i have some questions concerning a radiant in floor system i am building. currently i have 4 200ft 1/2 pex loops stapled to 2 high density foam board
with a 4in pour of concrete in the basement 1 inch expansion/thermal break between the floor slab and the walls -- upstairs on the 1st floor there will
be 4 300 ft pex loops with a 1 & 3/4" pour of gyp-crete . the heat loss calc is somewhat of a educated guess -- the building is 150 years old with 22 inch laid up limestone walls that have been tuck pointed inside and out -- the basement windows and door have been replaced and sealed --there is a 7 x 8.5 foot door that has been boarded up insulated (R10) with a plastic vapor barrier stapled over it and the basement has a ceiling with 10" of dead air space -- used https://www.usboiler.net/heat-loss-calculator.html
the calc say 23K for the basement which is what will be heated for now. (20 X 40 Ft)
when finished the upstairs should be pretty tight -- it currently has a new roof and windows and will be well insulated with a house wrap and new siding
total square footage is 2000, 800 in the basement 1200 upstairs.
this is the boiler i currently plan on using http://www.westinghousewaterheating.com/literature/WH-Combination-Heat-Hotwater-Wall-Brochure.pdf
the 140k btu floor model. one of the reasons i liked it was it looked like you could service it fairly easily and the sensor wires were accessible. i am not fond of 5lbs crap in a 1lb can
is the 140k model to big? i assume some of the 140K rating is going towards the DHW side as it is a combi boiler also i have not met a marketing man or brochure i totally trust.
my very rough guess is i will need about 60k plus to keep everything warm. the spec says a 5 to1 modulation on the burner but the tech says that has changed dropping the lowest
output to 14k. can i run it just for the basement? with just the basement pex runs the control piping and the boiler i am guessing total water load should be 10 to 13 gallons for the basement
is a mixing valve of any use at all? in the future when the upstairs is on line i think it will be <29 gallons will mixing valve be necessary? zoning with valves does not appear to be a good idea no clearly defined zones
i was planning on using a separate circ pump and thermostat for each of two zones 1 upstairs and 1 for the basement. I can set the CH water temp in the boiler over a range from 86 to 180 F
can i just set it to something in the lo 90's that works and leave it at that? this assumes i can get a delta change of 10 to 12 degrees between feed and return.