Hi got a customer who has a icon 45 bathroom extractor fan, fitted by myself and it develops water droplets on the front grill and drips on the floor. It is flush mounted in the wall through a 40mm polystyrene backed plaster board. I have put some expanding foam between the wall and the back of the plasterboard. Due to the nature of the wall I put a duct through the wall 150mm long, sloping out with a back draft flapper on the wall no water runs in the duct, it only forms on front grill. Any suggestion? Probably going to swop fan to a different brand. Never had this problem with this particular fan before
Hi Tex, when does it develop this condensation? Before it runs, while it is running or when it switches off? What are the conditions in the bathroom at the time? Condensation levels and bath full of hot water or empty, or shower running hot etc? It is just as much a case of identify the full circumstances like you would if fault finding an electric circuit ... without possession of the full facts you, or other members, may come to the wrong conclusion! That brings with it of course possibly expensive 'stabs in the dark' which do not solve the real problem.
If the condensation forms while the fan is running and the level of humidity at the time is high, it could be a case of 'you cannae change the laws of physics' as Scotty used to say! The lowering of air pressure in the room close to the fan as a result of the fan moving air out of the room and subsequent rise in air pressure at the stagnation points on the grill in front of the fan mean that the dewpoint falls and then rises again leading to the condensation on the grill. The only ways to avoid the condensation are to change the local atmospheric conditions at the grill; either:
- Heat the fan grill to above the dewpoint temperature for the combination of air pressure, temperature and humidity at that point.
- Heat the air so that the temperature of the air at the grill is above its dewpoint for the humidity level at the time; difficult if the surface of the grill is cold leading to cooling of the air and condensation ... refer to the above!
- Reduce the pressure fall and rise by reducing the fan speed and therefore extraction rate!
- Do what the Victorians did ... open the window and ventilate the room after bathing or showering! Closing the door after exiting the room of course to reduce the loss of heated ... and humid air from the rest of the house. Return to close the window when air has changed and condensation evaporated!
I think like many things, in the electrical and wider world, we forget that there are some things that those who went before knew and based their designs and installations upon. Victorian ... indeed the woodwork in any house will decay if exposed to moisture. Victorian houses are designed to be well ventilated! Wrapping our houses in insulation and expecting to live in temperatures of ~ 20 degrees Celsius + will, unless we also prevent the moist air from penetrating to cold surfaces, result in condensation and then rot in timber. It is a fallacy to believe that insulation and vapour barriers can prevent this ... you have been warned! ;-)) Friendly warning but serious none the less!
