Viessmann EM-EA1 Extension Installation And Service Instructions Manual page 10

Connections
Connecting External Functions
Legend
A Signal for external demand or external blocking
B Junction box
10
(continued)
Connecting the operating mode changeover: DI1 to DI3
Continuous operation or room temperature dependent
operation
As soon as the contact closes, the following demands
become active:
Set supply temperature demand for the system
Demand for all installed heating circuits simultaneously,
at the respective programmed temperature level of the
individual heating circuit:
DI1 Reduced supply temperature
DI2 Standard supply temperature
DI3 Comfort supply temperature
(Only with continuous operation)
External contacts at DI1, DI2 and DI3 must be
potential-free.
Weather-compensated operation
As soon as the contact closes, the following demand
becomes active:
Demand for all installed heating circuits simultaneously,
with the respective programmed set room temperature
of the individual heating circuit:
DI1 Reduced room temperature
DI2 Standard room temperature
DI3 Comfort temperature
Connecting external demand: fD
The demand is active if 120V voltage is present at digital
input 43-1. A demand is issued to the boiler.
The set values for the supply temperature and the speed
of the primary pump are specified with parameters
528.0 and 1100.2.
Connecting external blocking: fD
If 120V voltage is present at digital input 43-1, the
boiler is blocked. The message I.57 is shown.
EM-EA1 Extension Installation / Service