"John Aston" wrote in message ...
Thanks for your help to date. I've distilled the advice from various threads
in this newsgroup to come up with a possible heating design for my house.
The drawing HD01 at http://tinyurl.com/3zv2g shows the proposed hydraulic
design
Ooh, lovely. You'd said you were a plumbing amateur. Ha, ha! You've
done this before, haven't you.
Suggestions;
1) Put a DCV between the drinking water and the softener. The DCV
shown protects the mains, but not the drinking water from
contamination by the softener.
2) 15mm should be plenty for the drinking water.
3) Softener. You'd need a duplex model, with two resin vessels, to
ensure a softened supply at all times. A duplex softener would
regenerate as required by a meter, so would minimize the salt
consumption; costs more, though. The resin takes a 1 to 1.5 hours to
regenerate. Softened water at 0ppm can pinhole copper hot water pipes
in 2 or 3 years. A blending by-pass valve to give 40ppm is advisable,
but you'd need a serious test-kit.
4) The PRV symbols are the wrong way round. The symbol is derived from
steam PRVs which have small HP inlet pipes and large LP outlet pipes.
Pedant mode off.
5) Don't fill the heating with softened water. The fill water will
contain a minute amount of limescale, but softened water causes some
problem with the inhibitors which I can't recall.
6) You don't want a PRV upstream of the accumulator. The idea is to
accumulate a volume of water under pressure. A PRV downstream is OK.
7) I'd add the accumulator at a later date, if it proved necessary.
8) The PRV on the unvented HWS usually has a second outlet port for a
balanced pressure cold supply. The strainer should be upstream of the
PRV; often it's integral with it. The whole set of components comes
with the cylinder 'package'.
9) Given the size of this system, I would consider supplying the DHWS
cylinder with a pump (making 6) from the secondary side of the low
loss header.
10) On the low loss header, the temperature sensor has to be immersed
in the flow water and the primary & secondary pipes need to be
off-set. This is a schematic drawing, so they probably will be.
11) There would be IVs on the flow connections to the UFH headers.
These often have flow indicators to facilitate balancing.
12) On the heating flow connections, I'd put the CVs downstream of the
IVs. It makes no difference to the function, but you could service a
defective CV without draining the entire system.
13) You need IVs on the heating returns from the rad circuits, before
they connect to the 22mm secondary return header pipe. I'd put all the
IVs adjacent to the secondary header pipes.
14) Is 22mm pipe big enough for the secondary header pipes? There
should be a negligible pressure loss at the design flow rate.
15) Why do you need a control valve upstream of the mixing valves?
16) Towel rails; another pump, I'd think, No.7. There's some EU
regulation requiring low temperatures to towel rails, but I don't
recall the details.
17) You don't need the top-up tank, you can add inhibitors through a
radiator. A drain valve on a rad, after the rad valves, for this would
be useful.
18) I don't think you need more than one pressure gauge.
Stick it on The Wall at Heatinghelp and invite comments. There are
photos of similar systems posted there regularly. They appreciate this
sort of thing. Tell them you're a first-time amateur!
Is a 38kW boiler sufficient?
It depends entirely on the heat losses. No other response would be
sensible.
Wonderful - but who's going to understand it when you're not around?
Me.
I have a schematic somewhere that I once drew of an existing heating
system. It takes up an A0 sheet. Some details are difficult to read at
that size.