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Old 01-10-16, 12:53 PM   #5
Uber EcoRenovator
Join Date: Apr 2011
Location: Strathroy Ontario Canada
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Default Maintaining solar space heating in Canada

Happy new year.

It is now 6 yrs since we had installed the solar hot water system. It has performed well for all those years. We had the odd hiccup but nothing bad. A hose-clamp needed tightening, add a little more anti-freeze. Nothing serious.

The last couple weeks I happen to notice the heat-pump was running a little longer Hmm. About 8:00pm one night I went and felt the tube up to the solar panel- it was HOT -Oh not good.

Thermal syphoning heated back out to the panel. The problem is a sticky zone valve. My hard earned heat heading back to the heavens.

That night with outside temps of -18 Deg. C. was actually overpowering the geo-thermal heat-pump and cooling the homes heated floor.!!

A while back I had purchased a couple circ. pumps one for the shop and the other for our homes solar hot water system. Both pumps installed on the home solar collector and the shops DIY HP were used (inexpensive) and had lower flow rate curves. The change out was on my to-do list but up until now I hadn't found the time to change them out. So here's the impetus. Since I have to open the system to change the valve out anyway.

These new pumps are a larger capacity pump three speed Grundfos. (U26-99). I had found that lots of hot water was available but isn't pumped to the heat exchanger. I did consult flow charts and panel extrapolation of collector area and there seems to be a lot of wiggle room for the pumping capacity.

I had also run my idea by Mikesolar who does this for a living and he did question my endeavor. He did say that over capacity pump will not move anymore heat if its not available and if the heat-exchanger is not large enough. All the components of my system are DIY and the engineered data is a little vague. My other defense to change the pumps out is the used components have done their duty and hopefully the new pumps and valves will last a long time before causing me grief. The only other downside is the pumps do require a few more watts, but that's only a few more pennies a day.

The current performance heating my space is this. A bright cloudless day will provide enough heat that the heated concrete floor will carry us though 24 hrs without the back-up Geo-thermal HP starting. This is while outside temps are around the -10 deg. C. which is about average nightly winter temps. However much colder with wind and we may have the HP start before the next morning.

My thoughts are that increasing the flow will offer more heat up to the in floor heating. So possibly on the less than ideal partly sunny days I will get that whole day heat charge.

Now the last detail of the system up grade is another differential controller to the domestic hot water circuit. This will close the solar heated return as the temp. slowly falls as the suns energy tapers off in the late afternoon. As it is the valve was on the same circuit as the floors buffer tank and it would continue to supply heat to the floor and operate from a temp at high noon close to 60 Deg C. down to 36 Deg. C.

With this additional differential controller after the domestic hot water tank has peaked the valve will close maintaining the 60 Deg C. and not follow the heated floors buffer tank down to the lower temps.

As I had mention the system has worked flawlessly for many years saving many dollars and in true DIY fashion the system can be improved.

If there are eco-renovators on the fence it works well.

I would also like to thank Gary Reysa over at Builditsolar for his inspirational work.


Photos yard view of the panels, grey pump changed out to the larger red, replacement valve above red pump, differential controller mounted to valve

Attached Images

Last edited by Daox; 01-10-16 at 03:23 PM..
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