Drainback holding tank possibility?

[drew4justice]

I noticed that most of the DIY drainback solar water heat exchange tanks are created from plywood lined with a pond liner type material.

I was just curious if anyone has considered using an old, large, chest style freezer lined with the same pond liner material as a drainback container?  It seems that the insulation and lid seal would be built in.

Maybe they're not big enough?  I haven't done much research, but seems like it might be a viable solution?

[Bruce S]

drew;
It certainly would be a good start, especially if it keep the freezer from being tossed into a creek or off into the forest somewhere
Usually though the containers are specifically built to the sized determined by the amount of water/glycol being used for the system.
So instead of building the drain-back container to hold the specific gallons/liters you would figure out the amount of fluid the freezer would hold in gallon/liters and build accordingly.

Hope this helps.
Bruce S

[oztules]

Yes.

I have been using a chest freezer now for about 2 months. It is a 320 litre unit.

I found that you don't even need to use the pond liner, as the 2 inches of the urethane foam they use seals the unit water tight.

I also found that a layer of bubble wrap on the surface of the water seems to mean that you get no condensation on the inside of the lid, so when you open it, it all appears dry... cool stuff.

I use about 50 meters of 1" hose for the coil. I don't take it above about 70 degrees centigrade, and it is just too simple. I also use a 45psi (sureflo style) pump 12vdc.

I built a differential controller that turns it on or off as normal, but also speed controls the motor to keep the differential between panel temp and tub temp about 5 degrees apart max. It keeps the system running on a lower current for a longer time, and utilises the best the panels can do, without constantly all or nothing turn off and ons. Seems to work extremely well, and have only used about 5kwh in 2 months for the water heating..... it used to be about 8kwh per day.

Three days of no sun took it from 65 down to 31 degrees..... stilll good for my money (about 120 dollars all up)

May do a diary on it when I am satisfied the system is bullet proof.

I bought 4 digital temp gauges from China for $4, and $4 postage............... and four NTC probes with 3 meter leads  for about the same money.

The overnight temp loss is about 3-4C for a 65:5C differential.... not bad.

It looks better than any box I could build, and offers every advantage I can think of.

I threw away the 160 liter water heater and replaced with a 50 liter one...... with about 4"of insulation packed around it.....


The whole thing works a treat.


................oztules