[SOLVED] Big (overnight) water heater ceased functioning - manual says there's a cut-out button

M

MoreMoschops

Joined
13 Dec 2015
Messages
11
Reaction score
1
Country
United Kingdom
I've got a water heater of model Premier Plus Unvented Model Number PP210E.

It has, as far as I can tell, two heating elements. One near the bottom, meant to be run from the economy 7 overnight electricity (which has spent the last decade turned on), and one near the top that runs from 24 hour electricity supply (which has spent most of the last decade turned off).

Over the last couple of days, the water has been cold, and to get hot water I flip the switch on the top heater's supply. I hear something start working, and an hour later I've got some hot water. So my conclusion is that the lower one has simply stopped heating. I can't be sure if it's stopped completely, or is just doing an unnoticeable amount of work. I checked all taps to check nothing was dripping away hot water, and I checked the hot water immediately upon waking - cold. Not as cold as the cold tap, but definitely cold. Far too cold to do anything with. Less than lukewarm.

I dug out the installation manual of the water heater ( http://www.advancedwater.co.uk/STOMEMO/A540-088-2100/Santon Premier Plus Installation Guide.pdf ) , which says in its small trouble-shooting section:

DIRECT immersion heater thermal cut-out has operated
2. Check . Reset by pushing button

So I think maybe it's not totally broken; maybe this cut-out of which it speak has operated.

After turning off the power to the heater, I remove the cover to the lower section. It looks like this:

9YqI3lf.jpg


which does look a lot like the diagram in the manual:

Image013.gif


but I don't see anything that looks like a button I can push to reset some cut-out. Is there one, or is it time to call the electrician?
 
If it is really a decade old, could it mean that the element had worn out and failed?? - it is typical for economy seven overnight elements to fail under ten years, due to the very hard work that they do. Has the Breaker feeding it tripped out? - It is normally a B16 breaker, often coloured or marked Blue.
 
Let's take a look at the only thing in the flat that looks like a box of breakers...

Good skills. There are two in there marked B16, one in a bank of breakers marked with various household supplies in various loactions, clearly marked "Immersion". It's ON. There is another small set of three breakers, marked "Economy 7", in which the B16 marked "Immersion" is also ON.

It definitely is a decade old. It was brand new when I moved in just under ten years ago, and has never been touched. It's worked flawlessly for the last decade; if that's beyond the expected lifetime of an economy seven element, maybe it's simply had its chips.

I strongly suspect, but cannot be sure, that it might have failed slightly slowly. That the water went a bit colder on one day, and then outright cold from then on. Which would support the failing element hypothesis, and work against a single breaker or cut-off being switched (hmmm - although if the cut-out tripped in the middle of the night, I'd get the same effect; warm the next day, cold thereafter). Sounds like one for the professionals, then. Is this the sort of thing that can be replaced, or am I looking at a new boiler?

I'm actually renting, so it's not going to cost me, but I've no interest in alienating the landlord whom I have seen precisely once over the last ten years.
 
Last edited:
the cutout is the red rectangle marked 'safety' to the right of the round knob (at position 1 on the temp scale). It may push in with a small slot screwdriver.

http://www.cotherm.co.uk/uk/content/download/733/9210/file/-TSE_TSR GB.pdf

It's possible that the thermostat or the element has failed. Once you've proven supply to the supply terminals you need a plumber with an Unvented Hot Water certificate to separate the stat and heater and test each one individually and replace as necessary.
 
Looking at your picture I would say the cut-out is just above the number 1 setting on the thermostat. You can just about see the little red square.
You will need something thin to push it in to reset it.
If it has tripped you should be able to feel it click as you push it.
But as Kai says it could be the element which has failed.

Edit. Beaten to it.
 
Last edited:
The reset button in the tiny red plastic oblong to the right of the adjuster knob. If it has tripped there is a good chance the thermostat is faulty and it will trip again. If it hasn't tripped you will need to check the element and thermostat, and that power is actually getting to them.

Edit: Was way too slow in posting!
 
At risk of being thick, because I really don't want to screw anything up, is the consensus that "I should try pushing in the red rectangle marked 'safety' and, if the failure persists, get the professionals in?" Or is it "the cutout is that red rectangle, but don't touch it; just get the professionals now"?

You know what. I just know that even if it's "don't touch", at some point in the next day I will talk myself into poking it with a stick.
 
Try pushing it in. If is hasn't tripped, it won't move. If that doesn't work, you need to check for voltage on the terminals. Do you have a multimeter?
 
Just press it, it will 'click' if it has tripped. Make sure the power is switched off first of course.

An electrician will be able to fault find this in a few minutes with a meter.

Edit: Too slow again!
 
Certainly do have a multimeter. Got a couple. I can check for voltages, no worries. I see a terminal A, B and big chunky earth on there to test.
 
You will only get a voltage on it at night when the Economy 7 tariff is active.
 
In that case if the supply is good there will be 230V across a and b during economy 7 hours.

You can test the element and stat though if you want. With the power off a resistance test should show about 20ohms across a and b. If it doesnt, pull the stat off the element and take the resistance reading on the 2 connectors on the element. If it is 20ohms now, the stat is faulty, if it is substantially higher or no reading the element has failed.
 
Gave it a gently pushing with the thin, flat-headed screwdriver. A very noticeable click, and I believe it has moved back a little. Still visible as a little red rectangle. So maybe roundabout economy seven switching on time, it'll pop out again (or just work).

Addendum: First multimeter I tried gave me 22 ohms across A and B. Which seems hopeful.
 
Last edited:
They ofen pop out when the thermostat contacts weld together, if you get a tank of hot water tomorrow but it trips again you will need a new thermostat. Do not keep resetting it if it trips again. If you want to fit a new stat yourself you must buy a replacement that is identical to the one removed.
 
You must log in or register to reply here.
Back
Top