Immersion Heater luke warm

tech

left immersion on for 5hrs the other night to heat a 200/300 joules tank, after 5 hours the water was only luke warm at best , time for a new immersion? how long should it take to heat a big tank from cold?

John.G

A 3kw immersion should heat 200L from a now 18C to 60C in 3 hrs 16mins and should heat 300L in 4hrs 54 mins, say 5 hrs.

Can you show a photo of the cylinder and element or has it a top mounted dual element immersion with sink and bath switches?.

tech

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Immersion in middle of tank

John.G

That immersion is "only" heating half a cylinder so the heating times should be halved.

Are you sure the immersion was actually coming on and that the cylinder wasn't warm/hot from previous (boiler) heating from the heating coil in the bottom of the cylinder?.

Remove the cover from the immersion (switched off), you should see the thermostat which probably looks like this, note the setting (where the arrow is pointing at), keep turning it clockwise until you hear a click, note this setting, then turn it back anticlockwise until you hear another click, note this setting, return it then to its original setting. There is a hilimit stat incorporated in this thermostat, its reset button seems to be at the top next to the arrow, press this in with something to reset it (if it has operated), switch the immersion back on (leave the cover off) and see if your elec meters LED is blinking very rapidly (smart meter) or the disc rotating very rapidly if the old type meter.

Post a picture with the cover removed.

Have you got a multimeter or even a phase tester?.

tech

its looks like the pic above , ill try this tomorrow and let you know, i have a multimeter but unsure of where to connect it

tech

here is a pic of the immersion , when i turn on I can hear it powering up, and the immersion is getting power I have tested with a power detector

Also turned clockwise and anti clockwise, I can here the clicks

Termowatt.jpg

John.G

The Live & Neutral seem to be connected incorrectly, the brown wire should be where the blue wire is and the blue to where the brown is, but don't think that should make any difference.

If/when you turn the setting up/down slowly, is there much difference between the clicks, if you think of it as a clock face, is it say 5 minutes or less?.

You say you have a M.meter, if so, put the setting to 200 ohm resistance or nearest, the resistance settings have a "horseshoe" symbol, isolate the power to the immersion, insert one probe in one of the brass ferrules (holes), insert the other probe into the the other ferrule, (these are located just above the brown wire terminal screw) and note the reading, a 3kw element should give a 17.6 ohm resistance, a 2.5kw should give 21 ohm.

tech

See reading above. i have changed the temp from 60 -70 I assume this stat is only for immersion ? or would be for oil and immersion?

I dont get any reading if I touch off the screws holding in the wires.

John.G

That stat above has nothing to do with the (electric) immersion, it controls a motoroized valve that shuts the hot water off to a heating coil in the cylinder fed from your oil or gas fired boiler, this may have been keeping the water lukewarm from when the boiler was last on, set that stat back to 60C

The heating element is fine, 19.5 ohms = 2.7kw @230V, at the "9 oclock" position, you will see a hole in the body of the immersion stat, the hi limit manual reset is located here, you should see a little button in there, push it in to reset it (if it has operated), turn the stat setting up full you should now get 19.5 ohms betweem the brown&blue terminals, if not then a stat problem and requires a suitably qualified person to renew it, if you do get 19.5 ohms then probably a timer problem.

If the hi limit resets and cures the problem, reduce the stat setting to its former position. You shoud have plenty of HW after 2 and a half to 3 hours.

Wearb

A circulation pump running (for whatever reason) can also cool a cylinder that has been heated by an immersion.

tech

https://www.boards.ie/discussion/comment/122465724#Comment_122465724

So I should get a reading between the blue and brown screws once I find the reset button? Thanks again

John.G

Yes, if it has operated "in anger", these would normally operate at ~ 80/85C so theoretically required the boiler to have heated the cylinder to this degree or the control stat contacts are fused together, unlikely since you can hear the stat clicking. See what you get anyhow, if no reset then stat knackered IMO.

Wearb

If you can read your electricity meter, then do a background reading with let's say the TV and pc on for about half an hour. Then turn on the immersion for half an hour and take another reading. Be sure to not use the kettle or washing machine etc. During g this test. The difference between first and second reading should give you the immersion usage.

John.G

i have a smart meter but it only accumulates kwh (whole numbers) but I sometimes use the flashing LED where 1000 flashes is 1.0kwh, if the above element is on its own then take the time to count say 20 flashes, if it takes 15.0 secs then the immersion is producing 2.7kw.