HMH

HMH / HPH
HMH / HPH
HMH / HPH
Humidistat, 1 step and 2 step or proportional
For duct or wall mounting
• 1 or 2 steps
• Changeover contact 250 V AC 10 A
• Proportional output 148 or 1000 Ohms
HMH / HPH is a series of electro-mechanical humidistats
for controlling humidifying and/or dehumidifying in
HVAC systems.
• High degree of accuracy and reliability
• For duct or wall mounting
• Form of protection IP54
Construction
The humidistat has human hair as the sensor medium.
The hair stretches as the humidity increases and
shrinks as the humidity decreases.These changes are
transmitted to a micro switch (two switches) or, in the
case of the HPH, to a pin on a potentiometer.
The setpoint switch affects the position of the
micro-switches in relation to the hair element. The
setpoint can be set at between 10 and 100% RH.
This tried and tested construction with few movable parts
gives a high degree of reliability and accuracy.
As the contacts are of the changeover type the humidistat
can control both humidification and dehumidifcation.
2 step humidistat
This has two microswitches. The step differential between
them can be set by means of the adjustment screw.
As the contacts are of the changeover type the humidistat
can control both humidification and dehumidification.
Proportional humidistat
HPH148 and HPH1000 are humidistats with
proportional resistance output.
Depending on the setpoint chosen and the current
humidity these give output signals of 0 to 148 Ohms and
Mounting
HMH/HMH2/HPH can be mounted in a ventilation duct
or on a wall. The humidistat is supplied with a flange
which is suitable for both positions.
Calibration
The humidistats are calibrated at the factory before
delivery to the customer, but should be precision calibra-
ted after installation to ensure the best results. After that
annual checks and re-calibration are recommended.
Maintenance
The hair element should be dusted off with a soft brush
once a year.
Do not rinse the hair element in water as this changes the
calibration point.
For further information concerning maintenance see the
instructions which are supplied on delivery.
Typical applications
Can be used to control a humidifier or a dehumidifier or
for on/off controlling of a fan. Can also be used to alarm
when the humidity exceeds or falls below a pre-set level.
revision
08 2003