unvented cylinder advice/future proofing

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Hi all,

We currently have a gravity fed system with tanks in the loft and vented cylinder in the airing cupboard. 4 bed house- family of 4. We also have the benefits of 16 solar panels on the roof on the old FITS scheme, which we inherited- therefore I must admit that my understanding of exactly how this system operates is a little limited beyond the payments we get and not necessarily how we can further benefit from it.

We would like better hot water pressure in the upstairs bathrooms and this is what kickstarted the research into pumps versus unvented cylinders versus combis etc. Last option we have all but written off. Current boiler is fine. The unvented cylinder option definitely looks the best bet. Our mains water pressure is very good.

Am I right in thinking that we probably want to look at a cylinder with good direct heating elements- and that this could either potentially be linked to heat pump (if that is what the future holds) or also somehow linked to solar panels? Essentially I just wanted to check that what we should be looking for is a good option now for our gas boiler, but also one that provides some alternative means of hot water? Any specific advice therefore on what features we should be ensuring a new cylinder has, would be much appreciated.

Thanks
 
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1. Direct heating elements usually refers to electric immersion heaters.
2. Indirect heating elements are coils of tubing within the cylinder. Hot water runs though these coils and indirectly heats the hot water you use to bath and shower.
3. Look at cylinders (e.g. from Joules) with more than one coil, so that one could be used for the gas boiler and another for solar / heat pump. Until an alternative source of heat is installed you could use both coils on the gas boiler for faster recovery times, provided the boiler and pipework can supply sufficient heat.
4. You say your mains water pressure is very good. This is fine if it has been measured with a proper pressure gauge as both static and dynamic pressures. If its just an impression from a good flow at the kitchen tap, this doesn't mean it will support and unvented hot water system.
5. Measure static (no water flowing) and dynamic (one mains fed tap open) pressures, and the flow rate of the incoming mains. Measure flow rate at an outlet with no restrictive valves in the flow, and with the main stop cock fully open.
6. For an unvented cylinder you should have a minimum dynamic pressure of 2 bar, and preferably more, with a flow rate of around 25 litres per minute.
7. You might have to change the cold water connection from mains to cylinder. These are often 15 mm to the storage tank, but might have to be upgraded to 22 to get the flow you want.
 
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Your P. V solar array can be used to backfeed your immersion heaters in either a vented or unvented cylinder.
The only thing is you will probably need to upgrade your immersion heater to a Incaloy version if you want to use it all the time as most immersion heaters are low quality backups.
 
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