Worcester Bosch Greenstar 24i Pump Speed

[blade1623]

Can anyone tell me if the greenstar 24i circulating pump modulates? i have been looking at param 2.1c which references settings 0 to 4, i know the factory default setting is 4 (constant high pressure) which to me implies that it would not modulate on this setting, does it need to be setting 0 to modulate?. My reason for asking is firstly that the pump sounds like it is labouring when just hot water is on (the boiler is located less than 2 metres away from the hot water cylinder) and when the radiator TRV valves start closing down however there is a bypass on the circuit, and secondly i suspect there would also be a small energy increase on setting 4. I would appreciate a professionals thoughts as a homeowner i contacted worcester bosch but felt they were unable to answer my question satisfactorily, i suppose i would not have the same technical access as the professional installers do.

 

[ShaunCorbs]

How old is the boiler ?

 

[John.g]

Setting 4 is a quite modest setting for a 7M pump.
It is a 3M constant head which should suit most systems, it will modulate its speed only to maintain that constant head.
If you have a system with very large flow and return piping of say 28mm or even more modest 22mm then setting 3 at 2.5M might be fine, I wouldn't recommend much lower setting.

Setting 0 is apparently PP (proportional pressure) mode but they are showing the full speed curve, normal PP mode has a range where you might select say 4.6M (like mine) this means that the pump will modulate to maintain a flow rate of say 0 to 22LPM between pump pressures of 2.3M and 4.6M. So
at this setting the pump will run at ~ 3.5M to give say 12LPM, like mine and as TRVs are closing in will further reduce the speed and pressure.
The pump certainly won't be labouring at any of settings.
You can just change to setting to 0 and see how it performs, this mode might be PP Auto Adapt where the pump will automatically give the correct flow/pressure for any condition but I have yet to see any one that really works as advertised.

 

[Chuck]

You want the lowest of ranges 1-4 that gives satisfactory performance. For a traditional two-pipe system fitted with TRVs you probably want range 2 or 3.

The best setting should haven been selected by the installer. That said, a lot of installers seem to just leave the pump set on 4. The setting is in the installer's settings, which the end-user shouldn't really play with so be careful when experimenting.