First, much thanks to those who take the time to donate your knowledge and experience. I've got a NCB-175 on the way (and sacrificed dearly for it) and a lot left on the parts list. I'm having trouble arriving at a solid conclusion on number of pumps and loops to meet the heating needs, so any responses could potentially save me hundereds on the parts list along with wasted time so - thanks in advance!
Here is the application:
VERY leaky 2500 sq/ft house, 2 floor, and built in '72. Air handler for the heat pump is in the attic - I refuse to put a HX in the plenum (for a number of reasons, including my peculiar logic
)
I had hope for the NCB-175 heating the entire house on a 0*F day comfortably, doubt it will happen, but might get close. Of all the online calculators I get an average of 240k btu requirement on the worst possible day.
1. Primary HX, manufacturer claims 200k btu, it is a unit heater with big fan. This is overkill I'm sure, had plans of changing fan motor to 3 phase with an eaton motor drive to have full rpm control. This will basically be replacing what the wood stove was doing and in same vicinity.
2. Second, HX air will be pumped through the floor, center of house, the unit claims 100k btu, the inline blower pulling the air is 440 cfm and can't (doesn't need to be) changed.
3. Third, domestic hot water,, already configured in an unorthodox (but proven effective) manner. The details are probably irrelevant, but it does have a circ pump and differential temp controller from previous setup. A plate HX will be used along with another separate pump - water heater tank cannot overheat this way.
4. Low priority so lower performance is acceptable - shop HX. The unit I have is a 150k (claimed) and way overkill because the small (affordable) units have all been sold out, so I went BIG.
Being mindful of the implications that exist with the way I wanted to set this up, I see the status quo seems to be leaving the pump running 24/7, >150* return temps, and ~20* deltaT. There seems to be an obstacle with every good configuration that I've come up with, but here is my best thought -
1-2 and 3-4 are within close proximity to each other, and all entering the house at same location.
1 and 2 will need total loop length of about 150'. 3 and 4 will need total loop length of 70'
OWB feet are 7' higher than 1,2,3,4.
The underground pex I have is 1"
My math shows up as an estimated 12.5' effective head. Flow through 1 and 2 need to be 15gpm combined (according to my math). I was thinking it may be best to run a grundfos 26-99 through two loops paralleled coming off that same pump to feed #1 and #2. By some means a filter would be nice to add here.
3 and 4 may best be together on same loop (1") due to their location being within a couple feet and priority level the same. A grundfos ups15-58 for these?
OR
Would it just be better to run a 15-58 for #1, and another for #2, and another for 3 and 4, then another 15-58 for a backup (since they are cheap). Now how do you put filters on all these affordably?
Well, this turned into a book. My apologies. I will stay awake for nights to come thinking about this until the heat blows in this house again.
Big thanks.