solar problem

tipperary

Hi all

We have had solar panels in for the past couple of years. Today I checked some of the temperatures on the system, and things do not seem to be working very well Basically the temperature at the base of the tank does not rise above about 50 degrees. On the attached graph from last week it got to about 55, whereas today it only got up to 45 before the temperature started to drop! The system shows that the pump continues to operate as the temperature of the panels rises, but the temperature of the tank itself stops rising.

Does anybody have any idea of what might be causing this, or recommendations for somebody based south of Cork City who might be able to have a look? Is it likely to be something as simple as an airlock, or something more difficult to resolve?

One issue that did strike me the other day was the size of the pipework between the panels and the cylinder. There is about 15m of 1/2 inch copper pipework, with about 10m of the pre-insulated solar pipework as well. I thought the 1/2 inch seemed a little small, might this be an issue?

nmacc

Circulation is stoipping & the heat transfer fluid is boiling.
I doubt that the 1/2" piping is the problem. More likely air in the system is reaching the pump and stopping the ciculation. You can encounter this even when the system pressure remains high.

I suggest getting it pumped through; usually cures the problem.

shane0007

With the T2 rising but the T3 fairly flat lining, I would try this first:

Tomorrow with weather good, turn off the cold feed valve to the cylinder. (This is the valve in the hot press from your cwst feeding the cylinder, at the very bottom of the cylinder). You will obviously have no hot water at the taps during the test. If the temperature now rises to expected levels, you have leak somewhere in your hot water pipework, or taps. Make sure mixer taps are fully off.

ccsolar

Hi
Check your other heating sourced like oil / solid fuel .
It sounds like you have thermosiphining going on
Check the pipes at the back of your oil boiler/ stove and also check the water storage tank in the attic for temperature.
Cc

shane0007

ccsolar wrote: »

also check the water storage tank in the attic for temperature.
Cc

Yes this is a good one to check. System overheats & vents out of osvp into the cwst in attic, & circulates back through feed.

tipperary

Hi

thanks all for your replies. Got the system flushed this morning and things are working much better now, must have been some air in the system. I checked the other pipes at the cylinder today though, and sure enough the return pipe from the back boiler was quite warm. The pipe at the stove itself was at room temperature though so perhaps there is not too much heat being lost through this pipe. I will keep an eye on this though.
Thanks again to everyone for your help.

ccsolar

tipperary wrote: »

Hi

thanks all for your replies. Got the system flushed this morning and things are working much better now, must have been some air in the system. I checked the other pipes at the cylinder today though, and sure enough the return pipe from the back boiler was quite warm. The pipe at the stove itself was at room temperature though so perhaps there is not too much heat being lost through this pipe. I will keep an eye on this though.
Thanks again to everyone for your help.

You are having thermosiphining going on in your stove
You should get this sorted , can't really see your solar heating the water above 50/55 degrees while this is happening.

Cc

tipperary

cc, thanks for that. I will try to get it sorted alright. I understand the way to sort this is to have a vertical drop in the pipe after it comes out of the cylinder. There is a vertical drop in it at the moment, but it is only about 60mm or so as there were other pipes in the way. I can however add a vertical drop followed by a vertical rise to stop the thermosyphoning. What distance of a drop would I need to stop this happening?

The backboiler circuit to the cylinder is on a pumped line, and there is a gravity fed heatsink rad from the stove, so adding bends to the pipework should not affect the safety of the stove.