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HWH - Water temp drop normal?

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kredmore
kredmore Member Posts: 53
I have a old smaller HWH system with 2 zones, learning maintenance and potential upgrades as I go. I'm testing out Taco Delta T pumps, and all seems to work well in my application. I have noticed the supply temp (via strap-on pipe temp sensors) is lower than the boiler temp. Sometimes just 5 degree diff, other times 20+ degree difference. I know there are lots of variables, but should I be concerned with the 20+ difference? Maybe it doesn't even matter, as the main point of the Delta T is the diff/pump speed.

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  • Zman
    Zman Member Posts: 7,573
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    5 degrees sounds pretty normal. 20 degrees, not so much.
    Can you post pictures of your piping?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • kredmore
    kredmore Member Posts: 53
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    1 pic boiler, 3 pic piping on the backside top to bottom
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,619
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    Can't tell from pictures. You need to stand farther back
  • kredmore
    kredmore Member Posts: 53
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    More...let me know if other angles are needed
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    How do you know the accuracy of the boiler gauge and the strap on gauge?

    There was an error rendering this rich post.

    the_donut
  • kredmore
    kredmore Member Posts: 53
    edited May 2018
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    There are two temp gauges on the boiler, usually within a couple degrees. For the pipes, there are two supply sensors from two pumps that are also within a couple of degrees. I haven’t gone as far yet to install an actual gauge in the piping.
  • Zman
    Zman Member Posts: 7,573
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    I can't tell much from your pictures.
    If you are throttling the flow through the boiler back too far, that could be causing the issue. The sensors closer to the flame are reading higher.
    The boiler looks to be cast iron which is pretty forgiving of flow rates. If it where mine, I would increase minimum flow a bit.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • kredmore
    kredmore Member Posts: 53
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    Thank you. That would makes sense, as the temp difference is greater at slower pump speed, not as much at higher pump speed.

    I can easily take more pictures, just not sure the best way to make it easier to see my system. Any advice would be welcomed, as not trying to make it more difficult!
  • delta T
    delta T Member Posts: 884
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    From what I can see, there is a single supply, then an old (Bell and Gosset?) flow check valve, then a tee from which the two zones are pumping away. If there is not another check valve on the other zone (the one with the black Taco pump on it) then it is possible that the delta T pump is pulling water backwards from that zone when it is not in use. This could be the source of your strange temperature readings. Hard to tell for sure without being there. It does look like there is an old swing check valve on the return for the zone with the black pump, but it may not be operating correctly either.
  • kredmore
    kredmore Member Posts: 53
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    You have it right with single single to B&G flow check into a tee for the 2 zones. Good thought on the check valves, but both pumps are delta t with included check valves installed. Plus with one zone running, other zone still cold. Checked both zones this way, one at a time.
  • delta T
    delta T Member Posts: 884
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    hmmmmmm well, there goes that theory!
  • kredmore
    kredmore Member Posts: 53
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    The two boiler temp sensors are at the top front of the boiler, while the return is at the back bottom and supply is at the back top. Could the water temp at the supply side of the pump (at slow speed) be that different (up to 20 degrees) than at the front boiler temp sensors? Meaning is that expected, or sign of a problem?