radiators.)

The question is - how to pipe to a new radiator where there is a beam in the way? Slope down to a tee below the radiator. Steam up to the radiator and pipe down and over to the return?

Chuck_17

P.S. I presume the "return" drops below the water line of the return pump at some time but am not sure if the "return" pipe out in the subject wing is wet.

Abracadabra

A picture would go a long way to helping. If I understand you correctly, you'd need to run a pipe both above and below the obstacle and then continue the main on the same slope.

DanHolohan

Yes, and the centerline of the pipe that goes under the obstruction has to be a couple of inches higher on the radiator side of the obstruction to encourage the backward flow of the condensate.

Chuck_17

The question is about a runout to a radiator. Assume we can't go over the obstruction. See attached (I hope).

Fred

Chuck said:

The question is about a runout to a radiator. Assume we can't go over the obstruction. See attached (I hope).

From the looks of your drawing, if going under the obstruction, I would think any and all condensate that is returning down the main from Rads further upsteam on the Main will drain into that downward pitched radiator run. Gonna be a noisy pipe and may well not carry any steam.

Abracadabra

Chuck said:

The question is about a runout to a radiator. Assume we can't go over the obstruction. See attached (I hope).

You can pipe the runout similiarly to what I have shown. That diagram is not just for mains. If you can't go over the obstruction, then you have a problem if you can't reach a return lower than the lowest point that will be achieved on the runout.

Chuck_17

See my first post description of the main.
There is a "return" at the basement floor level (a few feet lower than the low point of the runout under the obstruction).
See attached which is more less what is there.

If I can get over the obstruction there is no problem (I just use the first of my two details).

DanHolohan

Not too crazy about the double radiators off the one takeoff, but it will probably work if that stretch the the far radiator isn't too long.

Drain to a wet return.

Abracadabra

Don't take the new takeoff below the main like shown in your sketch. Should be above. You don't want all the condensate in the main draining into your new takeoff.

Chuck_17

Thanks for the comments.
The double radiators are there (and have been for 100+ years). We are just adding small one nearby.
If the existing return is dry, will it be a problem?

DanHolohan

Where will it go wet? It's going to be a steam main if you keep it dry, so make sure you have enough Dimension A wherever it goes wet.

Chuck_17

See photo. Actually the steam main is maybe just below the obstruction so it may be possible to get under it without going down at all.

Fred

Where's the overhead obstruction? It looks like it is open all the way across. Oh, I think I see it (a contrete support?) It looks like you can run your radiator run between the joists and over that concrete support.

KC_Jones

I was thinking the same thing Fred, why not just run it between the joists?

Chuck_17

It may be possible to get over it (through the joists). It may be possible to get under it (without dropping). For the sake of learning something new and for future reference - how to pipe it if we need to drop below the steam main???

Jamie Hall

Make sure you are well above the water level in the boiler, as backed up by the boiler pressure. Then come down from the main to your "horizontal" runout (it has to be pitched, of course!) and take the runout off a T, continuing on down with a drip to a wet return somewhere. The runout should pitch back to that same drip.