UPS Neutral and Utility Neutral

What sort of input?

Yes.

There will be a problem of circulating currents.

Better not tie 2 neutrals.

Some times, for better safety, ultra isolation transformers are provided on the load side, so that 2 neutrals are not joined.

Since both neutral will be in any case grounded, these will be shorted through ground. There is no harm to short them and ground them.

Yes there is, if they are both grounded NOW, another connection will give a "ground loop". Not recommended.

Depending upon how the UPS is designed, something might burn of they are not both on the same ground, for instance, if they were never designed to be connected together.

You need a UPS designer here for some detailed facts.

My advice till then is not to do anything at all in that area......a properly designed UPS will have ground and neutral linked in some PROPER way. If its a Chinese ripoff, all bets are off.......

If so, wear galoshes and rubber gloves when using anything on the UPS (buy a bigger keyboard!)

What about the interference by DC leakage currents while joining the 2 neutralS?

Earth common via earth is not a problem. Joining Earth conductor to earth electrodes some times might be a problem, so isolated earths are required.

There should be a spacing of 3 times the depth of earth electrodes between the 2 earth electrodes, so , you get 2 distinct effective earth electrodes.

This code of practice is assumed that you follow.

For the utility supply the ground an neutral are tied together at the supply entry to the premises, with a separate ground wire from there. With the power network in the premises the ground is tied at various points, inadvertantly creating poor connections with some impedances. This in turn creates small potential differences which can be witnessed when neutral and ground is tied together further along the power distribution network. These connection impedances resonates also with certain frequencies so that some power spikes are amplified significantly - more seriously so between ground and neutral. In order to eliminate these ground-neutral residual and noise voltages a UPS is not enough. (If the ground-neutral voltage problems cannot be rectified, particularly for older installations,) an isolation transformer is used where the secondary neutral is also used as the ground - with a proper earth pin as ground. On this isolated side the residual voltage between ground and neutral is now eliminated (usually this voltage is bad news for electronics) and one can connect UPS neutral to isolated power neutral. Remember, the UPS cleans up noise from the power between live and neutral, not between any of live or neutral and ground.

GA for a first post!

Welcome to CR4!

1)Is it on line UPS or Off line UPS ?

2)If it is Off line UPS you can tie ups neutral and utility neutral together.No problem.

3)If it is on line UPS, not advisable to tie UPS neutral and utility neutral together,If tie together Voltage fluctuation may come.