Use BUS or self-install?

[oranjeboom]

Hi all,

 

I currently have two Willis heaters (Read more here) providing the 6kW for the slab (proving very expensive now), I am now looking to get an ASHP installed. Question is, should I go via the BUS grant or should I source a unit off ebay and either attempt a self install or get a local  fitter to install? I'd like to think that the grant would now cover the simple install!

 

Further questions:

 

How long does it take once the installer has applied for the £7.5k voucher?

I'd like to have an install completed ASAP before the temps drop and there's a significant demand for heating in the house.

 

The setup would be fairly straight-forward, with the heat just being fed directly into the slab, so no need for cylinder etc.

 

Previously (2019) I had a quote for a Mitsubushi 8.5kW which also included the installation only of 2 Sunamp units (previously purchased but now installed) which came to £8,000. Presume that would have been a 2 day install at max, so imagine that realistically, today's figure would be less! I expect of course to get a much inflated price back when I go back for an updated quote with the excuse being  short-supply of units, price increase etc. 

 

 

 

 

Self-install?

So the alternative is to self install (with electrician), but would like to keep the controller KISS and the unit install itself would need to be a relatively simple to install and connect. I've done all of the plumbing including the Willis heaters (except the Sunamps) so would like to think an ASHP install is within my grasp. Worst case, I'd have to rope in a local plumber who has some experience of installs - maximum of a day I would think?

 

Any feedback gratefully received!

Edited November 21, 2023 by oranjeboom

[joth]

As you want this done asap, the possibility of using BUS comes down to whether you can find an installer ready to move at a speed acceptable to you.

There's no doubt you could get it done entirely within the BUS grant if time wasn't a pressure, as yours should be a very simple install, no emitter or UVC changes needed whatsoever. So you could chose to put the excess money a DIY install would cost towards covering your excessive Willis bill this winter and hold tight until an installer gets to you. 

Depending where you are there maybe small installers available or have to rely on octopus and even BG now...

 

One other thought, are you eligible for BUS? There's no boiler being upgraded, and your self build is complete (?). Check the wording 

 

 

[JohnMo]

Self install is quite straightforward

 

If UFH only ASHP to manifold, no mixer or pump. Set either a fix flow temp and control with a decent thermostat or set a WC curve. If you do it as one zone no buffer required, but system may benefit from a volumiser (long run times at low demand). You will need expansion vessel and relief, filling point, vent valves and a strainer.

 

Biggest cost after heat pump is pipe, fittings, and insulation.

 

If adding a DHW cylinder, three way diverter is added.

 

I would look at a Grant heat pump, but install as Chofu intended. No other controls needed.

 

Realistically you are looking at £3 to 3500, all the little bits add up.

 

If you are adding a DHW cylinder an Ideal one are quite good price, good multiple coil comes with a 3 way valve. About £800 from City Plumbing.

[joth]

58 minutes ago, oranjeboom said:

The setup would be fairly straight-forward, with the heat just being fed directly into the slab, so no need for cylinder etc.

 

 

This makes you ineligible for BUS

 

https://www.ofgem.gov.uk/sites/default/files/2023-09/BUS PO guidance V2.3.pdf (my emphsis)

"4.25. The heat pump or biomass boiler must provide both space and hot water heating and be capable of meeting the full space heating and hot water heating demands of the property."

 

What is DHW currently supplied by?

 

(aside - it appears  upgrading Willis to ASHP is covered by BUS, so you can claim it on this basis regardless of being a self build vs any other new build. "4.23. The new low carbon heating system will need to completely replace an existing fossil fuel heating system or electric heating system which does not include a heat pump.")

 

 

 

Edited November 21, 2023 by joth

[nod]

We’ve contacted an installer for a 14 kw Mitsubishi 

12 k supplied and fitted Including commissioning the UFH 

It only leaves 5 k to buy the pump buffer etc 

[crispy_wafer]

16 minutes ago, JohnMo said:

I would look at a Grant heat pump, but install as Chofu intended. No other controls needed.

 

Without wanting to derail the thread too much can I ask @JohnMo a question

 

I've seen this Grant comment quite a lot and never really questioned as I don't really know wrong from right at this point!  Is this meaning the actual physical installation and the way the hydraulics are piped up, and/or the way the system is controlled via the interface.  I'm curious as I'm yet to connect my unit up and can still make amendments to my scribbled design!

 

The Grant install guide has 3 schematics to follow plus a high level diagram early on, the Chofu install manual just has a pretty high level diagram in it.

 

 

[JohnMo]

1 minute ago, crispy_wafer said:

 

Without wanting to derail the thread too much can I ask @JohnMo a question

 

I've seen this Grant comment quite a lot and never really questioned as I don't really know wrong from right at this point!  Is this meaning the actual physical installation and the way the hydraulics are piped up, and/or the way the system is controlled via the interface.  I'm curious as I'm yet to connect my unit up and can still make amendments to my scribbled design!

 

The Grant install guide has 3 schematics to follow plus a high level diagram early on, the Chofu install manual just has a pretty high level diagram in it.

 

 

The principal difference between the Chofu and Grant install.

 

Chufu have a fully functional controller with built in thermostat and scheduler. Grant basically by-pass the design intent of this. Grant have modified the install to match a gas boiler, with two port valves, which have to be timed separately so DHW water cannot get into the heating system. There are several versions if the Chofu manual kicking about.

 

This one has quite a few different schemes 

Chofu-Operating-Installation-Manual-R32.pdf

[crispy_wafer]

I think you pinged me that manual before, looks similar.  Thanks.

 

I'm right going with the 3 port valve that's on my pre plumbed cylinder then rather than trying to match the plumbing on grant cylinder?

[oranjeboom]

51 minutes ago, joth said:

 

This makes you ineligible for BUS

 

https://www.ofgem.gov.uk/sites/default/files/2023-09/BUS PO guidance V2.3.pdf (my emphsis)

"4.25. The heat pump or biomass boiler must provide both space and hot water heating and be capable of meeting the full space heating and hot water heating demands of the property."

 

What is DHW currently supplied by?

 

(aside - it appears  upgrading Willis to ASHP is covered by BUS, so you can claim it on this basis regardless of being a self build vs any other new build. "4.23. The new low carbon heating system will need to completely replace an existing fossil fuel heating system or electric heating system which does not include a heat pump.")

 

 

 

 

Bugger! Currently I have two Sunamp units, only one which is being used for DHW (other one not in use as currently low family demand for DHW).  IIRC, they are eDual units and not sure now whether they could be connected to ASHP. I did consider this a few years ago, but at the time there were limited ASHP units that could deliver higher temp demands to use with the PCM in the Sunamp units).

[joth]

If you get an R290 ASHP like Vaillant aroTHERM it will do 75C output and be usable with the SunAmp. It's a bigger project then of course, but will slightly reduce your DHW costs.

But if expediency is the goal, DIY looking increasingly favourable

[oranjeboom]

55 minutes ago, joth said:

If you get an R290 ASHP like Vaillant aroTHERM it will do 75C output and be usable with the SunAmp. It's a bigger project then of course, but will slightly reduce your DHW costs.

But if expediency is the goal, DIY looking increasingly favourable

Ahhh yes, I recall they had some initial tests with Vaillant and Samsung back in 2018 with R290. I imagine the COP isn't great at 75C though. I'll have to check what PCM I have in my Sunamp units, thought they required temps of around 50C (IIRC).

 

A 8kW Vaillant aroTHERM is £3,680 (inc VAT) but then a more complex setup and probably be well over the BUS grant.

 

Other thought would be to use a lower temp ASHP to preheat the water supply of the Sunamp at least to say 40C, if that's possible. But strictly speaking that would not meet "full hot water demand" aspect of the BUS requirement, unless I find an installer who is willing to do that.

 

[joth]

7 minutes ago, oranjeboom said:

Other thought would be to use a lower temp ASHP to preheat the water supply of the Sunamp at least to say 40C, if that's possible.

Which would be more complex, lower COP and probably more labour cost than just doing the conventional install with an R290 unit. 

If the pcm needs 50° then it may work even with the ecodan (55 max output) but I'd go with the valiant even if you run it at 60 you'll know you have headroom for the lifetime of the components. It's cop should be pretty reasonable at 60

 

 

[JohnMo]

10 minutes ago, oranjeboom said:

Ahhh yes, I recall they had some initial tests with Vaillant and Samsung back in 2018 with R290. I imagine the COP isn't great at 75C though. I'll have to check what PCM I have in my Sunamp units, thought they required temps of around 50C (IIRC).

 

A 8kW Vaillant aroTHERM is £3,680 (inc VAT) but then a more complex setup and probably be well over the BUS grant.

 

Other thought would be to use a lower temp ASHP to preheat the water supply of the Sunamp at least to say 40C, if that's possible. But strictly speaking that would not meet "full hot water demand" aspect of the BUS requirement, unless I find an installer who is willing to do that.

 

Or let them install a cylinder, which gets sold on later? Or let the heat pump try to heat the Sunamps, if it doesn't work well i.e. rubbish CoP, don't let it call for heat ever again. Tell installer what he wants to here, nothing more or less.

[JohnMo]

4 minutes ago, joth said:

If the pcm needs 50° then it may work even with the ecodan (55 max output) but I'd go with the valiant even if you run it at 60 you'll know you have headroom for the lifetime of the components. It's cop should be pretty reasonable at 60

Most R32 ASHP run to 60 without issue.

[Pip895]

I am facing a similar dilemma - you may have seen my other thread.  I think the pro's & cons for me (may well be similar for you) are as follows.

Self install Pro:-

1. Fast - can start as soon as I want so any savings will start this winter.
2. Kit seems relatively cheap (compared to the prices I have been quoted for a professional install) & I think the simpler install would be done in a day if a Heat pump team did it - will take us much longer though.
3. Low risk - I can keep my existing system as a backup to use in the very coldest conditions, if the heat pump breaks down or if there is a power cut.  (We have a battery backup so could run the pumps etc but obviously the Heat pump itself would drain the battery too quickly.)
4. The % of gas displaced would be done at a very good COP as the pump would work 100% at 35deg or below - The % gas (in our case) saved could be in the region of 70 to 80% if we size the pump correctly.
5. No need to replace our existing Hot water tank or otherwise mess with a working system.
6. Wont have to pay for expensive yearly maintenance to maintain warranty (as we wont get it anyway..).
7. R32 would be ideal at the low temperatures and Larger R290 units aren't yet available in all product ranges.

Disadvantage

1. No grant to help with the costs.
2. Warranty on the HP may be reduced or non existent after first year.
3. No reduction in costs of DHW
4. DHW tank is 15 years old and may need replacing in the next 10 years anyway at our expense.
5. Less far on the road to completely removing gas from the property (not relevant to you). 
6. House will have a less standard set up with no professional backup.

 

 

[JohnMo]

46 minutes ago, Pip895 said:

DHW tank is 15 years old and may need replacing in the next 10 years anyway at our expense.

Another thing to concider if you stay gas for hot water, is to install a heat pump cylinder anyway. The cylinder has a huge coil, boiler condensing for the whole heating period and lower flow temp settings, could save you 10 to 15% gas costs on its own.

[oranjeboom]

2 hours ago, JohnMo said:

Or let them install a cylinder, which gets sold on later? Or let the heat pump try to heat the Sunamps, if it doesn't work well i.e. rubbish CoP, don't let it call for heat ever again. Tell installer what he wants to here, nothing more or less.

 

I really don't have the room for a cylinder unfortunately! Unless I place that in one the unfinished rooms upstairs and have a 20m pipe run from the DHW manifold. Could be done...but a PIA...   Would they even install a cylinder (presume size-wise it would be based on bedrooms in house rather than actual occupants (1.5)?) plus an ASHP circa £7.5k grant?

 

 

On 21/11/2023 at 10:17, joth said:

This makes you ineligible for BUS

 

https://www.ofgem.gov.uk/sites/default/files/2023-09/BUS PO guidance V2.3.pdf (my emphsis)

"4.25. The heat pump or biomass boiler must provide both space and hot water heating and be capable of meeting the full space heating and hot water heating demands of the property."

 

Annoyingly I have just checked my Sunamp units and they are eDuals (both 12) and I have checked the manual that does state "These heat batteries should not be charged by an external heat source". That contradicts what I have in writing from Sunamp a few years ago prior to shipment!  Annoyingly someone at Sunamp confirmed that the Uniq HWi and eDual units "are the same product"  when I questioned them on this. So now I am left with 2 units that cannot be charged via ASHP which had been the intention at some point. Not happy!

 

 

 

[joth]

1 hour ago, oranjeboom said:

Annoyingly I have just checked my Sunamp units and they are eDuals (both 12) and I have checked the manual that does state "These heat batteries should not be charged by an external heat source".

Do they physically have pipework to connect an external source into? If they do, what is the point?? If not, then it was never going to work.

Are you reading an online manual, that they've modified since you purchased, to disadvise something that was previously advertised as supported?

 

[oranjeboom]

1 hour ago, joth said:

Do they physically have pipework to connect an external source into? If they do, what is the point?? If not, then it was never going to work.

Are you reading an online manual, that they've modified since you purchased, to disadvise something that was previously advertised as supported?

 

 

So the UniQ systems all have 4 ports that would allow 2 flows and 2 returns. See fig 4.6a below in the UniQ manual v2.3. Not seen the latest Thermino manual so can't comment on how things have developed.

 

s 5.4.1:

 

 

 

Presume the highlighted section refers to eHeat batteries and eDual (the ones I have).

 

The HW+i also has the 4 ports

 

s5.5.1:

 

The HW+i model ("heated by an external heat source (e.g. Gas boiler, Heat pump)...are fitted with a standby electric heater") has the capability of electrical heating too and yet this is contradictory again in this diagram where it states the electrical heater element only refers to the 'e' models:

I imagine the inside construction of that whole range is pretty much the same (with some having the electrical heater built in some not) and that the Sunamp Qontroller is where the systems really differ, but I am sure @Nickfromwales would know more.

 

Clearly I'm no expert on these units and that's why I relied at the time on Sunamp to confirm/advise things before the things were shipped! If they then confirm that the HW+i and the eDual systems are the same, you have to settle for that as they are the product experts.  I can see why they have moved away from dealing with customers direct as I'm another one who's severely disappointed with this outcome now!

 

[oranjeboom]

So from I gathered from my dealings with Sunamp and installer is that the controller on eDuals would need to be replaced as these have  " a switching circuit which won’t be compatible with most heat pump controls as they utilise a resistance reading to generate a demand or satisfied call"

 

Has anyone had an external controller replaced and what was the cost? I know they are now fitted internally on the Thermino models so can't imagine it's a very complex issue to provide me with an updated external controller?

 

Obviously I have enquired with customer service, but service is a hit and miss affair and often one is quicker to go via the BH way!

[JohnMo]

3 minutes ago, oranjeboom said:

controller on eDuals would need to be replaced as these have  " a switching circuit which won’t be compatible with most heat pump controls as they utilise a resistance reading to generate a demand or satisfied call"

Have a read at the bottom of the this thread two resisters and a relay is all you need to to convert on/off control to resistance

 

 

 

[TerryE]

On 19/12/2023 at 17:12, JohnMo said:

Have a read at the bottom of the this thread two resisters and a relay is all you need to to convert on/off control to resistance [load]

 

Not just any relay, you need a decent SSR or contactor rated at 240V AC and 16A load for a 3kW resistive load, and wiring these up needs some electrical knowledge, as it is quite easy to do this in a way that breaches code.  I played it by the book and got my sparky to do the 240V stuff and sign it off.  I used SSRs so I could drive them with 5V DC. You can get contactors that are driven by 12 and 24V DC.  You don't need low voltage stuff signed off.

 

Edited December 23, 2023 by TerryE

[JohnMo]

4 minutes ago, TerryE said:

 

Not just any relay, you need a decent SSR or contactor rated at 240V AC and 16A load for a 3kW resistive load, and wiring these up needs some electrical knowledge, as it is quite easy to do this in a way that breaches code.  I played it by the book and got my sparky to do the 240V stuff and sign it off.  I used SSRs so I could drive them with 5V DC. You can get contactors that are driven by 12 and 24V DC.  You don't need low voltage stuff signed off.

 

The bit answered is about measuring switching via a resistive temp probe i.e NTC or PT100. I pointed out away to simulate have a cylinder temperature probe.

 

On 19/12/2023 at 17:07, oranjeboom said:

eDuals would need to be replaced as these have  " a switching circuit which won’t be compatible with most heat pump controls as they utilise a resistance reading to generate a demand or satisfied call"

You are not switching any load directly you are just simulating two resistance output that coincide with a temp above and below a permissive to start heating DHW via the heat pump. The wire size in the probes in the order of 0.5mm² suspect the signal voltage is in mA scale. 

 

You would not be load switching that's a different animal as you point out 

[Beelbeebub]

Do you know what voltage the eduals use to measure resistance? If it's.low voltage eg 5v you could knock up a thermostat to resistance converter box from off the shelf parts (a.phone charger, and Arduino and a digital potentiometer) for about £30 of hardware and not much programming skill.

[JohnMo]

Two resistors, 10p each and a relay in a box £5 to £10. No programming or anything special. Plus you need to output a resistance not input it. Taking an on off call for heat from the eDual and output a resistance to fool the ASHP into starting DHW heating.