Dimplex Quantum/gas central heating temperature control

Maikeru

I'm really happy with my new Quantum heaters; as series G models they seem to have worked out most of the kinks customers experienced with the earlier releases and they run beautifully. I got a new Q-Rad for the 2nd bedroom as well (which also works great) but have barely needed to use it as the heat from the QM150 in my landing just flows in to both bedrooms and the bathroom just by keeping the doors open.

Having just switched to Scottish Power's new Cancer Research tariff I'm now paying 5.4p night rate and 11.3p day rate electric. Given the artificial intelligence of the Quantum heater's in only taking the necessary charge, heat retention capability (50% of unused heat carried over to next day), overall 'controlability' (you basically set it once when you install it and never need to again) as well as the fact that its shelf life is at least double that of a combi boiler (circa 30 years) with no servicing costs or extra standing charges; the energy costs for my 3 bed 1960s townhouse would now seem to be more or less on a par with GCH (which is unavailable in my cul-de-sac). As the only form of electric heating that qualifies for the new SAP category of 'High Heat Retention Storage Heaters' (which achieves an even higher rating than fan-assisted) I'm looking at a Band D for my next EPC assessment, which is good going I think for the type of property I have.

I just have one query about the system though - as I mentioned I live in a 60s townhouse with a flat roof and insulation standards of its time (besides cavity wall and recently installed triple glazing). I am finding that on very cold days of around 0 degrees or less I have to set the Quantum in my living room to the maximum 26 degrees in order to achieve 21. Conversely on warmer days of 10 degrees plus I'm having to set it perhaps one degree lower than desired temperature in order to achieve the latter.

The latter is likely caused by the fact that I am still using off-peak underfloor heating (the 'storage' type from the 1960s inside the concrete floor) in the kitchen/diner area, which is adjacent to my living room on the other side of the staircase as part of a large open plan room taking up the whole floor (45sqm overall). Because this heating is just left on for all 7 off peak hours overnight (it has no means of control except a room thermostat), this no doubt affects the temperature in the living room as well. I'm not overly bothered by this as it only happens with unusually warm days here and there during winter.

I am guessing the former is caused by my house's below average insulation. However, I'm still confused as to why I need to turn up the heater to 26 degrees to achieve 21 on very cold days - Dimplex advised that this was fairly common and happens with GCH as well in less well insulated houses like mine. However, I see that in many gas central heating FAQ's that the prevailing advice is that turning up your thermostat to a higher temperature than needed does NOT enable you to achieve your desired temperature more quickly; it will simply burn unnecessary kw and it will take still just as long for the room to reach 21 (or whatever it may be). This seems to be at odds with what I've been advised by Dimplex. So my questions boil down to:


1. Does turning up the thermostat higher than you want help achieve desired temperature faster with GCH, Quantum, both or neither?

2. If so, why is this the case? Surely the boilers/Quantum heaters are designed to work as hard as they can to achieve the inputted temperature as quickly as possible, and they should just cease operating when the temperature is reached (until the room temp starts to drop again)?

3. Again if so, how do I know what temperature to set it to in order to achieve 21 as quickly as possible? Do I just guess based on how cold a day it is?

Thanks in advance.

stirling-gorilla

I have the Dimplex Quantum heaters not sure my opinion on them yet as this is the first time I have only used electric to heat my home.

I am finding though with them the same thing if I have them set at 21 the rooms aren't heating to that.

I live in a 200 year old, Mill workers tenement flat I'm ground floor, the property was "full" insulated with internal wall cladding (listed building, conservation area, old sandstone) also when the council insulated the flat the seemed to have forgot it had a bathroom in it as that is un-insulated and is like a fridge no matter what I do with the storage heater in there.

I'm currently working through what is best for these heaters for my circumstances but think once I have them mastered and got on a good tariff for them - another story thanks to a small mistake by Scottish Hydro.

I have looked into the Quantum series information manuals to see what they say and IIRC there may be a possible point on them where a external thermostat can be installed, so this may solve the apparent poor room heating from them.

As for on par to GCH I would say once managed I will be on par with it if not possibly slightly better.

reeac

In answer to your first question, it depends on whether the heater can dissipate heat faster than it can generate it. If it can then it will stay switched on until the thermostat setting is reached and that will be the fastest heating up that you can achieve. In my experience with hot water central heating the boiler generates more heat than the radiators can dissipate and so periodically it will switch off , driven by its own internal thermostat. You can have some control over this situation by raising the boiler stat. setting so that the water gets hotter, hence dissipating more heat from the radiators. I don't know whether Dimplex Quantum heaters behave in this manner.
It sounds, however, as if your heaters haven't enough heat output to attain more than 21C.
I think that you are correct in thinking that the underfloor heating is interfering with the working of the rest of the system on mild days.

reeac

Further thoughts: I think that your Dimplex heater thermostats , being presumably built in to the heaters are being biased by the temperature of the heater rather than of the room. This would explain why you need to offset their settings to above the desired room temperature. This has always been my doubt about thermostatic radiator valves as compared with a room stat. placed remote from the heat source.

Richie-from-the-Boro

Comment

The whole understanding of Quantum as a system is self evident, however the start point is always the same and that start point is broken from the get go in the above post.

I'm looking at a Band D for my next EPC assessment

Insulation levels #1 suggests the O/P is on an E which is a spectacularly poor level of insulation for a Quantum type install. All landlords are being forced by Ed Davy's very big regulation stick to upgrade their 4.2m million properties to E or above minimum or be banned from renting that sub standard property. So the insulation levels are somewhere between borderline and inadequate.

I'm still confused as to why I need to turn up the heater to 26 degrees to achieve 21 on very cold days

Any property / insulation / heating type is only as good as its controller and that controller regardless of the tech is only as good as the information its given. In this case the Quantum has (1) an on-unit thermocouple location rather than an off-unit, this is being confused by a (2) secondary thermocouple linked to the underfloor heating which may or may not be part of the whole [boshing] ground floor slab. The Quantum then reads a night-cost static input that determines a whole 24 hour profile comfort cycle adjusted by the day-cost 13a supplementary direct acting heater.

Even the iQ controller is going to be compromised by the fact that at 7am its decided that its quite warm and you need the 16 bricks filled overnight to a level of 50% with cheap electricity only to find by 10am that it needed 16 bricks filled overnight to a level of 90% because the 4 ton storage slab in the kitchen / ? / living area floor is cooling down rapidly and it can no longer provide a dial-in comfort level without the use of the supplementary 13a radiant heater.

Best of luck.

Maikeru

The Quantum then reads a night-cost static input that determines a whole 24 hour profile comfort cycle adjusted by the day-cost 13a supplementary direct acting heater.

Even the iQ controller is going to be compromised by the fact that at 7am its decided that its quite warm and you need the 16 bricks filled overnight to a level of 50% with cheap electricity only to find by 10am that it needed 16 bricks filled overnight to a level of 90% because the 4 ton storage slab in the kitchen / ? / living area floor is cooling down rapidly and it can no longer provide a dial-in comfort level without the use of the supplementary 13a radiant heater.


The 13a direct acting heater only kicks in when the user decides to initiate the 'boost' function. Dimplex themselves have confirmed to me that it never kicks in automatically; if the stored heat runs out then the fan just stops and no heat is released.

Using a Quantum combined with underfloor heating in the kitchen/diner and living room has been fine thus far; I haven't run out of stored heat at all except perhaps on one or two exceptionally cold days when the fan shut down at 9:30pm - but the room temp still stayed above 20 till bedtime so I had no need to use the boost element. Dimplex did indicate that undercharging was possible when using it in combination with the underfloor heating but this has not proved to be the case.

And thus far I have been using on average 85 kilowatts off peak electric daily to keep a whole 1200 square foot three storey house nice and warm all day long in mid winter (my wife is home with the baby all day at the moment). I have Quantum 150s in my ground floor and top floor landings that keep the bedrooms nice and warm, and another in the living room used in conjunction with the underfloor heating. Based on my experience so far I see no reason to shell out on another QM150 for the kitchen diner area and run it on slave mode when the existing underfloor heating is perfectly adequate. This is the advice I received from a senior technical engineer at Dimplex:

I’d leave the heater to operate for a week with the same settings left active and see how well it responds. If the heating is satisfactory then I’d leave it there, however if not then I would activate ‘slave mode’ and leave it for three more days to see the effect. If it still does not provide sufficient heating then I would add an hour’s extra charge.

The product should certainly be made to operate correctly, however there will be an impact from this other heat source that we’d need to consider and account for. The main thing will be that the product will not adjust to change as accurately with the above measures, so either the QM or the under-floor (preferably both!) will need to be set to a constant programme to provide a ‘base’ from which to operate.

I would expect to see under-charging if the underfloor is set to significantly different programmes day-to-day as we’re restricting its ability to adjust to the environment by stopping it reacting to the other source of heat.


I have sufficient heating and have experienced no undercharging or need to use the boost function.

Richie-from-the-Boro

I am finding that on very cold days of around 0 degrees or less I have to set the Quantum in my living room to the maximum 26 degrees in order to achieve 21. Conversely on warmer days of 10 degrees plus I'm having to set it perhaps one degree lower than desired temperature in order to achieve the latter.

The heat design service works on a maximum 18.2kWh [ish] of stored heat per can-unit night, the slab that is underfloor will leech from kitchen to wherever the slab extends to. On particularly cold nights such as °C that leech will of course be greater.

Any property / insulation / heating type is only as good as its controller and that controller regardless of the tech is only as good as the information its given

So yes you will have to compensate with a +5 or more degree requirement which is outside the 0.3°C that Quantum use as as an important part of their algorithm or install an integrated off site controller monitor into the kitchen area. You seem not to want to accept that you have two ferrets fighting in a bag, one the Quantum thinks its in control until about 7am when the kitchen reverses and starts to lose its stored content then the other the Quantum finds it would be under-stored if it was not for the fact that you lied to it and told it you wanted a +5°C setting.

I am not an enemy of Quantum, I'm well known on this forum as a major supporter of both the Quantum and the CAT7 HHRS designation and the SAP 2012 criteria. Its been a consistent ardent desire of mine to see 'night store' cans, insulation and controls uprated, 'smarted' and integrated into TOU tariffs - look up any selection of the thousands of my posts over the years on this subject on this very forum. Take care Maikeru.