I have a heat pump with electric heat backup elements in my blower
unit. There are 3 elements in this 15KW unit. Each one has a
sequencer relay. Can sometime describe the function of the sequencer
relays and also the Limit Switches? I believe the sequencer are for
staging the elements so they don't all turn on at the same time but
I'm wondering exactly how it does that.
Also, if my thermostat has only one W output connect to the unit, will
all the elements turn on or will they be staged based on the
temperature conditions at the time?
Typically the sequencers have a bimettalic spring actuated switch that is
heated by your 24V thermostat voltage, unlike a magnetic relay there is an
inherent delay due to the time it takes to heat the bimetal portion--in
practical usage you will find these available having various delay
times...generally from 1/2 up to 2 minutes
The limit switches are for fire prevention due to overheating of the heating
elements from of loss of airflow or from some other cause.
Depends on the sequencers delay spec and the control / HV wiring--for
instance consider the case of 3 each 5 kw strips for a total of 15kw..here,
"staging" can be done by using sequencers all having different delay times
or it can be done by using 3 ea 2pole sequencers all having the same delay
rate, here one pole actuates a 220v heater element with the other pole of
the same sequencer passing 24v onto the next sequencer in your "cascade"..
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