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jamieF

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Posts: 269
Reply with quote  #451 
I stagnated the collector today while it was 100% sealed up (caps on the vent pipes)   It wasn't super sunny but we did get a couple of hours of almost pure sun.   The collector surface hit 108C.   I will need to make sure to remove the caps to keep temps reasonable during the summer.   Also I need to add a proper expansion tank I make it 100% enclosed system. Every stagnation event results in boiling about half a gallon of fluid out of the system...

jamieF

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Posts: 269
Reply with quote  #452 
I've made some changes.   I now have an expansion tank and I've replaced the pump with a proper much more expensive 3 speed grundfos after losing my 3rd or 4th cheap one.   I still need to fix the insulation in there and insulate the expansion tank.  I also need to drain the collector loop and fill it with antifreeze as it's mostly water now.     Also on the list with the expansion bucket being removed from the system I need to find a way to get a temp sensor into the loop before the exchanger outlet.   I could just build another T in the pex and solder one inside it like I did previously but I had the collector inlet sensor fail  and they're a real pain to replace.  I'll think of something.  

After all of those changes and some insanely hot long sunny days my tank is sitting at 59C right now.   I will update the software to stop it from going over 60C at the top as the weather is likely to hold out.    I checked the liner and so far no issues (knock on wood)   it's flexible and doesn't seem to be drooping or anything.  I could only touch the stuff in the water for a second or so though before it was starting to burn my hands so it didn't get a great once over.

I can do something about the pipe insulation, the expansion tank insulation and likely the exchange outlet sensor  sometime soon.   Hooking up to inside so all of this is actually doing something useful has to wait though as I had to buy a new heat pump and my hobby funds have been wiped out.  I may get some of the inside parts done this fall.   A tempering valve is the most expensive part of that and I need to redo the plumbing in the laundry room anyways.
IMG_20180723_172010.jpg 

jamieF

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Posts: 269
Reply with quote  #453 
I've had another ds18b20 sensor fail in my collector.   I don't think it's the sensor so much as being dirt cheap off of amazon with heatshrink and 6' of wire on it.   The failures have taken place during stagnation evens with the final readings being 105C - 110 C then a bunch of obvious garbage readings before it stops entirely.  I think either the wire coating or the solder is melting and allowing a short to take place.  

I may have to look into either a different type of sensor or just roll my own wiring wise like I used to do and make sure I use good high temp pieces. 
gbwillson

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Posts: 2,263
Reply with quote  #454 
Most of the wire coatings I have seen show them to be rated to 105˚C. But that is the highest rated temp, not the actual temp that it fails, which should be higher. But if you are experiencing temps to the rated high, a high temp wire should be used just to be safe.

Greg in MN
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