LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 21)

11
Service Manual - NeoTherm 500
Quick Check of Components in the Safety Chain
This procedure gives you a quick way of checking the safety switches
and some of the control functions in the unit. This will allow you to rule
out some large sections of the control system, and find the part of the
system that actually has the problem.
DANGER! - When the cover is opened, some of the areas carrying 120V
AC voltage will not be covered. Do not perform the following tests unless
you have been trained how to do this safely by Laars.
FIELD INTER-
LOCK
REMOTE ANALOG
INPUT
OUTDOOR TEMP
SENSOR
BOILER
PUMP
SYSTEM
PUMP
DHW
PUMP
H2309800E
ATTACH GROUND WIRE HERE
ATTACHEZ
LE FIL DE TERRE LCI
1. Remove the front panel assembly and front bezel.
2. Before you start troubleshooting, you should
disconnect some parts of the system to make
the troubleshooting simpler. If a sensor for the
Outdoor Reset function is connected, disconnect
it at terminals 1 and 2 on TB-7 on the control
board. See Fig. B1-1. (Remember to re-connect
the sensor when you are done.)
If the unit operates with the Outdoor Reset sen-
sor disconnected, go to Section B33 - “Trouble-
shooting the Outdoor Reset System.”
3. Turn off the Anti Short Cycle function by setting it
to the minimum value.
4. If you are working with a boiler which can pro-
duce both hydronic heat and domestic hot water,
work with just one function at a time. This will
make it clear whether the “call for heat” is coming
from the hydronic side of the system or the DHW
side.
5. Insert a jumper across terminals 5 and 6 on TB-7
on the control board. See Fig. B1-2. This will
create a permanent “call for heat” signal. (Again,
remember to remove this when you are through.)
Fig. B1-1 - Terminals for outdoor reset
TB7 1-2
FIELD INTER-
LOCK
REMOTE ANALOG
INPUT
OUTDOOR TEMP
SENSOR
BOILER PUMP
SYSTEM
PUMP
DHW
PUMP
H2309800E
ATTACH GROUND WIRE HERE
ATTACHEZ
LE FIL DE TERRE LCI
Fig. B1-2 - Simulating a “call for heat” input
TB7 5-6
B1