System flushed with hot water and a little detergent, then drained and charged with Tyfocor HTL to 27psi. This is a special propylene glycol mixture specified by Viessmann. I started with 5 gallons, but had to add approximately 1 gallon of water. Full strength was good for down to -35C, which is -21F. I checked it with an automotive anti-freeze tester (used to check ethylene glycol), and it only showed good for 15 degrees. I will buy another 5 gallons of Tyfocor and repump the system displacing the mixture before the real cold weather comes. I should be able to do it with introducing very little air.
Both circulation pumps that flow glycol to the collector, one for the DHW, and one for radiant heating, were ran and speeds set for the proper flow rates. All sensors were connected to the Vitosolic 200 controller (except for the one that will open zones in case of high temp in the radiant storage tank). The controller functions were checked by using cold and hot water to simulate temperature differentials that started the pumps.
I wanted to make sure that the collector circulation pumps would run so that when I install the vacuum tubes in the collector, the system would transfer heat from the collector and not overheat.
One last point about charging the system with glycol to 27psi. The specification is 37psi. I am guessing that the pressure is necessary to suppress boiling when the collector is running hot. I circulated some glycol through the DHW tank coil and heated up the system. The pressure came up to 30 psi when I got the temp up to 80F. So, I believe the pressure may not only come up to spec, but go higher when the system is in operation.
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