Someone explain Cooker Hoods and Steam Extraction?

[Adrian C]

(dug out of poor design rant thread)

On 14/04/2012 00:58, sm_jamieson wrote: > On Friday, April 13, 2012 9:04:24 PM UTC+1, Adrian C wrote: >> On 13/04/2012 19:27, Tim Streater wrote: >>

>>> >>>> Quite. We're currently shopping for a chimmney style cooker hood. I >>>> found one at John Lewis and downloaded the manual primarily for >>>> checking dimensions. However, the words "not designed for extracting >>>> steam" have now confused the selection process. >>> By "chimney style" do you mean it's a faux chimney? The only type of >>> cooker hood that's worth a damn is one that extracts to the

*outside* of >>> the house. >>

> Nope, it's a real chimney, a witches top hat above the hob. And a flat >> roof overhead to vent through, so can't see how it would not extract >> steam.... >> >> >> >> But Manual Says No... >> > > A quick web search reveals that many extractor instructions contain the phrase "will not extract steam". There appears to be a couple of variants of the phrase so maybe it is copied from some kind of regulation document. > I don't get it. > Someone suggested maybe it means most of the steam will condense in the filters or grease trap (the wire grid). > > I will have to choose an extractor hood soon also. > > Can anyone explain ? > > Simon.

[djc]

That seems a plausible explanation. I suppose it depends how much condensation. If enough to start dripping onto the cooking below then unacceptable. The other consideration might be that steam condensing within the hood might not do the fan motors any good.

[harryagain]

There are some poncy cooker hoods just recirculate the air through a carbon filter, ie they don't take the air.fumes outside. Maybe it's one of them?

[sm_jamieson]

An answer from justanswer.com

I have heard that stainless steel Cooker Hoods will not extract steam from = Induction Hobs. Apparently the Induction Hob does not generate heat like a = Ceramic Hob and when the hot steam hits the cold stainless steel Cooker Hoo= d the steam condenses and water drips onto the hob. Submitted: 1262 days and 23 hours ago. Category: Appliance Value: $15 Status: CLOSED Accepted Answer Picture Expert: The Home Smithy replied 1262 days and 20 hours ago.

HiCustomer

That is true to a certain extent. The amount that condenses is determined b= y the amount of airflow that the fan draws. If sufficient the diffrence is = neglegable.

If you consider that even with gas or electric power the hood is still goin= g to take some time to warm up, you can see that this shouldnt be a big con= cern.

The only time I can see it being a major concern is if you are constantly b= oiling water.

Even then a quick wipe with a dry rag handels that.

[sm_jamieson]

Had a look at some manuals with this warning, they all can extract to outside.

Simon.

[Adrian C]

Nope. These vent to the outside.

'Which' has recently tested some. As Quidco is paying £2 cashback per 2 month trial sign up (effectively putting me £2 in profit), I've done the deed and downloaded their "report".

It's not a complete test. Models I'm loooking at are missing, and comparisons and specifications I'd like to read about the products, compared with actual physical measurements in proper units are also sadly absent.

600mm chimney units that get 5 stars at steam performance are pretty expensive, was thinking £300 tops - nah, £490....

[js.b1]

It is a warranty / liability limitation.

Xpelair - your fan must be cleaned monthly by a qualified electrician. Most are AC fans with bimetallic thermal cutout. Should the fan or discharge vent become sufficiently blocked with dust the motor will get hot - so hot that if insulated by dust buildup and grease deposits the combination may ignite.

Cooker hoods - switch gear, motor, bearings, impellor are not IP-rated or temperature-rated for continuous steam exposure. The RCD may trip out, the motor may run its bearings, the plastic impellor or airflow guide may melt. Grease could me migrated past the filters via steam into the motor/impellor assembly creating a fire hazard.

Another point is steam is invisible, viciously hot close to a kettle's outlet. The visible "steam" is lower temperature hot water vapour. I suspect plastics used for motor housing, impellor & air ducting may not be tolerant of continuous high temperature exposure such as when used in recirculation mode - or even extract mode at low speeds against a barrage of steam sources. Likewise steam jets from pressure cookers I think can be a slightly higher temperature.

Most cooker hoods are made by Elica. Twin motor (>320m3/hr) units are good enough to get rid of heat, not just odours & steam. Single motor (>170m3/hr) are good at getting rid of moisture, they struggle on a hot summer's day. Obviously you can get single motor 550-800m3/hr units - but check the dB(A) figures carefully because things can get loud, likewise check hole size.

Ebay sometimes has oddball super high flow hoods at cheap prices, you do not have to pay the ?=A33.5k? someone did per cooker hood on Grand Designs.

[sm_jamieson]

I'm sure thats all true. But you'd have thought they would put something in the manuals to explain w= hats going on, especially when most people assume a cooker hood is going to= help remove "steam" (or water vapour) from their kitchen. And it will to s= ome extent.

Anyway since I have to choose a cooker hood soon, this is a very timely dis= cussion.

Simon.

[js.b1]

I think they should say "suitable for domestic cooking use only, prolonged exposure to steam may reduce the life of your new widget-&- co cooker hood and is not covered by warranty".

Most extractor manuals say "do not install directly above a hob or cooking appliance", re temperature & steam.

It does read somewhat peculiarly as you have found :-)

[js.b1]

That should say "Most extractor FAN (xpelair etc) manuals say"...

[Adrian C]

Thanks for that. Nope, not intending to spend loads.

Decided to fall to simple logic of picking something with the highest flow rate as we are limited to 600mm width.

Noise is her problem and she can do the work in keeping it and the grease filters clean - the John Lewis model we've found for £200, filters can be washed. If she fails, I suppose there's the smoke alarm - where do I dump in Halon gas in that event?

:)

[js.b1]

JL often give a 2yr warranty, which can be quite useful.

Fire blanket & 2kg CO2 with frost free horn (55B rated) are good. Powder makes a piggin awful mess. That is for general DIY use... heh- heh, just use the kitchen as the reason to buy on the domestic accounts.

Cooker hoods are excellent at getting grill toast smoke out quickly (not that I speak from experience, cough... splutter) and there is no mention against it in the manual of course... unlike the dark force known as "steam".

Smoke alarms are good at telling you when the oven needs a clean; quick chirp when you open the door :-)