Air Leak in PVC Service Entrance Head

I just installed a new service entrance on my garage. This is a farm and each building connects to a pole with a 400A main shutoff. I did however put a 100A box with it's own main in the garage. Anyhow, the wiring is not the problem. That works fine.
The problem is the PVC entrance head. I used 1 1/4 pvc and matching head. These heads have three pre-made holes. Each hole is about 3/4 inch in size. The wire is #4 copper which is about 3/8 dia. So, what I got is a huge air leak coming into the breaker box. Yes, this is only a garage, but the same heads are used on houses too, and I did try to make this garage air-tight when I rebuilt it, since I need to work in there in the winter and I use a space heater. Besides the air leak, I can see that head getting filled with wasps in the summer.
I went to the clerk at the Menards where I bought the supplies. The clerk was clueless. I had to show him a service head on the shelf before he knew what I was talking about. Then he said to caulk it shut, but cautioned me to use fireproof caulk, saying "the wires get real hot". OK, that was a waste of time..... If the wires got that hot, the pvc would melt.... I asked for the manager who told me there is nothing made to seal the holes and they are designed to keep the wires cool. So much for that advice.....
Anyhow, I am still facing the air leak and wasp nest problem. Does anyone have any suggestions how to plug the gaps around the wires? I did consider using silicone caulk, but I think the wires do need to flex from temperature changes and should not be sealed that tight. My only other idea is to stuff fiberglass insulation in there. Anyone got any other ideas?
Thanks in advance
George
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On Sat, 01 Nov 2003 11:10:29 -0600, snipped-for-privacy@nospam.com wrote:

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How about either a rubber or high density foam plug, with a cutout for the cable, and a slit from the edge of the plug to the cable cutout, so you can slip it over the cable? The high density foam you can get from a fabric or craft store for sure.
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On Sat, 01 Nov 2003 10:45:02 -0800, snipped-for-privacy@yahoo.com wrote:

It's been a long time since I've done an entrance, but, IIRC, there's a gasket made just as you describe.
...Jim Thompson
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----------------- From my experience with spray foam, it's too brittle. I think he needs something that has some springiness to it.
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snipped-for-privacy@nospam.com wrote in news:too7qvs09gf5bfg4spnho743m0ue04elch@ 4ax.com:

I think you want something called duct seal. It's a grey, non-hardening, removable putty available with the electrical supplies at Lowes/Home Depot/supply houses etc. Most places have it in 1 pound bricks for a few $$.
Doug
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This ductseal does harden over time.... Just use a small amount of Great Stuff Foam (I think that is the name) Spray a small amount into the leaking area. This and any other sealant will not cause any problems. Who cares if the cable flexes; it won't hurt any thing using this foam. Duff
32 years in the IBEW.
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