Peter Lennard Heating Repairs & Servicing

Preliminary checks that can be carried out:

If you have a Vokera combination boiler, or any other boiler, on a pressurised system

(Non-combi boiler? Click here)

1) Check the Pressure

2) Are there any danger signs?

3) Boiler sounds completely dead

4) Prepayment gas meter - has it run out of money?

5) Pilot out

6) Lockout (if electronic ignition)

7) Speed of hot water - has it noticeably slowed down?

1) Check that the pressure shown on the gauge marked 'Pressure' is correct. It should be between 1 and 1.5 bar when the radiators are cold (if the gauge is recording pressure in bars reading 1, 2, 3, 4 etc). Older boilers might display pressure on a gauge reading 10, 20, 30, 40 (mH2O) in which case the pressure should be between 10 and 15 when the radiators are cold. Back to top

2) Are there any danger signs? Smell of gas or fumes? Loud banging noises? Temperature gauge going higher than 80 degrees centigrade? If so do not attempt to relight/restart the boiler - it is safer to switch it off. Back to top

3) Does the boiler sound completely dead when either the heating or hot water are switched on? If you can't hear even a very slight hum or whirr and the boiler is completely silent then it is reasonable to suspect that the main fuse in the boiler's electricity supply has failed or someone has accidentally switched off the boiler's electricity thinking they were switching off something else, such as the fridge to defrost it or the washing machine. If the boiler's electricity has not been switched off accidentally then consider replacing the fuse which will be in the fused plug or spur. The correct fuse is three amps for a normal domestic gas central heating system, so never fit any fuse larger than that. If you fit a new 3amp fuse and it immediately blows then the boiler has a short circuit and should be left switched off and an engineer called out. Repeatedly changing the fuse will only risk damage to the boiler's electronic circuits or even ancilliary items such as the timeclock or room thermostat, if fitted. Back to top

4) Do you have a prepayment gas meter - one of those with a rechargeable key? Has the gas run out? (Yes, I have been called out when the gas had run out). Back to top

5) If the boiler normally has a pilot, is it alight? If not, and you know how, and you have no reason to suspect any danger such as a smell of gas then it is normally OK for a user to relight the pilot. If the pilot is alight the problem can sometimes be cured by simply extinguishing the pilot and then relighting it a few minutes later. However, if you have not been shown how to do any of these things then it is better not to try now without guidance. Back to top

6)Lockout - if the boiler has electronic ignition (i.e. it never has a pilot) it may have gone to 'lockout'. The first time this happens it can be reset if you are familiar with the reset procedure. If the boiler repeatedly goes to 'lockout' it is faulty and must be repaired and should not be repeatedly reset. Back to top

7) Speed of Hot Water - have all the hot water taps noticeably slowed down (combination boilers only)? If the hot water flow rate falls below a certain minimum level then the boiler won't switch on for hot water. Possible causes:

 - Thames Water (for readers in the London area) might be repairing a water main. While this will also affect the cold water supply, this is normally faster than the hot. If none of the other possibilities below apply, give them a ring on 08459 200 800

 - Another possibility is that you are sharing a mains cold water pipe with another flat. Has a downstairs neighbour had some builders in who may have turned off the water and then not turned it back on fully when they departed?

 - If the problem is new, but intermittent, and you are sharing a mains cold water pipe with several other flats, then it may be that one or more of the other flats which previously had conventional heating and hot water systems using stored hot water (i.e. a cylinder in an airing cupboard) have decided to save space and had a combination boiler put in, increasing the demand on the one mains cold water pipe. A typical problem time is early in the morning if several people try to run showers and baths simultaneously. The higher you are in the building and the more other flats there are, the worse the problem. Remedy? Examine your lease and try and work out who is responsible for negotiating with Thames Water to install individual water supplies to each flat. Can be fairly expensive. A typical Victorian house converted some years ago may well only have one 15mm pipe serving the whole building. Current standards for converting a house into flats require that each flat has its own individual cold mains pipe. Take a look outside - how many stopcocks can you see in the pavement? There should be one for each flat, not just one for the whole house.

- If only one hot tap has slowed down, then the problem probably lies with the tap itself.

 - Finally, the boiler may have a mechanical problem such as a stretched diaphragm, stiff (unlubricated) pins, or both which in combination with the reduced flow of water means it sometimes won't switch on. You may be able to defer the day you have to get that new water pipe installed by keeping the boiler in tip-top condition and getting me in to give it the once over. I have one 3rd floor customer with four neighbours all sharing one pipe in that situation! If the boiler won't switch on for hot water, and the speed of the water coming from the hot taps is normal, then there is a problem with the boiler that needs a qualified person to rectify.Back to top

Pressure OK? - 1
Danger Signs? - 2
Boiler sounds dead? - 3
No money in gas meter? - 4
Pilot out? - 5
Lockout? - 6
Water speed normal? - 7

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Peter Lennard, Vaillant, Viessmann & Vokera Specialist
020 8674 1166

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