Does anyone have a solar hot water system with electric boost?

Question

If I hit the boost button and it doesn't need it, do I waste electricty? Or does it know its full of hot water and doesn't do anything? I'm confused about the boost button.

For eg. If the tank was 99% full of hot water and I hit the boost button. After it has heated the 1%, does it stop heating using electricty or does it keep using electricty untill I turn the button off?

Any help would be appreciated. We live in Penrith NSW. We have had the system for about 1 mth and haven't needed to boost much at all..so far.

Answer 1

What brand and model is your system? Mine is a Rinnai E315S36. (315 liter, single element 3600watts) With the single element model a thermostat set to 70 degrees C kicks in electric heating. I set my water heater to night rate in the mains power box so that solar heating occurs during the day and and any electric temperature top-up required is done at night. I've never missed not having the extra boost element this way. The model with the boost function has the extra element set to only 60 degrees C and this can't be adjusted. As long as you haven't set the main element thermostat to less than the 60 degree setting the only thing hitting the boost will do is warm the water a bit more quickly from cold. If the water is already above 60, nothing will happen. I have found that I don't even need the main electric element most of the year and I turn it off at the beginning of summer..... about October. It stays off 'til I actually get cold showers.... about June. Then I turn the main element back onto night rate and wait 24 hours for it to heat all the water back up. If you did the same and ran purely on solar for as long as possible and then only hit the boost once a year to cut that 24 hours down a bit you would save on carbon and time. If you are having to run your electric element all year round and hit boost all the time then your solar water system is too small for your needs..... It will be costing you money, not saving it. Either get a bigger one or go gas. Also, you HWS should have a tempering valve on it somewhere. It has three copper pipes running into it and is made of brass. This mixes cold water into the 70 degree + hot water comming out of the tank. It should be set to about 50 degrees C but it can be set from about 40 to about 60. If you are getting tepid water no matter what you do, have this valve looked at. Finally, as a good tip for all hot water service owners, you MUST replace the zinc sacrificial annode in the top of your tank every five years or so....... otherwise the system will corrode out and die. I write the date the last one was put in on the side of the tank so as to not forget. I suggest you stick last months installation date on yours.

Chook