piping: heat loss or heat sink?

ralman

I have an oil fired peerless boiler 121,000 BTU gross output, 17 gallon capacity in boiler, about 18 gallon capacity in the system, Domestic hot water coil, 1 1/4 inch monoflo tee system, 185 feet of base ray CI baseboard. My aquastat setting are 180 high, 150 low, 15 differential. The monoflo pipe system has a split return. 20' of 1.5" iron pipe which is teed into 151' of 1.25" iron pipe. There is 176' of .75" iron pipe risers. The pipes are in the basement of a 1500 square foot 1950 ranch style home. The basement is finished and heated with the exception of the garage area. Garage stays above 60 degrees because of the bare pipes running through it.
As an example, At a 30 degree outside temperature, I clocked five 3 minute boiler cycles during a 1 hour time period. 3 for heat, 1 for just boiler low aquastat call, then 1 more for heat. I used an infrared thermometer on supply pipe above the flow check valve a few minutes after the boiler turns off, 122 degrees measured. The short side return was 109 degrees, the long side return is 98 degrees.
I am wondering if insulating my pipes will be worth the trouble and expense. I am thinking that the pipes are acting like a heat sink as boiler water flows through. I have looked at the chart for bare pipe heat loss and it does not seem like much heat loss, but I am wondering how much heat is absorbed by the cooler pipe as boiler water flows through.
If pipe insulation would eliminate one 3 minute boiler cycle per hour I could save 75$ on fuel per month.

Brad White_9

If the piping is bare copper

and you are using a Raytek or other infrared, you will find that they do not often read correctly. The IR is reflected off of bare metal and with some external oxydation may read better but still way below what the temperature actually is.

I have read 140 degree water in a pipe as near room temperature on bare copper and where polished even less by a degree or two. When painted it read very close to an immersion sensor reading.

Hit a few spots with flat black spray paint to get a better reading. It might just be in your method of measurement.

Quick thought, I had not had time to process your entire information presented. (Looks thorough though!). I may check back later.