Heating Help

Solar storage tanks

How do you  like EPDM liners for solar tanks?  Are you finding drain back systems are more ideal for the solar industry.

sure, maybe

as for the EPDM I think it has a lot to do with continuous operating temperatures. I have built a few tanks with EPDM liners that was built with roofing material from ABC roofing. After researching later I found there are different grades of EDPM and different performance specs.

I think the key is knowing what the fluid is, and the operating temperature range. Every product has a failure point. I think EPDM tanks live happily at 160- 180F solar temperatures. Maybe higher operating temperatures provided by wood boilers or higher tech collectors like evac tubes or the new solar dishes hitting the market could be a concern.

Drainback is growing in popularity. I think some of it is due to larger solar arrays being installed to cover higher solar heating loads. I see a movement in Europe promoting 50% and higher solar fractions for combi systems.

This in turns drives the development of more DB equipment. Many of the new solar controllers have DB functions included. More high head circs are entering the market aimed at the DB requirement. Also some of the smaller SDHW DB packages have arrived over here providing a plug and play option for first time DB installers.

We just introduced a packaged DB pump module built around a Grundfos 15-100 and will have a DB specific collector available soon.

hr

EPDM tanks are labor intensive

Very few systems inside the home would require this much labor, so I dislike them for that reason. Lots of fiddly details to get right, and all failure modes are costly.

The best overview on building them: http://www.builditsolar.com/Projects/SpaceHeating/DHWplusSpace/TankDesign.htm

Commercial style tanks CAN easily be used for unpressurized drainback:
http://www.solarheatexchangemanufacturing.com/NewFiles/products.html
But they only go up to 120gal.

One issue that I think hasn't been decided is whether to use dip tubes or bulkhead fittings. Dip tubes on the suction side of a circulator pump will eventually airlock the pump, but a bulkhead fitting in an EPDM tank is risky.

dip tube

"One issue that I think hasn't been decided is whether to use dip tubes
or bulkhead fittings. Dip tubes on the suction side of a circulator
pump will eventually airlock the pump, but a bulkhead fitting in an EPDM
tank is risky"

By dip tube I assume you mean an upside-down U shaped pipe over the edge of the tank, with the pump located outside the tank and below water level. Is that correct? I have no experience with this but I was under the impression that once the air is removed there won't be a problem. Is this really something to be concerned about? It seems like any bubbles that might be created by the suction of the pump will be entrained and end up back in the top of the tank, unless the dip tube is too large to maintain sufficient velocity, in which case there would probably not be enough vacuum to create bubbles.

Storage solutions

EPDM liners can last up to 25+ years.  Setting up a Hydroflex Systems tank takes only a few hours and ships through a regular man door.  Sizes available are 100 gallon to 5,000 gallon capacities.
see www.hydroflexsystems.com for more info

Storage solutions

EPDM liners can last up to 25+ years.  Setting up a Hydroflex Systems tank takes only a few hours and ships through a regular man door.  Sizes available are 100 gallon to 5,000 gallon capacities.
see www.hydroflexsystems.com for more info

Tank liners

EPDM can be a reasonable liner material for lower temperature tanks.
They do, however, break down over time.
Over the years, I have seen Solaroll (remember that one!), Entran 1,2 and 3
and various tank liners all fail due to their EPDM content.
Apparently the breakdown byproducts can affect copper heat exchangers causing premature failure.

Murphy's Law does rule the world. The image is of a 7 year old EPDM liner.

Failure Mode?

Tom,

Is that algae? What caused the failure?

What is in that tank?

The stuff you see in the tank is not algae, just residue that probably came off the copper as it aged. The big issue with the liner shown was the failure due to overheating.

plastic liner

there was someone making these cool modular plastic lined tanks but for the life of me I can't find the website or remember their name.

Maybe this?

Hello Zac,
I think this might be the company you are thinking of.
http://www.americansolartechnics.com/index.html

They use a non EDPM liner.
Nice looking stuff.

Peter

thats it!

That's it, thanks for that Peter.

No rubbers for me

No liners for me thank you.  Both high temp fiberglass and stainless steel will last longer and be easier to provide maintenance on than a lined tank.