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3 questions

remodel
remodel Member Posts: 68
in THE MAIN WALL
1) Is it worth it to put in a smaller boiler pump and smaller system pump?  Boiler a loch 155.  Right now I have about 8gpm to the system and 8gpm to boiler all zones calling.  One zone calling I have 4 gpm -5gpm to system and 8 gpm at boiler.  At 30%-50% fire boiler DT good, at 20%  - 7 degree DT.  System oversized by 25% so might be a moot point. 

2) Can I put cast iron rad/panel rads in place of fin tube BB at the end of my series loop or will I rob too much heat?  I would have to pipe it in series and this loop has one FCU off of monoflows right after rad replacement.  The remove and replace is about 50%-60% of the 1st floor emitter length.  

3) Is negative DT alright at start-up?   

Comments

  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    3 questions

    That boiler needs 15 GPM to operate properly and safely at full fire.

    At 8 GPM and full fire you are damaging the boiler.

    Yes you can install cast iron rads at the END of the fin tube loop. cast iron rads will operate at 160*. They will have a different heating characteristic. But why do you want to do this?
  • remodel
    remodel Member Posts: 68
    boiler pump

    1) thing is I never have full fire (oversized) and I limited her to 80% max for SH.  Issue was with the oversize and lacking emitters I get pretty hot return water and delta t was at 3 degrees so we reduced the speed to 1 on a 15-58.  On design day she went up to 65% and modulated down to 30%-35%.  Should I even bother to mess with this pump or just leave it and try and get best condensing with ODR?

    2) One long run (~20') of fin-tube likes to tick.  Even with ramp delay and a pretty nice ODR.  Just thought maybe CI BB would alleviate this. 

    3) Any thoughts on the negative DT for 10 sec...is that alright?  Thanks.        
  • Zman
    Zman Member Posts: 7,611
    Firetube

    It sounds like you have a WHN (firetube) model? Please confirm as it is important when it comes to low rates.

    Generally, mixing and matching cast and copper in the same loops make it more difficult to balance the room heat. One is high mass and one is low mass, this can create issues.

    Is the boiler sending an error regarding the negative delta t or is it something you are observing? It could be a sensor that is out of spec. What is the difference in temp? They should be about the same at startup.



    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • remodel
    remodel Member Posts: 68
    yep WHN

    1) Had some piping issues (that are fixed now, PONPC and air) just trying to get this sucker dialed in as best as possible, I have not had any lockouts since repipe.

    2) Any tricks to eliminate that ticking BB?  

    3) DT of 0* then observe -1* max and she comes out to 6*-7* DT.  Setting boiler pump on speed 3 gives me a DT of 3*. Is it just what it is.  I will say I did choke the outlet ball vale on the boiler pump and got a much better DT at the boiler but outlet temp increased looking like she would short cycle?   

       



     

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