10 vari-prime, Laars heating systems, Page 58 – LAARS MagnaTherm MGV - Installation, Operation and Maintenance Instructions User Manual

Page 62: Figure 30. vari-prime digital circuit board

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LAARS Heating Systems

Page 58

9.10 Vari-Prime

Vari-Prime is a variable pump control that is
standard equipment on all MGH boilers. Pump speed
is controlled to maintain a user-chosen temperature
rise between the inlet and outlet of the MagnaTherm.

General PCB Operation

1. The desired Delta T can be set to any of the
following values by moving or adding jumpers to the
JP2 terminal on the control: See Figure 30

-15 deg F/8 deg C

-20 deg F/10 deg C

-25 deg F/13 deg C

-30 deg F/ 16 deg C

By adding a second jumper, one on “15 deg F” and
one on “20 deg F”, it is possible to achieve 35 deg F
/19 deg C.

By adding a second jumper, one on “15 deg F” and
one on “25 deg F”, it is possible to achieve 40 deg
F/22 deg C.

2.

As shipped, the Vari-Prime has a jumper on

the JP4 terminal, to operate a 0-10 VDC output. If a
4-20 mA output is needed, move the jumper to the
JP5 terminal. Figure 30

3.

Vari-Prime can operate in

°F or °C. A jumper

on the JP1 terminal allows the user to choose the
temperature scale.

4

If Main Gas valve is “OFF” AND a call for heat

is “TRUE” then the PCB overrides the PID control
and runs the pump output at 100% (10 VDC, or 20
mA).

5.

Once the Main Gas valve is energized the PCB

will maintain pump output at 100% for 60 seconds
to allow the system to stabilize. Once the 60 second
timer has expired, the PCB will then run the pump
output speed based on the jumper setpoint. .
6. When “T-T” is satisfied, the PCB will run pump
at 100% output for the duration of the pump overrun
time.

7.

A jumper on the “JP1” terminal on the Vari-

Prime PCB will allow the Vari-Prime to operate
in degrees Fahrenheit or Celsius. (Factory set for
Fahrenheit).

8.

The Vari-Prime PCB has a low end cap to

prevent nuisance low flow trips. The cap is factory
programmed to 2 VDC.

9.

Factory settings are:

-Degrees - Fahrenheit

-Output Signal- 0 -10VDC

-Delta T setpoint - 30

°F/17 °C

2

6

4-20MA(-)

4-20MA(+)

0-10VDC(+)

0-10VDC(-)

N/C

COM

N/O

TB2

TB5

TB4

TB1

TB6

PCB

DIGITIZED

P/N E2345200

LED1

1

2

3

4

1

2

3

4

1

2

3

4

TB3

JP1

7&8 = F

1&2 = SPARE JUMPER

JP2

1&2 = 15 DEG F / 8 DEG C

3&4 = 20 DEG F / 10 DEG C

5&6 = 25 DEG F / 13 DEG C

7&8 = 30 DEG F / 16 DEG C

JP5

JP4

JP3

1

2

3

4

1

2

3

2

4

6

8

1

3

5

7

1

3

5

7

2

4

6

8

+24V

-24V

10K

INLET

SENSOR

10K

OUTLET

SENSOR

NOTE(S)
1.PURCHASED FROM DIGITIZED COMM. INC.

SERIAL NO. DC1002713

FIRMWARE SETTINGS

P = 20
I = 10
D = 0
ANTI RESET WINDUP = 600
CONTROL ERROR = 70

1

2

DWG NO.

E23452

SH

1

REV

A

AL 1-10-14

REVISIONS

REV.

CHANGE:

APPR

ENGR APPR

ECN

DRAFT

CHECK

UPDATED DRAWING PER SKETCH FROM LAB

A

14-002N-08

SM 1-10-14

SCALE: NONE

INTENDED SIZE:

SOFTWARE DWG. NO:

C

SHEET 1 OF 1

REV.

APPROVALS

DRAFT

ENGR

APPR

UNLESS OTHERWISE SPECIFIED:

DO NOT SCALE DRAWING.

THIRD ANGLE PROJECTION.

DIMENSIONS ARE IN INCHES.

TOLERANCES ARE:

MATERIAL:

FINISH

CJT 12/2/11

S

DECIMALS .X .1

DECIMALS .XX .03

DECIMALS .XXX .010

ANGLES 1

TITLE:

FRACTIONS 1/8"

DIGITIZED PRINTED CIRCUIT

BOARD

E23452

A

Figure 30. Vari-Prime Digital Circuit Board

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