electrical installations..

Hello domanic

You ask <"...can the dryer burn...."> ?

To what actual "burn" are your referring ?

1. Do you meant to ask: Do the dryer motor or elements burn out ?

2. Or Do you mean: Does the Dryer catch Fire ?

3. Or do you mean: Does the dryer burn what it is drying ?

I do not see the circuit diagram shown.

You do not advise where exactly <"...the neutral is loose..."> It may be at the substation, the meter, the main switchboard, the distribution switchboard, the contactor, or at the elements, if all equal resistances and connected in star - we do not know, and that means nobody can say, with certainty.

Some 3 phase 415 Volt dryers require a neutral, some do not, and until your reply with further information, it is impossible to correctly advise you.

If you have a commercially made dryer in mind, advise Make + Model, along with the size in kW of the dryer, and we may be able to assist you.

Please reply here, with

Kind Regards....

thanks for the reply..The circuit starts from the sub-board,then to the isolater and then to the contactor box in the dryer which have heating elements as well as motors connected in star...from my experience in a house single phase or 3phase..when neutral loose at the entry box or if its broken on the service mains then could lead to house shocking.but for 3phase(415v) equipements im not sure...esp dryers in hotels...i mean catch fire.....not burn....because i found that the neutral was loose at the contactor box...not from the subboard...i know that if neutral is missing then current diverts to earth...somtime if earth resistance isnt good equipements heat up...im not sure im just learning...let me know what you think...

domanic,

Just tighten it.

Let's assume the electrical service is a 415V line-to-line, 3 phase, Wye connected, with 240v present from each line to the neutral.

Now assume the 3 phase motor draws a perfectly-balanced 3 phase current and the current in the neutral lead is therefore "zero" amps. Then, since there is "no" neutral current, there are no watts dissipated in the high-resistance, loose, neutral.

If the dryer load was not balanced due to some single phase loading such as a control circuit, there could be some current flow in the neutral lead. Depending upon the resistance of the loose connection, some heat could be created in the connection. How much heat depends on the current flow in the neutral and the resistance of the loose connection. If the current and resistance are high enough, enough power can be present in the connection to melt the conductor materials in the connection. That could cause some problems. It is best to make sure neutral connections, like all electrical connections, are tight and do not form high-resistance. Be safe!

Some one else may address the safety issues that might arise if the motor winding fails to the enclosure.

hi Jim,

All your statements are coinvincing. but,,

I am just curious to know if the neutral connection at contactor box is loose, how will it cause dryer to catch fire.?

Regards,

Vikas.

Electricians discuss problems Over SCHEMATICS/ MULTIPHASE DIAGRAMS.

three-phase motors do not have neutral connected to their windings, heaters could, controls with 240V yes.

To be sure all tips have value for your trouble-shooting the best way is to enclose diagram(s) in your request.

If the heating elements are rated at 200 volts nominal and 4 wire Wye connected for parallel operation and control of the heating elements, the loss of the neutral will make the connection between the heating elements series connected. This shouldn't burn out the elements but will negate individual control of the elements. Check for high resistance connection which might burn out the connections to the elements.