"John Aston" wrote in message ...


OK. I was worried about a drop in the pressure/flow rate. My incoming
supply
is only 2.8 bar static and 30lpm.

It would probably be OK to just relocate the DCV shown. I think the
Water Regulations require a DCV on a softener inlet. The mains
pressure varies inversely with demand in the neighbourhood during the
day, so you'd work on the minimum. The flow rate achieved at the
minimum pressure should indicate whether you might need the
accumulator.

I never knew its effect on copper pipes! I'm surprised they don't
mention it


It's not something the manufacturers publicise and I don't have any
definite information. My understanding is that it's something that can
happen, but that the softener isn't always the guilty party. Erosion
and bad pipe-fitting have some role. My understanding is that water
softened & blended to about 40ppm hardness is fine for all practical
purposes and doesn't create the corrosion problems. Softened water can
be unpleasant stuff in the wrong place. I think the dissolved calcium
salts are mostly changed into sodium carbonate (washing soda?).

I've no experience of Kinetico.

The last test kit I used was made by Hach, supplied by a company
called CamLab. It was a titration test kit (colour change). I've found
dip strips can be misleading in some hands (RTFM again).

I guess it's set at 3.5 bar to comply with regulations. It might be easier to leave out the downstream PRV. The mains static pressure is only 2.8 bar anyway.

I think your original detail & IMM were right (Ow, that hurt!) & I was
wrong. The upstream PRV would be set to limit the pressure to the
design rating of the accumulator.

I once had a discussion with an HSE inspector who expected to see
every PRV accompanied by a correctly-sized safety/pressure relief
valve to prevent the equipment being over-pressurized in the (quite
likely) event of a PRV failure. We were talking about compressed air,
but his point is still valid here.

I did think about this but
(a) The cylinder is less than 8m pipe length from the boiler

This seems to be a compromise between the conflicting requirements of
supplying the cylinder with sufficiently hot water (to get the stored
DHW above 60degC), keeping the boiler return temperature low and
avoiding the need for lots of mixing valves. It's outside my
experience, so I'll shut up.

Yes, you're right. The header is a pre-fabricated assembly.

You could fabricate one, it's just pipe & fittings.


I'm hoping that these come as part of the manifold from the UFH
suppliers

Only if you specify them.
The flow-rate indicators are an optional extra. They usually become
unreadable after a few years, so are only useful for initial
balancing. You need to make a record of the settings and keep it in a
safe place.

Also, you can see on the diagram that I've written MAX. DISTANCE? I can't get any definitive answers

There is no maximum, so long as the pump(s) can handle the resistance
at the flow rate.

The UFH heating circuits have their own individual themostats.

Yes, but I was querying why you need a motorized control valve
adjacent to the UFH manifolds' mixing valves. If the pipe stat
temperature was exceeded, you could stop the pump and/or set the
mixing valve to 0%. Are the mixing valves thermostatic or electric?


The heat losses would be 31kW. I'm hoping that the additional 7kW will give
me some headroom plus a bit for the domestic hot water.

An additional 7kW should be lots, check the cylinder manufacturer's
spec. You won't need additional capacity if the HWS has priority, as
IMM said. I don't like the diverting idea, but I see the need for it.

A couple of other points;

The DOCs on the heating zones return pipes should be upstream of the
IVs. They should drain the zone when the IVs are shut, but will drain
the whole system as shown.

You have to ensure that the primary flow through the low loss header
is greater than the secondary flow at all times. If the secondary flow
is greater, then some of the secondary return flows back up the header
and you then get a reduction in the secondary flow temperature.

The drain pipe from the tundish on the cylinder has some rules to
determine the pipe size, depending on the pipe length and number of
elbows. It's usually not a problem, but needs to be considered if the
proposed cylinder position is a long way from the final "safe &
visible" outlet outside. Otherwise, you can end up with a huge drain
pipe or it can be impractical. The cylinder can't be in a basement.

Thanks, Aidan.
A pleasure.