Central Heating System Design Advice

[Eng33]

Existing system in 3 bed bungalow is Y-Plan, installed 10 years ago and comprises Wall Star oil fired boiler, indirect vented HW cylinder (on ground floor) and CW 'coffin' tank mounted high in loft space. New system modifications will include changing to S-Plan with three 2-port valves to supply HW, house rads and separate heating zone for integral garage. Will be installing larger 160lt indirect vented HW cylinder and new Grundfos 15/60 pump.

Questions...

As boiler is mounted in loft space (in gable end wall ~2.5m high), the hot feed from the boiler runs along loft ~4m, then down into airing cupboard to pump, which is next to HW cylinder. How much of an issue is feeding the pump from above, i.e. pumping vertically down, as long as pump motor shaft is horizontal?

Although I'm familiar with the general S-plan layout schematic, practically what’s the best / easiest way to plumb the outlet from the pump to the three valves and auto by-pass valve? Anyone got any pics of such a system? Assume all plumbed in 22mm?

Existing system has the feed to the HW cylinder coil in 22mm, but return to boiler in 15mm, is this typical? Was told the return would be better in 22mm as well, but install a gate valve to control return flow, but how? For info, the pipe run (boiler to HW cylinder) is currently ~4m horizontally, but boiler will be moving when extension gets built, and this will take that run to ~10m.

Many thanks!

 

[doitall]

Pumping down is never a good plan, especially on an open vented system.

 

[bengasman]

Pumping down has a slightly higher chance of having air bubble problems as they naturally go up, but other than that, it is fine.

New, high performance cylinders can absorb a lot of heat in a short time, so a 22 mm pipe along the whole circuit would be better.

Hard to say what the easiest way is to change to s-plan, as it depends on where the pipes run physically. In general, it is best to have the split shortly after the pump.

 

[Agile]

New system modifications will include changing to S-Plan with three 2-port valves to supply HW, house rads and separate heating zone for integral garage. Will be installing larger 160lt indirect vented HW cylinder and new Grundfos 15/60 pump.


Many thanks!

Its always a good idea to keep the car warm in the garage!

It seems a lot of work to change presumably a 125 li cylinder for a 160 litre.

If you feel there is a need for a change then why not fit at least a 225 litre?

Tony

 

[Eng33]

Many thanks for the replies and advice, really appreciated. Also great pic 'doitall', surely not a domestic system?!

So ideal pump plumbing in this situation would be effectively a U bend at bottom of the vertical flow feed from the loft, so pump inlet is vertically upwards? Would mounting the pump horizontally be an OK compromise?

Thanks!

 

[doitall]

Pump Horizontal as in the pic or vertical up is ideal.

No in this case it wasn't domestic, but it wouldn't have been any different had it been.

The take offs from the header is only 22mm, and one 35mm, but the pic is indicative, you can choose your own sizes.

 

[Agile]

Whoever installed the system in the picture has spelt "bypass" wrongly.

Presumably it was a 17 y.o. spotty apprentice?

 

[doitall]

Would you believe I've been told that dozens of times

The installer would have been about 60 when he did the job.

 

[Eng33]

Thanks guys.

Sorry, another question...

Is it very critical where the outlet from the by-pass valve tees into the return to the boiler? Currently the 15mm return from the HW coil runs along side the 22mm return from the rads, and only tees into it right next to the boiler.

Thanks.

 

[doitall]

They have done that to prevent reverse circulation in the hot water only mode.

The by-pass, no e, should be before the MV's and into the common or cylinder return.