Hello - we inherited, when we bought the house, about 12 years ago a Spectrum Energy solar thermal system with 10x6' evacuated tubes feeding a pre-heat tank which then fed the hot water feed. We changed much of this to twice the tubes, connected the sensor to the correct side of the panel array and fed the pipework into a 300L pressurised heat store. This was fine, using the existing fairly crude Spectrum Energy controller.
Recently, the controller went bang and so I set about making my own. I replaced the PT500s with PT1000s and used a Raspberry PI to do the controlling job. It seems to be working well and I have a little graph on the display showing the tank top, bottom and collector temperatures.
Since I can now see the three temps on a graph I can therefore see the responsiveness of the system but have no reference to know if things look right or not. I have a few observations and am hoping that those with experience can tell me if it sounds about right.
We have no other heat raising the temp of the tank at the moment and are in Devon. Almost mid-summer and a very sunny day. The tank top+bottom was at about 38C early this morning. When the collector gets to 5C more than the tank bottom the pump comes on. Today, the pump has been on for most of the day. I had imagined that a temp difference between the tank bottom and collector of at least 15C would have heated the tank quite quickly. Actually, although steady, the tank didn't get above 65C (we had showers in the evening, hence the bump in the graph).
Does the responsiveness on the graph look about right? If so, great, I can forget about it. (I reset it this morning to more clearly show today's activity - attached). I had imagined that the issue might have been too much heat for the tank but it seems not.
Many thanks, sorry for the long message.
Patrick
Recently, the controller went bang and so I set about making my own. I replaced the PT500s with PT1000s and used a Raspberry PI to do the controlling job. It seems to be working well and I have a little graph on the display showing the tank top, bottom and collector temperatures.
Since I can now see the three temps on a graph I can therefore see the responsiveness of the system but have no reference to know if things look right or not. I have a few observations and am hoping that those with experience can tell me if it sounds about right.
We have no other heat raising the temp of the tank at the moment and are in Devon. Almost mid-summer and a very sunny day. The tank top+bottom was at about 38C early this morning. When the collector gets to 5C more than the tank bottom the pump comes on. Today, the pump has been on for most of the day. I had imagined that a temp difference between the tank bottom and collector of at least 15C would have heated the tank quite quickly. Actually, although steady, the tank didn't get above 65C (we had showers in the evening, hence the bump in the graph).
Does the responsiveness on the graph look about right? If so, great, I can forget about it. (I reset it this morning to more clearly show today's activity - attached). I had imagined that the issue might have been too much heat for the tank but it seems not.
Many thanks, sorry for the long message.
Patrick
