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Vitodens 200-W B2HB 45, 57 Installation
Connecting a 24 VAC Thermostat
1. Connect normally open dry contact of the switching
relay ('T-T' contact) to terminal DE1, DE2 or DE3
of the EA1 module located in the boiler electrical
junction box.
2. Connect switching relay to thermostat and power
supply as per manufacturers instructions.
When the thermostat contact is closed, burner
operation is load-dependent. The supply water is
heated to the value set in the coding address "9b" in
the "General" group of the boiler.
The supply water temperature is limited by this set
value and the electronic supply temperature maximum
limit.
Codes
Extension EA1
Set "3A", "3B" or "3C" in the "General"
group to 2.
Note: 'Live' contacts lead to short circuits or phase
failure. The external connection must be potential-
free.
Note: When only using a thermostat (field supplied) for
room temperature control, the boiler standard and
reduced room temperature set points may be set to
37º F (3º C) to reduce boiler cycling.
Legend
A Boiler electrical junction box
B Switch relay (ie Taco SR501, Honeywell
RA889A-1001, field supplied)
C 24VAC room thermostat (field supplied)
D Internal EA1 module
E 120VAC power supply for switching relay (refer to
manufacturers instructions)
F Dry contact connection from switching relay (to boiler
'T-T')
Control Connections
51
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