solar-thermal panels

[GT2]

Wetspirit, John,

The way my system will be set up involves a 250' run from the "solar shed" to the house.
The DHW tank with exchanger loop was going to be in the house, so plumbing the panel return to the DHWT would involve quite a lot of tubing and a larger pump?
Wonder if it would be wise?
I could install the DHWT in the shed, but still a long way for the water to go.

Thanks for the info on the motorized valves. Very interesting and makes sense.

Also could you elaborate why its not a good idea to heat the solar storage tank with the back-up system?

Thanks, Tim

 

[Raspy]

Tim,

The main reasons to not heat the solar tank with the backup heater are that the collectors heat that tank and their efficiency is based on temperature. The cooler the better. So, if the tank is warmer because your backup system heated it, then the solar will come on later and the collectors will be running at a higher temperature. This means you will be losing more energy to the surrounding environment and more through the connecting piping and more through the tank insulation. Cooler is more efficient for the solar. Also, heating the solar tank while heating the floor means a slower response in the floor temperature because it has to not only heat the floor, but also the tank.

In my earlier post I suggested thinking of the solar heating system as a cooling system. In other words, design the system to cool the collectors as efficiently as possible. Heating the solar tank and then using that water to "cool" the collectors means your not cooling them as well as possible because you are using pre-heated water in the cooling system. Temperature is very important in the collectors!

With your long piping run and the DHW tank in the house it doesn't sound very efficient to pipe it the way I suggested. But you will still need to get hot water at times not related to floor heating. Maybe the hot water piping that was going to go to the heat exchanger and then on to the floor heat could go to the DHW tank and back as a separate heating zone. You know, go to the DHW as you had planned, but bypass the floor and go back if no floor heating was required. The DHW could call for heat or the floor could call for heat. A differeential controller and a zone valve could accomplish this. Sometimes, long distances are a problem.


John

 

[crazyal]

When do you use the floors for heat You burn 2-3 cords of wood to heat the house but have radiant floors Do you run the floors off the water heater or have the boiler and the wood stove going at the same time? Please clarify for me how you use what you have in place at the moment.

I use the radiant heat in the upstairs bathrooms early in the mornings so they are warm when getting up for work. I wasn't expecting to be able to heat the house so easily with the wood stove so other than in the early mornings the only other time I heat the house is when nobody is home for most of the day.

My real desire for solar panels is for domestic water mainly in the spring, summer and fall months.