A lot of heater chatter

Further to the reply from Brian Whitford (August, p15), regarding how he resolved his heater chatter by plugging the gap between the inner and outer flue pipes by using ‘packing’ fire rope.

To my knowledge, this rope, once known as asbestos rope (potentially dangerous on its own) is used for, as he states, packing but it is for specific uses only.

The reason, I believe, for the two pipes is that the outer pipe and corresponding air gap are to act as a heat shield against combustible materials from the high temperatures of the actual heater flue pipe.

These flues, which are known as balanced flue type, which you may have for the boiler in your own home, draw air through the air gap to the boiler for gas combustion and utilising the inner tube to remove the hot poisonous carbon monoxide.

The fact that Brian has access to the air gap suggests it is not a balanced flue.

The air gap in this case, as stated above, may not only provide a heat shield but may also be used in the ‘stack effect’, thus creating a flow of air to remove heat/gases in the event of the actual heater flue pipe having any leaks, therefore there may be a potential danger if this air gap is blocked, as with packing rope.

In addition, there may also be a legal requirement that any gas appliance, including flue pipes, can only be maintained/ repaired by a registered and certified gas engineeer.

If the unthinkable was to happen, this could also invalidate any insurance claim and may even also see the Health and Safety Executive become involved.

We all have good ideas, but some things are best left to the experts, especially when it comes to safety-critical areas such as gas and 230V electric.

I McGhee