Evacuated tube failure

clearcutacres

Our system is now about 15 years old and produces next to no hot water. After checking it, we disconnected one tube from the manifold. The copper bulb in it was cold. This would point to a failure of the tube(s). Has anyone else seen that?

pecmsg

I need to see pictures of this tube!

hot_rod

Sounds like a heat pipe type of evac tube. Is the glass cloudy? That indicates it has lost it's vacuum. It should still get a bit above ambient and feel warm on the bulb.

Mad Dog_2

Haven't seen them "degrade" like that just B-52 strikes from the Seagulls. Yep picture would be great   Mad Dog 🐕 

Derheatmeister

Yes.. We have seen massive failures on Vacuume tube type collectors in high attitude installs
Thermomax and Viessmann both used Kingspan to produce the tubes that did not last very long..
Additionally: If the tubes are subject to prolonged stagnating temperatures they do not hold up and "Burn out"
Apparently Viessmann now offers a better tube as replacement.
We will be removing a 30 tube system in about 4 weeks.

kcopp

Derheatmeister said:

Yes.. We have seen massive failures on Vacuume tube type collectors in high attitude installs
Thermomax and Viessmann both used Kingspan to produce the tubes that did not last very long..
Additionally: If the tubes are subject to prolonged stagnating temperatures they do not hold up and "Burn out"
Apparently Viessmann now offers a better tube as replacement.
We will be removing a 30 tube system in about 4 weeks.

Are you replacing?
Or are they doing PV instead?

Derheatmeister

kcopp said:

Derheatmeister said:

Yes.. We have seen massive failures on Vacuume tube type collectors in high attitude installs
Thermomax and Viessmann both used Kingspan to produce the tubes that did not last very long..
Additionally: If the tubes are subject to prolonged stagnating temperatures they do not hold up and "Burn out"
Apparently Viessmann now offers a better tube as replacement.
We will be removing a 30 tube system in about 4 weeks.

Are you replacing?
Or are they doing PV instead?

We did a solar pathfinder study and shading was a factor that also warrants the removal.
Trees and mountains would have to be removed.
The original uneducated installer increased the customers carbon footprint..

Derheatmeister

BTW... The replacemenmet Tubes are very pricey
Flatplates such as Sunearth produces are our goto preferably in a Drainback setup.

hot_rod

there is not a lot of additional energy available from tubes compared to flat plate
cold ambient, below 20F, is about where tubes start to have some advantage

The formula takes into account ambient and collector inlet temperature, divided by solar radiation

with the heat pipe style evac tubes you have two vacuums to maintain. The tube itself, and there is vacuum pulled inside those copper heat pipe bulbs. That allows the water alcohol mix inside to boil around 110F

It flashes to steam and that is how the copper bulb can get to 300F plus temperature

It is hard to know when the vacuum in the copper heat pipe is gone. 

Looking at the array with an infrared camera will show the tubes that have gone bad. Without getting on the roof or removing the tubes from the header.

Mad Dog_2

The Buderus Flat Panels seemed well made but I forgot who made them for them...I remember the Solar HW classes 25 yrs ago comparing Flat Panel style versus Evacuated Tubes...Evac. tubes definitely outperformed
FP.   That being  said, anything by The Salt water (Seagulls) is going to get beat up much faster when they constantly drop their payload (Quohogues) big clams..on the Evac. Tubes...You'd think they could make a more durable glass?? I'm sure, heat transfer, convection et al, are the reason...price too   mad 🐕