Maxim 255 Temperature difference

Cliff DeCarlo Posted By Cliff DeCarlo, Mar 13, 2019 at 10:40 AM

  1. Woodman1

    Woodman1
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    Jan 15, 2018
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    I'm pretty sure the "mixing valve" is central boilers attempt at boiler protection. Basically their version of a danfoss valve. I have never seen one personally so I don't know how they are designed to be plumbed. To go back to the original post I thought the question was why the op was losing 20 degrees of heat from the boiler to the valve. I'm still guessing he's not and the water leaving the boiler is the same temp as it is hitting the valve. Too bad he can't get an accurate reading with the ir gun this could be solved in 2 minutes! Lol!!
     
  2. Woodman1

    Woodman1
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    Anyone trying to push more than 7-8 gpm through 1" pex is going to be fighting an uphill battle. 5 gpm with a 40 degree delta t delivers the same amount of btus as 10 gpm with a 20 degree delta t. Just make sure you have the boiler protection installed correctly
     
  3. Cliff DeCarlo

    Cliff DeCarlo
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    Mar 12, 2019
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    O.K. I understand now. I'm not sure about the internals of the boiler (I will have to see if there is a diagram available to see where the water is being drawn from in the tank).
     
  4. Cliff DeCarlo

    Cliff DeCarlo
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    It was something the installer insisted was necessary for the boiler installation. Basically it only opens the valve once it gets up to 160 degrees F. I guess the thinking is that it will send the water flow directly back to the boiler until it gets up to temperature. Once the valve is open it will send water through the heating loop and when it is closed it just returns it immediately back to the boiler. And yes the 007 is the only circulator pump for the one loop.
     
  5. Cliff DeCarlo

    Cliff DeCarlo
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    That thermostatic valve is designed to be closed when the water temp is under 160 degrees and open at higher temps. When it is closed it sends the water immediately back to the boiler (bypassing the heating loop). I think they want that installed to help the boiler get up to temperature quicker when the water temp drops below 160. The IR gun did give me a temp reading of 180+ on the flange of the pump (but it is all over the place when shooting the pex and elbows).
     
  6. maple1

    maple1
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    Spraying the spots you want to measure with flat black spray paint might help. For me and my gun, sometimes it does and sometimes it doesnt.
     
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  7. Cliff DeCarlo

    Cliff DeCarlo
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    Thanks for the feedback everybody. I think I'm going to pick up the variable speed Taco 0015 (and maybe some in-line temp gauges) and see if that makes a difference on the temperatures. I'll post the results of the new pump so everybody is aware of the outcome.
     
  8. Eureka

    Eureka
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    https://www.supplyhouse.com/SharkBite-24441-SharkBite-Temperature-Gauge-with-1-Tee-Lead-Free
    These are a handy all in one solution for temperature readings. You can also do a tee and stick a temp gauge in that just make sure the well sees actual flow. If it’s just stubbed into the tee it won’t be accurate. Supply House is great for this stuff. I used Watts gauges into tees and also have a couple Sharkbite gauges. The latter are real handy just cut and push on.
     
  9. Cliff DeCarlo

    Cliff DeCarlo
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    So I installed the Taco 0015 pump this morning....no difference at all (all three settings). The temp at the thermostatic valve is still 170-175 when the boiler control unit is reading 185-190. I've ordered a pipe clamp temperature gauge and a long temperature probe and should be getting those on Tuesday. I'm going to take some readings at various spots along the pex (including right at the supply side on the boiler) and the temp of the water again in the boiler (I think the cord will be long enough to get it right to the bottom). Stumped.....
     
  10. maple1

    maple1
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    I'm not quite seeing the need for a mixing valve at all in this pellet boiler application. If the boiler can supply say 180 degree water and flows are correct, it shouldn't see close to 140 in the return with all good insulated piping everywhere and a typical 20dT thru what I think is only one heat exchanger? Plus there is also the factor that with a pellet boiler there should be little risk of creosote condensation since it should burn clean to start with.

    But I have no pellet experience....
     
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  11. Woodman1

    Woodman1
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    I agree. However, I don't know anything about pellet boilers but in my head they should be able to maintain a constant temperature similar to a conventional fossil fuel boiler. I still think op will find out water temp leaving the boiler is the same temp that the gauge at the valve is reading
     
  12. maple1

    maple1
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    I'm kind of curious about the boiler innards. Having the outlet at the bottom like that usually isn't the best (at all) for supplying the hottest water, but if there is a stand pipe kind of thing going on inside then he should be getting the hottest water. But with just the one circ for the whole entire business, there must be some stratification going on inside it. Maybe they put the outlet on the bottom with a pipe to the top inside to try to ensure that the circ got mounted down low so there would be more head pressure to it.
     
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