Pex for steam return line

Jamie Hall

This ^^^ and @ChrisJ 's comment. As those of you who read my comments, you will know that I try very very hard to suggest the best solution to a problem I can find -- sometimes even forced air! That said, I have never suggested changing a steam system to hot water, and never will. There are too many things to go wrong -- and only one possible advantage (hot water is a little easier to zone).

jblum

I am late to the conversation but want to add that I am always interested in checking the annual cost for heating per square feet or per residential unit to get a sense of whether to suggest that the customer start thinking about a change to decentralized heating down the road.
James Blum PE
NY, NY

mattmia2

Understanding a little math and using orifice plates or metering valves has been the answer to steam trap costs for over 100 years.

Shouldn't the return only have liquid water and air in it? It has been a little while since i read this, but what woudl be the problem with water sitting in pockets in this?

pedmec

Install a condensate pump. drain the condensate into the condensate pump would allow you to use small schedule 40 steel piping. do it this way will allow for a small pipe to be slipped into the shaft opening easily. and you don't have to worry about sags. even thou you are willing to use pex with sags.

HEATSPEC

As to Steamhead's reply:
In reply to Steamhead:

"1. A hot-water system runs with 10x, etc......or radiators."
Regrettably, a valid point, and the older the system the more leak-prone it is. In an ideal world, ALL leaks would be corrected, but the costs could be astronomical, as you'd essentially have to rebuild the entire system. Still in, say, 2 or 3 story systems it might be worth considering....

"2. A hot-water radiator can only emit roughly 2/3 the heat of the same radiator on steam...."
Assuming that's true, then if you embark on some insulation program to upgrade the thermal EFFICIENCY of the structure itself, then perhaps only 2/3 of the heat may be needed, in which case conversion to hydronic may be very feasible.
Also to be considered: if the radiators were designed to heat the structure during the old pre-depression "open-window" Era, then wouldn't they be oversized for steam anyway? I guess what I'm getting at is: are you SURE that these radiators aren't actually a bit oversized for the needs of the areas they are heating? Especially considering that hydronic heat would be constant, 24/7; I would think that in most cases the hydronic conversion would work just fine.
Just sayin'...

Jamie Hall

The problem with sags in dry returns is that you may have trouble with venting -- since the dry returns are the vents -- and PEX will sag quite happily even at 120 or so.

Yet again I see the supposition that heating systems in the pre depression era were deliberately oversized so that the windows could be open. Sometimes perhaps. However, this is an exceptionally bad assumption to make -- since by my observations in a number of structures it simply isn't true, and if you do make the assumption you may very well wind up with a system which won't heat the structure. This gives you an annoyed customer, a building inspector who won't give you a CO, and a very expensive call back.

mattmia2

Couldn't you fix that with another main vent before it goes to the building with the boiler?

ChrisJ

@Jamie Hall My understanding was before the Great Depression they were oversized so windows could be cracked, not "open" and then After the crash happened that trend died off fast.


My bedroom radiators are grossly oversized vs the rest of the house and I believe the system was added to the house in the mid 1920s. Geppetto would have absolutely no issues with Figaro opening the window a small amount for him in a bedroom when it was -10F outside.

Jamie Hall

Not saying that some installations weren't oversized to compensate for open windows. Perhaps even many. All I'm saying is that it's not a safe assumption to make.

ChrisJ

Jamie Hall said:

Not saying that some installations weren't oversized to compensate for open windows. Perhaps even many. All I'm saying is that it's not a safe assumption to make.

No,
That's why we do EDR calculations and I feel in addition a general heatloss should be done as well when sizing a steam boiler. Someone figures out they need less radiation than they have, they can safely cut down on the pickup factor. If they need more than what they have, they can go with the standard 33%.

I won't even entertain the idea of converting a system