Help with modifying control of a two zone store

championc

Hi all,

My solar store had two zones so I got an electric 3 port valve installed to zone load the store. My hope was that I could get the top of the tank heated first via the upper coil and once it reached a certain temperature, then the zone valve would switch to loading from the bottom coil.

It would seem that my controller (Kingspan SC300 / Steca TR0603), when configured for zone loading, wants to heat the top a bit, then allows the bottom to catch up, then does the top again, back and forth.

So I was thinking, the ideal scenario would be for me to set the system back to a standard single zone system, and then for an external control to control the 3 port valve for directing the heat into either the upper or lower section. So big deal, and external thermostat with a probe can then control the 3 port valve but the problem I see is for the system to then read the temperature from the PT1000 for the appropriate section of the store. If the system was loading to the top section, the solar controller would need to read the temperature of the upper PT1000 and if it was loading to the bottom, then read the lower temp.

It would seem like I would need a relay of some kind, triggered by the external thermostat (or a second one) which would switch reading of the temperature from either one PT1000 or the other,

Has anyone ever done this or have any suggestions ?


C

freddyuk

How about a simple temperature differential switch. It has two sensors to measure two temperatures and will switch on a pump (or a valve) at a pre set differential between sensor 1 and sensor 2. So if the temperature at sensor 2 drops below say 8c from sensor 1 the valve will divert the heat to the sensor 2 (bottom) until the differential is say 4c then it will revert to heating the top again and so on. Keeps the whole cylinder between a known temperature range.
I use it to transfer heat from a buffer tank to my DHW cylinder. If the buffer is X degrees hotter than my DHW cylinder it will pump the heat down until the difference is Y then switch off.

quentingargan

I've only seen this done with the Resol Delta Sol M or Delta Sol E, which have multiple cylinder options.

I think you are right about the idea of a relay switching over both the probe and the motorised valve, driven by a stat in the top half of the cylinder. A 3 pole double throw relay would do it OK. In fact, I think even a two pole one would do - one side of the PT1000 can be a common GND.

Do you have room for a stat and a probe at that point in the cylinder?

championc

freddyuk wrote: »

How about a simple temperature differential switch. It has two sensors to measure two temperatures and will switch on a pump (or a valve) at a pre set differential between sensor 1 and sensor 2. So if the temperature at sensor 2 drops below say 8c from sensor 1 the valve will divert the heat to the sensor 2 (bottom) until the differential is say 4c then it will revert to heating the top again and so on. Keeps the whole cylinder between a known temperature range.
I use it to transfer heat from a buffer tank to my DHW cylinder. If the buffer is X degrees hotter than my DHW cylinder it will pump the heat down until the difference is Y then switch off.

Hi Freddy

What you describe here I think is exactly what I HAVE. However, what I want to do is, if the bottom is 8 deg C, I want it to stay at 8 deg C until the top reaches 60 deg C and then get the bottom to start heating. So the bottom will never heat until the top is full.

I suppose, the easy way to think of this is me having two small tanks rather than one big one.

On Saturday afternoon, the top got to 48 while to bottom to 43 so by this evening, the top had fallen to about 40 which is below the 45 I need for hot water to go straight to hot taps

Thanks Quentin, I look at a 3 pole relay. I think the top, middle and bottom of the store have 3 holes / ports for PT1000 type probes so I would have an aperature free so for a probe from a stat.