Vaillant VCW GB 242 EH Boiler - Is it Diverter Valve?

[trelo]

Gas rate it and post back result...see FAQs

assuming the diverter isn't passing to the rads (and i agree with 'combispecialist' that it's very rarely a diverter fault) check burner pressure/gas rate when on hot water. Basic checks first really then come back

I didn't come back to this thread for a couple of days and missed the advice on checking the gas pressure. I'm no corgi but is there a simple test i can do with my gas meter to check consumption thus getting an idea if its gas pressure problem? I'm wondering if it could be the servo or water valve? Could the water valve/servo cause a problem with delivering tepid water to hot taps? because there's no problem with CH temperature. I can see that the servo/water valve detects HW demand and switches diverter but what else is it doing apart from controling flow to the HEx. Thanks

 

[trelo]

I didn't come back to this thread for a couple of days and missed the advice on checking the gas pressure. I'm no corgi but is there a simple test i can do with my gas meter to check consumption thus getting an idea if its gas pressure problem? I'm wondering if it could be the servo or water valve? Could the water valve/servo cause a problem with delivering tepid water to hot taps? because there's no problem with CH temperature. I can see that the servo/water valve detects HW demand and switches diverter but what else is it doing apart from controling flow to the HEx. Thanks

Sorry i just realised i posted twice!

I must admit I don't see any difference in flame height when boiler switches from CH to HW demand? From memory some years back I remember the Flame height used to significantly rise much higher in HW mode.

 

[Gasguru]

Ensure the boiler is completely cold, I suggest you shut the gas off at the meter and run the hot taps on full. This will cool the boiler down.

Shut the taps off and reset the lockout on the boiler.

Read the FAQ's on gas rating. Open the hot taps fully for gas rating. If you are not clear on the procedure just time a single revolution of the test dial on an imperial meter (in seconds) or for a metric meter note the readings over a 2 minute period (just the right 3 digits).

Remove the two screws each side of the lower panel. On the control box you will see 2 lights. When you open a hot tap (boiler initially cold) the right green light will illuminate after a short delay. You should notice the flame height increases at the same time.

 

[Andygasman2010]

Ensure the boiler is completely cold, I suggest you shut the gas off at the meter and run the hot taps on full. This will cool the boiler down.

Shut the taps off and reset the lockout on the boiler.

Read the FAQ's on gas rating. Open the hot taps fully for gas rating. If you are not clear on the procedure just time a single revolution of the test dial on an imperial meter (in seconds) or for a metric meter note the readings over a 2 minute period (just the right 3 digits).

Remove the two screws each side of the lower panel. On the control box you will see 2 lights. When you open a hot tap (boiler initially cold) the right green light will illuminate after a short delay. You should notice the flame height increases at the same time.

The green light means there is power to the modulation air pump, the brighter the light the more power to the pump (high gas) The yellow light means power to the operator (gas valve solenoid) High gas on this model is 5.1MB but if you're not an RGI just do the gas rate as the other guys have suggested. It should be 24kw on this boiler, hence VCW 242.

hope this helps!

 

[trelo]

Ensure the boiler is completely cold, I suggest you shut the gas off at the meter and run the hot taps on full. This will cool the boiler down.

Shut the taps off and reset the lockout on the boiler.

Read the FAQ's on gas rating. Open the hot taps fully for gas rating. If you are not clear on the procedure just time a single revolution of the test dial on an imperial meter (in seconds) or for a metric meter note the readings over a 2 minute period (just the right 3 digits).

Remove the two screws each side of the lower panel. On the control box you will see 2 lights. When you open a hot tap (boiler initially cold) the right green light will illuminate after a short delay. You should notice the flame height increases at the same time.

Thanks for that.... I just noticed the servo arm is not moving towards microswitch anymore... it was doing this intermitently before but very very infrequently...i was meaning to replace this some time ago...thing is now its not triping in the hot water so i think i need to change this before doing anything else. I beleive there is a rod that pushes this up thats out of view... can the water valve be serviced or should i just get another one? thanks

 

[Andygasman2010]

Ensure the boiler is completely cold, I suggest you shut the gas off at the meter and run the hot taps on full. This will cool the boiler down.

Shut the taps off and reset the lockout on the boiler.

Read the FAQ's on gas rating. Open the hot taps fully for gas rating. If you are not clear on the procedure just time a single revolution of the test dial on an imperial meter (in seconds) or for a metric meter note the readings over a 2 minute period (just the right 3 digits).

Remove the two screws each side of the lower panel. On the control box you will see 2 lights. When you open a hot tap (boiler initially cold) the right green light will illuminate after a short delay. You should notice the flame height increases at the same time.

Thanks for that.... I just noticed the servo arm is not moving towards microswitch anymore... it was doing this intermitently before but very very infrequently...i was meaning to replace this some time ago...thing is now its not triping in the hot water so i think i need to change this before doing anything else. I beleive there is a rod that pushes this up thats out of view... can the water valve be serviced or should i just get another one? thanks

The servo valve is prone to sticking, it's controlled by the water valve underneath it so it'll be worth checking that too. lift the servo valve off the water section and move it manually, there's a metal pin in the water section which you could clean/lubricate, DON'T adjust it though, i've tried it before and it's never right afterwards!

 

[trelo]

Ensure the boiler is completely cold, I suggest you shut the gas off at the meter and run the hot taps on full. This will cool the boiler down.

Shut the taps off and reset the lockout on the boiler.

Read the FAQ's on gas rating. Open the hot taps fully for gas rating. If you are not clear on the procedure just time a single revolution of the test dial on an imperial meter (in seconds) or for a metric meter note the readings over a 2 minute period (just the right 3 digits).

Remove the two screws each side of the lower panel. On the control box you will see 2 lights. When you open a hot tap (boiler initially cold) the right green light will illuminate after a short delay. You should notice the flame height increases at the same time.

Thanks for that.... I just noticed the servo arm is not moving towards microswitch anymore... it was doing this intermitently before but very very infrequently...i was meaning to replace this some time ago...thing is now its not triping in the hot water so i think i need to change this before doing anything else. I beleive there is a rod that pushes this up thats out of view... can the water valve be serviced or should i just get another one? thanks

The servo valve is prone to sticking, it's controlled by the water valve underneath it so it'll be worth checking that too. lift the servo valve off the water section and move it manually, there's a metal pin in the water section which you could clean/lubricate, DON'T adjust it though, i've tried it before and it's never right afterwards!

Yeah...I've seen this before...thanks again. So ths valve is servicable then? Is there anything in there that I should be looking for in terms of wear and tear? I was looking at the pipe loom that goes in and out of it and wondering what else it does apart from detecting the cold water flow?

 

[Andygasman2010]

If your going to strip the water valve down you might as well change the diaphragm when you're in there. Personally I would just unbolt the servo valve (don't disconnect the pipes) and lift it off the water section, you should be able to see the metal pin lift up and down as you turn on and off a hot tap. Remove the pin and clean it, make sure it moves freely. Also check the arm on the servo valve moves freely too, make sure spring pressure pulls it back firmly to rest position.

All this is vital in controling the movement on the diverter valve, also are the small copper tubes so check they're not blocked too.

I've got loads of detailed info on this boiler, i spent alot of time working in a part of London that seemed to have loads of them! Let me know if you need anymore advice

 

[trelo]

If your going to strip the water valve down you might as well change the diaphragm when you're in there. Personally I would just unbolt the servo valve (don't disconnect the pipes) and lift it off the water section, you should be able to see the metal pin lift up and down as you turn on and off a hot tap. Remove the pin and clean it, make sure it moves freely. Also check the arm on the servo valve moves freely too, make sure spring pressure pulls it back firmly to rest position.

All this is vital in controling the movement on the diverter valve, also are the small copper tubes so check they're not blocked too.

I've got loads of detailed info on this boiler, i spent alot of time working in a part of London that seemed to have loads of them! Let me know if you need anymore advice

Thanks agian... I did manage to feel behind the arm of the servo and i can move the pin out of its slot but it feels like whatever it rests on inside the water section is jammed because there's no movemnet up or down other than the movement of the pin when it moves off whatever its resting on. Could thiis mean that its not the pin and the problem lies inside the water section? thanks

 

[Andygasman2010]

Sorry, so does the pin move up when you turn on a hot tap? If so, is it enough to fully operate the servo valve?

 

[trelo]

Sorry, so does the pin move up when you turn on a hot tap? If so, is it enough to fully operate the servo valve?

No... The pin just stays stationary

Actually you can tell there's a problem because if i disengage the return spring and manually push the arm against the micro switch the tone of the flowing water through the boiler sounds wrong. Best way to describe it is the sound you get when water has tiny air bubbles in it flowing through something very restricted. I suspect (correct me if i'm wrong) that the water section may be partially jammed in the open position. Going back to original problem I now feel after your advice about gas pressure that i may indeed have a problem with the gas.... I'm sure i used to see the flames rise higher than half inch (where they are now) I forgot to ask you what could cause the flame to remain the same hieght wether HW or CH in operation? Thanks

 

[trelo]

Hi again... I measured the gas consumption using my meter.... It took 38 seconds for a complete turn on the right hand needle of the meter when the boiler was cold and turned on hot taps.... Is this the correct rating...thanks

 

[Gasguru]

It's burning sufficient gas.

 

[trelo]

It's burning sufficient gas.

Ok then thanks... I changed the diverter valve yesterday so it cant be that. And I've changed the HEX a week ago. So i'm back to the same problem with lukewarm/tepid water from hot tap.
Is there anything in the water section/servo that could effect the flow of water apart from too much water flowing through the HEX? I don't think its too much flow because It was a straight swap - like for like HEX. Its just that the temperature still don't feel hot enough when you touch the flow pipe into the HEX. Is there a block in the circuit? The rads are scorching so no problems there.

 

[trelo]

Ensure the boiler is completely cold, I suggest you shut the gas off at the meter and run the hot taps on full. This will cool the boiler down.

Shut the taps off and reset the lockout on the boiler.

Read the FAQ's on gas rating. Open the hot taps fully for gas rating. If you are not clear on the procedure just time a single revolution of the test dial on an imperial meter (in seconds) or for a metric meter note the readings over a 2 minute period (just the right 3 digits).

Remove the two screws each side of the lower panel. On the control box you will see 2 lights. When you open a hot tap (boiler initially cold) the right green light will illuminate after a short delay. You should notice the flame height increases at the same time.

The green light means there is power to the modulation air pump, the brighter the light the more power to the pump (high gas) The yellow light means power to the operator (gas valve solenoid) High gas on this model is 5.1MB but if you're not an RGI just do the gas rate as the other guys have suggested. It should be 24kw on this boiler, hence VCW 242.

hope this helps!

The lights are working fine and i gave gasguru basic figures on fireing boiler from cold and says they are sufficient....thanks for that. I'm stil stumped on lukewarm water problem. Changed HEX and Diverter valve. But i do have problems with water section pin getting jammed...I think i'll change that next?