Wednesday, November 12, 2008

making a difference on the electric bill.

The one thing that this water heater setup doesn't come with is probably the most important part; a user's manual. I was given a bunch of manuals, but they were mostly installation manuals for the various components. There's no comprehensive manual from velux which covers the basics such as:
  • ideal settings for your climate or weather
  • when does the electrical backup kick in
  • how does one optimize performance.
In the first month, we didn't do anything different from our normal routine. we did our wash later in the day, started the dishwasher late at night, and took our showers in the morning. As a result, our electrical usage became very high due to the electrical backup always kicking in.

Furthermore, the tank and control unit were both set to top out at 140 degrees F, although the tank can go up to 180. I was told this was done because if the panels get too hot, the system will try to protect them by pumping glycol through them (thus heating up the tank above your settings).

In the first place, the panels got to 375F in the summer when it was 110F outside and the pump never kicked in to lower the temperature (there's no instruction manual to tell you when it's supposed to kick in). In the second place, the tank seems to have a hard temperature setting which isn't effected by the control module. And in the third place, when I finally was able to find a little more detail on the tank manufactures web site, they specifically say to set your tank to above 160F in order to optimize performance. I personally think the system as a whole was configure wrong in that I think the tank should be set to say 170 but the control unit should be set to a max of 140 in order for the protective backup to kick in if the panels get too hot.

So, now we do simple things, like check the temperature of the tank before we run the dishwasher and try to start doing laundry in the late morning. These minor lifestyle changes made a measurable difference and started to drop our utility bills to lower then the year before. However, the biggest difference came after messing around for a couple months trying to increase the max temperature in the tank (I'll post these instructions in my next post since there's no comprehensive manual which will tell you how).

Ideally, I think one should have summer settings and winter settings. In both cases, I think the tank should be set to 175F and one simply adjust the conrol unit to the max you want (say 150 for the summer and 165 for the winter).