Dimplex Quantum QM150 Storage Heater Off-Peak Electric Supply Wiring Help

bigp26

Hi All,

I hope you are all enjoying your weekends!



Before I start, I just want to thank you for your help in advance…

To summarise, I had storage heaters installed a few weeks ago by an installer, and have experienced a few problems!

To cut a long story short, the flat I moved into used to have horrible storage heaters in the living room and hallway, which I replaced with electric panel heaters. I was told that my bills would go sky high (which they did), however at the time, I was a bit stuck as my refurb budget had run out.



Fast forwarding to a few weeks ago, I had 3 Dimplex Quantum heaters installed. Now the Quantums in the living room and hallway seem to be fine (as the off-peak supply was already there, ready to be connected up via a fused spur), however the bedroom Quantum has given me some issues.

As there was no storage heater in my bedroom before, there was no off-peak supply. As such, the electrician made the suggestion of simply plugging the off-peak element end of the heater via a normal 3 pin plug into a normal socket, via an electronic timer (to emulate the switching at off peak times to take advantage of Economy 10).

I asked him if this was safe, and he said yes it was safe, and that it is a much better solution than having to pull a new cable from the other side of the property (literally the other side!). This gave me comfort as I know this electrician also performs electricity safety tests for properties. The DImplex Quantum QM150 was therefore installed in my bedroom using this setup.



Now for the issues:

1) About 2 weeks ago, I found that the heater wasn’t charging up with off-peak electricity, and thus wasn’t giving out any heat at any time.

Having investigated this, I found that the switch for the socket that the 3 pin plug was plugged into, was stuck. I was thus unable to switch it from on and off.

To test this, I plugged in my iPhone charger and confirmed that no electricity was being output even with the switch in the on position. I put this down to a cheap switch that had gone faulty, and simply replaced it.

2) Last night, I could hear some buzzing/crackling from the off-peak socket whilst I was in bed. I therefore went closer to investigate, and smelt a little bit of electrical burning (similar to when using a soldering iron). As such, I quickly turned the switch off and took the plug out of the socket.

What I found was that the front of the timer socket (i.e. where the 3 pin plug goes into), was very slightly melted. I also found that the plug was slightly melted on the neutral side. Opening the plug up, I could see that there was damage on the neutral connection of the pin (i.e. to the plastic and screw etc.). Obviously the front of the plug was warm to touch at this point too.

This has made me extremely worried, and I have been doing a few hours of research this morning.

I understand that the off-peak elements of storage heaters are not really suited to be simply plugged into normal sockets (apologies if my terminology is incorrect, but I understand that the normal sockets are connected to the 30A ring main, and similarly, off-peak elements shouldn’t be connected to 30A ring mains).

I have also read that the storage heaters should be connected with 2.5mm wire (both from the heater to the socket, and from the socket to the fuse box).



So I’m just weighing up my options before I go back to the install company and start making a fuss:


Option 1:

I noticed that the connection between the plug and the timer socket wasn’t great i.e. the pins didn’t sit completely flush into the socket, but sat with a 1-2mm gap. Assuming that this was the issue (i.e. poor connection), the first option is to replace the plug and replace the timer with different models, which are a bit more compatible with each other and therefore don’t exhibit the 1-2mm gap.


Option 2:

Get rid of the socket and the plug, and replace this all with a Greenbrook T205-C Fused Timer Spur.


Option 3:

Ask the installer to come back and put in a new 2.5mm wire from the off-peak supply fuse box to my bedroom.


Out of the 3 options, my least preferable option is number 3, as the fuse box and the bedroom are literally on opposite sides of the property, which will mean lots of ugly trunking.

Option 2 therefore makes the most sense to me, but obviously this means that the off-peak element is still using the 30A ring main. The wire going from the heater to the socket looks like 2.5mm to me, but I think the wire going from the fuse box to the socket looks like 1.5mm (I’m not 100% sure about these wire sizes though – any easy way to confirm?). Considering these points, should this setup be OK?



Thoughts and suggestions would be much appreciated.

Kindest regards!
P.

EssexExile

In my opinion there are no options, it must be done properly. A 3.3kw heater via a plugin timer? A fire waiting to happen.

Rodders53

The QM150 http://www.dimplex.co.uk/products/domestic_heating/installed_heating/quantum/quantum/technical_specification.htm draws 3,300 Watts (3.3.kW) which is slighty over the max a standard 13A plug / timer switch will be rated for at 13.75 Amps.

Your electrician was probably negligent in recommending you do this rather than doing it properly as it has resulted in this fire risk.

A plug / socket / timer running anywhere near max rating will invariably run a bit warm due to contact resistance losses. Sadly 13A plug top fuses will supply up to 20A continuously so the fuse won't rupture.

NB the heater will exceed the current rating max of the fused spur/timer you suggested.

Option 3 is the only truly safe option... fed from a 16A mcb ideally.

bigp26

Thanks Rodders53!

Confirms my doubts so will get onto writing a fairly stroppy email to the installers today.

Just a couple of follow up points if you wouldn't mind:

- Although on the face of it, it looks like the QM150 draws 3300W (as per your link), the actual manual says it draws 3024W @ 230V (http://www.dimplex.co.uk/assets/kb/operating_instructions/0/Quantum_Series_F_Installation_Instructions_Issue_1.pdf). As such, this is slightly above the 13A limit that the plug and timer have. What about if I was to install say a 16A timer?

- Linked to the point above somewhat, does wire diameter matter a lot? i.e. why are storage heater elements recommended to be connected using 2.5mm, but all normal switches and sockets use 1.5mm?

Sorry if I sound dumb, but want to make sure I understand this in case another cowboy tries anything funny!

Cheers

ohreally

bigp26 wrote: »

- Linked to the point above somewhat, does wire diameter matter a lot? i.e. why are storage heater elements recommended to be connected using 2.5mm, but all normal switches and sockets use 1.5mm?

Your sockets will be connected with 2.5mm T&E.

Re your load, I regularly come across 3.7kW (~16A) appliances, connected to a socket outlet with a 13A plugtop - they appear to have operate quite happily for years like this (I always recommend a 20A supply is provided).

bigp26

Hi All,

Many thanks for your advice so far. Very much appreciated.

I've been exchanging emails with the installer all day, so I thought I would provide an update.

They have been very apologetic, and the last email I received said the following:


"Can you tell me what series your heater is please? (Under the flap on top it should say Series G or F or E, etc. If it is a G it can be programmed without the use of a timer.

If it is not a G then it will need a suitable timer capable of switching 3.3KW wired in correctly to a 20amp double pole isolator.

The heater will also need the 24hr supply for the timer/programming side which you already have with the socket outlet.

This arrangement has been okayed by Lawrence at Dimplex providing that the off peak supply isn’t on a plug top and correctly isolated (20amp double pole isolator)."

Any thoughts from you experts?

fluffpot

It's in that final paragraph - the OFF peak supply can't be on a plug top - but that's exactly what your electrician has done.

The storage heater element needs it's own dedicated circuit. Having a 20A double pole isolator makes no odds if it's run off a standard socket circuit!

As others have said, it was fire waiting to happen and the installer did not follow the wiring regulations or the installation instructions for the heater

they can't wriggle out of it...

[Deleted User]

Hi,

I would've though a panel heater would've done you in the bedroom, set to go on half hour before bed and rising, just to take chill off room, you don't need a warm bedroom during the day.

bigp26

Hi All,

Many thanks for all of your help so far. I thought I would post an update considering the installer returned on Tuesday.

p.s. I appreciate that some of the points in my update below may already mention things that you have all kindly advised about already, so I apologise in advance for repetition. I am starting to understand the basics, however am struggling with the exam question of “is it safe or not”?

Since the problem occurred, I have been in frequent email contact with the installer. The installer has also reached out to Dimplex, who have said it would be fine to install the off-peak element of the heater onto a ring main with the usual 32A breaker using a 20A double pole isolator before a 16A timer, assuming that loading, installation, grouping, Volt drop etc was in accordance with BS7671.

The installer therefore came round on Tuesday, and plugged this device into the plug socket which the heater was previously plugged into (before the plug melted). He took a reading of the impedance and explained that the low value means that installing the heater onto the ring main would be fine. Does this satisfy the tests that Dimplex mentioned?

He then proceeded to change the plug socket to a 20A DP switch, and connected it to a 16A timer which was installed beside it. This timer was then connected to the off-peak element.

We left the timer on an “always on” state temporarily to test that everything was working as expected, however after a few hours I noticed that the heater was blowing out cold air. All of the lights were on (on the 20A DP switch, and the timer), indicating that both new outlets were working, therefore I assumed that there was a lose/wrong connection between the timer and the heater. I switched the 20A switch off as I wasn’t going to be at home for a few days.

As you can imagine I was rather frustrated, thus I wrote a rather furious email back to the installer and demanded that these issues are rectified immediately. I also asked for written confirmation that the way in which the heater had been installed was safe and abiding to regulations. I therefore wanted them to accept liability if anything went wrong.

The installer replied and said that they would come and fit a dedicated wire from the fuse box to the room instead, all at their cost. They also said that they would hide the wire in trunking.

Fast forward to this weekend, when I turned the switch and timer back on and also factory reset the heater (I thought that if it was a charge problem, considering that the Quantum detects when it needs to charge and remembers when the electricity to the off-peak element is available and not, the factory reset would do the trick). I was surprised that the heater now worked as expected.

So now I am a bit unsure as to what to do. They have drilled a hole in the plasterboard to install the timer next to the 20A DP switch, so I don’t want a hole left there. At the same time, if there is any risk of danger in using the setup I currently have, I would rather them fit the dedicated wire and live with the annoyance of having a surface mounted wire extending from one end of the flat to the other, on my currently neat, clean and newly painted walls.

Advice would be much appreciated - they are scheduled to return to my flat next Saturday (12th March).

Many thanks in advance!
P.