is 1/2 pipe ok for baseboard

darren coughlin

Have had three different opinions on this one. hot water single
pipe(3/4) system with 1/2 feeds and 1/2 returns with monoflo tees. Somewhere
down the line the radiators were taken out on the first floor and replaced
with baseboard(upstairs still cast iron radiators) so 1/2 feed to 3/4
baseboard.( house is on one zone, upstairs comfortable downstairs chilly at
72 on thermostat)was told have to change either back to cast iron radiators
or repipe the feeds to 3/4 in order to properly heat house. any
ideas?????????
thanks
DARREN

bigugh_4

1/2" pipe allows a flow of 1 1/2 gpm 3/4" allows a flow of 4 gpm. that translates to 15,000 btu/h for 1/2" and 40,000 btu/h for 3/4" Now BB radiation needs about 800 btu/h for every foot in length. The length of the radiation should be calculated by a whole house heat loss calculation, have fun!

Art Pittaway

72 on thermostat

Is the thermostat in the room with the baseboard? If not it's a classic case of mixing two different types of heaters. The C.I. upstairs can take 160F water, get warm and when flow stops it delivers heat to the room for a long time. The baseboard has no mass, so if you run 160F water through it, it's output is lower than the usual 600 btu's/ft , output is determined by length of fin not cover (xxxbtu's per foot of fin tube at your boiler temp ie 180? X how many feet of fin tube is installed, see mfg. tables linked above) and when the pump shuts down you have seconds until it stops heating. The 1/2" feed will heat only so many feet of baseboard before it runs out of btu's but there are other factors. What temp. is the boiler set at? Cast iron radiator systems can be run at some real cool temps compared to baseboard and work well. Unless you have someone look at your house as a system and address the control of the baseboard and C.I. separately it will never balance. This web site is shared by people that have worked with these systems for many years and I think your asking for a simple answer to a complex question. When someone changed out the C.I. they did it wrong, now your stuck with it. Only education and sorting out what you want for your house will help you. Read some of the Tech Topics above and you may find info on these applications. Best wishes.