Quantum Dimplex Night Storage Heater Won't Charge at Max Rate

A Chinese ‘smart-breaker’ - operating on a fixed schedule to coincide with my tariff’s main, fixed night cheap rate which is only 6 hours long.  There are (as previously stated) additional daytime periods of the same cheap (7p/kWh) rates but they are random.  I might be able to make use of these with something clever like Node Red (https://nodered.org/) but that’s a learning curve I’d like to avoid climbing for the time being.

I’m afraid the tariff is most definitely one limiting factor - as clearly demonstrated by the screenshot of my energy monitoring kit above.  I have 6 hours (avoiding the tariff’s random daytime ‘on’ sessions) to charge the Quantum’s ~7kW of storage from only 680W-worth of heating element (being the other limiting factor - the ‘symbols’ you refer to are just connections… and offpeak is connected to 2 elements not 1 and they appear to be - going from the look of the PCB - to be mosfet-driven, not relay-driven).

However, there is a feature in the advanced menu which talks about programming the Quantum to store more energy than normal but it is a bit obscurely written:
“Charging Settings

If the output of the storage heater is not able to deliver the required heat demand throughout the day, it is possible to force the heater to store additional energy. This will manually adjust the charge calculation to store more electrical energy during the charging period.

This setting displays the available charge times for the Heater to store off -peak energy. It is presented like the Timer setup screen, but without a Target Temperature or Day Selection. This allows the Installer to set up to 4 charging On and Off times.

Charge Times

This setting displays the available charge times for the Heater to store off -peak energy. It is presented like the Timer setup screen, but without a Target Temperature or Day Selection. This allows the Installer to set up to 4 charging On and Off times.

Default charge times (Standalone) are:

Period 1 00:00 - 00:00

Period 2 00:00 - 00:00

Period 3 00:00 - 00:00

Period 4 00:00 - 00:00

Charge times should remain at the default settings (as shown above) for twin supply installations. This setting

should only be used in single supply installations. Values entered here always take precedent.”

Fortunately, this doesn't help because I'm still stuck with only having access to the Fixed six hours overnight for charging unless the third element can be brought into play somehow but this is where the instructions are not very clear. It reminds me of Chinese-made devices which have lots of functionality but whose user-manuals are so badly written it's next to impossible to make use of them all.
 

So I think I will be looking into Node Red after all…

I use Home Assistant on ours (Solar inverter/tariff control) which hasn’t been too bad considering that I haven’t really coded since ‘Basic’ days. The HA community is very good at sharing code.

I do know of others using Node Red but I’ve not experienced it myself

We’re getting into the realm of the configuration settings I touched on. You haven’t told us, I think, whether this installation is single- or dual-supply. It is a common arrangement for Economy 7 installations to have two supplies to a night-storage heater: one for charging, energized only during offpeak hours, and the other constantly live to power the heater’s controls, its fan and its booster element.

Since you’re apparently on a half-hourly metered Time of Use tariff, it would be natural to assume that there’s only one, constant, supply to the heater. Your statement “I'm still stuck with only having access to the Fixed six hours overnight for charging” is a bit worrying - in what way is access limited? It would be if the meter were controlling a switched charging circuit, but that doesn’t make sense with the tariff you’re on.

It looks like the instructions you were given would solve the problem you’re facing, but you’ll have to come clean about how power is currently delivered to the heater.

Hi Firedog,  Thank for your reply.  I did mention in my second post that there is a separate 24hour supply on the ‘peak’ connection - which is on a different ‘day-time’ tariff.

My offpeak tariff (as also previously mentioned) has a fixed ‘on’ time from 2330 to 0530 every day.  It is on 24 hours otherwise but if I use it outside the night period (or whatever random other daytime periods Octopus choose to provide and which I currently cannot take advantage of) then I pay more than 4 times more for the electricity, hence my reluctance to use it.

​@martinwinlow Now I’m confused, but that’s nothing unusual!

You have a dual supply to your heater, one - for charging - limited to six hours nightly, the other constant for the fan, controls and boost function. This is the normal arrangement for Economy n tariffs, where the meter controls the charging feed. Assuming you have a meter equipped with an ALCS, you are apparently not on a tariff like this, which when operating normally uses two distinct timetables:

1.   The tariff switching table, which tells the meter when to switch from recording on the offpeak and peak registers. 
2. The ALCS calendar, which controls the times when the time-limited (‘restricted’) circuit is energized.  

Your Octopus tariff apparently ignores the meter registers and bills you according to the half-hourly usage data. I’m not sure quite how it controls the timings, but it may involve (a) remotely setting the ALCS calendar to the overnight period 23:30 - 05:30, and (b) remotely activating the meter’s Boost function to operate for the extra daytime hour, which can vary from day to day. It looks as if the restricted circuit only powers two of the three elements in the heater, so any ALCS override (‘Boost’) would draw 680W, but it wouldn’t affect the fan setting.

I think it’s time we saw some photos of your installation, ideally:

• a close-up of the meter itself (with the display lit up by touching a button if necessary) clear enough to be able to read the display and the markings on the meter itself;
• A view of the whole backboard so we can see the main supply cable coming in from outside, and all the cables to and from the meter itself;
• If it’s not clear from the previous photo, a close-up of the meter exchange label - the card left by the engineer giving the numbers and readings of both the old and new meters (assuming he did leave one, as he’s supposed to do);
• A view of each consumer unit (fuse box) clear enough to be able to read any labels the electrician may have left to say which breaker is which.

Before posting, please obscure part of the Meter Serial Number - a dodgy operator could use it to find your address.

I may ask for more if we need more clarification. 

​@Firedog martinwinlow uses a smart switch programmed to coincide with the discount rate. Its further up the thread. So not using the smart meter to switch.

Peter 

That’s what’s confusing me. Why would there be two separate constant feeds to the heater where one would do? The logical explanation is that there were - pre-Smart - two feeds, one constant and the other restricted, to give offpeak charging on an Economy tariff. The engineer who installed the smart meter would normally have acted accordingly and fitted a meter capable of doing the same thing.

This doesn’t work well with smart ToU tariffs like Octopus’ Snug or EV offerings, and some customers wanting to avail themselves of this type of tariff have asked whether the restricted feed could be ‘derestricted’ by setting the ALCS to ‘always on’. This is what Martin’s “My offpeak tariff ... has a fixed ‘on’ time from 2330 to 0530 every day.  It is on 24 hours otherwise ...” looks like. The problem with that is, we’re told, that the secondary 100A contactor inside the meter is not rated for constant use*. A 2A relay controlling an external 100A contactor wouldn’t, I think, be subject to this limitation. 

Switching to single-supply (which might just involve swapping jumpers inside the heater) would enable Martin to take advantage of the full 1020W available for charging, which is where this thread started.

Photos would really help …
 

* One customer managed to unearth a manufacturer’s spec sheet which showed that the secondary contactor in his meter is indeed rated for continuous service, but I haven’t seen the document itself. This may not be the case for all ALCSs.  

​@Firedog Maybe I'm not seeing it but the Peak connection is the constant feed and the Off Peak is what is connected to the smart switch which is simulating what would be the E7 switched output from an E7 meter if he had one. But if that gad been the case I'm not sure why it isn't working correctly. Settings? 

Hi Peter E,

Sorry, but we do seem to be going around in circles, here!  My original post was about the fact that the specs for the QM050RF state it has an ‘input rating’ of ~1kW and has ~7kWh of heat storage implying that it can, on an Eco7 tariff, fully charge its 7kW of bricks ‘overnight’.  However, I can only see it charging at 700W max and therefore it does not ever fully charge, as confirmed by its own stored data; never charging more than ~4.2kW.  I do appreciate I only have six hours but nevertheless it could be storing considerably more energy than it currently is.

I can’t get any sense out of Dimplex as to a understanding how the unit works better or a work-around and they have now stopped answering my emails.  It is very disappointing.  I am resolved to the prospect of trying to use something like Home Assistant to take advantage of the additional random daytime cheap periods of power but, as I say, I kind of feel like I have been mis-sold the heater.