Can someone explain this 'problem' to a newbie please?

[inetdog]

Thanks for that Naptown. Some progress this end i'm pleased to report, namely that I have convinced the guy that the solar is not working properly, i.e. 108 on the roof and 40 at the bottom of the tank and constantly droppping over 5 hrs ! Anyway, it turns out that the flow and return from the thermal store to the solar tubes are connected the wrong way round. In other words the pumped line is connected to the top of the coil in the tank instead of the bottom. I'm just hoping that will solve the issue.....what do you think?

That will certainly make a big difference! But you may still have problem with the capacity of the system. Best thing is to make more measurements once the flow direction is fixed.

One possible remaining problem is that if you have a separate boiler/heater to that tank, the solar should draw from the bottom of the tank and return to the middle of the tank so that it is not cooling the higher temperature water heated by the separate heater. Only if the solar heater output temperature is higher than the temperature produced by the heater should you connect the return to the top of the tank.
In your case, that would correspond to the stove coil being in the top half of the tank and the solar coil being in the bottom half.

[nickbb]

carefully feel the pipes that go to and come from the collector Are they hot ? is the one coming from the collector hotter than the return to the collector.
do the same thing on the pipes from the storage. The return to the tank should be hotter than the pipe feeding the heat exchanger.
Verify that the pump(s) are actually operating and pumping fluid and water.

Thanks for that Naptown. Some progress this end i'm pleased to report, namely that I have convinced the guy that the solar is not working properly, i.e. 108 on the roof and 40 at the bottom of the tank and constantly droppping over 5 hrs ! Anyway, it turns out that the flow and return from the thermal store to the solar tubes are connected the wrong way round. In other words the pumped line is connected to the top of the coil in the tank instead of the bottom. I'm just hoping that will solve the issue.....what do you think?

[Naptown]

carefully feel the pipes that go to and come from the collector Are they hot ? is the one coming from the collector hotter than the return to the collector.
do the same thing on the pipes from the storage. The return to the tank should be hotter than the pipe feeding the heat exchanger.
Verify that the pump(s) are actually operating and pumping fluid and water.

[nickbb]

With the water at almost 60C during this time of year is actually not bad at all.

Ok, today was a really cloudless sunny and mild day. The roof (manifold I presume) temp got to 110, but the water temp in both the bottom and the top of the tank did nothing but drop over a period of 5hrs without any water (baths, washing up etc) being used. Can anyone throw any light on what the cause of this might be?
The bloke who installed it left it on the roof unconnected for a week and a half before connecting and filling, which I have read is not great. I have also read that some installers do that and that the tubes can stand 200 Deg before they go bad.
Any help is appreciated.

[nickbb]

With the water at almost 60C during this time of year is actually not bad at all.

To be fair though, the water temp in the thermal store that I have shown was the residual temperature from the pellet stove being on earlier in the morning. What concerned me was the fact that the solar seemed to have 'dragged' that temperature down to 43.5 from a starting point of 49.5 in four hours. But like you say, maybe that was due to a bit of washing up etc ?

[Naptown]

With the water at almost 60C during this time of year is actually not bad at all.

[nickbb]

A few things here
Is this an internal static heat exchanger or external pumped unit. With a pumped unit there is some mixing of the water meaning the tank will become stirred up mixing the cold at the bottom with the hot at the top cooling the top.
Secondly it appears that some hot water was used during the day as evidenced by the dropping bottom temperature which will reduce the manifold temperatures.

Thanks for the quick reply Naptown, ours is an external pumped unit. I'm just trying to get me head round what I should expect from a system like this. So I guess you're saying that until spring then this is pretty normal?

[Naptown]

A few things here
Is this an internal static heat exchanger or external pumped unit. With a pumped unit there is some mixing of the water meaning the tank will become stirred up mixing the cold at the bottom with the hot at the top cooling the top.
Secondly it appears that some hot water was used during the day as evidenced by the dropping bottom temperature which will reduce the manifold temperatures.

[nickbb]

Hi All

I'm new to this forum and to solar technology. We have just had a pellet biomass boiler system installed feeding both our water and rads which is 'complemented' by 20 Joule evacuated tubes on the roof. The issue is this. We have been monitoring the controller which reports the temperatures on the roof (presumably at the manifold) , the top of the thermal store, and the bottom of the thermal store. We live in the south of England on the coast and yesterday was a mostly cloudless day with bright sunshine and a temperature of about 14 degs. When the solar cut in at about 10:00am the temps were as follows:

Roof 59.3
Top of thermal store 56.7
Bottom of thermal store 49.5

The temp curve then proceeded as follows over a period of 4 hrs between 10:50am and 2:50pm


Roof 59.0 55.8 56.4 55.3 61.8 56.4 46.9 50.7
Top of thermal store 56.2 54.8 53.4 52.5 51.3 50.8 49.5 49.1
Bottom of thermal store 50 48.8 47.6 46.8 46.1 46.1 44.4 43.5

Now during this time the solar was the only thing running, i.e. no pellet boiler, correct me if i'm wrong but I was kind of hoping that the temp in the tank would have gone up not down, or am I expecting too much in that period of time at that outside temp. By the way, the pump is set to cut in as and when it's needed, which it does. Any help would be appreciated before I sign this job off, which i'm not inclined to do as you can imagine.