Gloworm Compact with Low Burner Pressure

[grill]

Alright guys,

Was out there at a Gloworm Compact that was having lock out problems.

When i read the gas valve outlet pressure i getting 4 mB. The manual siad it should be around 15 so i went adjust it at the PCB. Found that the potentiometer was turned up full. Checked inlet pressure and this was fine at 24 mB.

Anyway i stripped the gas valave down and found that it was blocked solid with Copper Sulphide. the worst case i have ever seen!!! Screwed the gas valve back together and rechecked my outlet pressure. I know had 8.5 mb.

This value was the same for the DHW as well. Its potentiometer was turned up full also. Why would i not be getting the 15 mb reccommended.

I checked the coil resistance on teh outlet side and it was reading 1.67 K ohms. When i first checke dthe other side i was getting 3 K ohms. I rechecked and then wasnt getting a reading or (OL). Is this a gas valve on its way out or what else could it be??

Cheers

Grill

 

[Dan Robinson]

Sounds pretty screwed to me.

 

[grill]

How come the boiler still runs okay then?? That was the bit that is confusing me.

I thought my meter had sh*t itself but i rechecked the other side and it was giving the exact same reading.

Do i replace i now or what until i dies completely??

grill

 

[Dan Robinson]

What do you mean by " the boiler still runs okay then"?

If the burner pressure is low and the dynamic pressure is OK then the boiler is not working okay by definition.

Assuming you can not adjust the burner pressure at the valve, and only the PCB then then valve itself is clogged, seizing, sha gged.

 

[GeckoGas-com]

That looks like the inlet standing pressure; you need to check the inlet working pressure.

If it's ok; replace the gas valve as you shouldn't really be running it that low under-pressure.

 

[Gasguru]

Anyway i stripped the gas valave down and found that it was blocked solid with Copper Sulphide.

Grill

I hope you mean you just removed the gas valve and removed the sulphide from the inlet filter. Anything more than this you'll need to change the whole gas valve.

The resistance of each coil is spot on. Have you set the gas valve up as per the MI? The valve itself has a minimum and maximum setting used in conjunction with the board pots. These horrible VK...05 valves often wander on their burner pressures and can be troublesome to set up.

As a guide you should be measuring around 24-32 VDC on the lower resistance coil and about 85-95 VDC on the high resistance coil( the voltage will vary as the burner is modulated). Take this as a very rough guide since the voltage is PWM so each meter will read different.

I have had a similar problem and the fault was with the pcb.

 

[grill]

Dan,

Fully take your point. What i was trying to say is how is there any gas getting through the valve if the resistance is zero??

Yeah the 24 mb was the standing pressure.

Will reccommend that they get a new gas valve and take it from there.

What damage will it do running it at this gas pressure??

Grill

 

[Dan Robinson]

As a CORGI you should know that standing pressure does not mean squat.

Running the boler at 8mBar will do no harm in itself, but the boiler will not produce the correct amount of hot water. They client might not notice this time of year; but give it a few months.

 

[grill]

Cheers Dan.

Sorry to labour on this point but what about this zero resistance reading and gas getting through. Im only starting out in the world of gas and want to get the story straight from the start.

I thought no resistance meant the coil wouldnt open hence no gas getting through??

Grill

 

[Dan Robinson]

Well not if you have been jabbing around in there and dislodged a spring. The valve might not be seating properly now. If that is the case then the boiler is now dangerous.

As GG said, you shouldn't really poke around inside gas valves unless you are 100% sure you know what you are doing.

What was the dynamic pressure?

 

[Gasguru]

If you had zero resistance on one of the coils the gas valve wouldn't allow gas through. The fist coil is a plain on/off valve. The second coil is modulated.

If you 've stripped down the valve I'd get round there ASAP and ID it. No one in their right mind would ever bother to pull apart a gas valve to repair it since there are no spares available and you have no way to test it is within spec.

The inlet filter normally traps the sulphide (the flakes are large).

 

[grill]

Hi again guys,

Firstly let me put your mind at ease. I didnt strip down the valve itself. Just took it out and removed as much copper sulphide as i could. There aint no way in this world im goingt o attempt to take it to bits. apologies for the confusion.

GG. When i tried to set the pressure on the board i turn the potentionmeter fully clockwise and was still only getting 8.5 mb. When i turned it anti clockwise the reading dropped down.

I did notice some brown burning on the board close to teh potentiometer. Spoke to a mate and he thinks this happens on all these boards and shouldnt be an issue. I did wonder whether it was a board problem though!!!

GG are you saying that this gas valve sounds okay then??

What steps should i take know to reach the 15.01 mb holy grail??

Thanks again guys

Grill

 

[GeckoGas-com]

First off; back to basics - Check the inlet working pressure....

 

[grill]

Right guys,

required info.

Inlet Standing pressure - 24 m bar
Inlet Working pressure - 11 m bar
Outlet Pressure before ignition - 2 m bar
Outlet working pressure - 10.5 mbar ( it has increased by 2 mbar!!!).

Doe sthis shed any light on the situation??

Grill

 

[GeckoGas-com]

Do you have 20 +/- 1mb WORKING pressure at the gas meter?


If not - CALL TRANSCO 0800 111 999
You need 20mb working pressure at the inlet +/- 1mb


If yes - Gas pipe undersized/blocked (Quote them for a repipe) or inlet filter (if fitted) blocked.