Drainage: it's not difficult to connect the unit drain to a soak-away under or adjacent to the unit. If the unit is on concrete pad or paving, core cut through this to the hardcore underneath, which is unlikely to ever have a penetrating ground frost. Condensate is pure water, so connection to either a permanent drain or a soakaway is possible. Drain pipe as short as possible and insulated, should not require trace heating that way.

Planning: Your personal choice, but planning responsibility is vested with the homeowner not the installer. I would seek retrospective planning permission as, if you ever want to sell your property, the lack of planning permission will surface in conveyancing and you may be obliged to either take indemnity out on behalf of the buyer or address the issue then. The Local Authority is very unlikely to refuse permission for ASHP if unit volume >0.6m3 is the only material planning issue. You might need to submit a completed MCS noise level assessment to prove noise level compliance 42.0dB(A) max at adjacent dwellings if relevant.

Heat Load Calculations: Essential? I would say so. Both to size the overall unit and, more importantly, to check individual room emitter sizing and capacities. For underfloor heating room emitter is less critical, because you have a very large surface area. But for retrofits where ASHP is married to wet radiators, the existing rads need to be checked and, often, increased in size to suit the lowest flow design temperature possible/practical for the room design temperature. Money spent increasing radiator sizes for lowest design flow temperature will be recouped several fold over the the life of the ASHP in lower electricity consumption due to higher SCOP.

You are right - the unit does cycle on and off frequently. The unit is definitely oversized and if that unit size is being installed in the appropriate house, a buffer will accompany to run efficiently 

Thanks I will explore this option. The unit drains onto hard ground and we generally don’t walk there except to check the pump.

Understand that planning is a personal choice though the installer should have advised on this. I’m already getting in touch with the LPA to see what is required and they have asked for installation design which the installer has not provided. Also yes it’s the unit volume that seems to be the only issue. Unit runs quietly on normal days but was audible when temperatures dropped to -5

I will be changing the radiators at some point but need the unit to be installed and working as a 10kw vaillant should do first.

They seem like proper cowboys these ones.

You could find any competent plumber, give them the manufacturers installation schematic (not the one from the merchant, or from some third party) that suits your system and tell them to get in with it.

The manufacturers produce these for a reason. Choose the one without any hydraulic separation for the best system efficiency.

As for the planning issue… if anyone asks, tell them it’s an air conditioner 😉

A heat loss calc isn’t technically necessary if you know that the property is adequately heated by the current boiler. I’d argue that rad sizing to rooms at a lower flow rate is more important. For example, my place has  an 11kW baxi Bermuda, installed when the property had no loft insulation and no double glazing, it managed to heat the place just fine back then, and still does now. So you could just say 11kW is fine and be done with it.

who is a competent plumber though? At this stage all plumbers are competent until things go wrong. Makes me want to stick to the devil I know and give them the opportunity to fix the issues plus it gets complicated with warranties etc

I specifically didn’t want to change the radiators at the time so I’m not complaining about that as it was my choice.

The pipes without insulation are inside the building. The pipes outside are insulated although not very well but they are.

Drainage: it's not difficult to connect the unit drain to a soak-away under or adjacent to the unit. If the unit is on concrete pad or paving, core cut through this to the hardcore underneath, which is unlikely to ever have a penetrating ground frost. Condensate is pure water, so connection to either a permanent drain or a soakaway is possible. Drain pipe as short as possible and insulated, should not require trace heating that way.

Planning: Your personal choice, but planning responsibility is vested with the homeowner not the installer. I would seek retrospective planning permission as, if you ever want to sell your property, the lack of planning permission will surface in conveyancing and you may be obliged to either take indemnity out on behalf of the buyer or address the issue then. The Local Authority is very unlikely to refuse permission for ASHP if unit volume >0.6m3 is the only material planning issue. You might need to submit a completed MCS noise level assessment to prove noise level compliance 42.0dB(A) max at adjacent dwellings if relevant.

Heat Load Calculations: Essential? I would say so. Both to size the overall unit and, more importantly, to check individual room emitter sizing and capacities. For underfloor heating room emitter is less critical, because you have a very large surface area. But for retrofits where ASHP is married to wet radiators, the existing rads need to be checked and, often, increased in size to suit the lowest flow design temperature possible/practical for the room design temperature. Money spent increasing radiator sizes for lowest design flow temperature will be recouped several fold over the the life of the ASHP in lower electricity consumption due to higher SCOP.

How concerned should I be about the drainage? The reviewing heat engineer mentioned the drainage and I’ve also seen posts about the drainage here. 

I think it depends where your pump is. Our condensation drainpipe froze over in the cold and the pump slowly dribbled water across the paving from under it, which then froze, but we don't use that path much when it's that cold, there was space to step over it and it slopes away from the house, so I'm not bothered enough to change the drain (wider-diameter pipe or steeper fall).

They seem like proper cowboys these ones.

You could find any competent plumber, give them the manufacturers installation schematic (not the one from the merchant, or from some third party) that suits your system and tell them to get in with it.

The manufacturers produce these for a reason. Choose the one without any hydraulic separation for the best system efficiency.

As for the planning issue… if anyone asks, tell them it’s an air conditioner 😉

A heat loss calc isn’t technically necessary if you know that the property is adequately heated by the current boiler. I’d argue that rad sizing to rooms at a lower flow rate is more important. For example, my place has  an 11kW baxi Bermuda, installed when the property had no loft insulation and no double glazing, it managed to heat the place just fine back then, and still does now. So you could just say 11kW is fine and be done with it.

I will explore raising with MCS too 

How concerned should I be about the drainage? The reviewing heat engineer mentioned the drainage and I’ve also seen posts about the drainage here. 

Well I am pursuing the buffer on two basis, one- that’s what I was quoted and it was changed without an approval or advise to me, two -the buffer is more suited to the pump size as explained to me. Although I was also advised that the pump is powerful enough to work without the buffer and llh, the buffer is the better of the two for the installation. The buffer can hold more volume of water to help the pump work efficiently without needing it to kickstart so frequently as it does now leading to high energy use. It will be marginally better but still better and I believe it will help the lifespan of the Heatpump too.

Thank you for confirming that a heat loss calc was necessary. When I asked the installer about this and the information they based the hp size recommendation on, they simply sent my bills and claimed that was enough to make the recommendation. I requested a heat loss report from another engineer and I know my installer definitely didn’t provide this. They seem unaware of the significance of this report . They did check the ECS of the building though. Could they claim this is enough and replaces the calculations?

There is an outstanding balance which I am currently using as leverage. If I had paid everything, I would be in a much worse situation right now. It is only leverage though as if they do not fix the issues, it will cost me potentially more than the balance to fix their mess. I intend to have all the issues resolved before paying the balance and I’ve informed the installer of this. 

Vaillant produce schematics without a buffer, and are perfectly happy without one “ providing system volume is big enough” and you don’t use on off controls

Over sizing is disappointing, but what is the actual heat loss? How many radiators? 

If MCS is behind this then how come a heat loss calculation was not undertaken? But you also need to appreciate heat loss calculations are only skilled guessing as you don’t know the building fabric and ventilation of an existing building in its entirety

At the end of the day a heat pump is just another heat source. It doesn’t really need a heat loss calculation to work effectively. 

is the lack of insulation indoors or outdoors?

If you didn’t ask him to get planning permission specifically it’s not really his issue (MCS may suggest otherwise)

I will explore raising with MCS too 

How concerned should I be about the drainage? The reviewing heat engineer mentioned the drainage and I’ve also seen posts about the drainage here. 

Well I am pursuing the buffer on two basis, one- that’s what I was quoted and it was changed without an approval or advise to me, two -the buffer is more suited to the pump size as explained to me. Although I was also advised that the pump is powerful enough to work without the buffer and llh, the buffer is the better of the two for the installation. The buffer can hold more volume of water to help the pump work efficiently without needing it to kickstart so frequently as it does now leading to high energy use. It will be marginally better but still better and I believe it will help the lifespan of the Heatpump too.

Thank you for confirming that a heat loss calc was necessary. When I asked the installer about this and the information they based the hp size recommendation on, they simply sent my bills and claimed that was enough to make the recommendation. I requested a heat loss report from another engineer and I know my installer definitely didn’t provide this. They seem unaware of the significance of this report . They did check the ECS of the building though. Could they claim this is enough and replaces the calculations?

There is an outstanding balance which I am currently using as leverage. If I had paid everything, I would be in a much worse situation right now. It is only leverage though as if they do not fix the issues, it will cost me potentially more than the balance to fix their mess. I intend to have all the issues resolved before paying the balance and I’ve informed the installer of this. 

There are clearly some basic issues, like drainage and damage. The buffer is a contentious subject, so one to avoid for now. And yes, a heat loss calculation should have been carried out to size the heat pump correctly.

The RECC angle is one worth pursuing, but I’ve yet to encounter an homeowner that has received a positive outcome. But I keep forwarding them cases, trying to add pressure.

Are any of the installers MCS certified? Also, have you paid them yet? If you haven’t, don’t pay until the matter is resolved.