Bubble Foil Bubble Trouble (ME

Nate Greenleaf

I will only comment on what I have seen and what we as a manufacturer would tell you to expect to see.

1. An EOS twin glass evacuated tube jammed 2 feet into a snow bank, leaving about 3 feet exposed on an overcast day (insolation value of under 300 W/m2) will provide you with an internal tube temp. of around 255°F.

2. EOS tubes typically don't hold snow due to their round shape and our engineered design provides adequate spacing between the tubes to prevent heavy loads from sticking around. The wind will usually force the snow off the tubes. What we typically see is a thin ribbon of ice that runs from the header to the foot clip down the front center of each tube.

3. A buried in snow evacuated tube collector is an improperly installed evacuated tube collector. (why wasn't the snow load accounted for in the frame design during installation?)

4. As a Maine based company we believe that we "know snow". We have yet to see a collector buried in enough snow to turn it into an inefficient pile of cold glass. Let me put it to you this way, Canada is our largest market. There is a reason for that.

5. I have dealt with a lot of people who declare that a flat plate collector is better than an evacuated tube. I have mountains of data that just doesn't support those claims. None of it is something that I have read on the web, or is promotional material from a manufacturer. I read all of that stuff too, and most of it is bunk... (one company claims that you can heat your house by installing PEX tubing behind the roof shingles.) What I talk about is real world evidence that I have gathered personally using our product. I will tell you what it can and CAN'T do. We don't have a panacea for all of your heating needs if you live in New England, but I can easily offset about 30% of them if you have a well insulated house and a well designed radiant heat system.

Some people just don't like to admit that there is a better mousetrap out there, but they will be happy to voice an opinion based off of their limited experience.

Not everyone will believe me... I understand that... I am simply trying to inform people with the information that is available. I would be happy to introduce any member of this forum to the differences in person at our facility in Rockland, Maine.

Mark Eatherton

Ummm...

It's been a LONG time since I cracked the books on solar, but if my mamories serve me correctly, for year round use it is EQUAL to latitude. For summer optimal operation its latitude MINUS 15 degrees, and for optimum winter operation it is latitude PLUS 15 degrees.

But then again, like I said, its been a LONG time...

No?

ME

Dennis Bellanti_2

You are probably right... because you usually are Mr. Smart Guy. I think the best answer is "It depends." We use 55 degree angle because many of the systems we sell are for space heating and DHW. The taller angle reduces the gain in the summer when the load is low. When we do a DHW only system, we suggest a flatter? angle. If the roof pitch is close to lattitude then surface mounting helps with asthetics.

[Deleted User]

Just wanted to make sure...

that soemthing hasn't changed. What with the advent of daylight savings time, which WASN'T around when I first studied solar, ya just never know...

And you are probably right. There is a WHOLE lot more sunshine available during the summer months than most people can use, unless you are like me and happen to have an underground solar thermal storage heat exchange well in which to slip extra free solar btu's...

What, EVERYONE doesn't have one of those in their back yards? Sure makes avoiding stagnation a breeze...

ME

ALH_4

snow

How much heat was being harvested from the buried evac tube collector at 255°F?

A properly installed evac tube collector can retain snow and/or ice as shown in the attached photo.

I wouldn't say either type of collector is better. I dont think that flat panels are one-size-fits-all, nor do I think that evac tubes are.

As I see things, the kicker is the difficulty in transportation and installation of flat panels. Also if the glazing on a flat panel is damaged, it probably makes more sense to replace the entire panel. With evac tubes, you can quickly and simply replace the damaged tubes.

Nate Greenleaf_2

None.. it is used to act as a demonstration to tradesmen. I suspect that the output of that one tube in those conditions would be something along the lines of 40 btus per hour. Not much granted, but certainly more that any flat plate.

As for the pictures of the snow bound collectors in Bavaria..

I would argue the point that the collectors were installed correctly in that study. The entire set should have been mounted across the top of the roof line preventing the "snowplow" drifts between sets, and would also provide for better 8 hr gains due to current shading. Upon closer inspection of the study, one would find that these lower evac tube collectors were mounted on the west side of the southern face of the house. This means that the lower sets were shaded by the large front conservatory roof for a good portion of the day, further influencing the inability to shed the snow or have sufficient gains. The collectors were mounted at a pitch of only 33°, nowhere near the correct mounting angle for space heating in Germany.. should be more like 50°-60°. (I wish people would stop digging up that horrible example.)

I have no idea what brand of collectors those were, but I do know that if they had been EOS collectors in that situation they still would have been producing full output in performance with that snow load. I suspect that they were the "super tube" style collectors, which do not perform the same way a twin glass tube does with frost on it. Very different animals.

It is snowing here now.. perhaps tomorrow morning I will swing by an installation and grab some photos to better represent what I am describing.

You are correct about the ease of installation, and decreased costs of service.

ALH_4

What about cost?

I think I may toss that "study" in the "recycle" bin. Maybe I am wrong, and the twin tube evac tubes do perform better in most situations.

The only other complaint I have about evac tubes is cost. If the cost is comparable and snow is not an issue, I see no reason to use flat panels. I know the Apricus collectors are relatively price-competitive (without discusing prices on this BB). Are the EOS as well?

hot_rod

But Nate

nearly every poster here agrees there is a place for evac tube style collectors. You seem to think flat plate don't have a place from what I gather.

A tough stance to take if you want shoppers to take your product seriously, I think.

My new Solar Today mag arrived yesterday. I see more and more solar "packagers" offering both styles of collector with their packages.

Stiebel Eltron has a full page ad offering Thermomax now. Let the buyer decide based on their research and opinion form those that have experience with all styles.

hot rod

[Deleted User]

Tell us more!!

Does it require pressure trnsducers?

Is this an add on control for their line?

Is it an ECM motor like the OTHER green pump?

What are its range capabilites?

When can I buy one off a shelf?

Curious minds WANT more info...

ME

hot_rod

Is it a 15 series or a 25?

I have a couple demos from Grundfos, Alpha Pro 25-40 and 25-60. The 25-60 is very similar to the 15-58 curve.

Does yours have a 230V- 120V matching transformer?

Mine runs 9W with the small zone calling 11, then 17W with all 3 zones calling. Heat output is just as well as the 15-58 it replaces. Fun to watch the digital wattage meter change.

hot rod

Dennis Bellanti_2

There are two in Colorado I know of, mine and Barry Engleman of GT Sanders. We are field testing them. No pressure transducers needed. Everything is internal. The ones we have are 240V so they supplied a transformer to 120V. What I am hearing is they expect to have approvals on the 120V version this spring. It is not an add-on control. It is part of the motor assembly. (See Hot Rod's Photo Below.) You can use them as a standard 3 speed pump or if you put the arrow on the dot, it self regulates as a proportional Delta P pump. I don't have much info on it yet because the paperwork that came with it is vague. All I can tell you is that it works well. At my house this morning it was -3 F, the house was toasty warm and the pump was running at 14 watts.

Nate Greenleaf_2

Not quite Rod,
I do think that there is a place for the flat plate collector.

I believe that it's use is limited to anything lower than the 38° Latitude. Above this I can safely say that a good quality twin glass evacuated tube collector like ours will out preform the flat plate in an annual study. How do I know? Experience in the field...

I have done enough trade based training sessions,home shows, and counter days to know that I am not worried about being taken seriously by our customers or the public, our product speaks for itself very easily.

As for cost, our 30 tube panel has a suggested retail price to the public for around $1,600. This includes the frame and mounting hardware. This is the cost to the public..it may very depending on which plumbing house it is bought from. At that price.. I almost don't believe a flat plate collector needs to exist.. almost.

We don't sell packages, we sell collectors and a really cool controller. We aren't big advocates of OG300.

Metro Man

Tubeless

Still on vaca... but just can't stay away from this discussion. Sorry but I just don't buy any of this. I would LOVE to visit an installation. Do you have anything in the Denver area? Make me a believer that there is a better mousetrap. The little do-dad goes to 200 ish* so what.. still need to exchange that to the storage tank... @ what efficiency??? Also would love to throw a 1" hailstone @ tube to see if I could bust.

Our systems are drain-back water into stainless steel storage tanks. On a sunny winter day I will max tank temps at 180*. If you have to install your systems at an exact angle for them to work then I won't be able to install on 80% of jobs. The flexibility and ease of a flat plate just can't be beat. But I welcome you to make me a believer.

Gotta great back to family and friends and beer....

Merry Christmas and Happy New Year!

Metro Man

yo Dennis

How goes the battle Dennis?? Last time I saw you was the Wilo demo. How about a tour of the install in the near future? Would like to see those panels in action. Heard that you can run water through them and make them into drain back panels. Will Buderus stand behind with warranty if used in this way?

Also, if glass needs replaced how difficult?

Some of the flat plates are a bear to work on... and some you have to just change the entire panel.

Nice to see the larger tanks. How big do they get?

Grass-E-**** Home-brey!

Metro Man