Heating, Hot water, ASHP, and Sunamp Design Needed

[LA3222]

28 minutes ago, Triassic said:

According to the blurb - The Aquarea Monobloc J generation heat pump supplies water for cooling, heating and/or for storing domestic hot water.

 

Can't  find any info on cooling for the Ecodan!

The Ecodan does do cooling, its in the dip switches.

[Triassic]

So its all down to price. One being £300 cheaper than the other?

[LA3222]

2 minutes ago, Triassic said:

So its all down to price. One being £300 cheaper than the other?

Are you getting a preplumbed cylinder? I find that the Ecodan one comes with the controller attached to the cylinder with all the wiring pretty much pre done which I like as it cuts down on the amount of thinking I have to do myself?‍♂️

 

Not sure if this is the case with the Panasonic types?

[Triassic]

1 minute ago, LA3222 said:

Are you getting a preplumbed cylinder? I find that the Ecodan one comes with the controller attached to the cylinder with all the wiring pretty much pre done which I like as it cuts down on the amount of thinking I have to do myself?‍♂️

I was thinking along these lines. I was going to look at pre-plumbed cylinders next.

[Stones]

The pre-plumbed cylinders are expensive, but do offer a complete package. 

 

We have a Mitsubushi Ecodan with preplumb cylinder package and it works flawlessly.  Taken in the round, yes you pay more for the cylinder, but its simple and quick connections (plumbing and electrical) so you save time and energy on that side if creating your own set up.  Perhaps also worth considering the peace of mind of going for something that has been designed as an all in one package- all the hard design work and testing has been done.  For us, worth every penny.

[Triassic]

7 minutes ago, Stones said:

For us, worth every penny.

Dare I ask, how much?

[Stones]

£4152.55 delivered (to Orkney) for 8.5kW ASHP with coastal coating, FTC5 controller and 300l preplumb cylinder.  That was in 2016 though.

[Triassic]

13 hours ago, Stones said:

£4152.55 delivered (to Orkney) for 8.5kW ASHP with coastal coating, FTC5 controller and 300l preplumb cylinder.  That was in 2016 though.

I might be able to get close to that price if I go for an off the shelf pre-plumbed cylinder rather than a designer branded package! 
 

What make of cylinder is best in terms of quality of construction and price?

[LA3222]

28 minutes ago, Triassic said:

I might be able to get close to that price if I go for an off the shelf pre-plumbed cylinder rather than a designer branded package! 
 

What make of cylinder is best in terms of quality of construction and price?

If you go for an alternate cylinder you will have to integrate the controller into the setup yourself or the trade will have to do it. How much will a trade charge for that? The manuals are hefty reads so it won't be a quick job, I'd hazard any savings would be lost on a tradesman day rate to set it all up.

 

If you're doing it yourself it is an epic task to get to grips with and you'll lose a fair few days which could be better spent elsewhere?

 

It may be a false economy to go for a non branded cylinder?

[LA3222]

Just checked, I paid £4870 for the 8.5kW Ecodan ASHP & 300l UVC. So in 5yrs that's a £700 increase, 3% a year isn't too onerous.

[Triassic]

4 hours ago, LA3222 said:

Just checked, I paid £4870 for the 8.5kW Ecodan ASHP & 300l UVC.

That’s a bit more than I’d budgeted for, but I am saving money by not having a Sunamp!

[Triassic]

On 06/03/2021 at 09:31, LA3222 said:

Just checked, I paid £4870 for the 8.5kW Ecodan ASHP & 300l UVC. So in 5yrs that's a £700 increase, 3% a year isn't too onerous.

I’ve just been quoted £4909 ex VAT, including ore-plumbed cylinder, the installation kit and some sort of Ecodan transmitter receiver? 
 

was your price Is with VAT or ex VAT?

Edited March 8, 2021 by Triassic

[LA3222]

48 minutes ago, Triassic said:

I’ve just been quoted £4909 ex VAT, including ore-plumbed cylinder, the installation kit and some sort of Ecodan transmitter receiver? 
 

was your price Is with VAT or ex VAT?

Ex VAT, dunno what the transmitter bit is - who is this with?

[PeterW]

3 hours ago, Triassic said:

I’ve just been quoted £4909 ex VAT, including ore-plumbed cylinder, the installation kit and some sort of Ecodan transmitter receiver? 
 

was your price Is with VAT or ex VAT?

Will be the Ecodan FTC unit which should be an FTC6 now as the old FTC5’s are finished now. 

[TerryE]

23 hours ago, Triassic said:

I’ve just been quoted £4909 ex VAT,

 

The price would be an issue for me as there would be no way to generate a realistic cost-benefit payback period at our level of use.  In our case, it is easier and cheaper to take the hit for the resistive heating costs which we can optimise on a green ToU tariff. 

[Stones]

@TerryE you've perhaps said before, what is your annual usage in kWh for heating, and the target internal temp you maintain?

[TerryE]

@Stones Jason, I'll need to run a SQL query to give my annualised actuals.  I'll post back later.  My target setpoint is 22.3 °C, but the way my algo work this is more of a typical lower bound and the house cycles between about 23.3 °C at peak which is around 11:00 to a minimum at 01:00.  Of course we could go lower but Jan like to wander around barefoot in sleeveless tops.  However on the actuals, one thing that we do know is that a thermal bridge in out slab (I discussed its mitigation in this blog post) adds maybe 10 kWh to our daily slab losses for the ~6 months of net heating -- say £150 p.a. on our energy bills.  We can estimate that by switching form UFH to space heating for a few days and letting the slab slowly chill down maybe a degree or so during this window.  Annoying but we can live with it.  

[MikeSharp01]

It will be interesting to see the overall figures and how the £150 compares to the full total. 

[TerryE]

I've just done the query.  The daily averages (rounded to nearest kWh) for Sep..May are 2, 16, 17, 23, 25, 22, 19, 9, 5 kWh or 4,148 kWh total.  I also run a small oil-filled electric heater on an overnight timer in my first floor study Nov-Feb with the hours per night depending roughly on the average external temperature.  I estimate that this adds another 480 kWh so the total heating load is around 4,700 kWh with about 90% at E7 tariff. 

 

I just had a look at my "JSH style" initial estimate.  The main error that I made in this was due to my assumption that all other electricity use ends up as waste heat which for heating days also warms the house: our new house electrics are more energy efficient so the base load is less than I estimated, and therefore we need more top-up.  I also used a temperature set-point of 21°C rather than our currently preferred average which is around 22.8°C.  Adjusting for both of these, the new estimate (to my amazement) was also 4,700 kWh .

 

On reflection, it looks like my 10kWh mentioned above was just a measure of the thermal banking in the main ring foundations within the warm slab.  It looks like the mitigation did its job. 

 

TL;DR: our as-built thermal performance is a good ballpark of the as-designed.

 

I am currently on an OVO 2 year fixed tariff at 9.19p and  15.81p per kWh + VAT, so totals roughly £490 for my annual heating cost.  DHW, cooking and all other use is on top.  Given that I use little or no heating for the 4 summer months, I can cross check my total annual bill against the annualised cost for these summer months and this is consistent with this figure. 

 

Incidentally I estimate that switching to use an ASHP would only save perhaps 50-60% of this (at an average CoP of 3 say, but more peak rate tariff), say £290 p.a.  That's why I find it difficult to justify the cost of installation of an ASHP.

 

I am going to switch to an Octopus ToU tariff but the process is that you have to switch to Octopus on an interim single rate tariff until they switch your smart meter, so I am waiting until April because I want to take advantage of the OVO off-peak tariff in the meantime.

 

I also have no components in the system requiring annual professional maintenance so I have no annual maintenance bills.

Edited March 11, 2021 by TerryE

[MikeSharp01]

Brilliant Terry - a very real energy view of a real house using the novel Willis approach. Also a great example of what good instrumentation can tell you.

[dpmiller]

A self-installed sub £1k unit would seem like a no-brainer to me.

[Stones]

On 10/03/2021 at 03:35, TerryE said:

I've just done the query.  The daily averages (rounded to nearest kWh) for Sep..May are 2, 16, 17, 23, 25, 22, 19, 9, 5 kWh or 4,148 kWh total.  I also run a small oil-filled electric heater on an overnight timer in my first floor study Nov-Feb with the hours per night depending roughly on the average external temperature.  I estimate that this adds another 480 kWh so the total heating load is around 4,700 kWh with about 90% at E7 tariff. 

 

I just had a look at my "JSH style" initial estimate.  The main error that I made in this was due to my assumption that all other electricity use ends up as waste heat which for heating days also warms the house: our new house electrics are more energy efficient so the base load is less than I estimated, and therefore we need more top-up.  I also used a temperature set-point of 21°C rather than our currently preferred average which is around 22.8°C.  Adjusting for both of these, the new estimate (to my amazement) was also 4,700 kWh .

 

On reflection, it looks like my 10kWh mentioned above was just a measure of the thermal banking in the main ring foundations within the warm slab.  It looks like the mitigation did its job. 

 

TL;DR: our as-built thermal performance is a good ballpark of the as-designed.

 

I am currently on an OVO 2 year fixed tariff at 9.19p and  15.81p per kWh + VAT, so totals roughly £490 for my annual heating cost.  DHW, cooking and all other use is on top.  Given that I use little or no heating for the 4 summer months, I can cross check my total annual bill against the annualised cost for these summer months and this is consistent with this figure. 

 

Incidentally I estimate that switching to use an ASHP would only save perhaps 50-60% of this (at an average CoP of 3 say, but more peak rate tariff), say £290 p.a.  That's why I find it difficult to justify the cost of installation of an ASHP.

 

I am going to switch to an Octopus ToU tariff but the process is that you have to switch to Octopus on an interim single rate tariff until they switch your smart meter, so I am waiting until April because I want to take advantage of the OVO off-peak tariff in the meantime.

 

I also have no components in the system requiring annual professional maintenance so I have no annual maintenance bills.

 

Thanks Terry.  Really interesting to see.  We use a bit more and over the past 4 years it has ranged between 6500 and 7000 kWh for heating.  We are achieving a CoP of 3.8 over the heating season, so an input energy requirement of between 1700 and 1842 kWh.  At my current tariff of 13.44p/kWh I'm paying £228 and £247 per annum, to keep the house comfortably at 21.5C

 

When I was deciding which route to go down I compared various different options and configurations and came to the following conclusion.  If DHW and Heating requirement were sub 2500 kWh then direct electric resistive heating was the most cost effective.  Between 2500 and 5000 kWh the balance started to shift to other solutions and over 5000 kWh then ASHP won out.  

 

Looking at your heating figures, and assuming you could get the same 3.8 CoP, would mean an input energy requirement of 1250 kWh per annum.  Split 750/500 between night/day would cost you £147 per annum.  Your in the realms of it making sense financially based on a ten year life of an ASHP (which is what I factored), but probably not enough for the hassle given you have a perfectly functional set up.  Of course the real beauty of your set up is the simplicity of the willis heater and ease of repair. 

 

This brings us full circle back to what we concluded a few years ago when we discussed this, different ways to meet individual requirements (which of course vary but may be the biggest decision drivers) but ultimately, the overall cost balances out for a given energy requirement (for low/lowish energy requirements).

 

[TerryE]

2 hours ago, Stones said:

At my current tariff of 13.44p/kWh

 

You want to investigate whether a Time of Use tariff might give you a better overall rate.  A simple strategy on moving as much use outside the 16:30 - 19:30 window when the rates pretty much treble would give you a far better average rate. 

[TerryE]

What I want to do is to update my CH scheduling algorithm after I switch to the ToU tariff.

 

The current algo has inputs terms: (i) based on external temperature, and (ii) a day-to-day feedback to prevent creep over or under-heat.  This has a number of limitations:

1. Solar gain.  Because the orientation of the principle elevation (SE) and our relatively small front windows we get little solar gain in the winter.  The one time we do on clear sunny mornings in heating days where this gain can still amount to 5-10 kWh -- occasional but when it happens this offset has a clear impact (maybe a °C or so) on our internal temperatures.
2. Visitors and visits.  Not an issue this last year, but adding say 2 kids and 2 grandkids to the house plus all of the extra cooking etc., is still another 5-10 kWh heat, and a similar step down when they leave.
3. The oil-filled electric radiator. This is an unknown addition from the perspective of the control algo.  Perhaps I need to stick to a fixed heat output and used a smart plug to control the heat input.
4. E7 boundary issues.  The control system computes a daily input and puts up to 7 hrs in during the off-peak window.  Any extra is input only when the hall temperature falls below a threshold, so looking at the event log, (1) and (3) mean that that the computed total is usually an over estimate and this drip-feed of prime rate heating means that the actual total is usually less that the planned total.  However outside of core winter, the planned total is significantly less than seven hours, so this is all dumped in during the E7 window.  If the morning is sunny, that I might get an overrun of 1°C or so.  OK, the daily feedback takes this out of the next day's heating, but you still get an avoidable blip.

   A ToU tariff softens the E7 peak/non-peak tariff.  Yes, I need to adjust for (1) and (3), but having done do it still makes sense to plan say 80% of the required load over the nighttime slump and then top-up as needed any remaining heat in the moderate rate windows.  I'll do a blog post on all of this once I have it working.