Dimplex Quantum storage heater will no longer fully charge, help

Mantis_Toboggan

Hi, I'm having issues with my QM125RF (from 2016).

About a week ago the display overheated showing error 32, after dismissing the error it went back to working normally for the rest of the day, however after that evening, it only charges 5.5Kwh, when it used to charge around 15Kwh (full charge). The core temp only reaches 62C now instead of the usual 110C. I tried a factory reset but it didn't help, any thoughts on what it could be? It's been like this for over a week now.

The off peak supply is still coming on as usual, so it should have plenty of time to charge.

I haven't changed any other settings and it has been very cold so I'd expect it to fully charge, I have another storage heater in a different room and that one is working normally.

Any help will be appreciated, I tried calling Dimplex but they were of very little help since it wasn't under warranty.

QrizB

Isn't the QM125RF meant to charge 19.3kWh? It's the QM100RF that takes 15.5kWh.

Looking at the various info available online it seems these heaters all have three elements. It sounds as though two of yours might have failed, and only one is working. (It might not be the elements themselves, it could be a break in a connecting cable - potentially related to the overheating you saw before?) Unless you're a confident DIYer you might need an electrician.

See the installation manual here, the wiring diagram is on the last page:

https://www.heatershop.co.uk/Cache/Downloads/quantum-installation.pdf

Gerry1

Do the Storage Heater Sanity Test.

Mantis_Toboggan

QrizB said:

Isn't the QM125RF meant to charge 19.3kWh? It's the QM100RF that takes 15.5kWh.

You are right, that's just what I could see on the Kwh usage history for the days before it started acting up.

I thought that it it could be the heating elements, but I found it odd that it's been charging exactly 5.5Kwh every night, I would have thought that if an element failed then the others would try to continue heating until the internal core temp was reached? 

Do you know if there is a way to check in the report screens to see if a heating element has failed? I had a look and couldn't see any obvious damage to wires or connections, but I'm not confident enough to mess with the wiring myself.

Mantis_Toboggan

Gerry1 said:

Do the Storage Heater Sanity Test.

I hadn't thought of that, so these are quantum so everything is automated, so I assume that since the core temp is below 30C that once the off-peak power comes on, it should start pulling 100% of the input rate?

I have a smart meter so I could monitor the usage there, since the input is 2760 W, I assume that any usage below 2.76Kwh would be a sign that one or more of them are not working?

If so, is there another component that could be the cause or just the heating element itself? The control module seems to be working normally.

mmmmikey

Mantis_Toboggan said:

Gerry1 said:

Do the Storage Heater Sanity Test.

I hadn't thought of that, so these are quantum so everything is automated, so I assume that since the core temp is below 30C that once the off-peak power comes on, it should start pulling 100% of the input rate?

I have a smart meter so I could monitor the usage there, since the input is 2760 W, I assume that any usage below 2.76Kwh would be a sign that one or more of them are not working?

If so, is there another component that could be the cause or just the heating element itself? The control module seems to be working normally.

It could be the wiring between the element and the control unit or the connection at either end. You need to be aware that even if the current problem is related to the heating elements that may or may not explain the original overheating issue. Although I haven't taken a Quantum apart, I have repaired various other storage heaters and the elements have always been easy to change if, and only if, you are experienced with working with electrical equipment.

Edit: note that it could be the thermostat (or temperature control circuitry) though my money would be on a heating element. Also be aware that it might only be one element with the thermostat cutting out all elements when it gets up to temperature at the location of the thermostat.

EssexHebridean

I'm wondering whether the elements on Quantums have separate thermal cutouts, and the overheating here means that one or two of those cutouts have blown. It will still need a sparky to open it up, but might just be resettable rather than needing a replacement part. 

My suspicion is that if this is a single element  or two not working, the heater's "brain" doesn't recognise that, so the heating up continues as "normal" - ie at the same rate - and so there isn't sufficient energy in + time to allow the heater to heat to the right level. 

Knowing how much power it's drawing when it first kicks in to charge will help establish what's happening. 

Mantis_Toboggan

Thanks guys, what you are saying makes sense and lines up with the numbers I've done below:

Last night I stayed up to see how much power it was drawing and it turned out to be 920w, the heater has three elements and the rated input is 2760w, so bang on 920x3. So it's definitely only one element running and since I had it set to charge for 6 hours, it lines up with the 5.5Kwh which is what it has been using each night for the past few days.

Looking at the wiring diagram and the wires, it seems like two of them might share the same thermal cutout? if it's that, can it be reset or does it need to replaced? In any case, I'd pay a sparky to do it.