Central heating pump positioning

[Bogart]

Am going to do away with my very old oil fired boiler and get a new one. I have an open vented gravity fed setup. With HW tank and pump in upstairs airing cupboard with the boiler some 20m away from the house in an outbuilding.
Got the local heating guys round yesterday to take a look and was okay except he suggested the pump is moved into the boiler house, to as he said get a better flow. Now am I missing something here I would not have thought the position of the pump mattered at all?

 

[Riley]

It can matter in terms of positioning on the system to stop it pulling air in or pumping over however I wouldn’t say that moving it from one end of the same pipework to another would matter? Although I can’t see the set up

 

[Bogart]

Yes I understand your point but like you cannot see it making any difference as you rightly say is just going to be in a different position
on the exact same piece of pipe. He was mentioning it is easier to push the water around than suck it around again that is an irrelevance that obviously just depends on what bit of pipework the pump is situated.

 

[Riley]

Common install is on flow now. Maybe it’s on return currently

 

[Brambles]

Try a different installer

 

[Rob Foster]

Common install is on flow now. Maybe it’s on return currently

So the principle of always putting the pump on the return is a load of tosh. I always thought so, cause when system is up to heat and modulating pumping the return because its cooler never made sense to me.
centralheatking

 

[SimonG]

Oil doesn't modulate.

A normal old school system would have the heating flow and returns off the boiler, diagonally, top flow and bottom return with the pump on the return. Then flow and return for cylinder off the remaining ports. Gravity upto cylinder with open vent and cold feed at cylinder.
At some point it sounds like your system has been modified.
I prefer to have boiler, pumps two ports etc all in one place. Easier to fault find down the road.

 

[Best]

Agree with SimonG that best the valves and pump all close together.
Ideally I prefer the pump close to boiler. Reasons (besides wiring and ease to service/replace) are that pumps can transmit noise and also if they leak someday it is better not inside your house.
(I know that lots of pumps are inside homes, including most gas systems, but just saying given the choice, keep them outside house)
The pumps fitted on return pipes generally lasted much longer due to lower heat. The higher heat damages the seals and the motor windings I think sooner.
The oldest pumps I come across on oil boilers are normally on the return.
Probably won’t matter much on these modern A rated pumps as they probably won’t last much out of warranty and electronics fail.

Back to the original post, new boiler will be all pumped circuits (no gravity) - a sealed system would be by far the best system if at all possible. Then just fit the pump wherever is best.

To leave system open will involve keeping vent and feed on negative side of pump in a close coupling pipework to prevent pump over, but I really am not fond of it and not a perfect system. Had to recently cut out and replace such c.c. pipework blocked with crud.

 

[Bogart]

Common install is on flow now. Maybe it’s on return currently

No is on the flow.

 

[Bogart]

Agree with SimonG that best the valves and pump all close together.
Ideally I prefer the pump close to boiler. Reasons (besides wiring and ease to service/replace) are that pumps can transmit noise and also if they leak someday it is better not inside your house.

In an ideal world yes but pump and valves are in property boiler is in a seperate outbuilding

 

[Best]

In an ideal world yes but pump and valves are in property boiler is in a seperate outbuilding

Has your plumber considered if your system can be converted to a sealed system?
Simple an inexpensive solution if system is sound - if no leaking joints or valves.
The pump can then be installed beside boiler outside if wished.
I wouldn’t have open systems on oil or gas where possible to seal them

 

[Bogart]

Have not asked him that. So if let us say I went the route of a sealed CH system are you advocating an unvented HW cylinder as well. If not
I might as well keep it open as will still need a header tank. One concern I have is about the outside water pressure at times it is not very good. I would need to get that checked.

 

[Best]

Have not asked him that. So if let us say I went the route of a sealed CH system are you advocating an unvented HW cylinder as well. If not
I might as well keep it open as will still need a header tank. One concern I have is about the outside water pressure at times it is not very good. I would need to get that checked.

No, I meant just to have your heating system sealed. You can still keep your hot water cylinder and cold storage tank.
To have your heating converted to sealed usually needs a small amount of parts.
If your system is sound enough, then sealing it will mean no air absorbed, no risk of pump over, very little corrosion possible and no need to bleed radiators often.
System will perform better when under higher pressure

 

[Bogart]

Righ okay I see your point there. So its basically an expansion vessel and a few odd bits. A couple of extra questions if I may
1 Why will it perform better if at a higher pressure?
2 How do I obtain this higher pressure?

 

[Best]

Righ okay I see your point there. So its basically an expansion vessel and a few odd bits. A couple of extra questions if I may
1 Why will it perform better if at a higher pressure?
2 How do I obtain this higher pressure?

The sealed system just fills up from mains via a filling loop.
Generally speaking your oil system will be filled to no more than 1 bar (it will then operate when hot at perhaps 1.5bar).
You could have it less pressure at 0.5 cold fill probably.
The pump circulates the water relying on the pressure within the system. On an open vented system the pressure is lower and decreases where the system is highest, closest to the heating feed tank.
On a sealed system the pressure is more balanced.
I also like sealed systems from the point that if you had a sudden bad leak somewhere, like nail in a pipe, you won’t get a constant flood. Once the pressure goes off the system the leak stops.

 

[Bogart]

With you now, the top of the heating expansion water ia approx 5m above ground floor level which I equate to about 0.5 bar, not a lot. I will investigate the mains pressure. I have a pressure gauge and a few connectors and am sure I can find somewhere to attach this to get a reading. Might even consider going for a complete sealed setup water also. I am quite partial to thermal stores. Many thanks for your input and time greatly appreciated.

 

[Bogart]

Would I get a decent reading of water pressure by using a guage attached to a shower hose replacing the rose?

 

[SimonG]

Outside tap or washing machine tap (without a check valve).

 

[Bogart]

Can I ask why you suggest these taps?

 

[Riley]

Can I ask why you suggest these taps?

Straight off mains with no restrictions

 

[Bogart]

Right am back finally. Connected gauage to outside tap, which is about 20m past house and fed in 15mm from somewhere! I can get 14
litres a minute. Static pressure is 1.75 bar, as soon as I open a tap guage goes to zero.