January 2010

[rt29781]

We had 132kWh from the PV in Jan 2010  so about 400kWh from the solar thermal. 

Attached is a typical trace for the Solar thermal system in January with a clear sky heating 80 m2 of floor in the house alongside our heat pump.  The heat pump comes on at 05.30 and heats the floor and the 500lt storage tank.  By about midday the solar panels are contributing well and heat the solar storage tank to 40C when the heat pump goes off and stays off for about 5hours.  The heat pump switches off at 21.00hrs.  The house is at 22C all day.  The heat pump draws about 2.5kW.  The outside temperature was between 0 and 5C all day.

[alex2504]

i installed system in october and since mid december i haven't had anything from solar hot water, is this normal for scotland aberdeenshire?

20 tubes, 140 litres

[dhaslam]

The frosty days in December and January have been very good  but did you  have a lot  of snow?   Also what pipe size and length do you have? 

[alex2504]

10mm pipes, 19metres

looking at controller, system hasn't been on since mid december, was concerned that the cold weather has done some damage even though i have sufficient anti freeze

[solarcycle]

I'm in Perthshire and the sunny days we've had recently result in a tank of around 42'C top to bottom. I have a twin cylinder setup though with 60 47mm tubes initially feeding 180l.

Are your tubes 47mm or 58mm? If 47mm you are  likely to be underpowered as its assumed around 5litres per tube. An extra 10 or 20 tubes would be useful but you'll need some form of heat dump.

[dhaslam]

Even if the pump isn't running the controller should be showing temperature readings.   Is another source  heating the bottom of the cylinder?   

[alex2504]

solarcycle,
Tubes are 47mm x 20 on a 140litre tank.

dhaslam,
I am seeing temperatures on the controller. On the panel temp I am seeing very little increase in temperature over the past 6 weeks only 2 or 3 degrees over the ambient, starting to wonder if there could be air in the panel manifold causing this as i don't have an automatic bleeder on the panel.

[langstroth2]

alex2504
Even on a dull day when there's no pumping the panel temperature should be quite a few degrees above ambient for a good part of the day, assuming they're not covered in snow. e.g. at the moment it's dull, 9am; ambient 3.7C, panels at 9.6C; yesterday also very dull; peaked at about 32C (no pumping).

I wonder if either:
- panel sensor not installed properly in manifold sensor pocket?
- air lock in manifold as you suggest?
- less likely, but tubes not fully pushed into manifold?

[dhaslam]

If you could get the pump running, I'm not sure how  to do this,  it might  get it started.  If it is an air bubble it would probably go to the top of the panel again  but at least it would narrow down the problem.   

[Greenbeast]

well the TDC3 has manual mode, where you can trigger the pump manually.

[alex2504]

Have previously left running in manual mode on pump speed 3 for a couple of hours, very little air was released from bleed point

[Greenbeast]

i assume the air valve is the highest point in the system?

[alex2504]

No the air valve isn't on the highest point. the highest point is outside at the panel.

[Greenbeast]

Well that's where the air will be if there is any.
Why many people fit air bleed valves higher than the panel

[alex2504]

well how silly do i feel.....  Temp probe had falling out of manifold and has been like that for over a month.