Help needed in designing a temperature sensitive exhaust fan

[[email protected]]

I am trying to design a commercial kitchen with large exhaust fan and
hood. My idea is to keep the kitchen temperature sensitive and smoke
free. There ned to be two options. One is only temperature sensitive,
which means to operate the exhaust fan when the temperature is high.
Other is to switch on hte exhaust fan either if the temperature is
above a level or there is smoke in the kitchen. Can any one guide me
with the circuit diagram for both of these. Note that the exhaust fan
motor is a 1/2 Hp motor connected to 230 v AC mains.
All feedbacks are sccepted. Thanks

 

[colin]

I am trying to design a commercial kitchen with large exhaust fan and
hood. My idea is to keep the kitchen temperature sensitive and smoke
free. There ned to be two options. One is only temperature sensitive,
which means to operate the exhaust fan when the temperature is high.
Other is to switch on hte exhaust fan either if the temperature is
above a level or there is smoke in the kitchen. Can any one guide me
with the circuit diagram for both of these. Note that the exhaust fan
motor is a 1/2 Hp motor connected to 230 v AC mains.
All feedbacks are sccepted. Thanks

An ordinary room thermostat will give you temperature control, maybe a smoke
alarm for the smoke detection ?

oh just a thought, does it need to detect if the kitchen is hot and smokey
due to it being on fire and avoid fanning the flames ?

Colin =^.^=

 

[[email protected]]

I am trying to design a commercial kitchen with large exhaust fan and
hood. My idea is to keep the kitchen temperature sensitive and smoke
free. There ned to be two options. One is only temperature sensitive,
which means to operate the exhaust fan when the temperature is high.
Other is to switch on hte exhaust fan either if the temperature is
above a level or there is smoke in the kitchen. Can any one guide me
with the circuit diagram for both of these. Note that the exhaust fan
motor is a 1/2 Hp motor connected to 230 v AC mains.
All feedbacks are sccepted. Thanks

You'll need a differential thermostat, a plain room stat would be no
good.

NT

 

[Rich Grise]

An ordinary room thermostat will give you temperature control, maybe a smoke
alarm for the smoke detection ?

oh just a thought, does it need to detect if the kitchen is hot and smokey
due to it being on fire and avoid fanning the flames ?

Even if the room were on fire, I'd think you'd want the exhaust fan going
so the room doesn't fill with superheated combustion products and flash
over.

Cheers!
Rich

 

[Rich Grise]

I am trying to design a commercial kitchen with large exhaust fan and
hood. My idea is to keep the kitchen temperature sensitive and smoke
free. There ned to be two options. One is only temperature sensitive,
which means to operate the exhaust fan when the temperature is high.
Other is to switch on hte exhaust fan either if the temperature is
above a level or there is smoke in the kitchen. Can any one guide me
with the circuit diagram for both of these. Note that the exhaust fan
motor is a 1/2 Hp motor connected to 230 v AC mains.
All feedbacks are sccepted. Thanks

It sounds like you want the fan if it's hot, whether it's smoky or
not; what if it's smoky but not hot? Do you still want the fan on?

If so, then it's an "or" circuit. Get a thermostat and a smoke detector
that have switch closures for output, and put those switches in parallel
to control the motor contactor.

Good Luck!
Rich

 

[[email protected]]

Dear Rich,
Thanks for that feedback. Let me convey my idea
completely. The temperature switch need to be above the burner or near
the vent hood, which means that when the stove is On or cooking is
being done the exhaust fan need to be switched on inorder to reduce the
temperature as well as smoke. But the smoke detector is to reduce the
smoke in the whole kitchen. It can be from another cooking device with
our vent or other means. Either of this situation the fan should start.
But my doudt is the real time circuit diagram to implement the idea. As
this is a place where more smoke & heat is involved i prefer to use a
bimetalic temperature switch than Lm135 or much electronic. Please do
let me know with all your comments & feedbacks & if possible with
circuit diagram.
Regards
Sanjeev

 

[Michael A. Terrell]

Dear Rich,
Thanks for that feedback. Let me convey my idea
completely. The temperature switch need to be above the burner or near
the vent hood, which means that when the stove is On or cooking is
being done the exhaust fan need to be switched on inorder to reduce the
temperature as well as smoke. But the smoke detector is to reduce the
smoke in the whole kitchen. It can be from another cooking device with
our vent or other means. Either of this situation the fan should start.
But my doudt is the real time circuit diagram to implement the idea. As
this is a place where more smoke & heat is involved i prefer to use a
bimetalic temperature switch than Lm135 or much electronic. Please do
let me know with all your comments & feedbacks & if possible with
circuit diagram.

You do not want the fan activated by a smoke detector. If there is a
real fire it will pull the smoke out, while pulling more oxygen to the
fire.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Rich Grise]

You do not want the fan activated by a smoke detector. If there is a
real fire it will pull the smoke out, while pulling more oxygen to the
fire.

Apparently, a whole passel of firefighting crews disagree with you:

http://en.wikipedia.org/wiki/Ventilation_(firefighting)

It will suck the superheated smoke and gases out, so you don't get a smoke
explosion and you reduce the risk of flashover, at least according to
these folks.

I'd also think that it would give cooler, fresh air to whoever's trapped
in the building, and/or their rescuers.

Thanks!
Rich