Main driver board or Gas Valve

[mrfish69]

Can any one help, i am trying to determine whether i need to replace my main driver board on my worcester bosch 280 rsf or the regulator valve. The output voltage from the PCB to the Regulator remains constant holding the gas open fully until the boiler hits over temp trip. how should this voltage behave should it drop steadily when temp increases or drop to zero at temp to reduce gas flow.

Many thanx

PS this is on DHW sorry

 

[gas4you]

Is this on ch or dhw or both?

 

[Rob]

Are you refering to the modureg. If so what voltages are you getting?

Id imagine this is fully modulating and should see a steady voltage drop to low burner pressure.

Possible a thermistor fault or blocked plate HE

 

[mrfish69]

Yes i do mean the modureg.... the voltage i'm getting is a steady 21 Vdc. when i disconnect the conections to the modureg the boiler will still flash up but at a lower burn rate (not enough to give hot water). i thought that this voltage should drop to regulate my self but wasn't sure...

 

[Rob]

The thermistors will tell the board to lower the voltage, so check the resistances at a few different temps.

It could simply be the plate HE blocked, very rarely will it modulate before overheating

 

[mrfish69]

Is the HE part of the water to water (heat exchanger) system?

 

[Rob]

Its called a water to water HE. Im assuming it does have one??

 

[mrfish69]

Yes i've checked the water to water and not calc'd up at all, live in a soft water area. this is pointing more and more to the pcb all the time, voltage from the thermistor drops as temp increases so thats working ok, oh well pcb here we go, cheers for your input.

 

[Agiile]

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Foolish post (by person using a fake name pretending to be another member) removed

Mod Rupert
++++++++++++++

 

[pannierstan]

Yes i've checked the water to water and not calc'd up at all, live in a soft water area. this is pointing more and more to the pcb all the time, voltage from the thermistor drops as temp increases so thats working ok, oh well pcb here we go, cheers for your input.

No he said check the resistances from the Thermistors.
I can tell you that when you find out the price you will want to change the thermistor before you plum for the board

Stan

 

[mrfish69]

the thermistor is working fine voltage drops as the temp rises!!

 

[gas4you]

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Foolish post (by person using a fake name pretending to be another member) removed

Mod Rupert
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Well spotted Rupert

 

[ollski]

Could well be the driver board, it does happen. What voltage is at the wires to the modureg?. I would always change the thermistor first before shelling out 120 quid on a board it's only another 5 or 6 quid and won't hurt to replace anyway.

 

[ollski]

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Foolish post (by person using a fake name pretending to be another member) removed

Mod Rupert
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Well spotted Rupert

Tickled me.

 

[corgiman]

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Foolish post (by person using a fake name pretending to be another member) removed

Mod Rupert
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Well spotted Rupert

Tickled me.

RUPERT TICKLED YOU

wow he must be softening up, tickling you into submission