Removed Insulation on return line during service...

Roddy

Residential single pipe steam with two return lines. Overall system works well. Finally had to do a permanent solution to my one return line that had developed a number of pin hole leaks. Had about 20 feet of 1 1/4" return pipe replaced ending about 1 ft. before the section entering my boiler room. Fix worked well. In preparation for the repair, I removed the fiberglass insulation that had been wrapped around the pipe and wedged very snugly, but haven't replaced it yet...thus my question: The basement is understandably and noticeably warmer with this insulation gone---and my wife loves that. Am I doing any harm/damage/wrong if I were to leave the insulation off, or if I only replaced part of it? I know the ideal is for ALL pipes, both supply and return, to be insulated, but... My basement is finished, and before this was a little cool in the winter/heating season. Please advise. Thanks in advance for your help.
Roddy

nicholas bonham-carter

Was this insulation on the wet return? If so, I would leave it off, as it may have been a contributing factor in the rust holes.
The most important pipes to insulate would be the supplies from boiler to main vents.--NBC

Roddy

Thanks, NBC. I'm a novice, so maybe erroneously I don't think of this as a wet return necessarily, but it certainly returns condensate to the boiler, so maybe it is a wet return. It's located in the ceiling soffit in my basement. I'd thought of it as a dry return, but not exactly sure why. Thanks again.

vaporvac

If it's above the water line, it's a dry return. (Or at least that's what I've understood from reading, etc..)

JUGHNE

I've seen a dry return rust thru with pinholes because it had no slope back to the boiler. It was sitting pretty level and stayed full of water. The steam run out next to it was also leaking for the same reason.....you might check the slope on your new pipe.

Jamie Hall

If it's a return -- dry or wet -- it doesn't need insulation. In fact, it may well be better off without, as @nicholas bonham-carter said. Granted, you may lose a bit of preheat for the condensate -- but not that much.

Now if it is a dry return and it's steam hot, you have another problem, as steam should never get into a return!

Jamie Hall

I beg, respectfully, to differ.

A return -- dry or wet -- should never, ever have steam in it. If it is a dry return, steam should be kept from entering by traps, or by ensuring that orifices prevent introduction of too much steam to a radiator/condensor, or by some other gizmo.

Like the French language, there are exceptions to the rules: on some vapour systems, there will be a device, such as a Hoffman Differential Loop, which will allow steam into the dry return to raise the pressure in the dry return if the steam main pressure rises to a certain, rather low, value in excess of the dry return pressure (12 ounces per square inch, give or take an ounce, for a Hoffman Differential Loop), thus forcing water back into the boiler. That is intended to be a very short term event, though.

On any two pipe system, however, a dry return absolutely must have vents on it, otherwise the air from the radiation has nowhere to go and you get poor and uneven -- or no heat.

Jamie Hall

One pipe systems do not have dry returns... although a parallel flow one pipe system may have a section of steam main beyond the last runout before the drip to the wet return. And I quite agree that that should be insulated.

Jamie Hall

You've got a point there...

Roddy

Maybe I'll try reinsulating most of the return, leaving a few feet uninsulated for warmth in my basement.

A comment on the above posts: My main vents are at/near the end of my two return lines just above the boiler (single pipe system), and the two returns ALWAYS heat up. After reading Dan's books, that's what I'd actually expected. If they didn't heat up by carrying some steam and the condensate, what would trigger/cause the main vents to close? Aren't the main vents heat or pressure activated?

Danny Scully

No, there is no semantic confusion...there can be dry returns on 1-pipe steam systems...

Danny Scully

Jamie is the confusion lol! Just having fun Jamie Read pages 84,85 and 91 of the lost art. It is a dry return and it does get hot.

Jamie Hall

In a very real sense, @Hatterasguy is quite right -- it is semantics as much as anything. I tend to restrict the term "dry return" for a pipe intended to carry air and condensate (but not flowing anywhere near full of condensate), "wet return" for a pipe flooded with condensate, carrying no air, and "steam main" for a pipe carrying steam under slight (hopefully very slight!) pressure.

Which is probably quite pedantic of me... but it helps me keep my head clear on which pipe is doing what, and why.

I would consider the dotted parallel flow pipe on 85 (and the pipes referred to in the table on 91) to be a steam main in my thinking -- and would insulate them! -- as it is carrying steam under pressure. It will most assuredly get hot!

A rose by any other name...

Roddy

Thanks to you all. Very much. As I'd initially thought, it's a dry return, and I'll insulate most of it.