[Robert Gift]

A fan pulls air into the house beneath the structural wood floor to keep the space dry.
Can a thermostat operate this fan directly from the thermostat's contacts, or must I place another switching circuit, operated by the thermostat, which switches the power to the fan on and off?

Thank you,

Robert

[tkrussell]

A line voltage thermostat is usually rated 22 amps, so you can use one stat to operate this fan directly.

How do you plan to use a thermostat? Do you want fan on when temperature rises or falls?

I would think that a humidistat would work better, as moisture rises, stat would close and turn fan on.

[Stratmando]

If you mean a 24 Volt thermostat, you may need a contactor, not sure their capacity for current.

[Robert Gift]

Thank you.

I want to warm our cold basement by pulling the cold air out which would pull warmer air inside.

120 Volt fan.
It is the amperage of a contact which matters more than voltage.

We happen to have a thermostat with mercury globule in glass tube which bridges two conductors. What kind of amperage that would allow?

Is that the same way a 15-amp mercury "silent" switch works?
I never see such switches any more. Banned due to mercury contamination if a fire?

[KISS]

Voltage, current, AC/DC, HP ALL matter.

Voltage: Contacts can arc
DC vs AC: Arc supression is done in some AC contactors
Current: Contacts get hot and melt
HP: Is a different animal where starting current can be larger than running current hence the peak current the switch can handle is more.

[tkrussell]

First you stated you wanted to remove moisture, now you want to heat the space.

Please provide ALL detail when asking a question.

Drawing warm air into a cold space can create more condensation to accumulate, and defeat the purpose of what your trying to do, whatever that is. So think about what your trying to accomplish.

This statement you made is incorrect:

It is the amperage of a contact which matters more than voltage.

Anything that handles electricity will be rated to handle a certain amount of amps and voltage.


The stat you have with a mercury bubble sounds like a low voltage unit, and not be able to handle 120 volts. You need to confirm the voltage rating of any stat you plan to use.

Second, stats using mercury are not allowed to be used any longer.

So, what do you really want to get done here?

[Robert Gift]

I want to do both.
Pull warm dry air into the space between the structural wood floor and barearth, and use another fan to pull cold air out of the basement which is replaced with warm dry air from outside.

Wish I could find a mercury light switch to see if there is a difference between the hermetically sealed ampules. This one mercury thermostat has a lot of mercury in two glass vials. Maybe it has four vials.

Thank you.

[ceilingfanrepair]

They make gable fans with built in thermostats. I use one to cool an attic storage space. Works great, around $50 at Home Depot.

[tkrussell]

Yea CFR, but those would be close on temp rise stat, and Robert, if I am reading him correctly, will need a open on temp rise stat.

[Robert Gift]

Thanks, CFR and TK.

Best to have fans ON when outside temperatureaches 70F.
The warm dry air is pulled into the basement both above and below the floor.

With thermostats I could experiment with what is most efficient.
Often I am too cold when in the unfinished basement but air outside is warm and dry.
A "humistat"(?) turns on the underfloor fan if the humidity gets high enough. But I have never seen the fan operate. When set to low humidity, the fan does turn on.

[Missouri Bound]

There are line voltage thermostats that can handle the switching for you. Specifically made for greenhouse cooling operations, then will turn on the load as temperature rises. You may want to consider a humidistat as well to prevent humid air from being introduced.

[Robert Gift]

There are line voltage thermostats that can handle the switching for you. Specifically made for greenhouse cooling operations, then will turn on the load as temperature rises. You may want to consider a humidistat as well to prevent humid air from being introduced.

Thanks MB.
I'll go look.