How does my water tank & immersion heater work... Confused.

Naf

I always thought that it just filled up with cold water, and the immersion heater just heated directly into the middle of the big volume of water. Then as water was used it refilled with cold, mixing with the hot and cooling the whole lot down.
However, having now been running one myself for a while, it seems this can't be the whole story. If showers in the morning don't use the full tank, somehow whatever's left seems to stay at least a little warm through the day. And even just a 20 minute 'boost' turns out red hot water, which couldn't happen if the immersion heater was heating the whole however many gallons, could it?

Basically, the reason I ask is that I currently run the heater for about 7 hours each night to get hot water for the morning, but when 20 mins produces water that hot, is 7 hours overkill?

Gloomendoom

Any hot water will rise to the top of the tank and the cold will stay at the bottom. It doesn't evenly mix. When you open the hot tap or shower, the water is drawn off from the very top of the tank


Edit: Yes, 7 hours is overkill for a shower in the morning. However, the immersion heater will, or should, be thermostatically controlled so it will automatically turn itself off when the tank reaches a pre-set temperature so it may not actually be on for the full 7 hours.

We run ours for one or two hours and that gives us all the hot water we need for the day.

Naf

I haven't seen any thermostat control anywhere, so is it something that would have been pre-set on production/installation?
I really want to start getting up before my E7 day rate kicks in, then the immersion heater can kick in briefly to give a quick top up. My shower usually seems to use up the lot...

cajef

The thermostat is inside the immersion heater cover, switch the power off, take the cover off you will see the thermostat and you can set the temperature.

http://www.diydata.com/problem/immersion/immersion_heaters.php

Gloomendoom

Naf wrote: »

I haven't seen any thermostat control anywhere, so is it something that would have been pre-set on production/installation?
I really want to start getting up before my E7 day rate kicks in, then the immersion heater can kick in briefly to give a quick top up. My shower usually seems to use up the lot...

You just need to set the immersion heater to come on for and hour or so and switch off just before the day rate clicks in.

As long as your tank has a some insulation on it, the water will stay hot for a long time, certainly long enough for you to have a lie in, if you want.

There isn't usually any need to fiddle with the immersion heater thermostat. If you set it too hot, you may get accidentally scalded.