SimonW

APOLOGIES FOR THE EXTENSIVE QUESTION...

Dear All,

My father owns a laundrette, it seems that there have been instances of fires starting when the excessive heat behind gas fired dryers has ignited the oil on the drive mechanism.

My question is..

1) What kind of sensor can I use to measure the temperature of the small room behind gas fired dryers?..... (LM35Z?)

2) Once the critical temperature has been reached how can I reduce the temperature... will extracting air have the same effect as blowing air into the small room.. The only problem is if I blow air into the room there is the chance of reducing the efficiency of the dryer and possibly blowing the flame out??.

Your comments and ideas are always appreciated

Cheers

Hero999

1) Thermistor, LM35Z, thermocouple etc.

2) An extractor fan should do the trick; what flame are you worried about blowing out? I don't think having naked flames around oil is a good idea.

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mneary

Excessive heat is normally due to lint build up restricting air flow. Removing the lint at regular intervals is probably the only solution.

If you put sensors in, they should shut down the dryers if it gets too hot.

Ambient

You may be able to find a temperature sensitive fuse, but I don't know where you would put it. You could also use a fan behind the dryer and simply turn it on whenever you use the dryer.

Gaston

i used to work on commercial laundry equiptment for a living. what kind of dryer is it? all dryers i have ever worked on have had a temp sensor in line with the gas valve to shut it off when the temp gets too high. it also has other saftey devices on it to prevent fires. do you have a schematic for the dryer that you could post? you shouldn't have to add any saftey devices to the equipment; it should already be there. if you don't have a schematic i may still have one. its been about 15 years since i fooled with one though

SimonW

Dryer = Huebsch 30/30 (Basic no modifications) 30 years old

Dear Mr Gaston,

If you are familiar with this model...

Place to get a full service manual?

Besides the open/close door sense switch, what safety devices does it include??.. what safety devices ??should it include??

In terms of health and safety... I am confident that there is an earth cable
on the metal chassis... do i need to perform any efficency tests?

Cheers!

BeeBop

I think the problem you are having is NOT with an individual drier getting too hot, but rather the room behind the driers, which they exhaust into it getting too hot?
I think what you want is not a sensor to shut down the driers when one gets too hot, this would make your customers really, and rightfully, angry.

1) Yes, that'll work. How will you read it?

2) It is not only better, but more efficient to pull the air out of the room than to push it in. The kind of extractor fan you want is common in restaurant equipment stores; squirrel cage, or inline vortex fans will work. You want one large enough to change the air in the room in a couple of minutes. You will also need to exhaust this air out doors to get any advantage. Also, you need an air inlet, which should be 2 to 3 times the area of your exhaust. (ie: if you are using an 8" fan duct, you need 3 - 8" holes, or one 16" hole as an inlet.)

Sceadwian

Those types of fans are usually called blowers. They're nice because they can pull relatively high back pressures, allowing good airflow especially in a constricted space, standard fans are only good at moving air if there is no back pressure. I've seen PC card style DC brushless blowers and I'm surprised they're not used in PC's more often as they're generally move more air using a quieter fan.

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Gaston

you can't go wrong vetilating the area behind the dyers. but it should not catch on fire if the safety system was working properly. now keep in mind that if the safety system does shut the dryer off there is a problem makeing it do so and you still need to find out what that problem is. i will explain how the system works which is really simple. the burner is on top off the tumbler, and the blower sucks the flame and heat down into it and out the bottom back. if the blower were to stop working the flame would no longer be sucked down into the tumbler and would catch on fire. so there is a light weight door on the back that gets sucked closed with the suction from the blower and it closes a switch in series with the gas valve. there are also two ( if i remember correctly) cabnet high temp limit switches that are also in series with the gas valve. they kind of resemble a TO3 transistor package. i believe one on the back and one on the top. just trace the wire back from the gas valve and you will find all three. oh and i forgot. there is also a centrifigal switch in series with the valve. it is inside the motor and only closes when the motor is running.