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

On Mon, 04 Apr 2005 22:31:08 GMT, Peter Sheppard
 babbled like a waterfall and said:


>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.


I don't think the man wanted the work at that figure.

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