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

JohnMckay101

-----------------------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: 

1st 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.

 
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)
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!

 

Reed_Richards

I know nothing about THTC but can answer questions about ASHPs:

1. For best economy you should make your flow temperature as low as possible.  In effect this means keeping your dwelling at as low a temperature as you feel comfortable with.
2. Storage heaters work best when charged at a cheap electricity rate, which is usually available overnight.  An ASHP will tend to run more efficiently during the day when it tends to be warmer outside.  So a system designed for storage heaters is unlikely to be compatible with an ASHP.
3. The Ecodan does not have storage heaters, you will either have radiators or underfloor heating.  Therefore, as (2), I think it unlikely you are on the best tariff.
4. Defrost mode is what de-ices the fan on your ASHP.  It should not be needed until the outside temperature is close to or below zero.
5. I have no idea about your controller
6. Unless you have special measuring equipment you cannot calculate your own CoP.

A heat pump will generally provide you with a tank full of hot water.  If you have a hot water cylinder it is more economical to use this hot water than to run an electric shower.

    

shinytop

@JohnMckay101

I have an Ecodan ASHP.  It has the FTC6 controller but it's very similar to yours. As @Reed _Richards says, lower flow is better/cheaper, as long as it still heats the house.  In general the ASHP will be less efficient at 45C flow than at 36C.  The short answer is that controlling the heating using flow temp is the best thing to do but the Ecodan has different ways of doing it, depending on how it's installed.  You really want to be using its Weather Compensation facility, which varies the flow temp according to the outside temp.  

If you answer a couple of questions I can help with the controller. 
(1) Is the main, wired controller mounted in the living space or in the airing cupboard
(2) do you have wireless thermostats and are they Mitsubishi or 3rd party 

I can heat my whole house to 21C with flow temps of 30C when it's 7C outside. That will go up when it gets colder but it shows you don't always need 40C plus radiators.   

You're not a HHP user are you?  

https://www.hebrideanhousing.co.uk/wp-content/uploads/2019/11/Mitsubishi-tenant-guide.pdf

Gerry1

In normal circumstances you'd probably be better off on the normal single rate.  However, those prices don't seem too bad today.  It would probably be cheaper to pay by Direct Debit.

THTC isn't widely available.  It was intended for very old storage heaters and is being phased out.  SSE are obliged to offer single rate without a meter change, but I don't know whether that would be at the capped rate: you could always ask.

Some of these links may be vaguely relevant, although they tend to assume you have storage heaters.  May be best to do nothing for the time being except change to DD.

matelodave

Generally the heatpump should be run at the lowest temperature you can get away with for maximum efficiency and lowest running costs.

As it runs most of the day and not so much overnight (depending on how your heting is set up) then ideally you want to be on the lowest cost tariff for the major part of the day and evening so it depend how your heatpump has been wired into the existing circuits. THTC  should have an "off-peak" circuit for storage heating, and a peak/offpeak circuit for other stuff, so you really need to sort out what the meters are telling you and when they are supplying power and when they switch  (I'd guess that to get the HP running all day then it's on the peak/off-peak circuit)

Although you've got two meters AFAIK  in the old arrangement one will be dedicated to the off-peak circuit ( just the storage heaters and hot water tank heater) and will only switch on at off-peak times (controlled by the supplier) and the second meter will be a peak/off peak meter which switches between peak and off-peak (again controlled by the supplier)

As said above the cheapest way to bath, shower and use hot water is from the hot water tank heated by the heatpump as it will be around a third of the cost of hot water heater by the shower or immersion heater. Make sure the hot water is kept below 55degress, otherwise the immersion/boost heater will kick in and increase your costs. Most heapumps have a sterilisation cycle that runs once a week and heat the water above 60degrees for a period to sterilise the tank so you dont need to keep tit hot all the time. We get away with our water temp at 45 degrees.

Gerry is right, the tariff costs that you are on are probably about as good as you can get at the moment. You can probably increase your benefit by making sure that the hot water phase on the heatpump only runs during off-peak times and make sure you use the wahing machine etc during off-peak times as well.

Regarding machine icing, it usually only happens when it's pretty cold and damp outside and TBH it really doesn't use all that much energy so get get wound up about it.

Dont bother about COP, it's nighon impossible to determine unless you have specialised measuring and recording equipment as its a variable, based on flow temp, input temp and the ouside air temperature, all of which are changing minute by minute. It's can be better than 4 in the summer and down to 2 or less when its everso cold outside. Trying to work it out will just give you a headache, you wont be any wiser and TBH it will just worry you if you dont really understand all the nuances.