Central heating questions.

[dobbslc]

One for the plumber types this!
I've done a "fag packet" design for the new heating system and want any comments or advice on if it'll work.

We're fitting a new oil boiler outside, all new pipes in copper as we live in the woods and have mices! So I don't want the pipes eaten. The downstairs will have a solid wood floor so I don't want any joints under there to fail as I won't be able to get to them without distroying it! I want to run 22 &15mm pipes to and from two manifolds using the copper coils that can be rolled out. Here's the drawing,

Is the pump and 3 port valve in the right place? Would I need two pumps? Please say something if you think it won't work. Any thoughts?

 

[grim_d]

One for @Kayos I think.

 

[Kayos]

Is it a sealed system? If not you need vent, cold feed then pump within 150mm of each other and in that order and then the 3 port

Google Y plan

All kinds of opinions on cold feed and vent position relative to pump but what I've described works for me. Unless its sealed then it doesn't really matter and pump close to the valve for wiring convenience

 

[RonA]

Your drawing is almost exactly what I have in my house, with only a slight difference
When the boiler was changed from simple wall mounted job to a combi, the combi DHW was connected in the conventional way, but retained the hot water cylinder for a power shower,
The cylinder is fed from a cold water storage tank (in the loft), this the feeds the hot water inlet of a double headed pump, the cold water inlet is fed from another feed from the cold storage tank in the loft. This gives almost equal pressure on hot & cold inlets of the double headed pump.
The shower thermostatic valve packed up a while ago but I was still able to use manual valves (while awaiting arrival of a new thermo valve) to control the shower & due to the stable pump inlet pressure the outlet temp was rock steady.
The normal vent for the cylinder was retained in case of overheating but the hot water cylinder has its own tank stat.
RonA

 

[dobbslc]

@Kayos yes its vented so I'll take a pipe from the nearest available point up to the header tank. The order you describe, vent, cold feed, pump then valve is that going away from the cylinder or towards it?
@RonA that's how I'm going to run the showers in my house and the reason I'm keeping a traditional hot water cylinder as the missus insists on a powerful shower! I don't want to rely on the mains pressure.
The trouble I'm having is what pipe to use for the rads! I want to preferably have no joints under the floors at all so need to run copper pipe from the manifolds to the rads in one single piece, is this possible? Would 10mm pipe be ok an runs up to about 6 meters? And how can I connect it to the rad valves?
My head hurts!

 

[brightspark]

either get 10mm rad valves or the adaptors up to 15mm if that's what your valves are. 10mm pipe will be fine for the radiators https://www.google.co.uk/search?source=hp&ei=fSpoXJu-CryDjLsP8vG9iA4&q=10mm+to+15mm+adaptors&btnK=Google+Search&oq=10mm+to+15mm+adaptors&gs_l=psy-ab.3..0i22i30.3199.13863..16268...0.0..0.209.1681.22j1j1......0....1..gws-wiz.....0..0i131j0.NwtrNz3d-NY

 

[Kayos]

The vent and feed are on the flow, behind the pump. The cylinder return must be the last tee on the main return or you will get issues with reverse circulation

 

[Tigman]

Vent and cold feed just before the pump as said , looks ok

 

[Tigman]

I used to put a bypass in as well just after the pump and back to the return with a Lockshield valve , and a Lockshield on the return out of the cylinder to restrict the flow through the cylinder , sends more around the heating !

 

[pedrobedro]

Pump on the return into the boiler, cooler for the pump.

 

[brightspark]

Pump on the return into the boiler, cooler for the pump.

not with y plan u cant only on gravity systems

 

[Kayos]

Pump on the return into the boiler, cooler for the pump.

No need on a modern system and could even cause blockages with the cold feed creating a neutral point