User Defined Parameters:
On the upper right hand corner of the board is a jumper wire with a number of posts to land the wire on. This area is labeled " Last Output Used". The number on the jumper will be set to equal the number of solenoid valves. For example: A 6 position timer board such as the NCC DNC-T2006-A10, combined with a square 25 bag filter that has 5 solenoids and 5 diaphragm valves would have the last output used jumper set on the number 5 pin.
Just left of center are the off (interval) and on (duration) potentiometers. The initial adjustment for fabric bag collectors is based on the following rules:
On Time
3/4" Valve ) Initial duration of 120 milliseconds (.12 on the dial)
1"" Valve ) Initial duration of 90 milliseconds (.09 on the dial)
1-1/2" Valve ) Initial duration of 60 milliseconds (.06 on the dial)
This is the starting point, and may be increased until a strong pulse firing sound is emitted from every row. These values assume 90 to 100 PSI of clean dry supply air. These values are not applicable to cartridge collectors.
Off Time
This setting is adjusted to clean through all of the bags in 3 minutes max. The initial setting for a 25 bag filter can be calculated by dividing 180 seconds(3min.) by 5, for a resulting interval of 36 seconds.
Mounting
Depending on the timer board size, and the enclosure it is to be mounted in, some timer boards must be mounted to a back plate that mounts to the back wall of the electrical enclosure, while some can be directly mounted to the enclosure. IAC enclosures are normally NEMA 4, even if the application only requires NEMA 12. If the solenoids are to be mounted in the same enclosure, they are normally installed prior to the timer board. Be aware that the solenoid penetrations and any bulkhead fittings that penetrate the electrical enclosure must carry the same or better rating than the enclosure in order maintain the enclosure rating.
Wiring:
Pressure Switch Input
Refer to the IAC publication "BENEFITS AND METHODS OF ON DEMAND FILTER CLEANING" for details regarding component selection and uses for the "pressure switch input". The function of this input is to interrupt the cleaning cycle when the input is electrically open.
This input is shipped with a jumper installed that causes the board to continuously time when power is applied (L1 terminal) to the board. This also causes the board to start timing on row #1 every time power is removed and re-applied.
Removing the jumper to install an external pressure switch system, or external source control such as a PLC, will cause the board to behave differently, and requires that power to L1 remains applied at any time the filter fan is running. When the switch is initially closed, the board will begin to time, and continue to do so until the switch is opened. The running board will simply pause the sequence until the input is closed once more, causing the solenoid valve number after the last one fired to fire.. This means that if a 16 valve collector started a demand cleaning on valve 1 (example at 4.5" w.c), and cleaned down to the low (or stop) set point (example 3" w.c.) by the time it reached valve 7, the input would be open now. The next time the input closes, the sequence would resume starting with valve 8.
Please be aware that there is a clever wiring method that will enable the use multiple timer board in succession to act as one larger board.
Solenoid Outputs
One lead from each solenoid should be wired common together, and landed on the solenoid common terminal. Please note that this is not the same as the L2 terminal on the board. Also note that the gauge of this wire need only be sized to fire one solenoid at a time in most cases.
The solenoid outputs are numbered 1 through the maximum number of the board (typically 3, 6, 10, 20, and 32 position boards are available). The remaining wire on each solenoid should be connected to the solenoid valve output number that determines it's firing order. The number 1 row of bags does not have to be the first row to fire. Some schools of thought believe it is better to work out from the center, or in a totally random pattern.
Voltage Inputs
Typically in the USA we will use 120 VAC boards, and apply 110-120 Volts AC to the L1 terminal and land the Neutral wire to the L2 terminal. The field electrician will ground the enclosure that houses the timer.
Our stock boards are in the DNC family, standard board, 6 to 32 position, 1.5-30 sec. "OFF TIME", and 120 VAC. Although we always check the voltage requirement, 220 VAC is more common overseas.
Only on rare occasion, or on very small units, such as 3 row units, will the off time need to be longer than 30 sec.
The number of solenoid outputs should be greater than or equal to the number of cleaning rows in the collector. There will be situations where a 12 row collector is being controlled with a 10 position timer. This requires two rows to be doubled up on the board. When this must be done it is best to space out the doubling. This is not an IAC recommended practice.
Alternatives:
DNC-T21 series feature an extended cycle (additional timer and adjustment) in the module that can be used as an offline cleaning enhancement.
DNC-T23 series add intelligence in the form of built in "On Demand Cleaning", and Photohelic emulation with it's integrated pressure sensor and bright blue vacuum fluorescent display. It can be purchased with an optional 4-20 mA transmitter for remote
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