-----------------------Ecodan System, NW Scotland, some questions.

[John Mckay]

-----------------------Ecodan System, NW Scotland, some questions.

 

Hello, first off; many thanks to the forum! Two weeks ago, I came across the forum and began furiously adjusting the settings on my FTC-5 controller.  I have further questions though, perhaps not urgent, but have been bugging me since moving into the flat earlier this year.

Description of space: 

1^st floor flat, 2 bedroom, myself, and my son only. I work from home (a relatively recent development) so at home most of the day. The meter is on THTC (total heating, total control), I am next to completely ignorant of the tariff and how it affects my bill – this has changed in the last couple of weeks since focusing on the flat - the heating, the drafts! the flooring, the lighting, etc.

I use the shower once a day, my son has three baths a week. The shower is electric.

 

THTC:

From SSE, ‘If your home is all-electric and you live in the north of Scotland, you could be on Total Heating with Total Control (THTC). It works best with electric storage heaters rather than gas, oil, or wet electric heating.

With THTC you get two meters. One is for off-peak energy you use and the other records all your normal usage like lights, kitchen appliances and sockets. Just so you know, energy used on the normal meter costs more than our standard rate.

What are the times for THTC?

The specific time for the off-peak rate depends on the weather forecast for your area, but you'll get between 5 and 12 hours each day. THTC works by storing up heat in your storage heaters and hot water tank during the off-peak times.

Other electric heaters and heated appliances can also be used on the cheaper rate. The off-peak rate is available 24 hours a day for panel heaters, focal point fires, bathroom heaters, towel rails, the hot water boost, and even electric showers. You'll need to get an electrician to make sure all those appliances are connected to your cheaper-rate meter if you're not sure.’

 

Okay, thank you for reading so far!

Now, my questions.

 

1.       Should I keep my system at a higher temperature? Now I am controlling it with the ‘flow temperature’ at 33/36’. The temperature in the flat is … mild, which I personally am fine with as I ‘run hot’. But I keep reading the system is best used ‘at max’/at 45’ – should I increase this?

2.       How does the billing work?! From the above my understanding is the Ecodan is running on a lower rate for 5-12 hours a day, the rest of the time – a higher rate than normal? And, if I have two meters (one of which I cannot find), how are the two meters tracking the THREE different rates? IE, the 24/7 off-peak for the shower, the 5-12 hours off-peak for the THTC, and the higher than usual rate for the cooker, etc?

3.       Is the Ecodan ASHP system suitable for the THTC, or should I push for another tariff? From my scant understanding, the THTC is for storage heaters, does the Ecodan have storage heaters?!

4.       Defrost mode, comes on quite a bit. Should I ask the installation company if the fan has de-icer, and if it does – does the defrost mode need to be one?

5.       Is there a way to download the data from the FTC-5?

6.       How do I calculate the COP, I tried to understand this two weeks ago and struggled!

 

I think that might be enough! I have tried to make the questions succinct as possible, as I am finding the whole system a nuanced beast.

As I said at the start, the forum has helped a lot already. I have duct taped a few drafts in the kitchen, and the front door.

 

Update, during the time of signing up to this forum I received a reply from SSE answering a few of these questions – I will copy below, as I think it is good reference for others searching for info. re. THTC.

Quote

 

Your THTC is one meter, split into two parts, a standard part and a heating control part. The standard part records your usage for lights and domestic appliances. Your heating control part is split into a stored circuit and a 24 hour circuit.

Stored circuit

We send between 5 and 12 hours for your storage heaters to store and between 5 and 6 hours for your hot water to store.

The amount of hours we send depends on the weather, the colder it is the more hours we send you. The times we send for your heaters and water to store can vary.

Your Heaters and hot water store automatically at the cheaper unit rate

You usually receive a charge overnight, in the afternoon and sometimes late evening.

 The 24 hour circuit 

You can use any of the following at any time and be charged the cheaper rate -an electric shower,  boosting the hot water, using any bathroom heaters or towel rails and any panel heaters you may have.

These heating/water appliances should already be connected to your THTC meter

Please find below the current unit rates you are on:

Standard THTC (Pay as you go)

 

 

[John Mckay]

Quote

 

Please find below the current unit rates you are on:

Standard THTC (Pay as you go)

Annual standing charge: £ 115.85 (or 31.74 p per day)

Standard Unit Rate: 21.91Pence per kWh

Heating control Unit rate: 17.62Pence per kWh

 

Please can you confirm what ASHP means and what type of electric heating you have (i.e storage heaters or direct heaters) and if you need to store your hot water. This information will help me advise if staying on the THTC meter is best or if there is an alternative meter better suited. I'll be able to advise how each meter works and provide unit rates for our credit meters (where you can pay by Direct Debit and receive quarterly bills).

 

 

Anyway, I know this is know a massive post!

 

[ProDave]

Right, this THTC tariff.  It was something unique to SSE (I believe also in the southern half of SSE) and at the time was sold as "total control"

 

It is basically a normal off peak tariff that I think broadly mimics Economy 10 in that you get 10 hours of off peak rate over 3 different periods.  The off peak supply feeds things like storage heaters, but it sounds like you don't have those any more.  That accounts for one of your electricity meters that is a normal dual rate meter.

 

The thing that makes THTC unique, is the second meter gives you a 24/7 always on cheap rate supply that is supposed to only be used for "heating appliances"  which includes a shower, electric panel heaters, and of course in your case the ASHP.

 

So check that when the ASHP is on, it is the single "total control" meter that is counting up and you are being billed at the cheaper rate for that.  Your fuse boxes will usually be complicated and at least 2 of them, one bank of circuit breakers should be labelled "total control" and it is one of those that your ASHP should be connected to.

 

Now the bad news, the SSE THCT tariff is not a good rate.  It is also very hard to switch suppliers as most other energy suppliers can't cope with the metering.  I believe @newhome did manage after a long search to find another supplier to take on the THTC supply and she got a better rate by doing that. Perhaps she can come and join in and give advice on that?

 

I am not familiar with the Ecodan heat pumps so I will let someone else answer specific questions about settings etc.

[John Mckay]

Morning ProDave,

 

Thank you.  Yes, I have an air-source heat pump (I forgot to add that detail into initial post !), which is why I am struggling to understand why the housing association would marry the two, there is no storage heaters to speak of!

 

 

I have attached a picture below of my two fuse boxes. I keep wondering, 'should the heat pump be part of the standard rate box?'  

 

 

''SSE THCT tariff is not a good rate''

 

From what I can see, if I do need to change it, I will be asking the housing association to pay for the switch.  

 

 

There is an excellent report (https://www.changeworks.org.uk/sites/default/files/ImprovingConsumerOutcomesFund_Report_April2020.pdf) from 2020 that explains the problems of THTC in the North-West; interesting read, if the TV is on the blink!

[ProDave]

Your heat pump is presently connected to the main 24/7 supply so will presently get billed at the peak rate mostly.

 

If you moved the heat pump to the bottom consumer unit, one of the bank in the middle like the now vacant one that used to feed Bed+Bath that would put it on the permanent cheap rate feed.  Any competent electrician could swap that over for you.

[Stones]

@John Mckay

 

What kind of heat emitters do you have - underfloor heating / radiators / fan coil unit? Generally speaking the lower the flow temp, the higher the CoP. 

 

I'm currently achieving a CoP of 4 with flow temps between 26/29C. Over the course of the heating season 3.5 CoP.

 

When you say constantly defrost mode, I assume you mean seeing frost on the evaporator fins melting and water dripping from the unit? How often does this happen as it is part of an ASHP operation, especially when working hard/higher temps (DHW)?

 

To get your energy usage on the line of four buttons on the controller, press the right hand button. That should bring up energy use for both consumed and delivered. Divide delivered figure by consumed to give you a CoP figure.