Central Heating Pump

[Ruth541]

My Central Heating system includes a Wilo Gold 50 pump. The heating was being noisy so I turned the pump down from 2200rpm to 2000rpm which does seem to have helped. There is also an option of 1600 rpm. How do I know which setting it should be on?

[buildersmate]

The one the installer left it at - 2200rpm in your case.
The whole system should be set to produce about an 11 degree C temperature drop across the rad (temperature differential input / output). If you slow the pump when it was set up correctly in the first place you will increase the drop.
You will do no permanent harm, but it may impact the efficiency of it.
Pumps are incredibly reliable given their job - maybe the bearings are going, if this is a 'new' noise.

[Prudie]

Hello again buildersmate! I know nothing about heating Ruth but I do have a similar problem with mine that I posted on a week or so back. My problem is the pump doesn't switch off at night (the boiler is off and the radiators cold) and the noise is keeping me awake. The general concensus of opinion is there's something wrong with the circuit board thingy in the boiler itself but until OH does something to fix it I've been turning the pump down to the middle setting at night. The downside, that may interest you, is if left like that then some of the downstairs radiators don't get hot enough. The one night I turned the pump speed down to the lowest setting the silence was bliss until 6 the next morning when we were woken by the bedroom radiator almost banging off the wall.

[gucciman]

prudie your problem could be caused by a pump over run stat, this bascially runs the pump for a period after the burners shut down to dissipate excess heat from the boilers heat exchanger.
your rad banging may have been due to you turning the pump down too slow so the boiler started to overheat.

[Ruth541]

Thanks for the replies.
The pump always switches off within a minute or two of the heating switching off, so not having the problem.
The noise does not appear to originate from the pump, but is in the pipes. They sound like the are rattling, or that something is struggle to get through (not sure I've described that very well!). The noises has been occurring on and off for a few months now. My gas mans due to service the boiler in a month or two, I'll ask him about it then as long as it gets no worse in the mean time.
Just for curiousity then, how does a heating engineer decide what setting to select?

[buildersmate]

You could ask him to try this sort of product.
http://www.sentinel-solutions.net/en/heating/d eposit

CH systems are set up by putting the pump onto the highest setting, then setting the individual radiators using the lockshield valves to control of water across each rad to 'manage' the amount of heat getting into each rad. The 11 degree temperature drop is a benchmark figure.
If too much water is flowing around the system when the balancing is done, the installer turns the pump down one notch, then starts the set-up process again.