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Posted by on June 9, 2007, 10:46 am
Any electric gurus? Just had a new roof put on. The roofers said the
vent that housed my thermostatically-controlled attic fan was about
shot and should be replaced -- it was only 37 years old.
So, ended up with a whole new unit. Of course, it was up to me to
rewire the beast.
>From the house is a romex cable with black, red, white and green 12
AWG.
The old fan was hooked up black to thermostat. White to White and
green to box ground clip, with the red wire taped over inside the box.
I hooked up new fan basically the same way, except I put a wirenut
(scotch lock) on the red wire and wrapped it up with electrical tape.
It has been fairly cool with outside temps hitting 70, so with the fan
thermo at 90, it hasn't kicked on. I did spend about 5-10 minutes
after the install with the thermo dialed down to 60 degrees, but the
fan didn't kick-on then, but I had to dash, so dialed it back up to 90
before departing the attic.
Maybe I am being a bit paranoid, but I am thinking it's not
working.....Would it be OK to bypass the thermostat -- that is just
hook the hot black lead directly into the fan to see if it works. I'm
pretty untalented in electrical works, but seems to me the thermostat
is just a fancy on/off switch right?
Or, am I just too anxious.....was my five minute trial at the 60-
degree setting enough that it should have kicked on?
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Posted by dpb on June 9, 2007, 10:59 am
timbirr@mailcity.com wrote:
...
>>From the house is a romex cable with black, red, white and green 12
> AWG.
>
> The old fan was hooked up black to thermostat. White to White and
> green to box ground clip, with the red wire taped over inside the box.
Sounds right --
> I hooked up new fan basically the same way, except I put a wirenut
> (scotch lock) on the red wire and wrapped it up with electrical tape.
That sounds good, too...assuming it's a 120V motor, not 240V, which
would also be the normal...
> It has been fairly cool with outside temps hitting 70, so with the fan
> thermo at 90, it hasn't kicked on. I did spend about 5-10 minutes
> after the install with the thermo dialed down to 60 degrees, but the
> fan didn't kick-on then, but I had to dash, so dialed it back up to 90
> before departing the attic.
>
> Maybe I am being a bit paranoid, but I am thinking it's not
> working.....Would it be OK to bypass the thermostat -- that is just
> hook the hot black lead directly into the fan to see if it works. I'm
> pretty untalented in electrical works, but seems to me the thermostat
> is just a fancy on/off switch right?
Sure, and yes, respectively...
> Or, am I just too anxious.....was my five minute trial at the 60-
> degree setting enough that it should have kicked on?
Should have kicked on very soon after you turned in on -- would be
highly unusual to have a time delay on a thermostat there.
Questions --
1. Are you sure the breaker to the thermostat is on? Maybe either it
was turned off to service or when the roofers disconnected the fan they
could have shorted the leads and tripped the breaker...
2. You should be able to hear the relay contacts of the thermostat
open/close as you turn the setting up/down past the current temperature.
If you have a VOM, you can test whether the contacts are closing or not
or simply use a light bulb type tester to check for power.
I'm guessing probably it's the breaker is off/tripped...
--
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Posted by RBM on June 9, 2007, 11:23 am
Sounds like you have it right. Those cheesy through the roof attic
ventilators don't kick on until it's pretty hot, so running the stat up and
down may not work. You can test it by connecting the hot leg to the load
side of the stat.
> Any electric gurus? Just had a new roof put on. The roofers said the
> vent that housed my thermostatically-controlled attic fan was about
> shot and should be replaced -- it was only 37 years old.
>
> So, ended up with a whole new unit. Of course, it was up to me to
> rewire the beast.
>
>>From the house is a romex cable with black, red, white and green 12
> AWG.
>
> The old fan was hooked up black to thermostat. White to White and
> green to box ground clip, with the red wire taped over inside the box.
>
> I hooked up new fan basically the same way, except I put a wirenut
> (scotch lock) on the red wire and wrapped it up with electrical tape.
>
> It has been fairly cool with outside temps hitting 70, so with the fan
> thermo at 90, it hasn't kicked on. I did spend about 5-10 minutes
> after the install with the thermo dialed down to 60 degrees, but the
> fan didn't kick-on then, but I had to dash, so dialed it back up to 90
> before departing the attic.
>
> Maybe I am being a bit paranoid, but I am thinking it's not
> working.....Would it be OK to bypass the thermostat -- that is just
> hook the hot black lead directly into the fan to see if it works. I'm
> pretty untalented in electrical works, but seems to me the thermostat
> is just a fancy on/off switch right?
>
> Or, am I just too anxious.....was my five minute trial at the 60-
> degree setting enough that it should have kicked on?
>
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Posted by on June 9, 2007, 11:34 am
OP here again:
Thanks for the replies:
1). As to the breaker, the roofers never touched them, they just took
out the old fan and fastened it to the rafters, never disconnected
power. When I did the rewire, I turned off all the breakers for the
house, except for the dryer, electric range and well pump, since I had
no idea which of the breakers controlled the fan. Then I flipped them
back on....of course, in the meantime, the responsible breaker could
have failed, but I hate to willy-nilly start replacing them, as I have
a "split buss" panel and there is NO main disconnect to the panel,
meaning "all hot, all the time."
2) According to the fan manual the roofers left me, the fan is 120.
3) Reacting to the "cheesy thermostat" idea, they did note in the GAF
install/owners manual for this new fan that the thermostat was only
"approximately" accurate....so I think I'll wait until the weather
warms, probably next week and see if it kicks on. If it does, fine.
If not, I guess I'll go pull it apart, try the direct connect and work
from that result (VOM, continuity tester, etal).
Only problem is I have an 1980's era analog VOM that I still don't
really understand how to operate.....
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Posted by dpb on June 9, 2007, 12:06 pm
timbirr@mailcity.com wrote:
> OP here again:
>
> Thanks for the replies:
>
> 1). As to the breaker, the roofers never touched them, they just took
> out the old fan and fastened it to the rafters, never disconnected
> power. When I did the rewire, I turned off all the breakers for the
> house, except for the dryer, electric range and well pump, since I had
> no idea which of the breakers controlled the fan. Then I flipped them
> back on....of course, in the meantime, the responsible breaker could
> have failed, but I hate to willy-nilly start replacing them, ...
Certainly no reason to replace any breaker, the only question was to
ensure you actually had power _to_ the thermostat...
> 2) According to the fan manual the roofers left me, the fan is 120.
As expected, but never hurts to be sure...
> 3) Reacting to the "cheesy thermostat" idea, they did note in the GAF
> install/owners manual for this new fan that the thermostat was only
> "approximately" accurate....
Yeah, but that's probably "only" 5F or so off of what the the numbers
stamped on the case indicate, not 30. If the temperature was 70-80 in
the attic and you turned it all the way down, I would certainly expect
the contacts to close. If it was way cool in the early morning, then
maybe...
...
> Only problem is I have an 1980's era analog VOM that I still don't
> really understand how to operate.....
Set it on the AC Voltage measurement and the range greater than 120V --
300V would be a typical choice. Simply measure the voltage across the
black and white wires to the thermostat. If there's 120V there, that's
step one. Turn the thermostat to lowest temperature setting and do same
measurement on the output to neutral. If voltage, all is well at that
point. If not, then you've isolated it to either a bad set of contacts
(or miswiring as remote chance) or the temperature isn't high enough.
Will, of course, have to do the above test at a temperature above the
minimum.
It's certainly no problem to connect the fan leads directly to the input
to the thermostat to make sure it does operate if you do have power to
the thermostat...
--
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