is there an easy way to setup a timer control for an attic mounted fan?
the only way I can think of is to install an Instamatic type (home depot sells
metal cased timer and wire the electric to the Instamatic which similarly like a
pump timer would then turn the fan on/off
the problem with this is that every time there is a power outage I would have to
roof to remove the attic fan covers to reset the time which is a major job
could a timer be wired to the breaker panel or another way?
Maybe a photo switch near a vent would work out.
Even in Winter, ventilating an uninsulated roof is good.
Moisture can condense into frost on the wood at night, and
melts when the roof warms. This might lead to some mold
in a poorly ventilated attic.
So a photo switch might help in Winter and Summer.
You lose some "good" air in the Winter, but with proper
floor insulation and vapor barrier, not a problem.
And for long Summer days, it would run longer than for
short Winter days. The switch needs a good relay,
since a starting fan needs more current than a light.
How about putting the timer in a more accessible place? Does the fan have
its own dedicated line to the breaker box. If so...ba da bing. Problem
solved. The Intermatic timers are grey, like breaker boxes. They'll be so
I believe that some of the newer timers have battery back up. (Digital
programmable and fits in a standard single switch box.)
I am not sure however that these timers will fair well in the extreme
temperatures in the attic.
I would just put a box near the attic access high on the wall or even
mounted up into the ceiling and rewire he fan to that.
A timer could be put near the breaker box if your fan has a dedicated feed.
The timer could also be put near the last box before the fan if by luck that
is in a convenient location. In the garage wall outlet or door opener box
In my case there are times in spring and fall where it is warm enough for
the attic fan to come on for a period of time during the day, but cold
enough to require the furnace to come on at night. In these times I don't
want the attic fan to come on at all and resetting the thermostat is a big
pain. So I installed a switch in the attic near the access door where I can
easily just turn the whole thing off. I am thinking of even moving the
switch to the ceiling where I can turn the fan on/off without opening the
access door. I do not see a need to install a timer as the OP wanted.
Absolutely. The instructions that came with my roof fan suggested
this. I ran some 14-3 Romex from the thermostat, I think it was, down
one of the trusses, though the top of the hall wall. It's easy to see
walls below when you're in an attic. The top plates are visible. They
are the wood parts that go where your walls go, as opposed to the
sheetrock you see up there, which are the ceilings downstairs.
I ran it to the a nice place in the hall, near my bedroom door, and
used a single gang old-work box mounted sideways, to hold a double
toggle switch. One turns it off when the thermostat would turn it on,
and the other turns it on when it would be off. The instructions
suggested the second one to turn it on when there is a lot of humidity
in the attic. I don't take steamy showers to I never have this
(afaik), but I put it there anyhow for the next guy. It was only
anotehr 2 dollars and 10 minutes time.
The normal setting for the two switches is one off and one on, but I
could never keep track which should be on, so I put them in the normal
position and used an indelible marker to make a black line on each, so
the two lines are in line, when the switches are in the normal state.
And I turn the fan off the same times you do, late fall and early
spring, so I can use the sun to heat the attic and the attic to heat
the house. It's about another 2 weeks to a month at both ends that I
don't have to run the furnace. (although if I add more insulation to
the attic floor, I may lose this heat. Not sure these days.)
I was thinking the same thing as Joe. Does the attic fan the OP
refers to mean a whole house fan, in the floor of the attic, or a roof
fan as I call them to avoid ambiguity?
The solution is a dymo label on each direction the
switch moves. My roof fan was in when I bought it
so I just added a third line (2nd hot) that by
passed the thermostat and put a double switch box
in the ceiling of the garage(course I use a stick
to move the switches). One switch is labeled
"Power" and "off" on one side and "on" on the
other, the second reads "fan" and "on" on one side
and "auto" on the other. That gives you full control.
the fans are literally cut out of the roof and have a sensor for both humidity
temperature. they are embedded into a barrel tile roof.
the reason I wanted a timer was to allow them only to run on the hottest part of
day (perhaps 3-4 hr max) as they literally make my heat pump system work harder
increasing humidity inside the house.
another option I like is the on/off switch which I can easily attach next to the
breaker but of course that requires me to manually remember to do this every
someone else suggested ripping them out and replacing them with a lower CFM
motors which have only a temperature control (no humidity sensor) and this would
them run strictly based on some high temp number (ie. 110F) and at a lower speed.
How does the roof fan increase the humidity in your house. Does the
air in your attic even come in contact with the air in your house?
I didn't see this last suggestion, but it sounds terrible. If you
want to get rid of the humidity sensor**, just disconnect one wire.
The humidity sensor is iiuc set pretty high so that the fan runs only
when there is very high humidity in the attic, such as from hot steamy
baths or doing the laundry and for some bad reason venting the dryer
to the attic. Humidity in Baltimore is sometimes 60% and I don't
think sensors are set to turn on just because of that. After all, the
humidity is everywhere when it's caused by the weather, and it's just
as bad outside the house as it is in the attic. Too high humidity
does some sort of damage to the attic.
They are controlled bey thermostat as have said.
One solution, also said, was to put a switch on it. Even drop the switch
in the closet by the access if that's where the access is.
The thermostat has an adjustment on it. The MasterFlow
(http://www.gaf.com/Content/Documents/20453.pdf ) goes from 60 to 120. The
recommended year round setting is 105. An option is to go up and adjust
the easily accessable screw setting twice a year. 10 second job once
you're up there. One week job to restore ceiling after stepping off truss
I would vote X-10 also. I just did an install at my church using this
e-bay store and they were original "X-10" equipment and fast shipping.
(I am in no way related to these guys) I did several days of price
checking and for what I was looking for they had the most reasonable.
The X-10 advantage is you can get a controller for many other items in
your house too. I did our set up with an RF remote so I can control
the lights from anywhere as I tend to wander some....
Sensible people wire the timer and/or switch in place such that it is
inside the house. The fan being in the attic does not mean the controls
for it need to be, or should be, in the attic. It's just electricity,
and wires move that to the place that is convenient.
The setup on ours is a low/off/high switch for the fan, plus a countdown
timer (up to 12 hours), so the thing is run only when the occupants feel
a need for it. If not going that route, it would probably be a good idea
to include some sort of thermostat to run your fan only when the attic
is hotter than the outside air, rather than wasting power ventilating it
when it's cooled off. In that case, a timer would not be needed.
This whole thread makes little sense to me. Zoe claims to have an
attic fan that she wants to run on a timer. That's because otherwise
it creates too much humiditiy in the house with the heat pump system
How is that possible? An attic fan would be moving air within the
attic and should have virtually no effect on humidity inside the house.
And if it is a whole house fan, as Joeseph suggested, then it
wouldn't be running when the heat punmp/AC is running.
If it is a std attic ventilation fan we are talking about, a timer
makes no sense. They come with a thermostat that can be adjusted to
come on at an adjustable temp. That is exactly the control you want,
as it is what you are seeking to control. With a timer, it would be
coming on during days when it's cool, cloudy or raining and not
needed. Thermostat controlled operation covers 95% of applications.
If for some reason you have an issue with humidity, there are
humidistat controls available that will turn on the fan when the
humidity rises above a set point. However, if the house is properly
built with a vapor barrier, etc, few homes or environments should need
this. After all, homes have survived fine for 100's of years with no
powered ventilation at all.
Jim Baber replies:
minutes) with a wholehouse fan and standard HVAC central system did
cause my house to cool faster than either the HVAC or the wholehouse fan
alone. I suspect quicker cool down occurred because the wholehouse fan
since it is in the ceiling pulls the hotter air (rises to the top) from
the house before it has time to mix with the cool air introduced by the
HVAC system. The air from the HVAC source tends to sink below the
wholehouse fans physical intake flow because it is cooler than the air
nearer the fan in the ceiling. There is some initial mixing and it is
increases the longer both run because of the properties of all gases.
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