Ravenheat CSI 85 - No HW & temperamental Central heating

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I have a Ravenheat CSI85 Combination Boiler. It was installed 4 years ago by a CORGI registered installer. All the rads and pipe-work were new (flat previously had storage heaters). System wash powerflushed and X100 inhibitor added. It is a sealed system. It has an external timer and thermostat fitted. Now out of warranty period.

A couple of weeks ago I came home and my electrics had tripped at the RCD in the fusebox. I traced this to the boiler/central heating.

Every time the timer came on it would trip the electrics. I replaced the timer with a new one. Same thing happened.

I opted for a fixed price repair from Homeserve. A contractor came. The only way he could get the electricity to stay on was to disconnect the external timer from within the boiler. I now have central heating however it is purely controlled by the room stat, no timer. When the room stat calls for heat the boiler also seems to wait for several seconds now before beginning it's start up process and firing. Sometimes it doesn't even do this.

Regarding the Hot water; The diverter is operating the microswitch, but the pump doesn't run. The plumber changed the Thermistor. This has not cured the problem.

He then declared it to be the PCB or Wiring harness.

Homeserve now say this is chargeable and not included in the fixed price as that only coved the first fault they found - the thermistor.

Form reading posts on this forum I can see they aren't necessarily the best boilers, but at the time all I could afford!

Before I complete/commission any more work on it I would like some of your opinions, is it likiley to be the PCB or could it be something else?

Many thanks in advance.

Stephen
 
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if the fuse keeps blowing / rcd trippig Id check pump and fan first, then possibly gas valve as use 240volts
 
It only tripped RCD when timer was wired into PCB. Timer disconnected now. Pump runs fine, and boiler fires too, just have no timer control!
 
so no hot water ?

how does the room stat work then if there's no timer... what powers the room stat?
 
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The room stat wires directly into the boiler.

No Hot water, and CH only works intermittently now
 
Is there power going to the pump when hot water is selected?

sounds like a pcb fault

when ch works intermittently, what exactly happens - is there a pattern to it or is it random?
 
When I run a hot water tap there is no life at all from the pump. The only action I can see is that the diverter pushes onto the microswitch. Pump/fan do not run. If the CH is on and I open a hot tap the boiler shuts down until i close the hot water tap again.

Re the intermittent CH. I can only control demand for the CH via the room stat. when I turn the room stat up & hear it click, i.e call for heat normally the boiler will start. but it doesn't do it 100% of the time. Sometimes nothing!
 
Sounds like the PCB is at fault, assuming the HW microswitch is working correctly. Would have been helpful if the RGI you had in actually tested it rather than guessing.

With the heating issue not being timed, you may find that the timer works once you have a new board. If not then you could always fit a programmable room thermostat in place of your existing stat.
 
Yes the PCB was what I was tending towards after following the fault finding in the instruction manual.

From what I've read on these forums PCBs seem to fail worryingly often!
 

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