Advice for Solar Water Heater Please

We have a solar panel with an external water tank in a property that is not used for long periods. Particularly recently.

We had it installed a couple of years ago and it has been great. It is in one of the Canary Islands so is exposed to a
lot of sun and heat.
We are getting conflicting advice as to whether the cold water supply should be switched off when the property is not used. Our insurance company want the water switched off but someone told us a system like this needs to be connected to the supply at all times to avoid damage. The instructions are not clear and the fitter is now unavailable.
Any advice from folk with similar systems would be very welcome as we have to leave the property on Sunday morning, probably for 6 months.
Edit: The only control which is accessible is the switch/clock for the electrical heater element which is used occasionally. The rest is on the roof.

Have you tried contacting Baxi.

If the water is turned off. Does that mean the water in the system remains, and stagnates.
Sounds like a serious legionella concern

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Good point. I believe you need to get water above 60 degrees every so often.

I suppose if it’s external, you could turn it off and drain it if that’s possible. If you don’t drain it then it may freeze over winter and split the pipes

Thanks for all the replies. It won’t freeze here but I am concerned about over heating. We have some neighbours who come in and switch the water on and run taps every month or two. Just wondering if any members were in the same situation. Cheers.

If water is static in system for 24 hours it needs to be run and circulated to minimize legionella risk

A very valid concern. Here at our flat in Germany last year we were visited twice by official inspectors who checked for legionnella. At work during lockdown my employer organised for anybody who was on site to run the hot taps, which in practice happened at least once a day during the week. In our motor home, best practice when decommissioning was to run the system dry (the pump was small enough to take out and upend to drain), then to run hot water through the system after refilling.

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Does your hot water system have a ballon fitted to allow for volumetric expansion due to change of temperature?

The idea is that a small vessel - about 5-10 litres with a bag of nitrogen will allow for volumetric expansion caused by changes in temperature. If water is in a ‘solid’ system then any increase in temperature can cause a large increase in pressure - up to 100 PSi per degree C.

Therefore if you isolate at the mains, there is a potential problem of increase in temperature causing a burst pipe. Perhaps consider draining the system of water, although not always practical, fitting a ballon to absorb pressure changes or fitting a high pressure relief to vent any excess pressure safely?

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Just took a look at the Installation instructions.

The advice is

In the case of lack of demand, or when long periods without removal of ACS are expected, protect the system with thermal blankets or drain the system. (I’m thinking ACS is Spanish term for DHW)

Edit. Not clear if the primary side (soalr panel) or secondary side (tank) need draining.

Link to instructions.

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