Laars sequencing controls document 4200 line neut output 8 output 9 output 7 output 10 output 11 output 12 increment auto off lead stage rotation select setting up down inputs 1 2 3 4 5 6 7 8 9 10 safety ground must be connected 11 12 sensor com shield + sensor com dry contact only dry contact only ...
Page 2 laars heating systems contents sc function chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 dip switch chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....
Page 3 laars sequencing controls sc function chart line neut output 8 output 9 output 7 output 10 output 11 output 12 increment auto off lead stage rotation select setting up down inputs 1 2 3 4 5 6 7 8 9 10 safety ground must be connected 11 12 sensor com shield + sensor com dry contact only dry co...
Page 4 laars heating systems dip switch chart 1 2 3 4 5 6 7 8 on switch 1 system output switch 5 rotation switches 6 and 7 input type 5 first on/last off lead stage rotates every 24 hours 5 first on/first off first stage on is the first stage turned off temperature 6 7 external set point available f...
Page 5 laars sequencing controls installation mounting the sc • select a location near the equipment to be controlled. • the surface should be fl at, and be suffi ciently wide and strong to hold the sc. • keep the control away from extreme heat or cold. Ambient operating temperature is from 20 to 120°...
Page 6 laars heating systems external set point - terminals 4, 5, and 6 • the sc can accept a 4-20ma signal from an energy management system (ems) or other signal source to change the set point remotely (see pg. 23). • dip switch 6 and 8 must be off and dip switch 7 must be off off on. These setting...
Page 7 laars sequencing controls wiring the stage outputs • for sc-6 and sc-12 see pg. 14. • for sc-6p see pg. 15. Wiring the system output combustion air damper • to select the combustion air damper mode of operation, dip switch 1 must be off. • wire the air damper to system relay terminals marked ...
Page 8 laars heating systems power up sequences • whenever the sc is powered up, it displays the software version number and then the operating parameters. Each display will remain on the screen approximately 5 seconds. If the parameters are correct, there is no need to make any adjustments. • once ...
Page 9 laars sequencing controls • the minimum water temperature can be adjusted from 110°f to 180°f. • to change the minimum water temperature, hold down the center button while pushing either the up button to increase the up up value, or the down button to decrease the value. Down down • when the ...
Page 10 laars heating systems adjusting the control setting • after the power up routine is complete, the display will show the system water temperature. • to display the other control settings, repeatedly press the center select setting button. • a setting can only be adjusted when it is being disp...
Page 11 laars sequencing controls set point control with oss sequencing dip switch 8 - off press select button display press and hold either the up or down button to adjust once set point the set point is the temperature which the sc will sequence stages to hold. Note that if you are using the exter...
Page 12 laars heating systems outdoor reset with normal sequencing dip switch 6 and 7 - off and 8 - on press select button display press and hold either the up or down button to adjust once♦ calculated this is the water temperature the sc will stage outputs to hold. It is based on outdoor temperatur...
Page 13 laars sequencing controls outdoor reset with oss sequencing dip switch 6 and 7 - off and 8 - on press select button display press and hold either the up or down button to adjust once♦ calculated this is the water temperature the sc will stage outputs to hold. It is based on outdoor temperatu...
Page 14 laars heating systems ♦ additional output relays can be ordered separately (ca002300). Each active stage output must have a relay. Warning this laars heating systems control is strictly an operating control; it should never be used as a primary limit or safety control. All equipment must hav...
Page 15 laars sequencing controls sc-6p output wiring installing the output relays ♦ • each output which is to be used must have a relay installed in the socket. Output output • each boiler has an individual pump associated with it. • the sc-6p also has a system relay which can be used for main or s...
Page 16 laars heating systems b oi le r3 b oi le r2 b oi le r1 o ut pu t1 o ut pu t2 o ut pu t3 o ut do or s en so r s ys te m te m pe ra tu re s en so r s ys te m p um p d h w d ry c on ta ct (o pt io na l) s c la ar s c on ne ct in g th e sc c on tr ol to th re e pu m p- m ou nt ed b oi le rs (o r...
Page 17 laars sequencing controls output relay charts 6 stage sequencer - sc 6 2 3 4 5 6 1 2 3 1 2 1 on/off on/off on/off on/off on/off lo/hi lo/hi lo/hi 3 stages 3 stages 4 stages output 1 limit limit limit limit limit limit limit limit limit limit limit output 2 limit limit limit limit limit hifir...
Page 18 laars heating systems operation set point control settings set point ( sp ) default: 70°f • the set point is the temperature value the sc will use to control the system. • the sc will either add stage outputs, subtract stage outputs, or maintain the same number of stage outputs to hold the s...
Page 19 laars sequencing controls outdoor reset settings calculated (cal) • this is the water temperature the sc will stage units to hold. It is based on outdoor temperature, the reset ratio, the offset, the setback/shutdown values (see pg. 24 and the dhw input (see pg. 25). • the calculated water t...
Page 20 laars heating systems offset (ofs) default: 0°f • the offset value moves the starting point of the reset ratio curves (see charts on the right). • therefore, any change made to the offset will immediately change the value of the calculated water temperature by the same amount. • for example,...
Page 21 laars sequencing controls purge time (pt) default: 0 minutes • many units must go through a purge cycle before they are brought on line and can begin generating heating or cooling. • the purge time should be set to the length of time of the unit’s purge cycle. • the purge time applies to eve...
Page 22 laars heating systems system output settings system delay (sd) default: 0 minutes sc-6 or sc-12 • in combustion air damper mode (dip switch 1 = off) when the last stage output relay is turned off, the system output relay will remain energized for a period set by the system delay. • in system...
Page 23 laars sequencing controls first on/first off rotation • for this type of rotation, dip switch 5 must be in the on position. On on • on power up, or any time the sc loses power, the lead stage will be the fi rst possible stage (as described above). • the lead stage will always be the fi rst sta...
Page 24 laars heating systems shutdown • this feature allows the user to shutdown all stage outputs on the sc from a remote location. • a typical use of this feature would be to turn off all boiler stages when the outdoor temperature rises above a certain point. The outdoor thermostat would close a ...
Page 25 laars sequencing controls dhw call • when the dhw terminals are closed, the sc set point immediately changes to 200°f. This will happen regardless of outdoor dhw dhw temperature, the status of the setback/shutdown inputs, or the external set point (if that function is being used). • typicall...
Page 26 laars heating systems troubleshooting no display, or display of 888 check the 120vac power input to the sc. Turn power to the sc off and back on. Temperature inputs display shows opn first check the dip switch (see pg. 4 ) to be sure the sc is confi gured to read a temperature input. If the d...
Page 27 laars sequencing controls there are more than one green lead stage lights on check the 120vac power input to the sc. Turn power to the sc off and back on. If only one lead stage led does not light, the unit may be damaged. Lead stage does not rotate when switch to increment only units which ...
800.900.9276 • fax 800.559.1583 (customer service, service advisors) 20 industrial way, rochester, nh 03867 • 603.335.6300 • fax 603.335.3355 1869 sismet road, mississauga, ontario, canada l4w 1w8 • 905.238.0100 • fax 905.366.0130 www.Laars.Com litho in u.S.A. © laars heating systems 0806 document 4...
