Possible Immersion problem

whitelightrider

Hi folks,

Just wondering if someone could take a look at this and see if its possible that there could be something wrong with the immersion? Or is it standard for an immersion left on for 3 hours to only heat a 300l water cyclinder to barely lukewarm?

[HTML]http://www.boards.ie/vbulletin/showthread.php?t=2055510044[/HTML]

willbur

where do :cool:you want me to look pm me:cool:

whitelightrider

willbur wrote: »

where do :cool:you want me to look pm me:cool:

Hi Willbur, sorry this is the link to the post on the Construction forum:

http://www.boards.ie/vbulletin/showthread.php?t=2055510044

eoghan.geraghty

I have a 300 litre stainless cylinder for solar application and yes it does take 4 hours to heat the water to 60 deg with the immersion.
Do not increase the temp on the stat to 80 deg, you will likely scald someone.
The reason why your oil heats the water in 40 mins is because the heating coil is situated near the top of the cylinder so is only heating maybe 60/80 litres of water, your immersion element is near the bottom.
It may sound like a pain and expense to heat water for 4 hours to have a shower, but the cylinder should be so well insulated that the water is hot for 2 to 3 days, most solar ones are.

whitelightrider

Hi Eoghan,

thanks for that. My only problem is that after 3 hours the water was still not hot. It was barely lukewarm.

fishdog

My only problem is that after 3 hours the water was still not hot. It was barely lukewarm.

You can work out how long it should take:

1 litre of water requires 4200 joules of energy to heat it by 1 degree.

Therefore to heat 300 litres of water by 1 degree will take 4200 x 300 joules = 1260,000

Your water is starting off at about 14 degrees I would guess. To get it to just 45 degrees would require 1,260,000 x (45-14) joules = 39,060,000

A 3kW immersion provides 3000 joules per second (watt = 1 joule per second)

Therefore it will take 3,906,000 /3000 seconds for the immersion to heat your water = 13,020 seconds = 217 minutes = 3 hours 37 minutes.

All of these calculations assume no losses (which will never happen). In reality I would guess it would take at least 4 hours to get 300 litres of water to 45 degrees.

fishdog

BTW this:

To get it to just 40 degrees would require 1,260,000 x (45-14) joules = 39,060,000

should read:
To get it to just 45 degrees would require 1,260,000 x (45-14) joules = 39,060,000

It wont let me edit!

P.S. did you check the stat???

whitelightrider

Hey fishdog, the stat is set at 65.
Just one thing to note. Thats fair enough if its going to take 3 or 4 hours to get hot water. But even after being on for 3 hours the water was barely lukewarm. The immersion is up about 1/3 of the tank. Is there a way to move the immersion to a higher part of the cylinder? Its a solar cylinder.

davelerave

there might be a flange higher up take a look.it would be simpler then to leave in the existing immersion and fit a 2nd one .(the two can be wired to an economy 7 controller if you have nightsaver)otherwise you would just connect the top one for a smaller quantity of hot water.

Justin_k

Hi

I just had my immersion fixed.. turned out that the bath/sink switch was broken (they arc over because of the high current it seems causing the switch to no longer engage)

Might be one more thing to take a look at.. just in case the switch is knackered and your hot water element is not actually getting any current at all.

J

paddymick

Justin_k wrote: »

Might be one more thing to take a look at.. just in case the switch is knackered and your hot water element is not actually getting any current at all.

J

I wouldn`t think its the switch these type of tanks dont usually have the standard bath/sink duel immersion and the fact that its heating a bit means its working.
I would go for extra element higher up the tank.you would have to have two seperate 20a d/p switches as a bath/sink switch wont work that way you can switch them on as needed IE the top element on by its self would be your sink setting and both on would be your bath setting