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The sketches are correct, but it wasn't so long ago that this came up and some people got it wrong, see this thread: http://www.diynot.com/forums/viewtopic.php?t=265643&start=15

It's worth specifying whether the boiler you want it for is modulating of not. If it isn't then the CM907 or CM927, but otherwise look for something that will take advantage of the modulating function. It's likely to give better control. It's all dependent on the age of the boiler really.

OK, I see you've tried bypassing the softener. Are the strainers in the PRVs dirty? See http://www.rwc.co.uk/Public/prv/PRV-001.pdf for a the way the PRVs operate. I can't see how two in series with the second rated higher than the first would be a problem, but it would be worth trying to...

So if I understand your readings correctly the garden tap delivers 22l/min and the bathroom and kitchen together deliver 17.25l/min. So I assume the garden tap is fed directly from the mains. My guess is that for a single tap the 22l/min sounds OK and that the flow shouldn't give you any worries...

Open all the cold taps that you can at the same time. Then whilst they are all running measure the flow out of each one at a time. Adding together all the readings will give you a better idea of the max flow you can get through your 25mm main and the cylinder PRV. It's no good measuring at one...

or a Priory Nail Puller.

It's not earthing, but equipotential bonding to ensure that all the metal work you can touch will always be at the same potential in the event of a live conductor making contact with something it shouldn't. That way you can't touch one tap that is live with one hand and the other tap that isn't...

What about his cholestrol?

You suggested earlier that you thought the 30 mins was not sufficient time to heat water fully. My calc above indicated you would need 8kW for 30 mins and you limited the boiler to 7kW. How do you know that 'yesterdays' settings were for a full tank reheat? How do you know that the starting...

It's the based on the specific heat capacity of water which is 4.18 kg/kg °C. So for every kg of water heated by 1 deg C you will need 4.18kJ. 1 kw is 1kJ/s so a 18 kW boiler could deliver 18kJ/sec to the water. I say could because that is only possible if the coil in the cylinder will transfer...

To heat all the 117 litres by 30 degC will take 8kw for half an hour. Therefore if you're limiting your boiler to 7kw then I'm not surprised that you're not getting the water fully hot. Also the 8kw figure is a simple calculation that doen't account for losses, etc so the real figure required...

The heat transfer via the cylinder coil will improve as the velocity of the water increases. Therefore to get the minimum heating time you should have your balancing valve wide open. Since I assume the system operates with priority DHW this shouldn't be a problem. If the boiler can be set to...

No doubt they could also turn their hand to surgery, but should they call themselves doctors. There are many prople with a lot of intelligence and practical ability who can turn their hand to anything, but does that then mean they can masquerade as a professional? I assume you would not...

+1

It's only relevant to consider the times when the system is actually operating. With the valve powered for CH then with your figures its powered for 7.5 hours less any DHW use. Switch it around and it could be off for CH and powered for say 45 mins of DHW use on perhaps 5 separate...

I should add that the CM927 worked very well with my old Glowworm Hideaway for 5 years or more.

My own experience of an Avanta 18S and a CM927 also suggests that they don't work particularly well together. Neither however is the control really bad. The CM927 cycles the boiler on and off so many times an hour and this can't be as efficient as running the boiler for longer on low power...

If the link is in place then I think d.8 should be permanently displaying 1