My first 110v project - Water pump

Hi mates,

Im planing my first 110v project and im very worried about my safety.

I got this relay module from Itead:
http://www.itead-europe.com/index.php/2-channels-5v-relay-module.html
ftp://imall.iteadstudio.com/Modules/IM120525001_2Channel_Relay_Module/SCH_IM120525001_2Channel_5VRelay.pdf

At relay piece (HK3FF-DC5V-SHG) says clearly 10A - 250v.
I see a zenner diode and a transistor to activate the coil (check the photos at site).

I want to drive a water pump motor (110v-7A).
Turning it on 2 times per hour - 5 minutes on

Can I trust in this module for this task? Im worried
about pcb tracks thickness and spaces. The motor
will melt the tracks, pcb, connectors? Some eletric leakage
can happens?

The bottom is the same of this module from DX.

Another question. The splited wire going into relay module
is the positive? Is better the positive or negative?

This zenner diode will protect the arduino from charges
when motor goes off?

The pump is plugged at outlet and right now i turn it on
manually.

Thanks in advance
(Sch attached)

I would switch the HOT wire (smaller of the two plug holes) not the Neutral wire.
I would also connect the earth ground wire to the motor frame if it is recommended to do it.
You may find you need a contractor too switch that much current.

Wouldn’t hurt to add extra solder to those traces on the bottom of the relay board to thicken them up.

I would check what the current requirement is, for the activating coil of the relay.

Using a transistor to activate the relay coil, means that the driving current for the coil does not have to be sourced entirely from the digital output pin of the arduino. But that current still has to come from somewhere. If you are going to provide that current from the +5V of the arduino board, you need to check that it is within the limits of the voltage regulator on the arduino board to supply, and whatever is upstream of that. Otherwise, you may need a separate +5V or similar supply, to provide the current for the relay coil.

I wouldn't trust a Chinese 10A relay at anything above 5A.

Try an SSR:

Only $5. No annoying clicking sound.

I second the SSR. They are much safer and more reliable than relays. Also you can drive the input of an SSR directly from an Arduino digital output pin. The SSR input is optically isolated from the Arduino and draws only 3-5 mA from 5V.