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PostPosted: Fri Feb 28, 2014 4:34 pm 
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Joined: Mon Dec 09, 2013 1:01 pm
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Hi all,

I just wanted to start a debate on the subject of testing 8" and 9" 110vac Grinders. I'm sure most of you have come across this 'issue' plenty of times and this appears to be a grey area that nobody appears to fully classify. For those who are not aware of this issue, please let me explain:

This size of 110v grinder state on their ID plate that they use between 1700 & 1900 watts (there about), also stating on the plate that they required 18 > 20amps (depending on make/model). The grey area is based on this amp rating would mean a outlet/plug would be required higher than a 16amps (standard 110v plug). I have been failing these plenty of times in the past on this fact of the ID plate verses plug size alone.

Several weeks ago I sent an email to Makita asking for their opinion on this matter a received a response stating that the unit only has a draw of 18amps for the initial start up of the unit after which it runs at 4amps unless put under extreme use. They then said there is no requirement for the unit to be fitted with a 32amp plug as a standard 16amp plug has the capacity of the initial load plus the circuit should have the circuit protection if the unit is put under extreme load for more than short periods of time.

However, all Makita 9" 110v grinders sold in the UK are supplied with a 32amp plug as standard. So I am still not 100% fully clear on this subject as to weather I should pass these units if they have been fitted with a 16amp plug while their ID plate states the unit requires 20amps to function. What is the opinion of this community on this subject?


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PostPosted: Sat Mar 29, 2014 3:17 pm 
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Joined: Thu Mar 27, 2014 5:24 pm
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Hello there im not to sure but i think this is correct.
The power in watts is 1900 so if thats divided by the voltage it should give a reading of 8.2amps so that would be the true amperage of the unit in question running at 1900w but when we test the unit we do not put it under load we only do an operation test or funcional test which runs the unit at its designed speed if im right i belive its only put under load when its applied to the job i.e a grinder cutting steel slows down if its starting to get overloaded by the operator. If thats the case then it will overload the fuse and blow as i have experienced using this equipment on site. So manny factors come into play though like how long the cable is that the operators connected into if hes run it all over the site then the power will be less and will trip a lot easier.
All the 110v 9" grinders we have had supplied have all had 32A 110v plugs all of which have always been cut off and replaced with 16A to allow them to use them with there own extension leads (Personnaly i think a bad practice as its supplied with 32A plugs for a reason) In my experience i have had a 9"grinder (BOSCH) trip on a 16A supply the moment i sourced a 32A plug and rewired the grinder and plugged into a correct independent 32A dedicated supply the grinder went on to complete the job without tripping the fuses in the distributor unit. But the 32A Cable would reqire to be 2.5mm MINIMUM C.S.A if i remember correctly. Standard on Bosch grinders.
Personnaly i would not fail the appliance because it has had the plug changed to a 16A version as although i dont really think its good practice and a bit hypocritacal i have never seen a cable burn out before tripping the distributor in over 20 years onsite and to try and get every tradesman on site to conform would be a knightmare.
Any feedback on his would be great as im only new to this forum myself and dont want to misadvise.
Another common sight is a cable convertor i.e 110v 32A to 16A but only made with a 1.5mm C.S.A cable which then does not match the cable size on the Grinder those i would fail just on visual but thats a personal opinion.
Just to add another note all 110v 9" Grinders supplied on a shipyard are plugged into 32A dedicated supplies only a differt enviroment i know but still an example.


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