help - bath pasteuriser problems with elements

[JohnCider]

Hi there
Thanks for the ad on the forum!

Ive been able to do most things my demanding wife asks of me, but this project is doing my head in. We had made an in-bottle bath pasteuriser and fitted it with 2 X 3kw universal flat heating elements. Now, Ive installed temp sensors and adjusted the fuses etc, and filled the thing and it does work, but blimey its sooooo slow! The capacity of the tank is around 90Litres (this is for the liquid in the bottles and the water surrounding the bottles too). The bottles sit on a SS mesh shelf which houses the elements at either end of the tank. Its taking around 5 and a half hours to get the temp from around 16 degrees to 70, and this is going to be too slow.
Now today, Ive checked that both the elements have power to them, and also tried bypassing the electronics by taking power straight to the elements (to check I wasnt getting cancelling out and running just one element) and its the same.
So, as Her Indoors is getting a bit narky - what are my options?
Should I replace the elements with 4kw ones? What are other options?
We are on single phase. The pasteuriser is fully insulated.
Any ideas?

 

[Darkwood]

Welcome to the forum, I'll approve for the general area for now for a faster response time, when Admin' is next on line you may be given DIY status and the thread relocated, this won't effect any posts already made.

Have you clamp tested the loads, have you designed it for the volume of water your trying to heat up or did you just guess?

Edit - Link shows how to calculate what you need.

https://elementsofheating.wordpress...-heat-a-volume-of-water-in-a-particular-time/

 

[Darkwood]

Doing the calcs myself I would suggest you check the voltage rating of your elements, you should be seeing 90litres getting to temp in approx' 1hr 20mins, either that or your controls are faulty or are not designed/wired correctly.

 

[JohnCider]

Doing the calcs myself I would suggest you check the voltage rating of your elements, you should be seeing 90litres getting to temp in approx' 1hr 20mins, either that or your controls are faulty or are not designed/wired correctly.

Thanks for the reply!
Its been a bit of guesswork and some questions to others and some copying other very expensive pasteurisers out there.
I know that there is power going to the elements, but even if I take the power direct to the elements bypassing the all the electronics its heating but incredibly slow....
so, these are the elements in it now Universal 3kw heating element ELYA CATERING EQUIPMENT | Kebab Machines - Chip Fryer - Pressure Fryer , but thinking to replace them...perhaps they are faulty or just not suitable?

 

[davesparks]

Is the water being heated able to circulate properly in the tank?

 

[JohnCider]

The elements are housed under mesh shelf, so water able to freely circulate, but no pump.

 

[R G]

My guesses are that the type you show are not suitable for what you want to achieve , I would use something in the way of standard immersion heater elements for your requirements , I would check current draw with clamp meter to ascertain that the elements are drawing the correct power and confirm the wiring is correct first though...


Are the elements at the lower are of the tank and not at one end of a flat tank

 

[davesparks]

Thanks for the reply!
Its been a bit of guesswork and some questions to others and some copying other very expensive pasteurisers out there.
I know that there is power going to the elements, but even if I take the power direct to the elements bypassing the all the electronics its heating but incredibly slow....
so, these are the elements in it now Universal 3kw heating element ELYA CATERING EQUIPMENT | Kebab Machines - Chip Fryer - Pressure Fryer , but thinking to replace them...perhaps they are faulty or just not suitable?

3kW is 3kW whatever element you put in it.
Measure the resistance of the element and check that it is correct for the stated power. For 3kW at 240V you should see around 19ohms.

How are they being controlled?
Have you got anything in there to encourage circulation of the water?

 

[Chris Watkins]

Have you checked the resistance a crossed each of the elements ? It should be around 17.6 ohms for each.

I take it they are wired each with its own supply & not in series.

Otherwise I am with dave, can the water circulate around them as it is the conversion currents within the water tank that carry away the heat otherwise heating by conduction will be very slow.

 

[davesparks]

Have you checked the resistance a crossed each of the elements ? It should be around 17.6 ohms for each.

I take it they are wired each with its own supply & not in series.

Otherwise I am with dave, can the water circulate around them as it is the conversion currents within the water tank that carry away the heat otherwise heating by conduction will be very slow.

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

 

[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