Pipe insulation

Keith_8

Any thought on how to insulate existing 2" copper mains in a tunnel?

We take of an apartment complex with a central boiler room.

One of the buildings is detached from the main building. The heat to the detached building is supplied by a set of uninsulated 2" copper mains that travel thru a 70' concrete tunnel under the parking lot. The tunnel is 18"x 18" and about 24" below grade. When the weather drops below 30* we need to run the boiler in high fire to raise the water temp and overcome the heat loss in the tunnel. Any suggestions for providing insulation with out removing the pipe?

If not then I'm thinking about replacing the pipe with Ecoflex.

Keith

Brad White

The excavation costs alone....

I just ran the piping on Siggy's HDS for 70 feet of 2" Type M bare copper in a 50 degree ambient.

With 30 GPM of 180 degree water, the piping loses about 9,700 BTUH per run for the supply and about 7,900 on the return if at 160 degrees.

The water temperature drop seems nominal, less than one degree each way. Not that it is free or anything!

(I figured 50 degree ambient being below grade with maybe not as much cover as I would like but also with a self-heat contribution. Let me know if that is unreasonable. Even if a 30 degree ambient it only goes to less than 12,000 and 10,000 BTUH, respectively; still less than one degree drop in the flow temperature.)

My question then is, if you have to boost the temperature that much to compensate, then by how much? How much are you really losing?

What I am getting at is, if the tunnel is flooded even in part, that is a lot more heat loss than I am talking about. What could be causing the difference?

I was going to suggest injectable foam (Tigerfoam) or if absolutely dry, dense-pack cellulose with long extension nozzles from each end. But if your tunnel is wet, that is another issue.

Edit: There is another material, DriTherm I believe, a white powdered marble or limestone-like material that is inert and made for direct-buried applications. Used on steam, hot water and chilled water lines.

Ron Huber_2

pipe run

You can look at the cost of the insulpex and the cost of injecting foam, I would think the foam is less expensive from a labor and materials aspect. We just bought 150 ft. of 1 1/2" insulpex, 4 fittings, cut charge,it came to $5,300.00 my cost.
You should get a quote or two from an insulator who can assure you that he can get the tunnel completely filled, without any missed spots.

ER

cellulose

My first thought was foam. But what if you need to get something out! What about blown cellulose? Seems like that would not be too hard to do and you can get it out if need be.

Eric

Ken_40

Dampness...

Ground water would wet the blown in, reducing R-values to zip/squat.

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Keith_8

Give a guy a little information

and he shoots the **** out of my theory!

Brad,
Now you got me thinking about this differently.

Possibly who ever installed the 2" mains didn't replace what was there but what they could fit in the tunnel. Or maybe the circ that serves this loop is on the borderline for GPM requirements.

Back to the drawing board.

Keith

Brad White

That makes sense, Kieth

It may not be just the circulator but a system effect. Good call to check that out.

How many SF or a finite load do you need to serve/deliver?

I figure 2-inch pipe at about 30 GPM (300 MBH at 20 degree drop), good for, say, 12,000 SF of building at 25 BTUH per SF.

Yes, I would start there first.

jp_2

insulation might not work

if the pipes are laying along the wall in the tunnel, insulation won't get you much unless you are able to suspend pipes more in the center?

redoing it might be the best solution.

Keith_8

I'm thinking

More towards a pump defeciency.

The building is about 11,000 sq ft. Being an old structure with no insulation between the brick and plaster we are closer to 30 or 35 BTU's per sq ft. That comes in at about 385,000 which the 2" can handle. The pump is a 1 1/4" HV B&G. My B&G book doesn't have the curve for this pump but I don't think it's capable of 38 GPM @ 12 Feet of head.

Thanks,

Keith

Al Corelli_2

Foam

Blow in the foam, but make sure you install one or two 4" and maybe a 2" or two, PVC conduit, so you can get from one place to another if you have to. You never know when you may need to get a wire, fiber optic cable, or pipe from one place to another.

Don't ask me how I know this.

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hot_rod

Pre insulated

PE makes the most sense. Less loss thru the wall being less conductive then copper. Easier to snake around, and less couplings. And probably a lot less $$ compared to copper.

In this system H&C with recirc and the radiant heating supply lines were installed with a Wirsbo product.

hot rod

Keith_8

Wisdom!

Al,
Good suggestion to sleeve a couple conduits for the future.

I had an older mechanic working with me (72 at the time), god bless him. He retired from the trade and went to work as a facility manager at a convalescent home. Made a deal for a room with a view when it's his time,anyway.

When we were doing an install he always said put in more valves and use tees instead of elbows where it makes sense. The stuff is cheap was his motto.
I resisted for the longest time, who wants to spend the extra $? More times than not we would be back in the BLDG 6 months or a year later and the tee or valve I didn't want to spend the $ on at the time would have saved me $$$$ in the long run. Wisdom!

Keith