solar control

Devan

What is recommended for dual coil tank solar install, preventing heated tank from boiler being reversed dumped outside via solar coil .

Is there a control with night time setback feature , turning off solar pump? What about winter weather.



THX

hot_rod

some thoughts

I like the dual tank option best. It presents a better load for the solar, as it is never warmed by the boiler. A single coil tank with and external HX is another option. You will get better performance for a couple reason. One you have two pumped flows. a coil in a still tank has some HX limitations.



Just make sure you have enough collector surface area to make it worth doing a heating load. Run a RET Screen or F-Chart to see what is available in your area through the winter months. It could be 1/3 or less what you see in the warmer or summer months. 130 maybe 140F may be about all you will see from flat plates in cold winter climates.



With an external HX you can size it exactly to the load, and it is easier to service and de-lime if needed.



Many of the solar controllers have a timer function. Ours does but it is a 1 program, same every day, no way to have a different weekend program. Just buy any timer and put it in that circuit. I like electronic timers as they keep their time and program when the power goes down.



For winter you can set a temperature the below which the system will not fire. So on a cold, low sunny winter day, the system should not fire.



hr

Devan

SDHW only

Just to clarify,

This is a SDHW only, no space heating.

Lower coil used for solar loop, upper back up DHW via boiler .

Just seems to me boiler loop would want to maintain min. tank temp. Yet when

cool or night time that heated tank would reverse thru solar coil. Even if sunny, but cold outdoor temps.

Trying to find a good control, without breaking the bank : )

hot_rod

you are correct

the top half of the tank will always be warmed by the boiler. So the solar has only the bottom half to work against.



Same thing happens when you use the electric element back up. Some installers use a timer to lock out the electric element while everyone is away at work. Of course you would not be able to switch an electric element from the I-solar control without a relay. But the boiler call for DHW could be switched via the I-solar control.



The Solar Pump Station has spring checks on both sides so you won't thermosiphon back to the roof at night or any time the solar pump is off.



Here is a drawing for boiler interface that uses arr. 3 to fire the boiler on DHW call. Remember the I-solar control has 120V outputs so an iso relay is needed.



hr

Devan

Nice solar control.

Thanks , I will research more on that control. That should do it

eComfortUSA

Solar Controls

Here is the link to the controls, i hope it would help

[url=http://www.ecomfortusa.com/index.php?cPath=188_137_248]http://www.ecomfortusa.com/index.php?cPath=188_137_248

Fortunat

solar control

In a dual coil tank, the boiler cannot heat the whole tank. That is the point.  The boiler heats only the top third of the tank, leaving the lower 2/3 to be heated by the sun as available.



Unless something is churning the water up (watch out for recirc lines), in a well designed dual coil tank you will never see boiler heated water in the area around the solar heat exchanger. The buoyancy of hot water ensures this to be true.



~Fortunat