Replies

1. 
   DanH | Sep 24, 2004 04:38pm | #1

   The only problem you might have with that unit, that I can think of, is if the contacts are way overrated for the load, they may not stay clean.

   You just need to pick the right pair of contacts to use, leaving the rest unconnected. (Generally, if you manage to pick the wrong pair the fan simply won't work, will run continuously, or will be on when it should be off and vice-versa -- no danger of smoke, if you have a basic comprehension of the circuit concepts involved.)

   Your other option (one I've used) is to use a transformer and control relay to allow you to use a low-voltage thermostat (even a heating-only one, since the relay can reverse the "sense" of the circuit). This also permits use of low-voltage wiring to the thermostat, if that's useful, though at the cost of added expense and complexity.

2. 
   BillHartmann | Sep 24, 2004 04:51pm | #2

   All you have to do is to wire through just one of the poles.

1. 
   mitch | Sep 24, 2004 05:24pm | #3

   thanks guys- i kinda figgered i could but my only experience is with single pole, heat only, models.

   m

3. 
   bake | Sep 24, 2004 05:26pm | #4

   Mitch, The way I am interpeting this is you want a line voltage thermostat like the type used for baseboard heaters.

   You can use it to drive a relay if you want a different set of normally closed contacts.

   Where's my spell checker!!!

   Edited 9/24/2004 10:30 am ET by bake

   
   

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   Edited 9/24/2004 10:31 am ET by bake

1. 
   mitch | Sep 24, 2004 05:59pm | #5

   so what you're saying is (if the 2-pole, heat/cool model won't work for me) i can set it up so that the switch is basically reversed?  triggers 'on' when the temp gets above a certain point instead of below?

   m

1. 
   BillHartmann | Sep 24, 2004 06:26pm | #6

   It you have accurate described it you have a double pole, double throw switch.

   One pole has a common, and then a contact that is closed on high temps, and another that is closed on cold temps. Depending on the design the heating and cooling might be different setings or it might have one setting and it is either heating or cooling mode.

   Then you have a 2nd pole which is identical to the first.

   The 2nd pole for 240 volt equipment so that both hots are switched at the same time.

   It will have 6 contacts.

   All you need to use is the common and the cooling contact on one pole.

   However, you should be able to get a cooling ownly line voltage thermostat. They are used for all kinds of ventaliation fans, including greenhouse and attics.

1. 
   mitch | Sep 24, 2004 06:43pm | #7

   now that you mention it, a cooling only, 110v thermostat shouldn't be all that hard to find.  i've just checked a few industrial catalogs i had handy.  haven't seen my graingers catalog in awhile- when i find it i'm guessing it'll have what i need.

   thanks,

   m

1. 
   BillHartmann | Sep 24, 2004 06:55pm | #9

   It is not clear, but I think that HomeDumpo has what you need.

   http://www.homedepot.com/prel80/HDUS/EN_US/diy_main/pg_diy.jsp?CNTTYPE=PROD_META&CNTKEY=Products_2%2fBuilding+Supplies%2fVentilation%2fPower+Ventilation+Access.&BV_SessionID=@@@@1266554685.1096041033@@@@&BV_EngineID=cccladcmjdeihkdcgelceffdfgidgjk.0&MID=9876

2. 
   DanH | Sep 24, 2004 06:49pm | #8

   You can use a double-throw relay to reverse the "sense" of the thermostat. Basically, set up so that the relay powers the fan when it is NOT "energized". So if the thermostat "calls for heat" it will energize the relay, causing the fan to not run.