Hi, Im just in the process of installing a 5kW Samsung Gen 6 into my 1850's extended bunglow, so my experience may be of use to you. Its EPC was a very optimistic C, mainly I think because it had solar panels but even then I think they were pushing the boundaries. 🙂 My primary CH pipes are 22mm with 10mm microbore teeing off for the rads.

I think you are right to be sceptical. It may be theorectically possible to heat your house with a high temp HP but running your heating at high temp will mean a low COP (efficiency) and your electricity bills are likely to be very high.

You need to assess how much heat you will need. There are various ways of doing this, I looked at how much gas I was using. This is a very good read (

ENERGY-STATS.UK "https://www.energy-stats.uk/what-size-heat-pump/)."

What Size Heat Pump? | Energy Stats UK

What size heat pump seems to be the number one heating question discussed on social media. So we go deep here trying to help you answer that question.

You will certainly need to upgrade your insulation (loft and walls) although the fact you are in a terrace is a plus as only two external walls to worry about. I suspect your CH pipes are too small, but if you can turn your oil boiler down to a viable temperature for a HP  (I went to 40 deg), you can see how your house feels.

Hope that is helpful 🙂

@alarch, welcome to the forums. We don't have a HT ASHP, but in theory, yes, they will operate at boiler temperatures. The issue with that though is that they require a lot more power to run at these higher temperatures which impacts on efficiency. The consensus from many credible installers is that HT ASHPs have been designed to satisfy the requirements of people that want hot rads, but it's a job a well installed and designed low temperature unit can do. 

@heacol will almost certainly have an opinion on this.

Posted by: @alarch

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I'm looking into the possibility of replacing an oil combined with a high temperature ashp, but am skeptical of the claims made by one company I have had a quote from. 

Our house is a stone mid-terrace circa 1850 with an E EPC, modest loft insulation and no wall insulation on the three foot thick walls.

Is it possible to install a workable high temperature ashp, such as the Samsung that came on the market in October of last year? Could this work with existing radiators and pipework? The primary pipes are 15mm external diameter, with 8mm pipes going into the radiators.  

Is it realistic to think that a high temperature ashp can function much the same way as an oil combi boiler - which is what I've been told? If not, what are the likely problems?

@Alarch

you won't get any ASHP to work like a combi boiler. i.e, deliver instant hot water.  You will need a HW cylinder designed for a heat pump.  

If you have a 'normal' loft space, you should insulate it fully no matter what sort of heating you have.  

Do you know what flow temperature your current system uses? 

Posted by: @alarch

↑

I'm looking into the possibility of replacing an oil combined with a high temperature ashp, but am skeptical of the claims made by one company I have had a quote from. 

Our house is a stone mid-terrace circa 1850 with an E EPC, modest loft insulation and no wall insulation on the three foot thick walls.

Is it possible to install a workable high temperature ashp, such as the Samsung that came on the market in October of last year? Could this work with existing radiators and pipework? The primary pipes are 15mm external diameter, with 8mm pipes going into the radiators.  

Is it realistic to think that a high temperature ashp can function much the same way as an oil combi boiler - which is what I've been told? If not, what are the likely problems?

It is quite possible to install a high temperature heat pump, and you can run it at high temperatures if you want to double your heating bill. However, there is no reason why you cannot install a heat pump (high temperature or standard) and connect is to a well-designed and controlled radiator system, which will supply you with a very comfortable heating system which may cut your current bill by 40% or more. Houses of your construction, perform exceptionally well with heat pump due to the high thermal mass.