28 inches.

ChrisJ

When measuring to see if you have 28 inches from your NWL to the lowest steam carrying pipe I assume dry returns also count?



My issue is if I want to go with an IN5 it appears I might only have 27 inches to the end of one of my dry returns.  The steam main is much higher obviously. 

Will this cause a problem?



I'm having trouble getting a perfect measurment as the boiler is on a concrete slab while the dry return is over dirt. I may need to make a water level to be sure.

Steamhead

Should be OK

there was a bit of extra headroom in the 28-inch "A" dimension.

JStar

Numbers.

Your A Dimension technically only needs to be high enough to match the steam's pressure loss in the main, plus a little extra. If the boiler runs at 2 psi, and the steam loses 1/2 psi at the end of its run, you would need an additional 1/2 psi of pressure to push the condensate back to the boiler. 1/2 psi = 14 inches. But just adding another 1/2 psi would only equalize the supply and return, so to make sure that the condensate really gets pushed back into the boiler, we raise the A Dimension to 28. 28 inches = 1 psi. So now the return has 1/2 psi more pressure than the boiler (1-1/2 plus 1).



In other words....27 inches is fine. It equals something like 0.96 psi.

ChrisJ

Ah

So theoretically something like say, 20 inches should work under most conditions?

I'm curious, is there a way to calculate the pressure drop in a steam main? 

JStar

Ummm.

A pressure gauge? I've never had the need to do it. If I had steam in my house, I would put a gauge at my main vent location just to actually see what it is. Supposedly, all/most/some/any? stream system should be sized for a 1/2 psi drop on the main. I know there's a way to calculate it but I'm sure it's in a book or chart somewhere that I just can't picture right now.