Yet another BIP to PAP thread

Maelos

Hey all,

I've been plotting a new combi-boiler to replace our aging boiler & tanked DHW. My timeline has been accelerated as my boiler has developed a leak and my local plumbing/HVAC company has said it would be best to replace the boiler.(Sidebar: I trust them as I'm good friends with the owners daughter and my wife is friends with the wife of another employee there) Part of my plotting involved replacing the BIP in the basement with PAP and a manifold.

The house is currently a single zone, and I am not looing to change that. We have CIRads on the 2nd floor, fin-style baseboard on the 1st floor and nothing in the basement other than the existing BIP that radiates some heat to the basement. The current BIP has two loops, both feeding a mix of CIR and BB. Current boiler is 90k btu, and largest radiator is ~16,000BTU. There are no TRVs on any radiator, and they are something I am considering implementing as my 2nd floor does tend to get hotter than the 1st floor.

I've been told by two different HVAC folks that running a manifold on a system like mine is not recommended, but all of the reading I have done on this forum as well as other locations makes it sound like it is very much doable. I was intending to feed the manifold with 1" PAP and then run 3/4" PAP to/from my radiators and the manifold. Using a manifold, would that be sufficient? Overkill? Are there other variables I need to consider that I am overlooking?

My other thought was to use a two-loop manifold, and essentially 1:1 replace the existing BIP loops with 1" PAP, reducing down to 3/4" as I would tee off the trunk to each radiator.

Any advice is welcomed.

hot_rod

it seems lime two dines would fve the temperature issues. TRVs would give you room by room control 
how many radiators ?
typically CI radiators and fin tube on the same zone do not mix well

Maelos

@hot_rod the first part of your reply has some typos and I can't quite parse it.

4 CI radiators on 2nd floor and 6 fin tubes on the main level.

I can certainly rework the existing loops to have the 6 fin tubes on one loop and the 4 CI rads on the other. 

EdTheHeaterMan

Your imbalance in temperature is twofold. Stratification is one reason you have a warmer upstairs. The CI radiators are the other. CI rad when on the same thermostat as fin tube baseboard will overheat ,or the baseboard under heat, based on the thermostat location. Proof is in your statement here

as my 2nd floor does tend to get hotter than the 1st floor.

I would recommend a separate zone for the second floor. If you want to get rid of the low hanging pipes in the basement, I would recommend oxygen barrier PEX home runs to the CI rads on the second floor from a central manifold in the basement (or boiler room level). I would do a series loop for the first floor baseboard radiators. Each zone should have a thermostat that measures the temperature of a room in that zone. Use a bedroom on the second floor, do not use the hallway location for the thermostat.

You can do separate loops for the baseboards, but that just makes purging air more difficult and there is little difference in comfort as long as you have about 60 feet or less of finned tube.

EdTheHeaterMan