Electrical Heaters

Hello

Humidistats have been around for many years, and they control a circuit just as a thermostat, but the sensor in the humidistat is sensing Relative Humidity, not temperature.

Years ago the humidistat was electro-mechanical, but these days almost all are electronic.

You do not give a line diagram of the HVAC air ducting.

Have a look here - disregard the Japanese language at the early part of the .PDF document: http://www.wipo.int/pctdb/en/wo.jsp?wo=1982002598&IA=JP1982000010&DISPLAY=DOCS

Click on "View" or "Download" re the " (WO/1982/002598) CONTROL CIRCUIT FOR A HUMIDITY SENSOR"

Also refer: http://en.wikipedia.org/wiki/Air_conditioning#Humidity_control

Advise if that is useful, with

Kind Regards....

Generally when you find a humidistat connected to a control system involving electric strip heaters the air-conditioning controls and the strip heat controls are linked together. Air conditioning is used to reduce the relative humidity inside a controlled environment, the strip heaters are then energize if necessary to maintain a preset temperature. At least this is the only reason I can see to have a humidistat involved in controlling electric heat. You might want to do some additional investigating you may well have a relay panel hidden somewhere.

Of course there's always the other possibility, the unit was installed or replaced by a technician that didn't know the difference between a thermostat, and a humidistat.

Or the difference between an oral, and a rectal thermometer.

The humidistat will try to control the humidity by adding heat to the space. This in turn will raise the temperature, bring on the cooling and the cold surfaces of the aircon will strip moisture out of the air stream. When the humidistat senses the humidity is low enough the heater will turn off and the control of space temperature will revert back to the thermostat. You have what could be called an energy hungry beast here.

Pete oz