Solar dump zone

Bob Gagnon plumbing and heating · September 2006

I have a friend in N.H. that has a solar domestic system and wants to add a heat dump to remove excess heat when he has to. Woud this be the best way to pipe it? Any ideas or suggestions would be greatly appreciated. Thanks, Bob Gagnon

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Constantin · September 2006

Hmmm...

... you could also consider a 3-way valve instead of the baseboard pump. Presumably the head loss would not be excessive and it might make the system a bit more robust.

Also, are you sure you want to pump into the expansion tank as shown?

kevin coppinger_4 · September 2006

would not a dump....

zone be best as a large storage tank (for future use) as opposed to a heat zone....that can be an uncomfortable proposition....kpc

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Bob Gagnon plumbing and heating · September 2006

not pumping away

The homeowner already piped it in that way, with the circ. pumping towards the expansion tank. I have been told that pump location dosen't matter if it is a closed loop glycol system, without any make up water connected. I always pump away, but I didn't know if I should have the homeowner change it. He does not expect to dump the heat often, maybe just when he is gone on vacation. An extra tank is nice but it could still overheat on an extended vacation.
Thanks, Bob Gagnon

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Simply Rad_2 · September 2006

solar dump

Bob
If your the system is only going to dump heat when the cusotmer is on vacation, use a control. I just installed a Stecca solar DHW control and when you use the vacation mode the unit will run the system at night and use the collector to drop the tank temperature. Where is the radiator located, I presume outside.
Jeffrey

Bob Gagnon plumbing and heating · September 2006

vacation mode

I'm assuming would have to be manually switched? he's trying to make it automatic. He thought about installing a bypass around the check valve and opening it when going on vacation, but he has evacuated tube collectors and we were concerned the manifold wouldn't bleed off enough heat overnight. The heating season up here is about 6 months, so he thought it was a 50-50 chance he would want the heat. Do you think 30 tubes would give off that much heat if the baseboard were installed in the basement? someone told me to put the aquastat on the storage tank and pipe it to a 3 way mixing valve. Do you like this piping better? He also said to turn the aquastat dowm to 150. Are they only rated that high? Wouldn't you want the tank to maintain higher temps? Thanks for your help, Bob Gagnon

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ALH_4 · September 2006

How about

How about adding another storage tank prior to the current tank for added storage and covering the panels if away for an extended time?

-Andrew

lund · September 2006

Rodney Summers · September 2006

solar overheating

Bob.

Have you considered installing a solonoid valve on the hot water outlet controlled by the aux contact of the controller (dump the hot water before the tempering valve)

Brendan

SVDW · September 2006

Dump zone

How about a motorized shutter? An aquastat on the return line to the array triggers the relay to close the shutter when temps are too hot & opens when it cools off again. I bet a simple controller could even partially open it for optimal performance. Pobably never be needed in the winter so ice/snow would not be an issue. I'm thinking of like a roll-up garage door style shutter here but lighter construction. Does it make sense to avoid making the heat in the first place rather than dumping it later? Any manufacturers out there try this yet? ......Now I want to find an old garage door opener & start tinkering.....

Ed_26 · September 2006

Solar

I thought evac. tubes were self limiting? (thermomax)How about converting to a drainback system?

hr · September 2006

how much

panel to storage does he have now"? If correctly sized he shouldn't have a lot of dump required??

The Shuco system uses a steam back concept. A special mix of fluid allows the fluid to boil when the pump shuts down and push back into the oversized expansion tank. Sounds too simple

I helped install a Schuco system in Colorado a week ago, but had to leave before I saw it "steam back"

hot rod

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Ron Huber · September 2006

3 way valve

I like the way the three way valve setup bypasses the tank, running the loop through the tank after the dump zone may still overheat the tank. The Apricus panels cannot handle stagnation temeratures, they have a heat exchanger that they suggest you install outdoors to give off the excess heat, otherwise their tubes will loose their vaccum.
The Viessmann/Thermomax tubes have the limiter that shuts down the transfer at 260 degrees and uses Glycol rated for 360, Apricus is still having problems with tubes losing their vaccum right from the factory before they are installed

Bob Gagnon plumbing and heating · September 2006

if you could get

a hail detector on that shutter door it would be really cool. Bob Gagnon

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Bob Gagnon plumbing and heating · September 2006

he has

30 evac. tubes and a 105 gallon storage tank. He is thinking it will only overheat when he is on vacation, but wouldn't the dump zone, with a 3 way mixing valve be reliable and inexpensive to install? Would you pipe it in like that Hot Rod? Thanks, Bob Gagnon

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hr · September 2006

30 evac tubes and money is an issue!!

I'd still rather see you add additional storage to harvest and save that energy that he spent 30 tubes recovering

Give me your fax number and I'll send a good piping option with 3 way ZVs.

hot rod

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Eric_6 · September 2006

re: Steca TR0301

Simply Rad is right. Why go to all the extra trouble on a DHW preheat system (extra material and labor) when if he knows he's going on vacation you just push the vacation/holiday mode button on the Steca TR0301 and push it again when you get back from vacation. Large DHW/spaceheat interfaces will need help in getting rid of heat but at 1.75 gal to 2.25 gal per sq. ft. of collector solar dhw is fairly efficient and provides a decent fraction of dhw if sized for the load.

Again, many of the european differential controls are light years ahead of what is available here (Goldline & Heliotrope) and for a great price. You can find the Steca TR0301 sold under the SunEarth name probably for less than $115 and it includes the sensors (PT1000).It is ETL listed.

Closed loop solar systems will inherently stagnate. Design well, make it safe, and maintenance, maintenance, maintenance (meaning yearly pH checks). It's a luxury investment, so the endusers need to realize that and spend the money on check ups to keep it tiptop shape (not an automobile luxury purchase that loses money for you but yet you maintain).

Solar dump zone

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