Baseboard hot water heat question
I am finally at the heating stage of the addition I am putting on my house and need some advice. My home has baseboard hot water heat. How do you figure out how much/many baseboard units to use in a given space to provide adequate heating? When I ran heat a few years ago I used all copper pipe but I hear the trend now is to use PEX tubing and compression fittings. Any advice or guidance would be greatly appreciated. Thanks in advance.
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Have a heat loss calculation done for the addition on a room by room basis at your local design low temp for your area plus about 10% extra for some insurance and the odd extra cold day.
I live in an area of 7600 F degree days and a design low of 0 deg F. Here for an average house (2"X6" walls, R20 / R40 insulation and some attempt at air tightness), we use a rule of thumb for rooms with average # and size windows of 25 btu's (or 7 watts electrical) of installed heat for each sq ft. If things vary much, it's better to do the calculations.
HW baseboards are rated for the # of BTU's output per foot of length based on the input water temp of from about 130 deg F to 190 deg F in 10 deg increments. So get your total # of btu's needed for each room on the coldest day and install the correct # of feet of baseboard for the output you need based on the temp your boiler runs at.
This is assuming that the addition circuit(s) is an additional zone or two being added to the boiler and not just adding on to an existing zone. By adding onto an existing zone, the water may be too cool by the time it hits the last of the rads in the zone!!
Thanks for input. Do you have any information about using PEX flexible tubing vs. copper for the runs between the radiators? It seems like the PEX would be alot easier to work with if it works. Also, do you have any experience using a high speed (velocity?) pump at the furnace to ensure circulation? I have heard that the high speed pump cause the copper to wear out sooner. Also, I live in MN so heat is sort of important. Thanks again.
PEX has been around long enough to have faith in it but if you don't have the right tools for installation, hire it out.
You shouldn't need a high speed pump unless you're running up against limitations with the originally installed one due to length of lines to the new section, mnuch larger house now, etc. Upsizing lines will drop the resistance that you may be anticipating as a flow problem. Insulate the lines also.
pex may not be rated for the temperature of the water, and the preassure in the system....I'd go with copper, in this case..IMO
Wirsbo, one of the more popular brands used in our area, is rated for 200 Deg F and 80 psi. Most boilers operate in the 12-16 psi range. with the water temp being 180-190 in cold weather. Here, it's rare to see a full copper system for HW baseboards going in anymore.
Just make sure one allows for the expanion.
PEX = 1.1" per 100 ft per 10 deg F rise.
A better choice is the composite PEX-Al-PEX which has an expansion rate of 0.156" per 100 ft per 10 deg F rise. (sold under Wirsbo's brand name of Multicor)
RBRBean
web: http://www.healthyheating.com
blog: http://wonderfulwombs.typepad.com
PEX-AL-PEX, all the way. Helps with expansion, and it stays where you put it, doesn't get all floppy when it's hot.And don't forget the outdoor reset control on the boiler if you don't have one already ;)-------------------------------------
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