LAARS M4-Ext - Installation Manual - Manual (Page 32)

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Manual The Manual Mode should only be used when testing a boiler. Manual overrides the Prove input. For modulating boilers,
the exact percent of modulation for a boiler can be set with the Manual mode. Once selected, the unit will immediately
turn on and modulate to the selected percentage. For staging boilers, switching the Mode to Manual will turn on all of the
boiler stages. See "Boiler Status" on page 30.
Off Any output Boiler A through D not connected to a physical unit should be set to Off. The Off Mode can also be used to
disable units that are being serviced.
On The On Mode should only be used when testing a boiler. The On Mode overrides the PROVE input. Once set to On the
boiler will immediately start firing at its highest rate.
igNiTiON %
(Modulating Boilers only)
Adjustable from 1% to 50% Default: 1%
Button: STAGE/Ignition %
• The Ignition Point is the percent of modulation that must be attained before the unit can be
activated.
• For most modern power draft units, the Ignition Point should be set at 1%.
• Older units or atmospheric units may require the modulating fuel valve to be open from 20-
50% before proper ignition can be attained. Check with the boiler manufacturer if you are in
doubt about the minimum position of the fuel valve for ignition.
STAGE A
- IGNITION POINT -
1%
[ ]
BACK ▲ ▼ SAVE
MOdULATiON START %
(Modulating Boilers only)
Adjustable from 0% to 100% Default: 75%
Button: STAGE/Mod Start %
• The Modulation Start determines at what modulation percent the previous boiler (lead
boiler) should be for the lag boiler to be activated.
• For example, if the Modulation Start for Boiler B is set to 75%, then when Boiler A reaches
75% modulation plus Ignition% (75% + 1% = 76%), Boiler B (if Boiler B is in Auto Mode
and is not already on) will be brought on at the Ignition % level.
STAGE A
MODULATION START
75%
[ ]
BACK ▲ ▼ SAVE
• When modulation is decreasing, the lag unit will remain on at the Ignition % modulation until the previous boiler reaches 40% of
lag boiler's Modulation Start, or 2% above the Ignition Point, whichever is higher.
• Using the same example, as the load decreases, Boiler B would modulate down to its Ignition %. Boiler A would then modulate
down to 30%. Only then would Boiler B turn off.
• If the Lag Delay is set to anything other than 0, a boiler must always go up to 100% modulation before the next boiler is activated.
However, the Modulation Start % should still be set correctly, because it will be valid when modulation is decreasing.
• Laars suggests that when Parallel is selected as the Modulation Mode to set the Modulation percent equal to or slightly higher than
double the Ignition %. See "Modulating Mode" on page 18. This way, the lag boiler will only start if the load is large enough for
two boilers to run at the lowest modulation.
COPY SETTiNgS - BOiLER A ONLY
(Modulating Boilers only)
Button: STAGE/Copy Settings
• If all the active boilers will have the same Ignition Start Point and Modulation Point, they
can be set for Boiler A and then copied to the other modulating boilers.
• It is still required to select the Mode for all other boilers as the Mode is NOT copied.
ALERT
The Mode MUST be set for each boiler. The Copy Settings command will not set the
Mode for the remaining boilers. Only Ignition % and Modulation Start % are copied.
-- COPY SETTINGS --
From Stage A to
all other stages
BACK COPY
LAARS Heating Systems
HT# 059104-00 B