Combi boiler potential problem

Why don't you get a u-tube manometer ( or make one ) and see if your theory is correct? You caould measure at the bleed nipple on your gas meter, or at an approprate point on your boiler ( see manual ), if you feel you are competent. It may require a bit of patience, but if it turns out to be a drop in the gas pressure, you could examine the gas pipe run from your meter to your combi and see if it could be beefed up. IIRC, it should be 22mm pipe to within a metre of the combi, and even then I suppose it depends on the power output of the combi ( though 28kW should be OK for

22mm pipe generally ). How long is your gas run? How many elbow joints are there?

Andy.

Reply to
andrewpreece
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I have a Vokera Linea 28 boiler which intermittently fails to ignite. The light on the front flashes red and I get an error number. The strange thing is that it is only when the weather is colder, and only usually between 5pm to 7pm. It might do this four or five times per year between Sept and March.

I'm led to thinking that this may be a localised gas pressure issue (5-7pm people will have their hobs/ovens on, and their CH systems will be getting the house warm for the evening), or maybe something to do with the gas pipe.

Question is, should I be concerned about this and seek a resolution, or just resign to re-setting the boiler now and again?

Reply to
Brett Jackson

I wouldn't know where to start with a manometer. I've done my own CH and replaced all the plumbing in the house but I'm not so keen to do anything with the gas.

The 22mm pipe runs to within 2m of the boiler where it drops to 15mm. There are 4 elbow joints and 2 90 degree bends in to 22mm pipe and 2 elbows + 1 bend in the 15mm pipe. Overall the length of pipe from the meter to the boiler is 11m all-in. The only other thing using the gas is the hob which is connected to the same 22mm run right next to the meter.

I wouldn't have though the pipe size would effect the ability for the boiler to fire in the first place?

Reply to
Brett Jackson

I would imagine a manometer is the only way to confirm your theory about the gas pressure dropping. It's just a u-tube of clear plastic tubing, about a foot fro tp to bottom, half-filled with water. Stuff one end of the pipe on the gas nipple/whatever to be measured, crack open the gas nipple or turn on the gas, and watch the water o down on one side of the tube, and rise up on the other. The gas pressure, in millibars, is the difference in height between the two columns of water, measure in centimetres. The pressure should be about 18-20 millibars I think. You could take a reading earlier in the day then watch how the water levels vary between 5 and 7pm, and see if they fall unusually low...be careful about gas leaks though.

Andy.

Reply to
andrewpreece

You have nailed down the circumstances so preciusly that I think it is almost certain that a gas supply pressure problem is involved.

Whilst Transco try to get everyone to have at least 21mBar +/- 1mb meter outlet pressure at all times I beleive they are legally obligated to provide 15mBar. This means all gas appliances are expected to work safely (if not effectively) with a supply proessure of >14mBar.

You might have somewhat poor pipework (house with totally compliant pipe work are few and far between) that's loosing say 3 mBar and the boiler is having difficulty.

You can either wait a few years to see if Transco dig up the road and give you a more constant supply, or you can have the gas pipe work brought up to scratch.

Reply to
Ed Sirett

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