Turn your preheat option off on your combi boiler!

Possetjohn

Mr Ted,

"pump" is the wrong term for a heating circulator, circulator is the correct term as little pressure is produced.

It is a low head centrifugal pump built into a circulation loop. By all means call it a circulator if you like

There may be a positive pressure on the outlet of the circulator, but a negative pressure at the inlet, however this is equallised thoughout a system very quickly and "flow" is achieved by the differential between the inlet and the outlet of the circulator due to the rotation of the impellor!

I think you mean differential pressure between the inlet and the outlet?

By varying the impellor speed the pressure is not increased in the system the flow is!

Only if the system has no flow resistance! To open the bypass valve in the boiler it needs differential pressure open it! A centrifugal pump works by creating flow by rotation of an impeller and will only not create a significant output pressure when it can achieve its maximum flow.

Look at the pump curves for typical central heating pumps (or circulators). At the highest speed setting they will typically create a head of up to 5 to 6m head of water (0.5 to 0.6 bar) at no flow to very little pressure at maximum flow. Even at the lowest speed setting there is typically a 0.2 bar pressure at no flow.

"The automatic by-pass valve also aids the operation of thermostatic radiator valves." only by maintaining an equal flow through the valve as the operation is via temperature control of the TRV head on a valve within the valve body which controls the flow!

I am confused by your clarification! The point Myson makes is that in a system which has all TRVs as the valves close down and the circulation flow decreases the pressure on the outlet side of the pump increases. At a certain pressure the boiler bypass will open and as you quite rightly point out allow a suitable minimum flow through the boiler's primary heat exchanger. If this did not occur the pressure on the outlet side of the pump would increase further and this would force more water through the nearly closed TRVs hence Myson's statement!

SYNERGY

Possetjohn wrote: »

Mr Ted,



It is a low head centrifugal pump built into a circulation loop. By all means call it a circulator if you like



I think you mean differential pressure between the inlet and the outlet?



Only if the system has no flow resistance! To open the bypass valve in the boiler it needs differential pressure open it! A centrifugal pump works by creating flow by rotation of an impeller and will only not create a significant output pressure when it can achieve its maximum flow.

Look at the pump curves for typical central heating pumps (or circulators). At the highest speed setting they will typically create a head of up to 5 to 6m head of water (0.5 to 0.6 bar) at no flow to very little pressure at maximum flow. Even at the lowest speed setting there is typically a 0.2 bar pressure at no flow.



I am confused by your clarification! The point Myson makes is that in a system which has all TRVs as the valves close down and the circulation flow decreases the pressure on the outlet side of the pump increases. At a certain pressure the boiler bypass will open and as you quite rightly point out allow a suitable minimum flow through the boiler's primary heat exchanger. If this did not occur the pressure on the outlet side of the pump would increase further and this would force more water through the nearly closed TRVs hence Myson's statement!

Thank you for well detailed and accurate observations. :T

It is a low head centrifugal pump built into a circulation loop. By all means call it a circulator if you like.

The whole unit could be, and is occasionally, called a circulator.

Ted appears to forget that the 'circulator' is comprised of several components, the two main ones being a motor and a pump. :rotfl::rotfl:

Just off to check the water[STRIKE] pump[/STRIKE] circulator in my car isn't leaking. :eek:

Cardew

SYNERGY wrote: »

Just off to check the water[STRIKE] pump[/STRIKE] circulator in my car isn't leaking. :eek:

I have just checked my circulator - 130/75 and 73 revs per minute.

Mr_Ted

spinningsheep wrote: »

good god mr ted you are at it again!what is wrong with you you nasty little man! as cardew has said in the short while you have been posting on these forums you have done nothing but antagonise and insult people, why?! We cant all be wrong, take some Christmas spirit and stop being so vile!!!

When were you, or anyone else for that matter, elected judge jury and executioner, particularly as you comments are far more offensive than mine and anyway
DILLIGAF

Opinion may differ on technical matters, that can constitute an open dialogue, but on safety matters that can affect or endanger life and property I will not compromise!

:TSYNERGY hairs and split come to mind and you ought to patent that PUMP powered car :rotfl:

:eek:Possetjohn you really need to have determined the definition of HEAD in relation to flow HEAD in respect of system Head and pump curve calculations :rotfl: