PLATINUM HALSTEAD BOILER

PLUMBER FITTED ONE OF THIS LAST WEEK TO AN OLD HOUSE I OWN, IT IS NAT GAS.
FROM DAY ONE THE FLOW SWITCH ON THE C/H WONT MOVE UP AND DOWN AS THE BOILER CHANGES FROM C/H DEMAND TO HOT WATER.
HE HAS ALL MY RADS ON 10 MM PIPEWORK RUNNING FROM 2 MAINIFOLDS JUST BELOW THE BOILER.
HALSTEAD SAY THE MANIFOLDS ARE TOO CLOSE CAUSING THE SWITCH TO ACT LIKE THIS BUT MY PLUMBER SAYS IT IS OK.

HELP!

always follow MI.Then its down to them.

Finest Platinum is a Band D non condensing boiler - did the assessment allow this?

The radiator circuit has no effect on the boiler when it is in hot water mode.

If the differential flow switch does not operate there may be reduced flow around the boiler when in hot water mode perhaps due to blockages.