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Andrew Smith
Andrew Smith, Plumber
Category: Home Improvement
Satisfied Customers: 3757
Experience:  City and Guilds Qualified plumber
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Greenstar 28i Junior (2007 fit). Replaced leaky flow regulator

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Greenstar 28i Junior (2007 fit). Replaced leaky flow regulator (and flow sensor turbine just to be sure) Leak fixed. prior to fix, CH and DHW normal. After fix DHW but no CH. Pump running OK, suspected diverter valve - slid valve motor out, kept valve lever pressed up - DHW and CH OK. Slid motor back in switched on with temp to max and CH permanently on. CH worked but when demanding DHW only got cold. Observed valve lever in full down position think it should have moved up on DHW demand. Question is therefore:- is it
a. Faulty diverter valve.
b. Faulty valve motor
c. Spurious signal to motor from PCB

If valve to be replaced how do I drain down below the valve level to fix


1. To start with - Are you able to test if the valve motor is getting power?


If so, then you will need to monitor if the voltage fluctuates the same as the motor, if the power is constant but the motor is not, then it is the motor


When I removed the motor and switched the boiler on the motor moved to the fully extended position. After I replaced the motor in the valve housing and switched on again I noticed the motor had moved to the lower position (CH only ?) and there it stays regardless of demand (CH/DHW)


Further to last reply, had a"lightbulb" moment, my water supply pressure is strong, so I turned it back to approx. 30% and tried the DHW


flow, it worked, and the central heating also, valve lever position is currently at the up position and CH and DHW seem to be OK for the moment. This leads me to think that its a pressure issue within the diverter valve itself. CH pressure is at 1.5 bar (about right I think) The ECO function is on, don't know if the diverter valve will move to the CH only function again or not it has't so far

XXXXX XXXXX : Is it working correctly now? You may have to limit the water pressure to 3 bar as recommended in the manual, this could be achieved by a fitting a pressure reducing valve on the cold inlet to the boiler

Seems to be working OK for the moment, 3 bar you reckon, boiler label and instruction manual both say Max 10 bar, intend leave mains water tap at approx 30% turned on for the moment and see if that continues to work.1.3 Bar is the minumum and I think it's comfortably above that. Already have small inline valves on hot and cold tap supply both only half way on as water was bouncing off the sink and on to the floor! With all the rain we've had in the UK not surprised the water pressure is robust. Do you consider we've now reached a solution.

XXXXX XXXXX : Ok, just checked and you are right for the water pressure - but I would like to put it to the test!
XXXXX XXXXX : just bear in mind that you are reducing the water flow and not the pressure by turning down the stoptap
XXXXX XXXXX : *would not!

So you want me to crank up my mains water pressure to the max?

XXXXX XXXXX : The only real way to reduce the pressure is a pressure reducing valve if it causes a major problem

OK, will look into that, fairly straightforward to fit inline valve I think. Seems some sort of balance between CH pressure and mains pressure is required here. Perhaps I've arrived at the balance by accident.

XXXXX XXXXX : Ok, just monitor and come back if you need me again

OK, thanks for your help, signing off now.

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