A delta-connected system is described as being a three-phase, three-wire, system, and doesn't have a neutral. But a balanced star (wye) connected load (e.g. a three-phase induction motor) doesn't actually require a neutral.
condition of three phase in which there is no need of neutral
Not usually, if the three phase pump is a three wire pump then the disconnect does not need a neutral. The pump control may or may not need a neutral depending on the voltage system that the control panel needs.
As far as I understand, you don't need neutral line for connecting appliances that is 3-phase compilant. You only need the neutral line to connect a single phase appliance, which you connect along with one of the three lines.
No, three phase motors do not actually have neutral line unless you are referring to the motor control centre where a neutral line is required when your control coils and other components are single phase operated
If the heater is rated as a 3 phase 480 volt heater then a neutral is not needed. If the voltage stated is 277 volts three phase then a neutral is needed.
There is no neutral in a delta connection, because that is the definition of delta, a power configuration where current flows from phase hot to phase hot. The loads are A-B, B-C, and C-A. Contrast this with star, where there is a neutral, and the loads are A-N, B-N, and C-N.
The current carried by the neutral of a three phase four wire system is the un balanced current. If the three phase system was completely balanced on all three phases there would be no need for a neutral, eg a three phase motor. This neutral current will be less that the phase current so a reduction in the neutral size is allowed.
If the motor is operated from a three phase three wire distribution system the motor will not need a neutral wire.
Not usually, if the three phase pump is a three wire pump then the disconnect does not need a neutral. The pump control may or may not need a neutral depending on the voltage system that the control panel needs.
As far as I understand, you don't need neutral line for connecting appliances that is 3-phase compilant. You only need the neutral line to connect a single phase appliance, which you connect along with one of the three lines.
No, three phase motors do not actually have neutral line unless you are referring to the motor control centre where a neutral line is required when your control coils and other components are single phase operated
If the heater is rated as a 3 phase 480 volt heater then a neutral is not needed. If the voltage stated is 277 volts three phase then a neutral is needed.
The neutral provides a path back to the source for the electricity. In a three-phase circuit, it is mainly used to carry the unbalanced load back to the source. In theory, a perfectly-balanced three-phase circuit would not need a neutral, but this is almost impossible to achieve in actual practice.
To use a single/one phase motor instead of a three phase motor is possible if you have a three phase power supply as you will only need to tap one of the three phases together with neutral and an earthwire, however to use a three phase motor instead of a single phase will require the provision of three phase power supply.
The reading on the 3-ph meter would equal the sum of the three separate readings on the single-phase meters. The neutral sides of the single phase meters do not need to be connected to the neutral wire as long as they are connected together.
There is no neutral in a delta connection, because that is the definition of delta, a power configuration where current flows from phase hot to phase hot. The loads are A-B, B-C, and C-A. Contrast this with star, where there is a neutral, and the loads are A-N, B-N, and C-N.
No a 208 volt outlet does not need a neutral. 208 volts is the line voltage between any two legs of a three phase 208 volt system.
You don't. You hire a qualified electrician who doesn't need to read this page for the answer. That said, if you are merely curious as to the methods: "480" Volt will be 3-phase with either Delta wiring (480 phase-to-phase, NO neutral), or Wye wiring (480 phase-to-phase, and 277 phase-to-neutral). You can use this directly, to run three phase equipment from all three phases, to run equipment at 480 from just two phases (being careful to keep loads balanced), or to run lighting circuits from the 277-to-neutral (being careful to size the neutral conductor carefully). You can also step it down to "208", which will be 208 phase to phase and 120 phase to neutral -- "standard" line voltage. But seriously, if you need to ask the question, you SHOULD NOT be touching 480 switchgear and wiring, for the safety of both yourself and others.