Replies

1. 
   Eric_Svendson | Dec 21, 2001 03:29pm | #1

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   There is, unfortunately, no simple, short answer. The main reason being that devices like hot water heaters are intermittent in operation. The "laboratory" efficiency of a HWH should be posted on the device with a sticker just like furnaces. This would at least give you a common baseline measuring system from which to compare.

   The fact that your selection had a PVC exhaust is a good indication that the efficiency was pretty high and that you made a good choice. FHB had an article on installing HWH's about 5-6 years ago and maybe this would shed more light on the efficiency question. Basically, the efficiency of any device is (energy out) divided by (energy in) but it can get far more complex.

1. 
   Rob_Susz_ | Dec 21, 2001 05:51pm | #2

   *Jeff, Gama routinely publishes efficiency ratings for water heaters. Got to this link:http://www.gamanet.org/consumer/certification/certdir.htm-RobP.S. - A .65 EF equates roughly to 81% AFUE when used for space heating. Most "good "units will be a .62 EF or about .78 EF. Be warned, there are some PVC vent water heaters that have terrible EF's, perhaps due to poorer insulation or something. It seems Bradford White and AO Smith have the highest efficiencies of mainstream units.

1. 
   Bob_Walker | Dec 21, 2001 06:00pm | #3

   *My understanding is that the draft induced direct vent water heaters can use plastic flues because the draft inducer mixes enough room air in with the flue gases to cool them down.It's not like the high efficiancy furnaces and boilers where there is a secondary heat exchanger where we grab the calories produced by condensing the water vapor and thus cool the flue gases by using the heat.I can't "prove" that by giving an extact source of information; that's something I learned here or there.

1. 
   Jeff_Maras | Dec 24, 2001 12:02am | #4

   *Well that ruined my day. I thought I had a pretty decent system installed and now I'm not so sure. I suppose if you pump enough room air out with the exhaust you would lower the temperature but still pump out quite a bit of heat.Anybody have any suggestions? I toyed with the idea of replacing the PVC with Aluminum to extract more heat to basement. Any thoughts on that?Thanks,The Wood Doc

2. 
   Jeff_Maras | Dec 24, 2001 12:02am | #5

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   When looking for a hot water heater for my radiant floor system I could never find out the efficiency of the units. I finally would up with a direct vent heater that could use PVC for the exhaust. I figured if the PVC didn't melt, there couldn't be that much heat going out the flue.
   Any Thoughts?