Section b - troubleshooting procedures, Quick check of components in the, Safety interlock chain – LAARS NeoTherm NTV (Sizes 150–285 MBTU/h) - Service Manual User Manual
Page 21: See “quick check of components, In the safety chain and, Firing sequence” - section b1, Fig. b1-2 - simulating a “call for heat” input, Tb7 1-2, Tb7 5-6
11
Service Manual NeoTherm 80 - NeoTherm 285
Quick Check of Components in the Safety Interlock 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 B29 - “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