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boiler gauge reads 190; out put reads 175

kcrib Member Posts: 2
have been lurking and learned a lot and it has been really cold. so i took a look at my gas fired hot water heating system. everything seemed ok, but i noticed that while the gauge on the boiler read about 190 the outflow pipe read about 175 on an infrared thermometer with the boiler firing and the pumps running. is this ok or do i need to look further.

thanks again for all the good advice and hard to find knowledge



  • Jamie Hall
    Jamie Hall Member Posts: 23,675
    Infrared thermometers are reading only the surface temperature of the pipe, and are influenced by the finish quality -- a flat black finish, for example, will read close to the actual temperature, but a tarnished metal finish will read significantly less. They are great for making comparisons -- but not always so wonderful at absolute correct readings.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    I think you're fine. If you have an aquastat with a digital readout, compare that to your boiler gauge.
    Even a K-Type clamp on the output of my boiler reads about 10° less than the boiler gauge (which matches the aquastat reading).

    There was an error rendering this rich post.

  • kcrib
    kcrib Member Posts: 2
    thanks for the replies. i will leave it for now and take a good look at everything in the summer.
  • Gordy
    Gordy Member Posts: 9,546
    Use painters tape on the pipe then shoot it. See how that compares.
  • mikeg2015
    mikeg2015 Member Posts: 1,194
    Infrared doesn’t read metal as well since it reflect IR energy. a thermocouple works best. Clamp on thermocouple better.

    Tape might work as mentioned.