Hot Water tank losing heat?

Getting into the nuts and bolts of wind and solar power components, installation and performance issues, ask technical questions, answers and tips

Hot Water tank losing heat?

Postby gpigeon » Sun Dec 04, 2011 7:24 am

I have a 26 yr old Beasely Solar HWS which has worked very well since buying it new for about $1300. (Probably a lot of money back then - and no subsidy either!)
About 5 yrs ago I stripped both panels, cleaned & painted the galvanised sheet cases and replaced the glass fibre insulation behind the copper panels with sheets of styro foam insulation.
However, I am noticing that the water is not maintaining temperature as it used to. After only one cool cloudy day the water is hardly warm enough to shower comfortably. This was never the case earlier and I believe it is getting worse!!!!
There is some condensation on the underside of the panel glass. This could indicate a slight leak in the panel tubing or could just be atmospheric moisture that has been drawn into the panel housing and now cannot get out. There are no obvious drips. The panels themselves seem to working okdespite the condensation, because after only one hot day the water temp is good again.
I am thinking that the problem is with the tank insulation itself. The tank is SS and encased in what looks like yellow expanded foam with a "colorbond" outer sheet steel casing. Does anyone know if these styro foams break down with age?
The system also has a wood fire heating circuit but there is no temp differential (unless the fire is going) in the feed/return lines so I don't think this is the problem.
Another possibility is "reverse cycling" of the hot water through the panels??? Has anyone had experience with this phenomenon?
Last edited by Gordon-Loomberah on Sun Dec 04, 2011 12:48 pm, edited 1 time in total.
Reason: subject spelling
gpigeon
Solar Evangelist
Solar Evangelist
 
Posts: 96
Joined: Sat Sep 26, 2009 6:37 am
Location: NSW (Northern Rivers) - Origin (ex Country Energy)

Re: Hot Water tank loosing heat?

Postby Helipos » Sun Dec 04, 2011 12:25 pm

Reverse cycling. Get up there during the night and see if the panels are notably warm. That will confirm or deny that.
It could be that the styro foam is breaking down or has gotten wet. I'd be tempted to replace it with fibreglass.
If you feel around the system during the night it will tell you if there is significant amounts of heat leaking. If there is no leakage then I'd start to suspect the panels.

Some HWS have a separated loop that goes through the panels to heat the tank. Like a closed loop heater system on a power station where the boiler and steam turbine water is kept separate from the cooling water. Could it be that that is running out of fluid?

Cam
User avatar
Helipos
Solar Crusader
Solar Crusader
 
Posts: 296
Joined: Tue Oct 06, 2009 10:18 pm

Re: Hot Water tank losing heat?

Postby Smurf1976 » Sun Dec 04, 2011 2:07 pm

Run your hands over the entire surface of the tank feeling for any hot (warm) spots.

Also remove any covers (anything that gets you access behind the outer cover and look for any signs of water). If it's wet then you've got a leak in the tank which at 26 y.o. wouldn't be too surprising (what are these tanks made of?).

With regard to the insulation breaking down, I'm not familiar with these particular tanks but I can say the following about normal non-solar electric units, specifically the Rheem ones. In short, any thermostat setting over 75 degrees voids warranty since this will (1) accelerate wear on the the internal lining and (2) cause the insulation to break down. Most plumbers don't like to set them over 70, since it seems to be accepted that whilst the manufacturer allows up to 75, the unit will last considerably longer at 70 or below.

I know of a situation where a Rheem 50 litre electric HWS was intentionally set to about 85 degrees in order to increase hot water capacity to the shower it supplied. This was a temporary situation until a larger HWS was installed a year or two later. When the 50 litre one was removed, you could quite readily see that the insulation had begun to deteriorate (shrink) in the vicinity of the electrical connection box.

How hot does the water get in this system? Does it go over 70 regularly?
Smurf1976
Solar Crusader
Solar Crusader
 
Posts: 916
Joined: Mon Oct 26, 2009 12:56 pm

Re: Hot Water tank losing heat?

Postby gpigeon » Mon Dec 05, 2011 6:13 am

Gents.........
Thanks Gordon for correcting my spelling error! Pretty slack of me!
Thanks Smurf & Helipos. Good tips re feeling for hot spots in the evening. I will get onto it.

The system does not have a separate heating circuit. The water runs through the panels.
The tank is stainless steel. 304 or 316 ?? Dont know and manual does not say. So it will have no lining and as such, high temperature should not be an issue. I originally chose the "Beasely" because it had a SS tank. I think most of the others have a carbon steel tank with vitreous lining.

If the tank insulation is in fact the problem then it is a big job to fix it. It appears as if the foam was injected after the outer steel casing had been fitted around the ss cylinder. However, I am not one to throw out something that still has life in it so I will tackle it. That expanding foam is available by the tube (cartridge) so maybe I could use that again, if the system survives for another 26 years I don't think I will be too worried about the next re-line!!!!!
Thanks again.
Rgds. Bill.
gpigeon
Solar Evangelist
Solar Evangelist
 
Posts: 96
Joined: Sat Sep 26, 2009 6:37 am
Location: NSW (Northern Rivers) - Origin (ex Country Energy)

Re: Hot Water tank losing heat?

Postby bazzle » Tue Dec 13, 2011 11:58 am

IF the insulation has deteriorated you can get external hotwater tank blankets fron Enviro shops etc.
To see if the water has a rev flow just put hand around each of the pipes from the tank to the roof at night. You will soon tell.
There should be a anti reversal valve that may be leaking.

Bazzle
bazzle
Solar Fanatic
Solar Fanatic
 
Posts: 35
Joined: Sat Jan 29, 2011 2:25 pm

Re: Hot Water tank losing heat?

Postby gpigeon » Wed Jun 05, 2013 8:45 am

I have still not sorted this problem out and it is getting worse and now at the stage where I must really do something about it.
Following all the suggestions put forward, I found the following:
1. There are no hot spots on the tank at night. so, this would suggest that the tank is not the problem.
2. There is condensation on the underside of the glass on both panels. This would decrease radiant efficiency but more importantly the insulating material behind the panel is probably wet. Whether the moisture is coming from a leak or moist air drawn into the during temperature changes I do not know. When I dismantle the panels I can pressure test them. If the moisture is from a leak then it is a very small one because no liquid water comes from the 6mm dia drain hole in the lower end of the panel box.
3. At night time both the inlet and outlet pipes of the panels are warm. This may indicate reverse cycling??? There is no check valve fitted to stop this so how it is normally prevented I do not know.

Any further suggestions/tips before I dismantle the panels?

I have looked at discarding the flat panels and retrofitting a 20 glass tube system using the existing SS tank.
Any comments on this idea?

Thanks.
Bill.
gpigeon
Solar Evangelist
Solar Evangelist
 
Posts: 96
Joined: Sat Sep 26, 2009 6:37 am
Location: NSW (Northern Rivers) - Origin (ex Country Energy)

Re: Hot Water tank losing heat?

Postby bazzle » Wed Jun 05, 2013 9:15 am

Flat panels do / can get condensation in them, its a natural thing. They should dry out when the weather is hotter. As they are not double glazed with a separate sealed gas in there it will happen just from the change in temps both sides of the glass.If there is no water coming from the small drain then they are not leaking .
You see it on Dux panels that work quite well and it doesnt seem to affect performance.
If the pipes are both warm go to a plumbers shop and get an 1/2" one way flow valve and fit to the inlet.
bazzle
Solar Fanatic
Solar Fanatic
 
Posts: 35
Joined: Sat Jan 29, 2011 2:25 pm

Re: Hot Water tank losing heat?

Postby Gordon-Loomberah » Wed Jun 05, 2013 9:26 am

I'd seriously consider evacuated tubes, they are more efficient, especially in marginal conditions, and don't suffer from condensation. Make sure you get the tubes with the 2mm thick outer glass wall, which are able to withstand fairly large hail. Some tubes use thinner glass, and are more prone to breakage.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 3825
Joined: Thu Sep 24, 2009 10:41 pm
Location: Loomberah NSW Australia

Re: Hot Water tank losing heat?

Postby Tracker » Wed Jun 05, 2013 10:00 am

gpigeon wrote:.
3. At night time both the inlet and outlet pipes of the panels are warm. This may indicate reverse cycling??? There is no check valve fitted to stop this so how it is normally prevented I do not know.

Any further suggestions/tips before I dismantle the panels?
.


Heat rises.. even ovens have holes at the base..
Why don't they have drains or vent at the lowest point of these collectors.

With the heat at the Inlet and Outlet, that would be generally normal. .
How far up/down the pipes will determine what is happening..
Ie. Normal heat conduction would suggest that the fittings would be warm... foam tube insulation would help there..
Now if one pipe is noticeably warm away from the tank, then that would suggest circulation.. but WHY.. why would it be circulating if not being used..

I have to fix a Siddons system which boasted a SS tank.. Fantastic indeed..
Only problem is the steel outer - case that rusted out.. badly ..!
A new skin should fix it.. but I do wonder about the insulation.
..
.
Tracker
Solar Crusader
Solar Crusader
 
Posts: 4651
Joined: Wed Sep 23, 2009 6:54 am
Location: SYDNEY --- EA - Network, Retailer - EA

Re: Hot Water tank losing heat?

Postby Helipos » Wed Jun 05, 2013 11:26 pm

I assume your tank sits above your panels?
User avatar
Helipos
Solar Crusader
Solar Crusader
 
Posts: 296
Joined: Tue Oct 06, 2009 10:18 pm

Next

Return to Components, Installation And Performance

Who is online

Users browsing this forum: Bing [Bot] and 3 guests