solar panel dhw temperature

daithihalton

Hi I have a 30 tube 300 liter system the tubes are directly south facing at a 35 degree angle the run from the solar tubes to the tank is about 18 meters, i fitted it during the winter but over the last week i expected to have piping hot water but the hottest the tank has got to was 40 degrees and the tubes were 50 degrees these are the max recorded over the last week of very good weather
is this a poor expected temperature as my friend is getting 68 degrees in his tank with a similar system
my pump station is working as i checked it out during the day
one of the days i had the pump run continuous from 11:00 to 15:00 and still it only managed 40 degrees
any ideas??
regards

quentingargan

daithihalton wrote: »

Hi I have a 30 tube 300 liter system the tubes are directly south facing at a 35 degree angle the run from the solar tubes to the tank is about 18 meters, i fitted it during the winter but over the last week i expected to have piping hot water but the hottest the tank has got to was 40 degrees and the tubes were 50 degrees these are the max recorded over the last week of very good weather
is this a poor expected temperature as my friend is getting 68 degrees in his tank with a similar system
my pump station is working as i checked it out during the day
one of the days i had the pump run continuous from 11:00 to 15:00 and still it only managed 40 degrees
any ideas??
regards

Very hard to diagnose over the web, but on the face of it, there is something amiss. As usual, don't mention brand names, but can you say what the total aperture area of your tubes is? (Or how much your SEI grant was - I can work out what sort of tubes you have from that).

There are many possible causes. If there was anything wrong with the circulation, then the panel would be over-temperature. The following are possibilities;

1) You may be using a lot more water than your friend. If your cylinder is starting at 12 degrees because you used all of the hot water the night before, you would have a different result to someone with a cylinder that was starting at 40 degrees because all they do is brush their teeth:eek:

More likely though;
2) There is heat being lost from the cylinder. Are any of the pipes coming from the cylinder hot? Often the installer insulates everything on the solar circuit, then connects the heating pipes into the top coil, ignoring heat loss from that circuit. If any pipes come out of the cylinder and then rise, the heat will also rise.
3) Is your system open vented (i.e. fed from an attic tank)? If so, the vent pipe may be running hot. It should run horizontally for about 500mm before heading uphill.
4) I assume that everything in the solar circuit is thoroughly insulated, and that you can't see any metal pipework, valves or anything else on that circuit?
5) Is there a heat dump radiator on the system? Any chance that the valve feeding that has been set up incorrectly, and there is heat from the circuit leaking into your heat dump?
6) Any of the tubes damaged? Usually if tubes have lost their vacuum, there will be white streaking up the side of the tube visible from the ground. I have seen tubes fail that this didn't happen with.
7) Again, without naming names, is the system the same brand as your friend's?
Q

daithihalton

thanks for the reply
1. the heat pipes going to the upper coil on the tank one goes straight down the other is horizontal for about a foot and a half then goes to a t piece then up and down they are all insulated and are only warm to touch mostly directly on the tank

2.the tank has no attic tank its supplied direct from the mains

3.the solar circuit is well insulated

4.I have a radiator in the hotpress as a heatdump but have never felt it warm i dont think ive reached a hot enough temp for it to be used

5.I cant see any white streaking, but all bar one tube have approx 8 inches of them all black just before they reach the manifold one is still copper colour looking at them from underneath
6. without naming my system its a h*200 model irish manufacturer with a 300 litre alb*** tank it was a complete matched system im not sure what my friend has have to call out to him but as far as I know its a totally different system he has a family of 5 i have 3 so was expecting to have more hot water

I suspect the tubes are not outputing what they should today the max temp for the tubes was 49 deg c and the tank reached 42 degrees c
hope this helps

quentingargan

daithihalton wrote: »

thanks for the reply
1. the heat pipes going to the upper coil on the tank one goes straight down the other is horizontal for about a foot and a half then goes to a t piece then up and down they are all insulated and are only warm to touch mostly directly on the tank

2.the tank has no attic tank its supplied direct from the mains

3.the solar circuit is well insulated

4.I have a radiator in the hotpress as a heatdump but have never felt it warm i dont think ive reached a hot enough temp for it to be used

5.I cant see any white streaking, but all bar one tube have approx 8 inches of them all black just before they reach the manifold one is still copper colour looking at them from underneath
6. without naming my system its a h*200 model irish manufacturer with a 300 litre alb*** tank it was a complete matched system im not sure what my friend has have to call out to him but as far as I know its a totally different system he has a family of 5 i have 3 so was expecting to have more hot water

I suspect the tubes are not outputing what they should today the max temp for the tubes was 49 deg c and the tank reached 42 degrees c
hope this helps

Thanks. Unless there is heat leaking somewhere in the system, it would probably be down to the panel.

I'm not sure why the tubes appear to have 8" of black. That may just be reflection and if you look at it at a different time of day, it may appear more consistent.

Is the pressure normal in the system by the way?

I'm afraid I would suggest you contact the manufacturer or your installer. There isn't anything that can be diagnosed at a distance from what I can see..

Q

daithihalton

the pressure is about 1.5 bar and has been since installation
Ill contact the manufacturers tech support
thanks for your help

bakerbhoy

Check that the tubes are turned the correct way. When i had mine installed they were left 180 '' down as my system was not been drawn from and the heat was only going to 50'' max for protection.They are now rotated correctly and are banging 72'' at the moment.
6m sq mtr ..... 750 ltr buffer

quentingargan

bakerbhoy wrote: »

Check that the tubes are turned the correct way. When i had mine installed they were left 180 '' down as my system was not been drawn from and the heat was only going to 50'' max for protection.They are now rotated correctly and are banging 72'' at the moment.
6m sq mtr ..... 750 ltr buffer

Good point. I don't use this type of tube, but some installers put them in upside-down to stop them heating up until everything else is plumbed in. But I thought the OP could see them as black from the ground?