immersion heater element length

[ChrisR]

Obviously it'll take longer to heat

You won't get circulation up the cold feed to any extent because it has nowhere to circulate. But the primary connections can provide a circuit and they're higher up the cylinder. See?
Copper is such a good coductor it'll hardly slow the thermal process at all.

 

[doitall]

Parastatic circulation Chris, circulation in a single pipe.

 

[JohnD]

it will be nice to see some pictures

//www.diynot.com/forums/viewtopic.php?t=129539

if it losing lots of heat through a pipe, good insulation will help a lot. But you should be able to feel the pipes to see if any are hot when the taps are not being used.

 

[ChrisR]

Parastatic circulation Chris, circulation in a single pipe.

Yes I know. Happens on every cylinder at the pipe at the top. Not significant in cooling the cylinder compared to a piped circuit though, is it.

 

[Agile]

It its not properly warming the cylinder then either

1. The thermostat is turning off prematurely.

OR

2. A lot of heat is being lost somewhere.

I just dont see that "2" could possibly be happening just because the element is 3" longer!

Therefore SOMETHING is causing the 30" element to turn off the thermostat before the target temperature is reached.

A photo might show us the clue.

Tony

 

[matt1e]

Obviously it'll take longer to heat

sorry, thought that was the jist of what the op's the problem was and had my vodka head and eyes on

agile,regarding your number 2 scenario could this not happen if the extra length of the element means it is now touching the indirect coil or the casing of the cylinder which is now acting like a heatsink?

 

[Agile]

No Matt, because the water has already heated the copper parts to the temperature of the water.

Its such a simple fault that the required pictures will almost certainly tell us what it is.

Tony

 

[matt1e]

No Matt, because the water has already heated the copper parts to the temperature of the water.

.

Tony

not if the water isnt getting hot enough to heat it in the first place
ie element touching metal from cold
(mind you not stating fact here tony just giving suggestions)
matt

 

[doitall]

I still think it's going up the cold feed and heating the st up.

Or,

The extra length is enough to start a gravity circulation in the primaries.

 

[mrpeevly]

Sorry for not responding sooner, I thought I had email notifications setup on this thread, it was working initially, in any case here are answers to the questions above, I think I have got them all:

Cold feed is not getting hot
Cylinder size:200 litres (using approx Volume = π r2 × height)
Cylinder has three insulating jackets
Thermostat set to 70c circuit is live

I would add a picture, but I am currently running with a 27" element, which although heating the water, not heating enough of it, oddly not as much as the previous 27" element, which was JUST heating enough water.

I think I will buy another 30" element, tank is big enough to take it, thanks for the info on that above, and try again.

I will update with my results

 

[JohnD]

photos will be nice

it would also be interesting if you are able to monitor electrical current usage, to see if the heater is cutting off before it is up to temp (either watch the electricity meter, or a but a cheap Clamp Meter that you can put round one (not both) of the conductors and it will tell you how many amps are going through it. If it is cutting out to early, turn the stat up a bit and see if it comes back on

If you are looking at the meter, turning the element on and off will make a noticable difference to its speed of turning or flashing, unless you are running other electrical heaters, including tumble driers and washing machines, at the same time.

If the water is not getting hotter, and you are sure that heat is not escaping up any pipes, out of a tap or from poor insulation, then the element must have stopped putting heat in.

BTW 70C is pretty hot, for hot water.

 

[picasso]

what voltage do you have at the thermostat and if possibe and you have a clamp meter, could you measure the current the element is taking.

 

[WDIK]

what voltage do you have at the thermostat and if possibe and you have a clamp meter, could you measure the current the element is taking.

at last, faulty thermostat, loose neutral? 3kw is 3kw 12.4A

 

[mrpeevly]

Well I received a new 30" element yesterday fitted it, and as if by magic everything is now perfect.

I guess all the issues were down to a faulty elements, the missus did later inform me, that the kids did drop the box one of the elements came in, before I got back from work, so that of course did it no favours.

Thanks for all the informed help, I am off to have a bath.