Heat pump quote

QrizB

barker77 said:

QrizB how can I get that type of data from my octopus smart meter please ? 

The image is a sceen capture from the "My Energy" page in my online account at https://octous.energy and I would expect you to find the same information in yours.

70sbudgie

Thank you all so much for your comments. I feel like I am finally getting my head around heat loss calculations and HP sizing! 

I have come to the conclusion that the difference between our "actual" heat loss of ~6kW and the MCS calculated heat loss of 8.4kW is how we currently run our heating compared to the standard. For example, we have living areas at 18.5°C and bedrooms at 16°C. Also, cooler bathrooms mean shorter showers. And much to the disgust of my children, I am obsessed with shutting doors, so I guess the air changes are lower too. I am now going to have an attempt to show this with Heat Punk. 

All this information means that I am more comfortable with the 11.2kW Ecodan unit that has been specified. 

Now I just need to work out if my way of running the system, along with a tariff such as Octopus Cosy, will save me money.

FreeBear

QrizB said:

70sbudgie said:

Using this method, I get 6kW! Surely that can't be right?

I've got a model of my house in the MCS spreadsheet and it calculates a 7.38kW space heating load, but the most gas I've used on any day in the past winter was ~94kWh, and that ws the day we came back from a week away when the heating was turned right down and we had to re-heat the building structure from ~10C. 94/24 is near-as-dash-it 4kW. And that's consistent with the amount of gas my boiler burns when maintaining a steady temperature.

Here's my Octopus gas smart meter chart for that day:

This post has prompted me to have a look at data collected over the last few months. Highest gas consumption was on Jan.8th at ~44.45kWh (billed). According to the heat meter I have plumbed in close to the boiler, I used 40kWh to heat the house. Bars are one hour intervals...

In more detail, 5 min plot of indoor/outdoor temperatures (left axis), against power from the boiler (right axis).

Peak output was 11.6kW at 20:30.

Could do with a sustained period of subzero temperatures so that I can collect more data.

Reed_Richards

FreeBear said:

In more detail, 5 min plot of indoor/outdoor temperatures (left axis), against power from the boiler (right axis).

I'm amazed at the amount of variation in your indoor temperature, particular when your boiler stops doing anything between about 3 & 7 PM and allows the indoor temperature to fall a lot.  Was that you turning it off for a while?  I take it you do not have load compensation enabled?  This should give you a much more even indoor temperature and a more even use of gas hour-to-hour.

matelodave

Have you actually checked the temperatures at which a heatpump churns out it's rated output and what it can manage when it gets ever so cold.

Its sometime since I had my system installed but its 11kw rating is based on 7degrees outside to a flow temp of 35degrees and as the outside temp drops then output also drops so it doesn't always produce 11kwh when the temp drops. I guess new systems are a bit better than that and the specs may be better.

AFAIR it drops down to around 7-8kw at -2. When I got my system in 2010 I got access to the Daikin heatpump configuration programme which allowed you to do quite a few "what ifs" and it was interesting to see how the performance and output varied over varying temperature ranges. Not sure if its still available.

One of the interesting parameters was called the "equilibrium point" at which the heatpump managed to balance the heat load and how it varied depending on the size of the unit and the temperatures. In fact the simulation would also quote the anticipated number of days that the back-up heater would be required to maintain the system output level and show the amount of time that the unit output exceeded the requirement

You really need to check the system specs (assuming that you can find them) to see how different input/output temps affect both the output power and the COP. 

benson1980

Agree with matelodave. Not all ASHP ratings are equal and the how they rate the badged output will vary.

We have not too dissimilar calculated heat losses and have a 12kW unit. 

Couple of observations having read through this thread. I would concur with the danger signs regarding the installers you refer to in your initial post. Is this who you are still conversing with? 

Regarding your 'preferred' indoor temps, closing doors, cold bathrooms- I put in inverted commas as I wonder if these are indeed your (and your familys?) ideal indoor temps. The inference that the bathrooms are cold to limit shower times would perhaps indicate not. Not ASHP specific as such but the biggest benefit of our install and WC etc is the liberating feeling of it mostly being open loop and much more comfortable throughout with steady indoor temps (TRVs in bedrooms only to stop them getting too hot). You won't be saving much if anything in terms of running costs trying to zone, and shut doors. 

FreeBear

Reed_Richards said:

FreeBear said:

In more detail, 5 min plot of indoor/outdoor temperatures (left axis), against power from the boiler (right axis).

I'm amazed at the amount of variation in your indoor temperature, particular when your boiler stops doing anything between about 3 & 7 PM and allows the indoor temperature to fall a lot.  Was that you turning it off for a while?  I take it you do not have load compensation enabled?  This should give you a much more even indoor temperature and a more even use of gas hour-to-hour.

Heating is dialed back to 17°C from around 15:00, then at 20:30 is set to 19°C - This is done automatically as there is no point in keeping the temperature up high whilst I'm out. Since this data was collected, I've adjusted the PID parameters and tweaked the times & temperatures. Other days, the boiler has been ticking over quite nicely at 4kW for several hours.

70sbudgie

matelodave said:

Have you actually checked the temperatures at which a heatpump churns out it's rated output and what it can manage when it gets ever so cold.

Its sometime since I had my system installed but its 11kw rating is based on 7degrees outside to a flow temp of 35degrees and as the outside temp drops then output also drops so it doesn't always produce 11kwh when the temp drops. I guess new systems are a bit better than that and the specs may be better.

AFAIR it drops down to around 7-8kw at -2. When I got my system in 2010 I got access to the Daikin heatpump configuration programme which allowed you to do quite a few "what ifs" and it was interesting to see how the performance and output varied over varying temperature ranges. Not sure if its still available.

One of the interesting parameters was called the "equilibrium point" at which the heatpump managed to balance the heat load and how it varied depending on the size of the unit and the temperatures. In fact the simulation would also quote the anticipated number of days that the back-up heater would be required to maintain the system output level and show the amount of time that the unit output exceeded the requirement

You really need to check the system specs (assuming that you can find them) to see how different input/output temps affect both the output power and the COP. 

Yes, I have found a copy of the Ecodan databook. But at 466 pages, it isn't an easy read. Also, I don't necessarily understand what I am reading.

To me, it looks like the Ecodan range output their rated temp down to -5°C. 

benson1980

70sbudgie said:

matelodave said:

Have you actually checked the temperatures at which a heatpump churns out it's rated output and what it can manage when it gets ever so cold.

Its sometime since I had my system installed but its 11kw rating is based on 7degrees outside to a flow temp of 35degrees and as the outside temp drops then output also drops so it doesn't always produce 11kwh when the temp drops. I guess new systems are a bit better than that and the specs may be better.

AFAIR it drops down to around 7-8kw at -2. When I got my system in 2010 I got access to the Daikin heatpump configuration programme which allowed you to do quite a few "what ifs" and it was interesting to see how the performance and output varied over varying temperature ranges. Not sure if its still available.

One of the interesting parameters was called the "equilibrium point" at which the heatpump managed to balance the heat load and how it varied depending on the size of the unit and the temperatures. In fact the simulation would also quote the anticipated number of days that the back-up heater would be required to maintain the system output level and show the amount of time that the unit output exceeded the requirement

You really need to check the system specs (assuming that you can find them) to see how different input/output temps affect both the output power and the COP. 

Yes, I have found a copy of the Ecodan databook. But at 466 pages, it isn't an easy read. Also, I don't necessarily understand what I am reading.

To me, it looks like the Ecodan range output their rated temp down to -5°C. 

It is the datasheet that you want to have a look at. For example:

https://midsummerwholesale.co.uk/pdfs/mitsubishi-ecodan-6kw-datasheet.pdf

It looks like Mitsubishi badge theirs according to heating output at -7 if I'm reading it correctly. Not all manufacturers do this; for example Clivet use positive temps (7) thus their actual heating output will be lower than badged at minus temps. It is all slightly confusing.

shinytop

benson1980 said:

70sbudgie said:

matelodave said:

Have you actually checked the temperatures at which a heatpump churns out it's rated output and what it can manage when it gets ever so cold.

Its sometime since I had my system installed but its 11kw rating is based on 7degrees outside to a flow temp of 35degrees and as the outside temp drops then output also drops so it doesn't always produce 11kwh when the temp drops. I guess new systems are a bit better than that and the specs may be better.

AFAIR it drops down to around 7-8kw at -2. When I got my system in 2010 I got access to the Daikin heatpump configuration programme which allowed you to do quite a few "what ifs" and it was interesting to see how the performance and output varied over varying temperature ranges. Not sure if its still available.

One of the interesting parameters was called the "equilibrium point" at which the heatpump managed to balance the heat load and how it varied depending on the size of the unit and the temperatures. In fact the simulation would also quote the anticipated number of days that the back-up heater would be required to maintain the system output level and show the amount of time that the unit output exceeded the requirement

You really need to check the system specs (assuming that you can find them) to see how different input/output temps affect both the output power and the COP. 

Yes, I have found a copy of the Ecodan databook. But at 466 pages, it isn't an easy read. Also, I don't necessarily understand what I am reading.

To me, it looks like the Ecodan range output their rated temp down to -5°C. 

It is the datasheet that you want to have a look at. For example:

https://midsummerwholesale.co.uk/pdfs/mitsubishi-ecodan-6kw-datasheet.pdf

It looks like Mitsubishi badge theirs according to heating output at -7 if I'm reading it correctly. Not all manufacturers do this; for example Clivet use positive temps (7) thus their actual heating output will be lower than badged at minus temps. It is all slightly confusing.

They do, but even that's slightly misleading because it's at a flow of 35 deg.  Very few set ups would have a flow of 35 deg at -7 ambient.  That's not Mitsubishi's fault; it's a standard they have to quote. Having said that Mitsubishi is much better than others at not overstating power on their badges.  The 11.2kW Ecodan can deliver its badged output and more in realistic scenarios as the below extract from the data book shows.

The other thing to remember is that for your HP to output say 11kW continuously, your rads/ufh setup has to be capable of emitting that amount of heat at whatever flow temp you're using.