Darn! Lost glycol

[lile001]

I had a glycol system stagnate for a while this winter before I noticed. Got an air bubble in the system and the little El-Sid pump couldn't overcome the airlock. Once stagnated, any decent solar panel will boil water. Once boiling, the T&P valve blows, and then I have a bigger air bubble. Expensive mistake! The first lost glycol went on my roof and was lost, once I realized that I ran the T&P valve into a 5 gallon bucket through a hole in the lid. Just went up to check and I've caught about 3 gallons. At least I didn't lose it, but there is more reoutble in the system because of this.

If I ever get the system stable, and all the air out, and keep my pump going when it is sunny, this won't be a problem. Do other folks end up running the T&P to a bucket just in case? What is common practice?

[Mike90250]

I would look in to a coolant recovery tank, like a car has. With any volume of water, you will have lots (1-3 gallons) of expansion with heat. If you have 20 gallons of fluid, I can see needing an expansion/overflow of 2 gallons easily. Water needs to flow in and out of this on a daily basis.

[mtmtntop]

thats what i did ever since i had a similar thing happen. i have the pipe that heads down out of the ptv going right into the lid of the 5 gallon bucket.
but to prevent the boiling basement flood, i put a radiator pop off valve up on the array itself. it will allow glycol to blow off as steam, but it prevents the basement problem. since the last time this happened i was out of state, i just fixed the problem and i have never had it overheat since. for me it was to install a air handler with a controller that dumps heat immediately partly because it has a 70' uninsulated run just to get to the air handler located in my garage. when this kicks on, i drop 15 degrees in the 75 tube array in less than 2 minutes. its pretty amazing.

[russ]

No expansion tank like on a well pump in the system?

[mtmtntop]

yes, but it may be that my system is different. i have this solar array sharing a boiler loop, and the boiler loop requires an expansion tank. i started with this configuration so i do not know if it would have been necessary if the boiler was not involved. what i think is comparable, and important, is that i had the glycol over the basement floor problem even with an expansion tank.

[Mike90250]

Pressure bladder expansion tanks (the look like a 3gal BBQ propane tank, with a water fitting on one end, and a Schrader valve (bicycle tire valve) at the other end.) run about 50 PSI, which may blow out heat collectors. You may need an open top reservoir.

[mtmtntop]

the pressure in my closed loop system runs 12-15 lbs. not sure of the pressure in the bbq sized tank.

but rather than design a way to deal with a boil over, i'd change the system so it can't boil over. you have to have a way to release the pressure, whether its on the basement floor or on the panels. or both. like i said, i put in an air handler and problem is gone. when the temp of the glycol returning to the panels goes over 125, the air handler kicks on cooling it immediately. this has been working whenever i need to dump heat. plus i don't have a glycol mess and an air lock that i still need to deal with when i come home to the nightmare!

[russ]

Right - there is an air vent valve at the top of the panel as well - had forgotten about that.