Grant 36e combi internal

[magicno1]

Had a call early today to a Grant 36e internal combi.
Fault was no heating but had hot water.
Turns out various engineers had visited and the customer has lost faith.
Forts thing I noticed was an array of parts strewn across the floor, solenoid, oil pump, pressure switch, 2 air vents and a flow switch which had been nibbled around the paddle which the customer said that’s what engineers do when it don’t work!!!!
So the system doesn’t have enough expansion so I’ll return and sort that.
the boiler was staying in hot water demand with flow and I tested and found out the flow switch was broken and also not installed the correct orientation.
Having changed that the boiler heated up the tank but took about 20 min after the burner stopped to switch to CH. After 2 to 3 minutes of firing with the CH on it switches back to hot water again and this happened all the time I was there. The boiler doesn’t always fire when it goes back to HW and the flow light on the panel is never on only if you open a tap. Therefore the heating never stays in long enough to heat properly.
So is the fault a faulty HW (white) thermistor or the phial it goes into on the slave tank scaled up possibly?
Would appreciate anybody’s experience if you have had this issue and possible remedy please?
Regards

 

[exedon2]

First I would go back at a time when you can talk to Grant technical they will be happy to talk you through any tests required we have found them excellent to deal with.
I would suspected the board is problem new thermistors come with it.
As for changed parts the auto air valves are a common problem we just fit manual ones (as fitted on new boilers) likewise the pressure switch not fitted on new boilers
So we take them out and put a link on board they also if caught tend to snap easily if caught! And only this week changed a flowswitch supplied by customer and it struck open! When I compared it with existing the paddle it was around 1mm bigger carefully filed down worked perfectly.

 

[The Ancient One]

Agree - Grant Technical absolute gems; never talk down to anyone.
Agree - I would go with the PCB and you must use the new thermistors supplied.
Agree - HW Paddles do sometimes seem to be too big - I reckon the man making the paddles doesn't talk to the man making the body!