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Help wiring a blower, heat switch, and rheostat

Discussion in 'Firewood, Heating and Wood Burning Equipment' started by bsearcey, Jan 9, 2010.

  1. bsearcey

    bsearcey ArboristSite Operative

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    Anybody out there wired a blower with a heat switch and the connected everything to a rheostat? I know it can be done, and it is probably pretty simple, but when it comes to electricity and wiring I’m lost. If someone has done this can I get some step by step instructions? Thanks in advance.
     
  2. kam

    kam ArboristSite Operative

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    Wire everything in series. Wire from the power cord black to the switch..thru sw to rheostat...thru rheo to motor...thru motor to white power cord wire...

    Don't forget to ground (grn wire) all the metal.
     
  3. projectsho89

    projectsho89 ArboristSite Operative

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    If you're trying to vary the blower speed of an AC motor, a rheostat can be the wrong thing to use.

    You might tell us a bit more what you're trying to accomplish and what type of electric motor is used on the blower.

    What are you calling a "heat switch"?
     
  4. ericjeeper

    ericjeeper Addicted to ArboristSite

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    If you are going to use a light dimmer switch ,think again. You will need to use a ceiling fan control switch. Otherwise you will smoke the dimmer switch.
     
  5. Wood Doctor

    Wood Doctor Edwin

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    That could be true, Eric, but I believe the squirrel cage blower he may be talking about only draws half an amp--about the same as a 60-watt bulb.

    What I have run into is that rheostat light switches sometimes have pactically no control on the motor's speed. Some fan motors always want to look back at 120 volts in order to run and light controls usually just vary the voltage. So, the motor just shuts down or growls at you.
     
  6. KsWoodsMan

    KsWoodsMan Addicted to ArboristSite

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    A simple rheostat is the wrong part for the application of speed control for an induction motor. The motor tries to stay in sync with the 60Hz from the utility company. A fan/speed controller will vary the hertz going to the motor allowing it to change the speed of the motor.

    Rheostats are for resistive loads NOT inductive loads. Incandescant light bulbs are resisive loads.

    Find a speed controller as suggested.
     
  7. mga

    mga Tree Freak

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    the rheostat should be the last thing wired before the motor. basically, you don't want the blower to turn on until something reaches a certain temperature...right?

    and the rheostat is going to control the motor speed when the temp sensor says it's OK to turn on..right?

    it's really simple to do, but, follow the advice of others and get the right rheostat.

    dc motors are best suited for speed control.
     
  8. Billy_Bob

    Billy_Bob AboristSite Guru

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    Be aware that electrical wiring, if not done right, can cause a fire or electrocute someone. And it can take years of learning to be able to wire things in a safe manner.

    At a minimum I would suggest you read a book on electrical wiring cover to cover first before attempting to do any wiring.

    Wiring Books...
    http://www.google.com/search?hl=en&q=book electrical wiring&btnG=Search&aq=f&oq=&aqi=

    DON'T get these wiring books which have been recalled...
    http://www.cpsc.gov/cpscpub/prerel/prhtml10/10104.html
     
  9. bsearcey

    bsearcey ArboristSite Operative

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    Here are the components I'm trying to wire up. I'm posting a link to the actual website. In addition this company plus another one I've found has tons of blowers at prices way lower then what I've seen on websites catering to woodstove burners. If anybody is looking for a blower check these places out first.

    http://www.globalindustrial.com/p/hvac/blowers/centrifugal/fasco-centrifugal-blower-115-volts-2900-rpm-2?utm_source=nextag&utm_medium=cpc&utm_campaign=Blowers-Centrifu-nextag&infoParam.campaignId=WI

    http://www.cshincorporated.com/advanced_search_result.php?keywords=19-sf2-115

    http://www.cshincorporated.com/advanced_search_result.php?keywords=k177-1002&osCsid=259i8bo27u0k0atraqm6cjvm23

    Man. I hope that worked. I'm not sure what other information you guys might need, but I think everything should work together. The thermal switch is set for 115 degrees. I figure that would be a good range for it to come on/turn off at. It will be mounted on the back of my stove. What do you guys think. Is that too low of a temp to start blowing with?

    Thanks again for the help.

    Billy_Bob. Thanks for the words of caution. I'm probably overly safe when it comes to electricity. You should see how much electrical tape I've used on some of the little things I've done around the house.
     
  10. mga

    mga Tree Freak

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    115 is good.
     
  11. Wirenut2266

    Wirenut2266 AboristSite Guru

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    As stated: Power goes into snap switch, into fan controller, out to fan motor. Snap switch is good. Fan controller that was linked will work fine, but MUST be fan rated. Some are 1.5 amps, others are 7.5 amp rated. A good fan controller will be $20 plus, will not make motor hum or heat up too much. If you plan on a $5 dimmer, don't bother. Never switch the neutral, hot lead only as already stated. Ground everything, then ground it again, then maybe a third time for good measure. It just may save your life or a home fire!
     
  12. Billy_Bob

    Billy_Bob AboristSite Guru

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    So what is this blower going to do? Blow air directly into the woodstove?

    Following are some safety things to consider for your project. These are some of the things electrical engineers do with the electrical products you buy in the store to be sure they are safe. And things electricians do to be sure the wiring in your home is safe...

    One thing to check when "designing" electrical systems is amperage. You need the wiring, switches and controls to be able to handle the electrical load.

    In this case it says the blower is 0.81 Amps, which is quite low. So commonly sized 14 gauge wire would be large enough to handle the load. And a regular 120 volt 15 amp circuit should easily be able to handle this load. (Regular outlet.)

    It does not say the amperage rating of the thermal switch. You need to make *sure* when you are the "designer" of an electrical system that each component can handle the load! I would call and ask. They go to this effort with every electrical product you buy, best to do it for your own designed system as well.

    Then that speed control does not list wattage or amperage either. I would call to find out the wattage or amperage rating is - again to be *sure* it can handle the load. And be sure you can connect this to the specific blower you are buying and it will not burn out the motor. Ask.

    I'm sure those will easily handle the load, but you can't tell by looking. You need to know for sure when designing electrical systems.

    Here is a calculator to convert watts to amps. Use the one under single phase...
    http://www.jobsite-generators.com/power_calculators.html

    Then how hot will it get in the area where the wiring will be run? You MUST know this so you can purchase and install the correct temperature rated wiring. If you look at the wiring inside a kitchen electric range or a space heater (where it gets to be quite hot), you will notice that special high temperature rated wiring is used.

    The danger with using "any old wire" is that the insulation on the wire can melt, a bare wire could touch the metal frame of the wood stove, the woodstove could become electrified, and then a small child or someone in your family might touch it and be electrocuted.

    Then a "strain relief" or "romex clamp" must be used where the wire enters the electrical box for the fan. If this is not done, the wire could scrape against the sharp metal edges of the electrical box, this could electrify the metal fan and the wood stove, then you again have an electrocution hazard.

    Romex clamp...

    [​IMG]

    Then for making electrical connections, the following "High Temperature Wire Nuts" are rated to 302° F...
    (Electrical tape will melt.)
    (Make darn sure it does not get hotter than that!)
    http://cableorganizer.com/wire-connectors

    Then because it is possible that metal parts could become electrified, it is necessary to ground everything metal. That is use a 3 prong plug and connect the ground wire to the fan, woodstove, and metal parts of speed control and thermal switch.

    I would use metal flexible conduit to protect the wiring from the fan to the speed control and to the thermal switch. And I would use a metal electrical box for the speed control. And cover the thermal switch because that would have live 120 volt electricity at its bare connections. A small child could walk up and touch it, then be electrocuted. Or an animal. And again ground all metal parts.

    What grounding does, is if an energized electrical wire touches a metal object, it creates a short which turns off the house circuit breaker and the electricity. Keeps everything safe.

    On grounding...
    http://www.electrical-forensics.com/EquipGnd/EquipGnd.html

    http://www.tva.gov/power/homesafety.htm

    The Case of the Do-it-Yourself Home Electrocution...
    http://ecmweb.com/mag/electric_case_doityourself_home
     
  13. lobsta1

    lobsta1 ArboristSite Operative

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  14. loadthestove

    loadthestove AboristSite Guru

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  15. Wood Doctor

    Wood Doctor Edwin

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    +1. Thumbs up. I just may order this, even though my blower has two speeds. The lower speed only drops the RPM by about 15% and that 21-year-old blower may be on its last leg. The new ones are usually only single speed.
     
  16. Wirenut2266

    Wirenut2266 AboristSite Guru

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    Wood dock: Good reply, you like to type much more than me!:cheers:
     
  17. Wood Doctor

    Wood Doctor Edwin

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    Not really, I am a lousy typist. However, I have written millions of words through the years. I've always had a knack for that. Mom was an English teacher and Dad was an engineer. I tried to extend both and perhaps a little bit rubbed off.
    :)
     
    ray benson likes this.

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