IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Today's teaser
Topic Summary: "Green" hand drying
Created On: 05 September 2012 12:43 PM
Status: Post and Reply
Linear : Threading : Single : Branch
1 2 Next Last unread
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 05 September 2012 12:43 PM
User is offline View Users Profile Print this message



perspicacious

Posts: 7031
Joined: 18 April 2006

A lot of toilet hand dryers are promoted on their environmental "benefits" when compared to the paper alternative and most are proximity sensed.

Today's teaser: If left in its dormant state for a year, how many minutes/hours of hand drying would you get if you replaced it with a manual push button type?

Regards

BOD
 05 September 2012 12:48 PM
User is offline View Users Profile Print this message


Avatar for stateit.
stateit

Posts: 2088
Joined: 15 April 2005

Dyson airblade claims a standby energy consumption of 1W.

So go figure...

-------------------------
S George
http://www.sg-electrical.com
 05 September 2012 12:53 PM
User is offline View Users Profile Print this message



perspicacious

Posts: 7031
Joined: 18 April 2006

I have done the maths on a typical, rather than seldom seen, type and the figures are surprising, mindful of the topic summary......

Regards

BOD
 05 September 2012 03:25 PM
User is offline View Users Profile Print this message



Ricicle

Posts: 829
Joined: 23 October 2006

With a 1w standby on a sensor dryer, I make it equate to approx. 45 secs. drying time per day on a manual dryer of 2kw.
And that's without any drying energy from the sensor dryer !

-------------------------
Empty barrels make the most noise.
 05 September 2012 03:34 PM
User is offline View Users Profile Print this message



impvan

Posts: 705
Joined: 07 September 2005

In a previous life I installed and repaired hundreds of Redring AD300 'traditional' hand driers, rebadged for that famous national rat-catching company.
I never measured the standby power, but given the failure rate of the 2W w/w resistors in the simple capacitor-diode-resistor power supply, I reckon the consumption was *at least* 2W... So heading for 20kWh per annum. With the 3kW driers then (I think they were 3.1 actually), about 6 hours' worth of drying time.

In an office washroom, standing time at the drier is assumed to be 25 seconds (gents) and 35 seconds (ladies).

Or about 600 drying visits.

A number of locations we had to install the things, I doubt they were used once a day.

I expect the effects of the increase heat & humidity on the air handling plant eclipse even the standby power consumption....
 05 September 2012 03:40 PM
User is offline View Users Profile Print this message



fredman

Posts: 221
Joined: 26 July 2007

Be totally green.. Shake the water off

On the serious side, why can't some of these large places use the wasted heat off the AC plant, always think it is great to stand on the top of a building in London in the winter at night and watch the amount of cooling tower vapour that is going up in the air.
 05 September 2012 07:24 PM
User is online View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 18917
Joined: 23 March 2004

On the serious side, why can't some of these large places use the wasted heat off the AC plant, always think it is great to stand on the top of a building in London in the winter at night and watch the amount of cooling tower vapour that is going up in the air.


very often it is at too low a temperature to be of use - Q(kW) = mass x specific heat capacity x temperature difference. For the same fluid, the temperature difference dominates so you need as high a rejection temperature as possible to be able to reclaim. That's not efficient for the cooling system.

Many chillers will have free cooling cycles that make use of low ambient temperatures

That said, for many buildings, the cooling load dominates - you don't actually want the heat at any time of the year - so systems are constantly rejecting heat to some lesser or greater degree.

If we are serious about it, actually the building regs promote the problem - take an aspect as a minimum U value on a window - it's intended to stop winter heat loss - but it effectively stops summer heat loss as well - so you need more cooling power in summer - which equals more energy - much more than in winter as most buildings are almost self heating due to occupancy, PC and lighting loads etc. Relaxing the glazing U value would result in more heat energy being lost - but would also mean less cooling energy - balanced over a year a cheap single glazed window would actually be more energy efficient - can we do it, no - but thats building control for you

Going back to BOD's original post - in some cases using "efficient dryers" the quiescent load can be quite frightningly high - we had one building that used to trip a consumption alarm on landlords core power boards at night as the systenm was set to asume very low amps - but the hand driers used to achieve a trip point even if there was no usage

Regards

OMS

-------------------------
Failure is always an option
 05 September 2012 07:42 PM
User is offline View Users Profile Print this message


Avatar for slittle.
slittle

Posts: 3372
Joined: 22 November 2007

I always thought that trousers make ideal hand dryers. They certainly work in those places where the paper towels have run out and the electric dryer is broken


Stu
 05 September 2012 07:49 PM
User is offline View Users Profile Print this message



perspicacious

Posts: 7031
Joined: 18 April 2006

Both dryers tested out at 49 mA so just shy of 12 W each equating to 103 kWh annually or 20 male drying visits every day (as if).

Regards

BOD
 05 September 2012 09:33 PM
User is offline View Users Profile Print this message


Avatar for KFH.
KFH

Posts: 199
Joined: 06 November 2010

I worked for one company that replaced all the electric hand dryers in their new office with roller towels as they considered the aerosol effect of the hand dryers to be a health risk. That was before the Dyson type of dryer.
 05 September 2012 10:20 PM
User is offline View Users Profile Print this message


Avatar for sparkingchip.
sparkingchip

Posts: 5695
Joined: 18 January 2003

Our local boiler factory owned by the highly efficient Germans have boilers on Z tests which means that they have had some them running flat out for over ten years, I passed comment that they are must never be short of hot water for the cloakrooms and was told that actually it is all sent to waste, calculate that one!

Andy
 05 September 2012 10:30 PM
User is offline View Users Profile Print this message



peteTLM

Posts: 3082
Joined: 31 March 2005

Is that the dyson one that blasts all the water onto the floor then?

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 05 September 2012 10:49 PM
User is offline View Users Profile Print this message


Avatar for sparkingchip.
sparkingchip

Posts: 5695
Joined: 18 January 2003

The one that embarrasses us old men making it look like we dribbled on our shoes.

Andy
 05 September 2012 10:53 PM
User is offline View Users Profile Print this message


Avatar for sparkingchip.
sparkingchip

Posts: 5695
Joined: 18 January 2003

It isn't considered polite is it to put your bits in the dryer is it?
 30 April 2013 03:47 PM
User is offline View Users Profile Print this message



oshta

Posts: 25
Joined: 30 January 2013

Originally posted by: sparkingchipOur local boiler factory owned by the highly efficient Germans have boilers on Z tests which means that they have had some them running flat out for over ten years, I passed comment that they are must never be short of hot water for the cloakrooms and was told that actually it is all sent to waste, calculate that one!

Ditto engines/gensets on dynos, where the energy all goes into..... load banks!! Cost of an inverter to stuff it back into the grid anyone?


Daniel
 30 April 2013 04:21 PM
User is offline View Users Profile Print this message



rougediablo

Posts: 112
Joined: 09 November 2011

Originally posted by: sparkingchip

It isn't considered polite is it to put your bits in the dryer is it?


Dyson Air Balling
 30 April 2013 07:29 PM
User is offline View Users Profile Print this message



mikejumper

Posts: 1670
Joined: 14 December 2006

Originally posted by: slittle
I always thought that trousers make ideal hand dryers.

Yes, but whose trousers?
 01 May 2013 12:36 AM
User is offline View Users Profile Print this message



SKElectrical

Posts: 892
Joined: 01 February 2009

Originally posted by: OMS
Relaxing the glazing U value would result in more heat energy being lost - but would also mean less cooling energy - balanced over a year a cheap single glazed window would actually be more energy efficient - can we do it, no - but thats building control for you


How would you counter the cold air brought in by fresh air requirements? With single glazed units it would take a colossal heating supply.


Or you thinking natural ventilation via infiltration?
You're on to something though - there is so much energy waste in office blocks.
 01 May 2013 09:44 AM
User is online View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 18917
Joined: 23 March 2004

Originally posted by: SKElectrical

Originally posted by: OMS

Relaxing the glazing U value would result in more heat energy being lost - but would also mean less cooling energy - balanced over a year a cheap single glazed window would actually be more energy efficient - can we do it, no - but thats building control for you




How would you counter the cold air brought in by fresh air requirements? With single glazed units it would take a colossal heating supply.

same as we always do - frost protection battery, pre heat battery and re heat battery depending on the amount of recirc or via two stage heating if 100% fresh with heat recovery on the AHU's (plates, run around coils, regenerative thermal wheel, heat pipes of heat pump)

The relative heat loss and gains of a single compared to double glazed unit isn't that great contrasted against the energy consumed in the shoulder parts of the year for cooling. There has to be something wrong with a building in a temperate maritime climate like the UK that has chillers runing in April because the heating is off and the building is overheating on nothing more than internal occupancy and equipment gains which can't easily "escape" because weve double glazed everything with low iron glass.




Or you thinking natural ventilation via infiltration?

nope - natural ventilation is a properly designed ventilation arrangement - infiltration is just uncontrolled air movement due to crap building practices on site.

Build tight - ventilate right, remember



You're on to something though - there is so much energy waste in office blocks.

Exactly - that's why I made the comment


regards

OMS

-------------------------
Failure is always an option
 01 May 2013 04:31 PM
User is offline View Users Profile Print this message



amandalewin

Posts: 121
Joined: 19 December 2007

I just want to know why men spend less time drying their hands?! Surely they have bigger hands, so would need MORE time?

-------------------------
Amanda

'At some point we all must chose between what is right and what is awesome'
IET » Wiring and the regulations » Today's teaser

1 2 Next Last unread
Topic Tools Topic Tools
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.