Fired it up, and loosing prs

[ChrisW]

OK folks .....I am new to this game and looking for some start up help.

I have just installed a two panel solar thermal system at my home. Yesterday, I filled the system w/ a 100 psi air. Woke up and 100psi, so I filled the system w/ 30 psi of water for my fist day of free energy. The system worked great, I have digital display and could see the system cycle on and off, as the collector heated up throughout the day to maintain the 12 degree delta T. I left for a couple hours noticed the prs gauge popped, and was left w/ less than 10 psi by the evening.

I refilled the system to 30 psi and watched it fall as the temp lowered for the evening. I understand the relationship between temp and prs, but thought my expansion tank would minimize this. I am new to plumbing so some clarification on this would be great.

Chris

[Mike90250]

Not knowing how many gallons are in the whole system, but a plumber would know what size expansion tank you need for x gallons and y temperature range. Does your system drain the collectors at night? And you ALWAYS need a relief valve, because you don't want to blow your system . We need more details about it.

[russ]

Air trapped in the system? You needs air bleeds at strategic points as well.

[ChrisW]

I think that may be the case also.....I have heard various recomendations about when and how long to keep the air valves open. What do you think?

[russ]

You have to vent until you get water only from the vents. Should be no air in the system.

[ChrisW]

]'think i got it

My 17 lb prs tank came pre-charged at 35 PSI. I think that was to much prs for my system to work against, and thus prs continually rose.

[Mike90250]

Don't be useing a residential PRESSURE tank when you should be using an EXPANSION tank. pressure tanks are not made to handle hot water, expansion tanks are.

[peakbagger]

Something is strange with your setup. Usually the expansion tank is set at a minimum to roughly the cold system pressure on the coldest time of the year. If the water is set to 30 PSI, the expansion tank should be set to the same amount. Precharging the expansion tank with 100 PSI means that it really isnt expanding until the system pressure exceeds 100PSI (which isnt really difficult as water is not compressible). From cold to hot on a summer day, the system pressure will rise 20 to 30 PSI, so if you had your expansion tankcharged at 100 PSI you would hit 125 to 130 PSI and probably pop the relief.

[ChrisW]

the system was leack checked w/ 100 psi

[Mike90250]

the system was leack checked w/ 100 psi

Was that air, or water.

As mentioned before, water is incompressible, and it requires air to pressurize it. pumps and seals are seldom rated for 100 psi, for solar, you should only be 5-30 psi. High pressure adds nothing to the system.

[ChrisW]

From my original message I leak checked w/ 100 psi of air

[viralshah]

However not really sure there is really any reason to since you can find panels from a watt or two up to 220 watts with everything in between. Is there some specific voltage you need?