Is it OK to insulate pipes emerging from boiler

Al Cobrin

In response -- couple of weeks ago -- to my question whether retun lines in a steam systm should be insulated, I was advised that it's good practice to insulate all lines. So I did insulate the return lines with 1-inch preformed fiberglass sections.

But I recently read somewhere that "the return pipes should be uninsulated to promote condensation."

Question: Did I do right or wrong in insualting the retun lines?

Al Cobrin

Insulating pipes emerging from boiler

When my Weil-McClain replacement boiler was installed 3 yrs ago (in my 71-yr-old house), the contractor removed the insulation around the pipes coming out of the boiler. Consequently, I have about 3-1/2 feet of 11-inch circumference pipe(with elbows and fittings)that's unisulated. I also have about 5-feet of 8-inch circumference pipe branching off of that which is also uninsulated.

With natural gas at a premium, I now wonder whether those pipes should be insulated with fiberglass. If the answer is yes, then please tell me what size insulation I should choose that would be right for the circumferences I mentioned.

Brad White_11

Insulation

cannot hurt assuming there is clearance to the flue pipe (so that the insulation jacket does not burn). Let's assume you have an all-clear in that regard.

You do not say if you have steam or water. Not knowing that, I would recommend fiberglass as a default. If steam you do not want to use the foam insulation types -it melts.

From the circumferences you mentioned it seems the larger pipe is 3 inch IPS (iron pipe size) and the smaller maybe 2-1/2".

As a point of reference and assuming steam, the 3-inch pipe surfaces will emit 220 BTU's per hour (BTUH) per linear foot and the 2-1/2-inch pipe will emit 160 BTU's per hour per linear foot. If hot water at 180 degrees this will drop to 138 and 100 BTUH respectively. So right now you are "losing" (distributing in an uncontrolled manner) about 1,570 BTUH if steam and about 970 BTUH if hot water.

If steam, model energy codes and good practice require 2 inch thickness and if hot water, 1-inch thickness for the pipe sizes you seem to have. Know that the first inch knocks the heat loss down to about 1/6th of what it would be bare. If two inches, 1/12th. Point being you never stop heat flow, just slow it down a bit. You should be able to get the heat loss down to what a human body emits.
Hope this helps.

Brad

Al Cobrin

insulation

Thanks,Brad, for your response.

Yes, mine is a steam system. Would you please elaborate on the statement, "cannot hurt assuming thre is clearance to the flue pipe (so that the insulation jacket doesn't burn.)" The pipes I'm referring to are iron pipes, which are nowhere near the flue pipe. Incidentally, the insulation that was removed 3 years ago when the previous Weil-McLain boiler was replaced, was asbestoes. For reasons not explained to me, the contractor simply didn't replace it with anything.

Al Cobrin

Insulation

As a follow-on to my previous question concerning steam pipe insulation, I'd appreciate knowing where on Long Island I can buy fiberglass insulation to wrap the 2-1/2 and 3-inch iron pipes so I'll end up with 2-inches of insulation on them. Also, will such insulation accommodate changes in diameter owing to fittings and does it to have to be tied on or is it self adhering?

Phil_6

Try

Blackman PS. They're all over LI. at least 8-10 branches

Brad White_12

Al, Hi

My statement about burning was geared to if the pipe jacketing (ASJ a paper/foil material) might be too close to the flue pipe. Asbestos and plaster finishes, now gone, would not have been a concern. Because the steam pipe insulation OD has at least several inches of space to the flue, you should be fine. If closer than an inch or two, it may not burn right away but char over time which can flash. Just a cautionary note is all. As you said, the pipe and flue are no where near each other. Good luck!

Brad

Rodney Summers

Blackman Plumbing is located in

the following locations on the Long Island area.

http://www.blackman.com/main.html

Click on "Showrooms" link.

Constantin

Insulate everything...

... the better the pipes are insulated, the less heat is lost to areas of the house it has no use in. Plus, insulating the returns may slow CO₂ from being absorbed by the return water, which prevents carbonic acid from forming and then eating your boiler from the inside out. So, IMHO, you did right.

Speaking of energy efficiency, are your main and other vents up to snuff?

Al Cobrin

Main and other vents

Constantin,

Thanks for the reply. By "main and other vents," I assume you mean the various vent valves; that is, those at each radiator and the two I have at either end of the system in my basement.

Although I have no problem that I'm aware of with any of them, how can I really tell? All my radiators heat up ok, and I have no hissing or banging. The system is quiet.

The two main vents were replaced a long time ago -- maybe 20 years.

thfurnitureguy_4

a test for main venting. with the boiler cool, run it until it makes the header, steam hot. Start the clock. move to your main vents. listen and feel to see when they stop blowing air or get, steam hot. Stop the clock. The time to vent the mains should be in the 1 to 2 min. range. assuming a normal residential system.