Externally mounted extractor fan for kitchen?

[deano]

Hi.

Did some internal improvements a couple years back which involved some steelwork at the rear corner of my house. Instead of leaving unsightly bulkheads, protruding down from the ceiling in the kitchen, I lowered the whole ceiling to the bottom of the steels. Result... very low ceiling in kitchen!

My range cooker (baumatic) has a large hood with internal fan mounted above it (also baumatic). This vents directly up to flat roof, via an aluminum duct to a mushroom cap.

Problem: when missus cooks, the kitchen really fills up with a haze of smoke and odors, leading to 'orrible grease deposits (even when she's not burning things! ;)

Even though the extractor fan motor looks impressive and sounds like it could suck the chrome of a car bumper... the smoke seems to being going everywhere, except up the hood!

So, I'm not sure where to start looking to resolve the problem... motor? duct? mushroom cap?

Having seen one on a property recently, I was thinking of installing an external "in line" extractor fan to the pipe that comes out the roof and maybe a better cap that allows improved airflow?

Obviously, cost is an issue and I don't want to spend unnecessarily.

Any ideas on how I could go about resolving the problem, methodically would be gratefully received.

cheers, deano.

[John]

Is there an easy supply of fresh air to make up the air that could be going up the extractor. Whatever the cubic feet/min rating is - this needs to be matched with a supply of fresh air otherwise the fan cannot do its job.

[Donwill]

Who connected up the duct for you? some of the extractor hoods are designed to recirculate through a filter or depending how it's arranged to extract to outside. Are you sure the fan is properly connected to the duct. How long is the duct? does the duct go up vertically from the cooker hood? if it's a flex duct, are there any bends in it that may have collapsed? opening a window would easily satisfy a lack of air supply problem. If you are extracting vertically from a cooker hood to a flat roof you shouldn't be having any problems provided the pipe is of adequate diameter and it is of a reasonable length. Don

[Pete Verdon]

It's not running backwards, is it?

Pete

[js.b1]

1 - Still set to recirculate Remove the grease filters, find the destructions, check where the levers are set. 2 - Insufficient vents for air to be drawn in If you are trying to exhaust 440-850m3/hr you need vents that can match it. People assume the duct is the limiting factor, generally it is not.

[ransley]

Exterior extractor vent motors are easily double the power or more if you wish, just shop by cfm and the watts-amps of the unit. But I wonder if the ducts can take it. The exterior extractor motor will make the kitchen alot quieter as well. My interior unit I pull out every few years and soak clean the blower wheel and oil the motor, it does help alot, but exterior is what all commercial places have.

[robert]

I use an inline Elici? extractor mounted halfway up the chimney ( 3 storey house) with 6" ducting above the motor. Works very well , the kitchen is very quiet , it does pull the kitchen door open when switched on.

As has been said already the outlet vent can make a big difference - I noticed the difference when I removed the ventilated cap from the chimney and replaced it with a vent designed for use with open fires.

[deano]

Thanks for all the responses...

In the end, I braved the snow on the flat roof and went up for a look... Good job I didn't glue on the mushroom cap to the outlet pipe...

When this was removed and I looked down... the aluminium ducting had come off the bottom of the 4" pipe!

Some duct tape and a couple of large jubilee clips later (plus a hole in the ceiling for access) and it's all working back to what it should do.

Had to apologise to SWMBO's tho... for accusing that she wasn't putting the extractor on, while cooking :)