help - bath pasteuriser problems with elements

[R G]

If this little lot is fed from a 13 amp supply via fused spur or plug top then I assume these elements are wired in series ...??

 

[Chris Watkins]

230V not 240 Dave, like you it around.

 

[kjgreen3]

How did you get 17.6ohms for 3kW at 240V?

EDIT: Already answered in above post.

 

[davesparks]

230V not 240

Why use 240V when the element is going to be 3kW at 240V? The power at 230V will be different due to the lower voltage.
230V is a mythical figure which only exists in paper, in the real world everything is still manufactured exactly the same and just has a lower 230V rating put on the label to satisfy the paperwork.
A standard 3kW element will only be 2.75kW at 230V.

 

[Chris Watkins]

Why use 240V when the element is going to be 3kW at 240V? The power at 230V will be different due to the lower voltage.
230V is a mythical figure which only exists in paper, in the real world everything is still manufactured exactly the same and just has a lower 230V rating put on the label to satisfy the paperwork.
A standard 3kW element will only be 2.75kW at 230V.

Well thanks for the info Dave, 240V it is for all calculation from now on.
Of course as you well know the supply voltage is allowed to be +10%, -6% from 230v (216.2 to 253v range) and does change through out the day as the load shifts.

 

[R G]

Perhaps the op could come back with some info and photos ??

 

[davesparks]

Well thanks for the info Dave, 240V it is for all calculation from now on.
Of course as you well know the supply voltage is allowed to be +10%, -6% from 230v (216.2 to 253v range) and does change through out the day as the load shifts.

And all substation transformers are set at 250/433V output, even the new ones.

 

[Leesparkykent]

Shouldn't you calculate the resistance from what voltage the manufacturer says? Ie 3kW at 230V or if it says 3KW at 240V.....last immersion I looked at said 3KW at 230V-240V

 

[davesparks]

Shouldn't you calculate the resistance from what voltage the manufacturer says? Ie 3kW at 230V or if it says 3KW at 240V.....last immersion I looked at said 3KW at 230V-240V

You should yes, but in reality the manufacturers haven't bothered to spend all that money changing their machinery to manufacture a slightly different element to give 3kW at 240. Much cheaper to change the printing on the sticker.

 

[davesparks]

I've checked my notes on a job I did a couple of years ago.
It was a system for storing, heating and pumping water for rain and stuff for an interpretive dance piece ('arts council funded' etc etc)
We had a 3000 litre tank in which we fitted a 6kW TP immersion heater at one end of the tank low down (approx 1/4 height)
Control was by a precision temperature measuring device with a remote sensor suspended in the tank.
A small submersible pump was also suspended in the tank to keep constant circulation of the water within the tank.

It took a few hours to get it up to the required temperature which was in the 40's