Canadian collector source?

[sunspot]

I'm starting to think about the solar thermal collectors I'm going to be needing. Building them is an option for me but I thought I'd find out what's available commercially. Flat plate or evacuated tube. I'm on Vancouver Island in BC Canada so shipping is a concern. Can anyone recommend a good panel manufacturer that would have a distributor at least semi local to me? ~ 150 sf to start and will be used on a homebrew drain back system. Thanks.

[Mikesolar]

The only real Canadian manufacturers are Thermodynamics Ltd (Nova Scotia) and Enerworks (london Ont). Of the 2 Thermodynamics are the most honest IMHO. Viessmann had distribution in Vancouver and makes a good flat panel and a good Vacuum tube but for space heating, I would not look at tubes unless you had a lot of replacement tubes and a way to keep the panel temp below 100C most of the time.

TD will ship anywhere and sells container loads to Switzerland. It is my favorite panel for drainback and glycol systems.

There are no North American makers of Vacuum tubes. They are all imported from Germany or China.

[SDMCF]

Originally Posted by Mikesolar

for space heating, I would not look at tubes unless you had a lot of replacement tubes

Can you explain your reasoning behind this?

[Mikesolar]

Originally Posted by SDMCF

Can you explain your reasoning behind this?

That is quite simple.

Vacuum tubes, no matter what situation they are placed in, have a high failure rate. Industry rates vary but range from 0.5 to 4% annually. The worst offenders are the basic Chinese made tubes with heat pipes ( some people on here have commented on trying to fix their heat pipes) and I have gotten tired of being asked to come and fix a solar system that is not performing as expected just to see 20 or 30% of the tubes have lost vacuum after just a few years operation.

Flat plate collectors don't work under the same stresses and can go 30+ years without a problem, as long as the glycol is changed regularly.

It is true that tubes can outperform flat collectors IN SOME CIRCUMSTANCES......but we don't see those circumstances as often as people think. For example, a tube will be more efficient at temps above 100C where they lose less heat than a flat collector per m2 of area but residential solar doesn't operate at those temps.

To my mind, if you want 4m2 of tube collector area, great but if you want better longevity and less maintenance put in 6m2 of a good flat collector and the performance will be better.

[SDMCF]

Interesting statistics. I have had an array of 100 cheapo chinese tubes for about 8 years and I am happy with it. I have had 2 tubes "fail". These have not lost their vacuum, but the dark covering on the metalwork within the tube has disappeared. I suspect this happened when the system overheated during a power outage (so no circulation). I bought some spare tubes when I bought the panels, so replacing the faulty tubes has not been a problem.

From the figures I have seen there is no great difference in the performance of flat panels v tubes, and either would work for most people. I selected tubes for ease of installation. A tube system is installed piece by piece whereas a panel is indivisible and must be installed in one hit. I didn't fancy manhandling a large panel at height up a ladder on my own. Much easier to carry one tube at a time.

[Mikesolar]

My stats are only partially anecdotal. There will be systems with few if any failures. I have had some of these as well but on the whole, a tube systems more maintenance than a flat system with little if any output improvement to show for it.

I'm moving away from AC pumps these days as well and more towards 12DC systems. This past bad winter has seen more controller failures (staying on at night at -20C) than usual and when that happens, the HX can split and eventually split the piping and collectors. PV based 12V systems are more fool proof.

I totally agree on the ease of install for tubes. I would have to say that the single biggest PITA is pulling the 40kg panels up a ladder sometimes 3 storeys. The rest of the work I can do myself but not that.

[sunspot]

Originally Posted by Mikesolar

I'm moving away from AC pumps these days as well and more towards 12DC systems.

This is interesting to me. There's electronics - controller - associated with either system. Why would one be more failure prone than the other? At this point I can still go either route so I'm all ears. My rough-in piping is 1" and I'll likely exceed the 6' self priming ability of the vane pumps. Thanks for your insight.

Greg

[Mikesolar]

Controllers are almost all differential controls so they have at least 2 if not 3 thermistors (almost all the good ones are European and use a PT1000 thermister). They also have triac based variable speed control of the circ pump and are usually limited to 1A or less. Some have fixed on/off control and can take 4A but that usually limited to drainback systems. remember that in Europe 1A is 220w and here it is 120w so we are limited to the size of pump we can use for variable speed systems.

There is a reason why electronics typically have only 1 year warranties. It is still the weak link in the solar system. Lightning strikes hurt and the problems I have seen are due to the controller thinking the panel temp is hot enough to pump when it is night time out. This has been true of almost all the controllers I have seen.

If I use the PV system, the pump is light activated so cannot run at night. There are many types of pumps out there and if you can use a glycol system, a "positive displacement" pump can be used such as the Thermodynamics E-mag pump. It has a head of 100' and a suction head easily over 6'. Any of these type pumps, if kept below the top of the HX will do fine anyway.

[strider3700]

slegg lumber used to sell a evacuated tube system for water heating. I heard it was pretty cheap (both in price and quality)

BTW building your own collectors is against code here so make sure your neighbours won't turn you in to bylaws

[Mikesolar]

Originally Posted by strider3700

BTW building your own collectors is against code here so make sure your neighbours won't turn you in to bylaws

Shhhhhhhhhhhhh