Converting a wet return to dry return

Hap_Hazzard

Last fall I had to do an emergency repair on the condensate return piping of my venerable one-pipe steam heating system. A leak developed where one of the vertical pipes joined the horizontal at a tee and the threads on one of the horizontal pipes had rusted through. I actually had a hard time finding a place where the pipe was thick enough to cut threads in it, but replacing a whole section of pipe involved tearing out the wall, and I didn't even know what I'd find when I got to the elbow. Eventually I got it together with no leaks, but now I need to fix it for real before fall rolls around.



My question is about the wet return. What is the advantage of having 50 feet of steel pipe constantly full of water? It looks like I could just as easily run the return pipe 3 to 5 feet higher, increase the downward pitch, and flip the Hartford loop 180 degrees. (See pictures.)



I'll probably be dead before the pipes rust out again either way, and the system has always worked great just as it is, so I don't want to buy any trouble, but since it's just as easy to run the pipes higher, and it makes them last longer, why not? The only drawback I can see is that you lose a little reserve water capacity, but it's not that much, and I'm considering installing a probe-type low-water cutoff and automatic feeder anyway.



Are there any other advantages to a wet return that I'm not seeing?

nicholas bonham-carter

wet return

as long as the wet return is in place, even for a few inches, there is no harm in extending the dry return piping over to the boiler.

there must be a point where the return drops down well below the waterline of the boiler before it connects to the boiler.

while you are doing this work, don't forget to check your main vents, so you are not paying big buck$ to the fuel company to squeeeeeeeeeeeeeeeze the air out of the pipes, and boiler, in order for the steam to rise up to do its work!!!--nbc

Hap_Hazzard

Thanks for the advice

Currently the Hartford loop connects to the equalizer at about 2" below the water line. Is that enough, or would you recommend dropping to about the level of the bottom of the boiler a few feet before it gets to the Hartford loop? I wouldn't feel too bad about that, since I could keep the wet portion within the boiler room so who ever has to change it doesn't need to rip out walls like I'm having to do.



I will check those main vents, and I'm also going to insulate the pipes. Right now the only thing wrapped is the big pipe between the two risers, but I've never had a problem with noise, the steam gets to the radiators on both floors fairly quickly, and it hasn't been terribly expensive to operate. I think their excuse was that the uninsulated pipes were heating the basement, because there's no radiation down there, but we all know that's not the right way to heat a basement, and besides, it gets ungodly hot down there when the furnace is on anyway. If it ends up being too cold down there after I wrap the pipes I may put a baseboard on the part of the return that's not behind a wall.

Greg Maxwell

Insulation

I definately would insulate as much as you can. When you create the steam in that system, it immeadiatly wants to shed its latent heat, resulting in condensation, and as a result you have lost some capacity. Insulating keeps that latent capacity there to do what it was intended to do, and thats deliver heat to your living space, not your basement.

As far as your hartford loop goes, that 2" is exactly what you need. Please do not mess with that.

Hap_Hazzard

Definitely sold on insulation

I just need to find the time to wrap the risers and headers, but with the wet return threatening to leak, that's a little more urgent right now.



I think you misunderstood what I was saying about the Hartford loop. I wasn't thinking of moving it; I was just wondering if that was enough pipe below the waterline or if I should leave a small, 3-4 foot section at the level of the current wet return before it gets to the Hartford loop.

Steamhead

If you switch to a dry return

make sure the lowest point on that pipe (where it elbows down near the boiler) is at least 28 inches above the highest possible boiler water level. This is called the "A" dimension., and is essential for getting the water back to the boiler.



And the main vent can stay at the end of the steam main. Three's no point in filling a dry return with steam.

Hap_Hazzard

Just to be sure I understand

Is the dimension you mean the one I've indicated in red in the picture below?



I don't think this will be a problem, but I'll make sure I can maintain that distance and still have enough pitch.



Thanks for the tip!

Steamhead

That's the one

28 inches or more.