Recently have hit “logger heads” with a homeowner over the installation of a 3ton AC unit in his home. The home,located in southern Ontario, is approx. 4000sqft,two storys, and equipped with a venmar active HRV system. Owner is claiming that according to 1998 CSA revisions, the current unit is insufficient. Somebody PLEASE clue me into these “revisions” and/or the process for determining such !
Replies
Depends on the heat-gain calculations of course, but 3 tons sounds small for our area.
might be able to find it here:
http://www.csa-international.org/default.asp?language=english
http://www.keyhvac.com/faqs.html#sizeac
http://www.hvacmall.com/hvacmall/associations/an_az.htm
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Drew,
Are you the installer? Have you or antone else run loads on the house? What is the construction? What kind of windows? 3 tons could cool a 6000 sf house if it is heavily shaded, with lots of insulation, good windows, etc. On the other hand it may not be enough to cool 1000 sf house with lots of poor glass, no shade and no insulation.
If you and the homeowner are just guessing, then neither one of you are correct.
Good answer Tim.
Thanks for the response...Yes, is the answer to your question. Our mechanical contractor has done gain/loss tests on the house, and the figures show it to be quite adequate. As far as the insulation , the home ,by far surpasses even Ontario Building code req'ts....R40 blowin in the attic, R28 in ext.walls(including r value of the codeboard. Am thinking now that the answer to finding "correct" figures, lies in INCLUDING the active HRV system into the calculations...Whatchya think?
" Am thinking now that the answer to finding "correct" figures, lies in INCLUDING the active HRV system into the calculations...Whatchya think?"
Absolutely must be figured into the system. If your contractor sized the unit for a given amount of outside air (based on whatever governs), then the energy recovery unit/ventilator will "recover" anywhere from 30 to 95% of the energy required to cool or heat that outside air, depending on the unit. In a house , the IMC 2000 Code does not require forced ventilation (outside air) if you have enough windows that open, and most do. Even then, the OA requirements are low, something like 30 cfm/person or 0.15 air changes per hour, which ever is greater. At those rates, the erv seldom makes a difference in equipment sizes. You gotta check to be sure.