Glad I was sat down!!

[SteamyTea]

8 hours ago, G and J said:

But, if I’ve understood it I could put a unit like this literally next to the MVHR unit, and not have the unit in the garden, maybe get even better efficiency by using exhaust air, and save myself capital too.   If so why does anyone have an outside ASHP?

Basically because you do not have enough air in the house, so it would have to draw cold air in from outside.

To put some numbers to it.

A m³ of air has a mass of 1.25 kg.

The specific heat capacity is 1 kJ.kg^-1.K^-1

There are 3,600 kJ in a kWh.

So to extract 1 kWh out of your house air you need to shift 4,500 kg (4.5 tonnes) of air for a 1K temperature drop across the ASHP.

[G and J]

4 hours ago, SteamyTea said:

Basically because you do not have enough air in the house, so it would have to draw cold air in from outside.

To put some numbers to it.

A m³ of air has a mass of 1.25 kg.

The specific heat capacity is 1 kJ.kg^-1.K^-1

There are 3,600 kJ in a kWh.

So to extract 1 kWh out of your house air you need to shift 4,500 kg (4.5 tonnes) of air for a 1K temperature drop across the ASHP.

Thank you Steamy, although I can’t pretend I really get those numbers I do understand that such a unit would need to draw its air from outside to work, so I’m no longer contemplating a connection with the MVHR unit.

 

So it using direct air means no efficiency advantage over an external monoblock ASHP methinks.  
 

However it still has cost and convenience advantages potentially for us.  But, worryingly, a hunt around the net last night (guess who couldn’t sleep) yielded no noise figures, and given Steamy’s numbers I’m wondering if the unit will end up sounding like a chip shop extractor when running due to required air volume, which would not make for happiness.  

[TerryE]

There is possibly one thing worse than having an ASHP outside and the neighbours complaining about the noise.  That's having it inside the house and all of the occupants complaining.

 

In most weather conditions the temp drop across the ASHP air flow will be higher, maybe more like 5°C but the heat demand is also higher so the ASHP still needs to move tonnes of air per hour across the heat exchanger.  You need large exchange areas and big slower fans to keep the noise down.

[SteamyTea]

2 hours ago, G and J said:

wondering if the unit will end up sounding like a chip shop extractor when running due to required air volume

Chip shops (restaurants in general) I know about.

The noise level is totally different, as are the tonnage shifted.

Most ASHPs are very quiet. Badly set up ones, or damaged ones can cause problems.

[G and J]

OK, I now accept that there really is no such thing as a free lunch.

 

I can’t find sound data on the Activair unit, which should in itself tell me all I need to know.

 

A totalhome 300litre water tank with integral 0.43kw ASHP (HPW300) generates a sound level of 55dBA at 3m and has 160mm ducts and half the power of the Activair unit.

 

A Samsung 5kw monoblock ASHP generates 45dBA at 1m, less than an eighth of the sound at a third the distance.

 

Back to plan A methinks. (I’d be grateful if I’m wrong and someone corrects me, mind).  But it’s good to explore options….    😕

[JamesPa]

21 hours ago, TerryE said:

 

Thanks, IIRC the Planning Portal says that any ASHP installation can fall under Permitted Development if the installation complies with MCS 020 and part of this standard requires that the installation must be carried out by an MCS approved installer. Without a PD exemption, normal planning and building control applies.  This is all a lot simpler if the installation is done as part of the initial build and part of this planning and building control approval, but in our case that was over 6 years ago.

 

As a post sign-off install, this control itself introduces a shed load of bureaucracy and costs.  In the case where the proposed ASHP is to the rear and within the property curtilage, you would need to demonstrate to BControl that the installation complies with gas-safe, positioning and noise regs.   In this last case it would be practically impossible to get BC sign-off of your calcs unless the ASHP unit is an MCS approved model.

 

BTW that Trianco unit has a heat output of 3 kW and a nominal power draw of under 1 kW. 

The law is the law.  Government 'guidance' is often an imprecise approximation (during COVID it was sometimes just plain wrong!). 

 

In this case building control and planning, which are two totally separate branches of law dealing with different aspects of development, are being wrongly conflated.  Its best to keep a clear head and separate them.  So to unpick this

 

"Thanks, IIRC the Planning Portal says that any ASHP installation can fall under Permitted Development if the installation complies with MCS 020 and part of this standard requires that the installation must be carried out by an MCS approved installer"

 

'Can' is not the same as 'does'  The actual law on permitted development (in England), which is definitive, is here.  See specifically Schedule 2 part 14G.  There are quite a few requirements beyond MCS-020.

 

"Without a PD exemption, normal planning and building control applies. "

 

Without a PD exemption, normal planning applies, however building control is a separate and parallel branch of legislation to planning.  It applies whether or not the development is done under PD.  Building Control doesn't say a lot about ASHPs but what it does say is totally independent of the planning regime under which the development takes place.  Building Control rules do, however, depend on whether it is a retrofit or part of a new building/major refit/change of use.

 

"This is all a lot simpler if the installation is done as part of the initial build and part of this planning and building control approval, but in our case that was over 6 years ago."

 

Yes, because in this case the Local Planning Authority (LPA )focusses on the bigger picture not the minutiae of the ASHP!  The Building Control regulations in this case are, however, much tighter, but in most cases  easier to achieve because you are not constrained by what is already there.

 

"As a post sign-off install, this control itself introduces a shed load of bureaucracy and costs.  In the case where the proposed ASHP is to the rear and within the property curtilage, you would need to demonstrate to BControl that the installation complies with gas-safe, positioning and noise regs."

 

No.  Gas safe regs are irrelevant because there is no gas.  Building control doesn't care about positioning and noise regs, that's a matter for planning.

 

" In this last case it would be practically impossible to get BC sign-off of your calcs unless the ASHP unit is an MCS approved model."

 

If its done as a retrofit BC has very little say about efficiency or anything else of relevance to swapping fossil fuel heating for ASHP (other than G3).  BC doesn't care about MCS, its not even mentioned in the BC rules. 

 

If its a newbuild then BC does have quite a lot to say about efficiency, but it says nothing about MCS or any of the MCS rules that appear to be troubling you..  

 

 

Edited May 8 by JamesPa

[TerryE]

@JamesPa, I agree with most of what you say and you explain more coherently that I have. 

 

Certain control regulations mandate the use of appropriate experts who must be approved and registered for certifying work carried out, e,g. electricals, gas boilers and fittings  and who then issue an appropriate certificate.  For replacement windows, control is effectively delegated to a FENSA registered fitter.  Using one isn't mandatory, but if you don't, then normal building control applies.  There is a similar situation fitting log  burners, etc.   In the case of ASHPs most seem to use HFCs as the refrigerant and most monoblocks are not prefilled and so must be installed by a Part F certified gas-safe engineer.  MCS installers have this as part of their training / qualifications.

 

I think fair to say that using an MCS approved installer is mandatory if you want an ASHP installed under PD. The installer "signs-off" on compliance with regulations and in practice there is no need to get separate Building Control engagement.  Without PD, you have to make a planning application.  AFAIR, successful Notices of Decision invariably make sign-off conditional on BC sign-off, so you have to register the work with Building Control. 

 

Or are you saying that there is some path where you can install an ASHP without using an MCS approved installer, whilst also avoid getting the bureaucracy of getting the LPA and BC involved? 

 

If so, then can you explain how in simple terms?  If not, then we agree on the turd; it's just that you are putting a different polish on it.  🤣🤣

 

[dpmiller]

5 hours ago, TerryE said:

 In the case of ASHPs most seem to use HFCs as the refrigerant and most monoblocks are not prefilled and so must be installed by a Part F certified gas-safe engineer

 

methinks you're confused. Splits need filling, not monoblocks...

 

[LA3222]

1 hour ago, dpmiller said:

 

methinks you're confused. Splits need filling, not monoblocks...

 

Agreed. My ASHP which I installed myself along with the UVC had two bits of 'plumbing' - Flow and Return. That's it, not sure why an MCS bod would need to do that?

 

 

[JohnMo]

7 hours ago, TerryE said:

Part F certified gas-safe engineer.  MCS installers have this as part of their training / qualifications.

F-Gas certified is for refrigerant, gas safe is for natural gas.  Not all MCS certified techs (they are not Engineers) do not need to hold F-Gas certification, so probably don't.

 

Monobloc ASHP always come pre filled with refrigerant.

[sharpener]

8 hours ago, TerryE said:

AFAIR, successful Notices of Decision invariably make sign-off conditional on BC sign-off, so you have to register the work with Building Control. 

 

The Vaillant 12kW unit is physically too big for the PD route so I have had to obtain express PP. The notice makes no mention at all of either MCS installers or Building Control. The Environmental Officer's internal report says it will be satisfactory from the noise pov without reference to the MCS standards, only the mfrs data sheet (which I provided).

 

As @JamesPa says upthread the BC process seems not to be very interested in HPs as retrofits, though the electrical work must of course satisfy Part P. I got them to add installing an HP to a previously opened Building Notice (for EV charging point) in case I wanted to do (some of) the electrical work myself.

 

A further point is that to give you the extended warranty terms mfrs will insist you use their approved installers who in the case of big name brands will all be MCS registered so in practice you have little choice.

[sharpener]

2 hours ago, LA3222 said:

My ASHP which I installed myself along with the UVC...

 

Does this mean you had to get a G3 certificate or did you not bother? I am perplexed why there is such a fuss over G3, the requirements are quite straightforward (and explained very clearly in the instruction booklet for my Ariston tank, though it was not installed by me).

[TerryE]

@LA3222 you have an Ecodan ASHP don't you?  I download the Ecodan PUZ 5 kW installation manual a few years back and it said that the unit was delivered not prefilled, and so needed a F-Gas certified engineer to do the install.  I guess things have moved on since then.  Sorry for the confusion. 

[TerryE]

2 hours ago, sharpener said:

I am perplexed why there is such a fuss over G3, the requirements are quite straightforward (and explained very clearly in the instruction booklet for my Ariston tank, though it was not installed by me)

 

The issue is that a typical UVC stores 200-300 ltr of very hot water under 2-3 bar of pressure.  One of those going pop could badly scald anyone next to it, so it has to be installed and regularly maintained by an appropriately qualified engineer.

[JamesPa]

12 hours ago, TerryE said:

I think fair to say that using an MCS approved installer is mandatory if you want an ASHP installed under PD.

I agree in practice, although others argue that there is a bit of leeway because the law actually says 'MCS Planning Standards or equivalent standards', and then contend that they can themselves install to 'equivalent standards'.  I would counter argue that there is no recognised equivalent standard and so, if it came to a challenge (which is the only time it matters), you would need to convince your LPA of your interpretation, which they would be disinclined to believe.  Given that all development is unlawful unless its expressly lawful, that puts you on the back foot and you would need to contest your case with the planning inspectorate or ultimately through the courts (in the latter case with MCS likely being called as an 'expert witness'), whilst risking enforcement action the effect of which is to disable your heating. 

 

This is hardly an attractive prospect.  So if you do want to claim 'equivalence' then you would be well advised IMHO to seek, prior to installation, a certificate of lawful development (specifying the methods to be used so its clear you wont be using MCS).  If its rejected you can then appeal to the planning inspector and make your 'equivalence' case before you commit.

 

Of course if you are a long way from neighbours much of planning law can, in practice,  be safely ignored, on the grounds that nobody is likely to complain and thus the LPA wont bother taking action.

 

12 hours ago, TerryE said:

In the case of ASHPs most seem to use HFCs as the refrigerant and most monoblocks are not prefilled and so must be installed by a Part F certified gas-safe engineer.  MCS installers have this as part of their training / qualifications.

As @johnmo says monoblocs are pre-filled and do not require f-gas or gas safe qualifications.  They are different, most plumbers have gas-safe but relatively few have f-gas which tends to reside in the aircon industry.  Splits do generally require f-gas.

 

12 hours ago, TerryE said:

AFAIR, successful Notices of Decision invariably make sign-off conditional on BC sign-off, so you have to register the work with Building Control. 

I have not seen this condition applied to a planning consent (and I have looked at a fair few decision notices).  I'm not sure it would even be lawful to do so because building regulations are, so far as I am aware, not a material consideration in planning which is (or is intended to be) solely concerned about the public impact of development.   Planning decision notices may remind you of the need to comply with regulations other than Planning law, but that's not a condition just a helpful reminder of a requirement which applies anyway.

 

However compliance with building regulations is always mandatory anyway (albeit that the regs themselves have many get-out clauses)

 

12 hours ago, TerryE said:

Or are you saying that there is some path where you can install an ASHP without using an MCS approved installer, whilst also avoid getting the bureaucracy of getting the LPA and BC involved? 

 

If you have express planning consent then you don't need MCS (unless the LPA has made that a condition of the consent, which is unlikely). 

 

You must always comply with building regulations when you do any building work, but only some activities are notifiable (ie require you actually to tell BC).  The ones I am aware of which are relevant to an ASHP installation are the installation of a new electrical circuit and the installation of a UVC.  Both of these must (in England), so far as I am aware, be notified to building control unless they are carried out by a tradesman that is a member of an approved registered body.  MCS is not an approved body for either of these, but almost any plumber/electrician will be a member of an approved body.

 

12 hours ago, TerryE said:

If so, then can you explain how in simple terms?  If not, then we agree on the turd; it's just that you are putting a different polish on it.  🤣🤣

 

Yes.  If you have express planning consent then you can cheerfully self install without any further ado, either notifying BC about the UVC and/or new circuit (they may or may not care) or getting pretty much any plumber to do or sign off the UVC, and any electrician to do or sign off the circuit installation.

 

It you apply for consent for a new build or major extension, and it happens to include an ASHP, then LPAs seem quite frequently to concentrate on the bigger picture not the minutiae of the ASHP itself.  You are thus quite likely to get consent which includes the ASHP and you are good to go.  Many on this forum have done exactly that.    

 

However if the development is solely the retrofit of an ASHP to an existing building, then you either have to go PD = MCS or you have to ask for express consent for the ASHP alone, which of course focusses the LPA attention.  Depending on your LPA you may be faced either with an impossible task (eg mine) or they may wave it through with little fuss/constraint (eg @sharpener).  If you do get express consent then what it says about new builds applies.

 

In either case if you don't use MCS you don't get the grant.

 

Otherwise its a turd.

 

The hope on the horizon is flexiorb, which is developing standards alternative to the MCS ones.  They have started with solar panels, but say they intend to go onto ASHPs.  Its currently unclear to me whether they will gain much traction or be any more sane, although that appears to be their aspiration.

 

Edited May 9 by JamesPa

[sharpener]

16 minutes ago, JamesPa said:

Planning decision notices may remind you of the need to comply with regulations other than Planning law, but that's not a condition just a helpful reminder of a requirement which applies anyway.

 

My LA goes out of their way to inform you they are quite separate:

 

"Building Regulations - This decision is not a decision under the Building Regulations and the applicant should ensure that all necessary approvals for the same proposal and same plans are obtained before commencing any work on the site. See www.countybuildingcontrol.gov.uk for further information."

[sharpener]

1 hour ago, TerryE said:

The issue is that a typical UVC stores 200-300 ltr of very hot water under 2-3 bar of pressure.  One of those going pop could badly scald anyone next to it, so it has to be installed and regularly maintained by an appropriately qualified engineer

 

Yes. But no more hazardous that allowing unlimited flammable gas into the building via a 22mm dia pipe. Or 240V mains. Or using a cooker. I continue to think that the fuss is overdone and the annual "maintenance" can be carried out by anyone who can follow printed instructions.

 

My disillusion with maintenance contracts was complete when I discovered that if you take one out with BG it does not even include carrying out the boiler mfrs recommended annual service tasks, merely an "inspection". So for example they would not remove the covers to clean out the condensate trap on my Vokera  boiler, which does require GasSafe certification.

 

And I bet they do not remove the cartridge on the UVC pressure reducing valve to clean the strainer, or check/adjust the expansion vessel pressure, which should all be part of a G3 service.

[JamesPa]

8 minutes ago, sharpener said:

 

Yes. But no more hazardous that allowing unlimited flammable gas into the building via a 22mm dia pipe. Or 240V mains. Or using a cooker. I continue to think that the fuss is overdone and the annual "maintenance" can be carried out by anyone who can follow printed instructions.

 

My disillusion with maintenance contracts was complete when I discovered that if you take one out with BG it does not even include carrying out the boiler mfrs recommended annual service tasks, merely an "inspection". So for example they would not remove the covers to clean out the condensate trap on my Vokera  boiler, which does require GasSafe certification.

 

And I bet they do not remove the cartridge on the UVC pressure reducing valve to clean the strainer, or check/adjust the expansion vessel pressure, which should all be part of a G3 service.

Totally agree, although 'anyone who can follow printed instructions.' would seem to exclude many in the construction/plumbing industry judging by what we hear on this forum.  To my mind its a classic 'job for the boys'. 

 

As you know I'm equally frustrated by the rigidity and sheer lack of innovation with which G3 is interpreted.  @JohnMo will doubtless tell me to stop flogging a dead horse at this point, but its yet another factor holding back ASHPs.

[JohnMo]

4 hours ago, sharpener said:

The issue is that a typical UVC stores 200-300 ltr of very hot water under 2-3 bar of pressure

That's not really the issue G3 protects against, it's the phase change to steam and the expansion of circa 1500 times and the resulting side of the house turning to rubble.

[sharpener]

2 hours ago, JohnMo said:

That's not really the issue G3 protects against, it's the phase change to steam and the expansion of circa 1500 times and the resulting side of the house turning to rubble.

 

It would require a lot of things to go wrong simultaneously on a boiler system for there to be a tank full of superheated water. And more or less a physical impossibiity for one with a heat pump.

 

The requirement for two separate thermostats on an immersion heater have more or less ruled that out as a cause as well.

 

It wasn't always like that. Decades ago during the Edinburgh festival a bunch of theatre technicians wondered why there was steam rising from the WC pan in our rented flat.

 

Turned out there was no thermostat at all on the HW tank.

 

 

[JamesPa]

3 hours ago, JohnMo said:

That's not really the issue G3 protects against, it's the phase change to steam and the expansion of circa 1500 times and the resulting side of the house turning to rubble.

Ok, if this is the case then only protection (logically)  required is to guarantee that the tank never reaches 100C.  With a heat pump it's impossible so we only need to bother about any immersion/resistance electric heater. 

 

So in a retrofit ashp replacing a gas boiler move the immersion out of the cylinder to somewhere there is both a convenient drain and heating pipework (eg where the condensing boiler used to be!) fit a thermostatic valve to divert any water reaching 95 somewhere other than the cylinder (in addition to the various electrical protections), job done.  No need logically for D1, D2 malarky at the cylinder itself, and no new  pipework needed.  Lots of disruption and money saved.  

 

Not compliant with the guidance but compliant with the actual regulation so far as I can see.

[LA3222]

12 hours ago, sharpener said:

 

Does this mean you had to get a G3 certificate or did you not bother? I am perplexed why there is such a fuss over G3, the requirements are quite straightforward (and explained very clearly in the instruction booklet for my Ariston tank, though it was not installed by me).

I had to get G3 for Build control but to be honest as @TerryE said, these things can explode under certain conditions so I would have had it looked at anyway. Plumber spent 20mins checking it over and charged me £300 for the pleasure - still a big saving overall by doing it all myself.

 

As far as servicing goes, its the PRVs and expansion vessels which need checking - easy enough to do DIY so no need to pay a plumber.