Hybrid Air Source Heat Pump vs Air Source HP

leesrubberroom

I wondered if anyone had experience or opinions on the Hybrid air source heat pumps? I know Daikin produce one that gets some good reviews, and Mitsubishi do a system as well. I'm doing a new build this summer, hopefully to be completed by Christmas or early next year. I want an airforce heat pump but, i don't want a storage or header tank, as it's a flat roof property, with nowhere to put it, and i still am a fan of only using energy when it's required (rather than loosing it whilst it sits in a tank all day while we're at work). I'll have underfloor heating for the majority of the home, and obviously it will be thermally efficient. My worry with the airforce heat pump is that it seems to let people down when it gets most cold, and i don't want to be left without hot water. I can't get mainstream gas, so i'll be reliant on LPG, so i thought that the hybrid would supplement the system when needed. The only thing that confuses me is the mitsubishi system says it's not really suitable for new builds, and i'd have thought there would be a lot more hybrid systems on the market if they were such a good solution. Am i missing something?

Erik_V_EyeKing

Which Mitsubishi system are you looking at? This from the Electric website (as oppose to the Heavy*) :

The smallest capacity unit in our Ecodan range is the W50 which is 5kW and is perfect for use in new build applications due to their modern day thermal efficiencies. Able to ​work at variable capacities, the W50 is ideal for many applications ranging from smaller existing homes or flats to medium sized newly built homes.

Not sure if that system requires a hot water cylinder though. Be careful with what you expect any ASHP system to deliver. A lot of the issues with these units arises from the misconception that they can match the performance of conventional gas/electric heating systems.

The output flow temps for both hot water & heating are unlikely to be as high as for conventional systems & if a proper design (accounting for all relevant scenarios & variables) isn't carried out, the estimated efficiencies might never be recognised. Being an electric appliance, running costs can be high when operating flat out.

That said, in the right environment with a proper design, they are very efficient & often the most cost-effective solution.

* Mitsubishi have two separate arms of manufacture, Mitsubishi Electric & Mitsubishi Heavy.

leesrubberroom

It was the Mitsubishi Electric system i'd looked at. They do a system that let you work their ASHP in tandem with a conventional combo boil, but because i'm new to the forum i can't post a link, so i'll have to do it like this. if you paste this in to your browser you should get the pdf.
heating.mitsubishielectric.co.uk/KnowledgeBase/Public/Hybrid_Systems_Brochure.pdf

The way i see it, the combi comes online when the demand is too much for the ASHP alone. To me, you get the best of both worlds. Obviously the savings won't be as much as a straight ASHP, but i wondered if there were any other downsides apart from this?

Cardew

leesrubberroom wrote: »

I wondered if anyone had experience or opinions on the Hybrid air source heat pumps? I know Daikin produce one that gets some good reviews, and Mitsubishi do a system as well. I'm doing a new build this summer, hopefully to be completed by Christmas or early next year. I want an airforce heat pump but, i don't want a storage or header tank, as it's a flat roof property, with nowhere to put it, and i still am a fan of only using energy when it's required (rather than loosing it whilst it sits in a tank all day while we're at work). I'll have underfloor heating for the majority of the home, and obviously it will be thermally efficient. My worry with the airforce heat pump is that it seems to let people down when it gets most cold, and i don't want to be left without hot water. I can't get mainstream gas, so i'll be reliant on LPG, so i thought that the hybrid would supplement the system when needed. The only thing that confuses me is the mitsubishi system says it's not really suitable for new builds, and i'd have thought there would be a lot more hybrid systems on the market if they were such a good solution. Am i missing something?

Welcome to the forum.


A couple of questions if I may.


1. Why 'reliant on LPG?' Oil CH is currently cheaper than gas and whilst oil prices might not remain that low, all the forecasts indicate that oil will remain lower than yesteryear.


2. If you are 'a fan of only using energy when it is required' why use any kind of heat pump? IMO the biggest disadvantage of a heat pump is that you have to run it very long periods - even 24/7 - to have acceptable warmth in your house. This means that the heat pump is running when you are out during the day or in bed at night.(wasted energy) A conventional oil CH system can be set to come on, say, 30 minutes before you return to the house or get up in the morning. Thus if you require, say, 15,000kWh to heat and provide Hot water with a Heat pump, oil CH will require considerably less kWh.


Have you read the Energy Saving Trust report on 2 x 12 month trials with loads of heat pumps.

[Deleted User]

leesrubberroom wrote: »

It was the Mitsubishi Electric system i'd looked at. They do a system that let you work their ASHP in tandem with a conventional combo boil, but because i'm new to the forum i can't post a link, so i'll have to do it like this. if you paste this in to your browser you should get the pdf.
heating.mitsubishielectric.co.uk/KnowledgeBase/Public/Hybrid_Systems_Brochure.pdf

The way i see it, the combi comes online when the demand is too much for the ASHP alone. To me, you get the best of both worlds. Obviously the savings won't be as much as a straight ASHP, but i wondered if there were any other downsides apart from this?

14kw Ecodan here. Large detached house in rural central Scotland. Snow outside and about 0c. House a nice 21c drawing 3.6kw [whole house] but... the solar is producing about 2kw this afternoon so all in all pretty cheap to run. If I want it hotter there are always the log burners to light Prior to the ASHP this was a very very cold house on LPG, now it's the complete opposite for currently £74.50pm with EON.


I know quite a few people with ASHPs, Biomass LPG, Oil etc but never a hybrid system. If the heating system is sized correctly there should be no need.


Cheers

matelodave

I agree with JJ above - we've got an 11kw Daikin LT unit in a 1986 averagely insulated 140sq.m detached bungalow. Doesn't have any tanks in the loft, just a non vented hot water tank for the hot water (provided by the heat pump as well).

We are very exposed out in Fenland and it keeps the place quite warm enough (even for my chilly mortal wife) and we've been cosy down to -10 and lower.

Cardew has a valid point about having to heat the place all day though as they rely on low temperature heat emitters and thus can't give a rapid reheat if the house gets cold. But i'd guess you'd have that problem with any sort of underfloor system as they tend to work like a storage heater heating slowly and releasing it slowly as well.

So possibly not ideal if you want a quick heat up when you get up or get home from work.

We are at home all day every day so it's suits us perfectly but it takes about 36 hours to get the place up to temperature from stone cold.

We don't have solar and on a single tariff supply - our total energy use last year was 6500kwh about £60 a month

leesrubberroom

Thanks for the replies everyone, this is all good food for thought. In reply to Cardew, i'm open to any suggestions, and you raise good points which i will look in to. I guess i need to document my personal needs along with the plans to my building once they're complete, and then get advice from a professional on what would be most appropriate.

[Deleted User]

jeepjunkie wrote: »

14kw Ecodan here. Large detached house in rural central Scotland. Snow outside and about 0c. House a nice 21c drawing 3.6kw [whole house] but... the solar is producing about 2kw this afternoon so all in all pretty cheap to run.

I don't think I worded that well. Overall 1.6kw after solar


Fenland? My fav place is the Norfolk Broads


Cheers

matelodave

Wrong side - I'm in Cambridgeshire. Norfolk is about 100yds to the north with Suffolk about half a mile to the East.

It gets ever so windy here though as there's not a lot to stop it