fault finding

[freddyguy]

evening. new to breakdowns but seem tobe doing ok for some reason. i got called to ideal wf2000. fan running no ignition. checked aps that was fine. after potterting around i disconnected h/t lead on b oard reconnected and hay presto spark , pilot ,main burner!! fixed.

however im curious. before i attached the lead i tested for voltage to gas valve which was present. surely there should be no voltage to gas valve if spark ignition hasnt occured. what i learned about fault finding is where ever the voltages stop on the pcb that is your inbuild fault finder. as i said curious about that.ta

 

[bengasman]

hey, it is an ideal, be grateful for any voltage you get.

 

[Homesafe]

where did you check for voltage?

 

[gremlin16]

@ the consummer unit

 

[Homesafe]

ask a silly question i suppose

but if he was getting volts. at gas valve would that mean it was letting gas through (or is that another silly question)

 

[gremlin16]

Could not resit it newgas

 

[twgas]

ask a silly question i suppose

but if he was getting volts. at gas valve would that mean it was letting gas through (or is that another silly question)

it wouldn't light if no gas got through.

 

[Agile]

but if he was getting volts. at gas valve would that mean it was letting gas through (or is that another silly question)

Dont get too excited!

He does not seem to have actually found any fault!

He probably found there was 240v on the gas valve! That does not mean it was being powered though. To do that it needs 240v ACROSS the gas valve coil.

Many ( most ? ) boilers apply a permanent live to the various components and switch on the neutral connection to power it.

Tony

 

[Homesafe]

Dont get too excited!

He does not seem to have actually found any fault!

He probably found there was 240v on the gas valve! That does not mean it was being powered though. To do that it needs 240v ACROSS the gas valve coil.
Many ( most ? ) boilers apply a permanent live to the various components and switch on the neutral connection to power it.

Tony

that has clarified the question, with 240 it,s not necesserally powered to work /open.
credit is due to , you know your stuff

 

[Homesafe]

[
To do that it needs 240v ACROSS the gas valve coil.

Many ( most ? ) boilers apply a permanent live to the various components and switch on the neutral connection to power it.

Tony

to check for this you would test accross terminals N to E am i right
Tony?

 

[Agile]

To check fully, and for safety, you should ALWAYS measure between live and E and then neutral and E after taking off the case BEFORE you touch anything else. That will confirm the earth is really connected to earth.

I would check from boiler chassis (E) to gas valve live

then

from the chassis (E) to gas valve neutral

If there was 240v across valve and it was not passing gas, then remove both terminals and measure the coil resistance ( possibly open circuit in this case ).

Gas valves are usually 1-4 K Ohm if 240v.

Tony

 

[Homesafe]

thanks for clarifying Tony.

 

[bengasman]

good point, would not be the first time i found reverse polarity.

also walked out on a job last year where i spotted the "electrician" had not bother to connect the c/u to earth.
year before that got a shock from the outside of an appliance and found out the entire kitchen had no earth at all.

 

[Agile]

When working on high power 11kV to 15 kV BBC equipment we had an interlocked enclosure but before touching anything we had an "earthing stick" connected to earth by a 10 mm² cable just in case any of the earthing switches were not making properly.

You dont want to touch a capacitor charged to 11,000 VDC. You only do that once!

Tony

 

[bengasman]

remember those 440v 47uf big ones from valve tv's?
great fun pitching them at someone and call: CATCH!