Solar in Seattle
Just commisioned this system yesterday. Put in the 30 evacuated tubes at 2:15pm and the collector header was 88 degrees. By 2:45pm the system was at 230 degrees, and within 5 minutes had stabilized at 115. We installed a Thermomax HP250 array with a Caleffi pump module and Controller. The Viessmann B-79g dual coil tank was installed 21/2 years ago. The owner wanted to make sure he got the federal tax credit. We had originally specified a Viessmann Vitosol 300T array and pump module, but there was no local inventory.
My only critique of the Caleffi module is that it doesn't hold an air test of over 25psi. I wouldn't want to fill a glycol based system without knowing all piping is tested and leak free. I love the special check valve in the expansion tank that allows disassembly for charging the bladder without loosing more than a few drops of glycol.
Sun in seattle
I did not know the Sun shines in Seattle. If that is the case Solar will work anywhere! haha
Better than the check valve/drain for the Xpansion tank is the Glycol hand pump to fill the system if you do lose a few drops of fluid. Did you use a pre-insulated lines set? They are great for Retrofits. At our last Vitodens class I saw some flex boiler vent. That could come in handy on some occasions. Nice looking work, and quite simple. Did you use panel rads and TRVs .I like to make peoples lives simlier.
The system..
...uses a staple up with transfer plates for the heating. A lineset would not have worked; we ran copper from the roof. I'm aware of the new polypropylene chimney liner vent for the Vitodens.
The sun does shine in Seattle, although this summer was the wettest and coolest on record. Typically we have a 5 month 'dry' season. Not this year.
pressure in the pump stations
Those pump stations are assembled with fiber gaskets as they are all BSP straight threads. The gaskets need to get wet to swell and seal completely. It only takes a few seconds for them to swell and seal if you test with water.
Like you, I prefer an air test first to make sure I didn't miss a connection. Then test with water to flush out any crud in the piping, tank, hx, etc. After it seals up, flush the water, with air and fill with glycol.
I know it adds extras steps and time, but it does flush the system, which is good also.
In Europe closed loop glycol systems are filled to 60- 65 psi to raise the glycol boiling temperature. Notice that they ship with a 6 bar, about 87 psi, relief valve due to higher operating pressures used over there.
I think 60 psi fill pressure is what we should all consider with closed loop glycol systems, especially the tube collectors with higher operating temperatures.
We have had some inspectors concerned with the potential to have higher pressure in the glycol side that the potable water side of a tank or Hx in event of a leak.
That's why the non toxic glycol is a must.
hr
Testing
Hi Hot Rod, we did wet the gaskets...still wouldn't hold. We left the system at 30PSI. Thanks for the tip to raise to 60PSI.
