thermomax tubes - some are hot, some are not

[hanksterr7]

Hi

We have had a thermomax system for several years now, and performance is deteriorating. I opened up the Mazdon unit that tubes connect into to transfer their heat and I noticed that for about half the tubes, the heat transfer pipe that goes from the tube into the heat exchanger is very hot. For the rest, the pipes are cool. I assume this means one of several things:
-- some of the tubes don't work, so they are not generating heat. So, a cool pipe means the tube is bad.
-- the coupling, where the tubes connect to the heat exchanger, is not working for some of the tubes. So a hot pipe means the tube is good but the coupling is bad. A cool pipe means the tube is good and is passing heat into the heat exchanger.

Thoughts on which of these possibilities is correct?

I notice that some of the tubes have some liquid in them at the bottom (maybe a few cc's). I assume this is a bad sign. I also see rust on the heat plate inside some of the tubes. Also doesn't sound good.

Any suggestions for what to do next? Our contractor is out of business, and I've seen posts saying Theromax has been bought by another company that is not honoring the Theromax warranty.

Thanks
-- Hank

[Naptown]

When you take the rubber part off the bottom is the bottom of the tube silver or a whitish color. Whitish means vacuum failure. If the tubes are not getting hot the heat tubes are bad. I can't remember if you can replace the heat tune only in those but seem to remember that they are sealed.
Kingspan in Maryland are the folks you need to contact as they bought that line

[hanksterr7]

Thanks! Will check. If I take the rubber part off the bottom of the tube, won't that cause the vaccuum to be lost? Why would i want to remove the plugs? Is it possible to re-vaccuum-ize the tubes? (I would think that would be done only by a pro).

[inetdog]

Thanks! Will check. If I take the rubber part off the bottom of the tube, won't that cause the vaccuum to be lost? Why would i want to remove the plugs? Is it possible to re-vaccuum-ize the tubes? (I would think that would be done only by a pro).

The rubber part is mechanical protection, not a vacuum seal.

As to the temp at the top of the tube, compare the tube-top temperature to the manifold temperature. If it is a lot hotter than the manifold, then the thermal connection is not good but the tube is collecting heat. If the top is cooler than the manifold, the connection is also not good and the tube is not producing any output.
For the heat pipe effect to work, there has to be at least a small amount of liquid inside the bottom of the inner tube when it is cool. And it may be discolored by additives. But liquid in the vacuum space between the outer and inner tubes must be the result of a vacuum loss and/or a leak in the inner tube. Freezing can damage some of the tubes but not others because of variations in the freeze protection. (inconsistent manufacturing.)

[Naptown]

The rubber part is mechanical protection, not a vacuum seal.

As to the temp at the top of the tube, compare the tube-top temperature to the manifold temperature. If it is a lot hotter than the manifold, then the thermal connection is not good but the tube is collecting heat. If the top is cooler than the manifold, the connection is also not good and the tube is not producing any output.
For the heat pipe effect to work, there has to be at least a small amount of liquid inside the bottom of the inner tube when it is cool. And it may be discolored by additives. But liquid in the vacuum space between the outer and inner tubes must be the result of a vacuum loss and/or a leak in the inner tube. Freezing can damage some of the tubes but not others because of variations in the freeze protection. (inconsistent manufacturing.)

Actually I have some thermomax tubes sitting in the warehouse. It has been a while but I will check. I believe the entire tube sits in a vacuum.
Apricus uses a welded glass almost insulated glass construction which is not the same as the thermomax.
Will report back

[LucMan]

And yet the AET flat plate panels just keep on going. Something to be said for old school technology.

[Naptown]

And yet the AET flat plate panels just keep on going. Something to be said for old school technology.

and now come with a 30 year warranty

[hanksterr7]

Well, a number of my pipes are very hot, but the manifold is not. Haven't gotten back on the roof yet to check whether we have a tube in a tube or not.

How does one improve the thermal connection between the heat pipe and the manifold?

[Oldstockthermomax]

Not sure if this thread is still active. Manifolds are doublelined and insulated so outside is never hot but exit pipe will be at full heatpipe temperature if system set up with minimum flow. I made a test stand for my pipes to check

[inetdog]

Well, a number of my pipes are very hot, but the manifold is not. Haven't gotten back on the roof yet to check whether we have a tube in a tube or not.

How does one improve the thermal connection between the heat pipe and the manifold?

Make sure is it not corroded and is a tight mechanical fit. Maybe add some thermal grease of the kind used for semiconductor heat sinks?

[Oldstockthermomax]

Not sure if thread is live still. Manifolds are double lined and insulated so never get hot. But exit pipe will get to heatpipe temp under min flow. I built a test stand to check my tubes but this requires draining manifold but not entire system. Heatpipe temp should be 95% of rating. A bad heatpipe is easy to isolate and replace. A bad heatpipe will scavenge the heat from the manifold.