Hot Water Cylinder - checking installation


Our Combi Boiler has just died after a good life of 16 years. We've had a local plumber round to quote for a replacement and to cut a long story short, the new regulations mean it's going to cost around 2700 for installing just the boiler.
So, we've decided to go away from "wet" central heating to electric panel heaters (all individually timed), storage heaters and a wood burning stove with back boiler for hot water. It's this last item that I want to check my understanding on.
I see the domestic hot water as having three separate water "circuits". The following is based on my memory and some details from the stove manufacturer, so please correct me if I have got anything wrong.
1. Heating circuit. This is a thermal siphon from the back boiler (22mm pipe). It is connected between the boiler and the indirect coil in the hot water cylinder. There is a cold feed from a 4 gallon tank to keep the water level topped up (15mm pipe). There is also a pressure relief valve. The tank is fed using 15mm pipe at mains pressure to a ball valve.
2. Domestic Hot Water This comes out from the top of the cylinder in 22mm pipe and feeds the domestic hot water. There is an "overflow" in 15mm that feeds back to the water tank in the loft (in case it gets too hot and needs to expand). (Is there a special fitting needed at the top of the tank, I vaguely remember something...)
3. Cold water feed. This is in 22mm pipe from a 42 gallon tank in the loft that feeds to the bottom of the hot water tank. (42 gallon was chosen as the hot water cylinder is estimated to be around 36 gallon). The tank is fed using 15mm pipe at mains pressure to a ball valve.
There will also be an electric immersion for when the boiler is not running.
The loft floor is literally that, it has been designed as a floor (I live in a three storey Victorian Terrace). The tank will be sited in the eaves, where there are no floorboards. Should I use a sheet of timber to spread the load across the joists?
Is there anything that I have got wrong, or have missed?
Cheers
Peter
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On Mon, 04 Apr 2005 22:31:08 GMT, Peter Sheppard

I don't think the man wanted the work at that figure.
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I was hoping for criticism of the hot water installation, rather than the quote.
Anyway, to install the boiler it required the following work:
1. Relocation of the boiler to a new position in the utility room. The old one was non-viable due to the fact it was flued up an existing chimney and all other potential flue positions were not allowed by building regs. Bear in mind that from 1st April ALL replacement boilers have to be condensing which require access to a water drain and the flue gasses plume is in excess of a metre long (which restricts where you can put it).
So in our case, the boiler had to move to the opposite end of the utility room and a new flue put through the concrete tiled, pitched roof.
2. The boiler would have been Worcester'/Baxi, so around 800- 1000 for the boiler alone.
3. It is recommended (mandatory?) that in hard water areas (where we are) a water softner is fitted.
4. There is a requirement (maybe of the company, but could be of the boiler manufacturer) that for any new installation, to satisfy the 12 month guarantee the radiators have to be "power jetted" (that was 300 alone!)
So, it soon adds up.
Anyway, I have heard that the life expectancy of a condensing boiler is not that long. So I am happy going down the route I am.
So, back to the hot water tank......have I got the design right?
Cheers
Peter
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