HVAC and Plumbing Questions and Answers

We take for granted the unobtrusive white box on our wall that is the modern boiler. That is until the day we push the button or turn the knob and nothing happens. Then we panic at the thought of being without hot water or invariably, when it stops working during the winter months, we panic at the thought of being without hot water and heating. There are a number of surprisingly simple reasons why boilers refuse to work, so simple in fact that it’s often more hassle making the trades person their obligatory cup of tea than to fix it yourself.

Of course, it’s better for the boiler not to stop working in the first place, so just as with our cars, give it an annual service. Book the service before winter or the engineers will be at their busiest (and most expensive.) Make sure the engineer you employ is registered by the appropriate body to work on gas appliances.

So, you have a certificate from your boilers annual health check. It was noted that when it was stripped and cleaned last month, the gas rate values and the carbon dioxide ratios were within required limits and everything was working properly, just as it was last night when you went to bed. Why then have you got up this morning to a cold house and no hot water? The following scenarios are the most common, simple problems associated with combination boilers. If you come to the end and have not found the problem, then it’s time to call a licensed HVAC professional. Always refer to the manual supplied with the boiler and follow all advice given.

Is the boiler turned on?

If you see a light or a symbol on the display or hear it making a noise, you know it’s turned on. It sounds obvious but it’s surprisingly easy to accidentally turn off the boiler. This is due to the switched supply to the boiler often being located next to sockets powering other household appliances. There is usually an on/off switch on the boiler itself. Again, check if it has accidentally been switched off. If there still seems to be no power to the boiler, check the appropriate breaker in the property’s main fuse box. A recurring fault with a fuse or circuit breaker indicates a problem requiring professional help.

Is the boiler turned on but not providing heating or hot water?

Check the pressure gauge on the boiler. If this registers much below one bar, the boiler will not work. Somewhere on the pipework, usually below the boiler, will be a filler loop. Normally this is a silver braided flexible pipe with two black levers. Turn the two levers on the filler loop and watch the pressure on the gauge rise. Turn off the levers when the pressure is between 1.2 & 1.5 bar. Systems with old radiators and pipework can gradually release pressure over a period of time and this re-pressurising may become a frequent task. If one day the pressure gauge suddenly reads zero, there may be a broken pipe or fitting it’s important to call a HVAC professional.

Is the temperature outside below freezing?

To reach the high efficiency required by law, most modern boilers condense their flue gasses. The upshot of this is that they have an extra pipe to discharge the collected condensate. If this pipe runs outside to be discharged into a drain or soak-away, the condensate can freeze inside the pipe. This blocks the pipe and causes the boiler to stop working. Read the user instructions to identify the condense discharge pipe (It’s usually the only plastic pipe coming out of the boiler.) Trace it to its destination and check for ice build up. Freezing condense pipes that cause problems may be lagged or re-routed for internal discharge.

Do you know the location of the gas meter on your property?

You should, because this is the main isolation point in the event of a gas leak. Check that the isolation lever has not been moved to the off position, preventing the gas supply to the boiler. It’s surprising how many call out charges are attributed to the kids pulling this lever! Get instant expert contractor advice in case you need a pro.

Does the boiler supply hot water, but not heating?

Check that the season knob on the boiler is set to winter. Ensure that the boiler and external thermostats (if fitted) are set to their maximum temperature. Turn up any TRV’s (thermostatic radiator valves) to their highest settings. These are the numbered knobs located on the ends of the radiators. If the bottoms of the radiators are getting warm or hot, but the tops remain cool, then the radiators need to be bled. This is a simple task. Remember though to top up the pressure afterwards using the filler loop.

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