insulation and heat sensors

pippi Z

I live in a large mixed use comercial/residential space that used to be an old library with a double pipe steam system. Been reading the discussions on insulation thickness for the piping and have a few questions.

1) It seems that 1" thickness is pretty standard for insulating piping from residential boilers-- Is it pretty much the same for a commercial size boiler? I'm wondering if that because I have some 3" to 6" pipes that I should go 2" thickness on the insulation here and 1" on the smaller pipes. Someone wrote that "At 200 deg. operating, 80 deg. ambient, 1" insulation reduces heat loss 86%. 2", 91%. Surface temp is 93 deg. vs. 86 deg. Meanwhile, the 2" insulation is 2.6 times more expensive. " So, I was looking at the heat loss charts at my local insulation dealer and was wondering -- How damn hot do those pipes get? Do I need to consider the heat of the outside of the pipe over 200 degrees? The chart goes up as high as five hundred degrees and I'm wondering what temps I should be concerning myself with.

2) We have recently installed a fire alarm system as is code in Rhode Island for all commercial spaces. Over the summer we turned on the heating system to check something out and it triggered a heat sensor. basically - not sure on the rational on this- there was a heat sensor installed just a few inches above the 18" galvanized steel exaust pipe right before it connects with our chimney. I know that because it was summer- and the air was warmer and there was less heat needed to trigger the sensor -- but it seems that we need to insulate this exhause pipe so that this doesn't happen again - What would you use to insulate the exhaust pipe? Is this normal?

thankyou so much for any advice!

Brad White

Temperatures

Low pressure steam is typically about 215 degrees give or take two. Not a strong issue when insulated. Your surfaces will be safe to touch, for sure, maybe 10 degrees above ambient at most. (I have tables to tell me more precisely just not next to me now.)

As for the heat detector, that exhaust pipe well could have set it off, sure. Most heat detectors are set for a 125 degree limit or "rate of rise" such as might occur as a fire starts. Entirely probable, that condition. If you had generator exhaust, it could be 900 to 1,100 degrees and takes a special mineral wool insulation or calcium silicate.

Insulate.

bruce_21

There may be some esoteric reason why the heat sensor was placed where it is. I'd call your building inspector and ask him about it. It's in the boiler room to tell you if it gets too hot in there (like a fire), but you probably can move it a couple feet away from the smoke pipe to avoid this nuisance alarming. That will be the least hassle option. You can also cut the heat from the smoke pipe a good bit by just "roofing" it with another piece of metal. Put some 1/2" copper couplings between and run some screws thru them to hold it all together.

pippi Z

heat sensor

Getting the fire alarm system installed was pretty much a drawn out, way more expensive than estimated, beaurocratic hell. Fire code laws in Rhode Island (because of the Station nightclub fire) are out of control. It's impossible to get anyone to sign off on anything these days. I'd prefer not to deal with inspectors again - knowing that it could open another can of worms....
The comment about the generator exhaust system confused me a little. How do I figure out what sort of exhaust system I have, so that I may insulate for the proper temperatures?
thankyou all for your suggestions!