Heat pump advice: Daikin Vs Another

fergallyons

Hi All,

Use boards.ie all the time but first time posting on here. We are looking for some help with regard to a heat pump for our house as we are at decision time and could do with some guidance.

Our situation:

We bought a house 15 months ago. It is 15 years old, C1 BER, approx 3000 square feet with the attic converted. It was pretty cold when we moved in and has been a struggle to heat it effectively or efficiently! The boiler is on its last legs and the misses was looking for a new stove in the kitchen and with these combined costs I decided to look at alternatives and have arrived at the possibility of an air to water heat pump,

Steps so far:

Since moving in we have taken a number of measures to improve the house. We have insulated the attic, pumped the walls, installed an insert stove and blocked up the second chimney (all bar the wall pumping have been done since the last BER).

Since then we have had an SEAI advisor out to assess our house for suitability to install a heat pump. We are waiting for confirmation next week but he feels confident that we will be under the cut off point of 2000km heat loss.

We have already had Unitherm in Galway come out to assess our house. We will be retrofitting this system through our current heating system (we don't have underfloor heating and putting it in now would be nuts expensive). Many of the radiators in the house are oversize for the rooms so we have been advised we won't need low temperature aluminium radiators in many rooms. There are currently 20 radiators in the system and will be looking at replacing about 8... Is it ok to have both types of radiators in the same system.

Questions:

So I suppose we are just looking for some guidance overall. Everyone who has an air to water system says they are delighted with it (but none we have spoken to have it installed without underfloor heating). So is hooking it up to the current radiator system an runner and if so is it ok to have a mix of radiator types?

For our size house and needs a 16kw Daikin has been recommended (approx 8000 plus vat). In recent weeks there has also been a suggestion of a new Hitachi system coming out in January that operates at higher water temparatures and may be more suitable to our system (its about 1000 more expensive than the Daikin). Any feedback on these systems or any other recommendations?

We have been dealing with Unitherm because they are in this game a long time, are trusted and have a cousin working for them. I appreciate that they may be a little more expensive but have a good reputation. Is there anyone else reliable and cheaper? We are based in Clare.

Finally, any other thoughts? This is a significant amount of money that we don't overly have so really want to get it right.

Thanks in advance

Latro

There are so many factors here. It is almost impossible to give you any good advice imo.
First of all what are you trying to achieve? Why do you think changing from oil to heat pump would make your house warmer?

When you turn the heating on are the rads hot with your current system? If they are and considering that you have so many of them changing to heat pump or any other source of energy will not solve your problem which is most likely massive heat loss.
Or you subjectively trying to achieve too high temperature. It can only have better or worse affect on your bills but the temperature is unlikely to improve with only changing the heat energy source. You need to insulate more, reduce bridging and drafting or pump more heat into your house by extending "hot radiators" period.

BER rating does not take under consideration people habits, life style, thermal bridging or air tightness (I'm not sure on that one).

If you have oil up and running try to calculate the house heat loss yourself by reverse engineering. It will probably be more accurate than any assessment from any paid services that you already did. They will be more of real life numbers and not just theoretical ones.

Lets say you use 2000L of oil per 6 months to heat 280sqm worth of house space. Oil 1l=10kWh of energy at 100% efficiency.
Check whats your oil burner efficiency and deduct at least 10%. The manufacturers have their ways to make these numbers look better then they really are. You need specific conditions to achieve declared efficiency.

Lets say your boiler is rated at 80%. So for you 1L of oil is worth 7kWh of heat energy at best.
Now 6 months = 180 days, 2000L of oil/180 days=11.1L per day on average. 11.1L=111kWh at 70% it is 77.7kWh and that's you average heat loss per day, 2331 per month, 13986 per 6 months that you heat your house. If you want to know how much it would be per 1 sqm just divide the number by 280. All the numbers are examples and you need to use your own.

From here you can calculate how much it would cost you to heat your house on any kind of fuel/boiler.
All you need to know is kWh/unit of fuel and "engine" efficiency. All can be googled.
The colder the water feeding the radiators the bigger area surface of them you need. But that you already know.

You can be even more accurate and figure out using the same method how much oil you need for your domestic hot water during the months that you don't use your heating and deduct it from the previous number. I'm quite confident this method in your case is far more accurate than any BER assessment and it's free. That's because you know how much oil you use right now. It is your real life number that has all included. Thermal bridging, lifestyle, air tightness and anything else we or best BER specialist my not even think of.

I'm not heating specialist of any kind so feel free to criticize what I just wrote. I simply used my own common sense.

Latro

And regards Daikin Vs Another.
All heat pumps use same laws of physics to generate heat. All of them are fridge like devices with hot radiator inside your house and the cold radiator outside. Some of them use electrical coil to boost the temperature of water even more but that for the cost of expensive 1 to 1 efficiency ratio.

If you decide to go with heat pump just pick known big brand so it's easier to service it in case of any future problems.

I'm quite sure most of them would have very similar performance if they were tested independently given exactly same conditions.

Wearb

I think that you have already had a good answer to your questions (above).

Just let me add that I have noticed an increase in questions about air to air and air to water heat pumps since the new grants became available. Don't let that influence your decision too much.
I would be really reluctant to go down that route on anything less than a house designed with that (heat pump) in mind. IMHO, you really need very close to an A rated house for a satisfactory result from a heat pump. Check the output from radiators with the delta T that you might get from a heat pump.

I am not an expert on this. This is just from anecdotal observations.

Dtp1979

Try this forum.
https://touch.boards.ie/forum/1041

Wearb

Latro wrote: »

There are so many factors here. It is almost impossible to give you any good advice imo.
First of all what are you trying to achieve? Why do you think changing from oil to heat pump would make your house warmer?

When you turn the heating on are the rads hot with your current system? If they are and considering that you have so many of them changing to heat pump or any other source of energy will not solve your problem which is most likely massive heat loss.
Or you subjectively trying to achieve too high temperature. It can only have better or worse affect on your bills but the temperature is unlikely to improve with only changing the heat energy source. You need to insulate more, reduce bridging and drafting or pump more heat into your house by extending "hot radiators" period.

BER rating does not take under consideration people habits, life style, thermal bridging or air tightness (I'm not sure on that one).

If you have oil up and running try to calculate the house heat loss yourself by reverse engineering. It will probably be more accurate than any assessment from any paid services that you already did. They will be more of real life numbers and not just theoretical ones.

Lets say you use 2000L of oil per 6 months to heat 280sqm worth of house space. Oil 1l=10kWh of energy at 100% efficiency.
Check whats your oil burner efficiency and deduct at least 10%. The manufacturers have their ways to make these numbers look better then they really are. You need specific conditions to achieve declared efficiency.

Lets say your boiler is rated at 80%. So for you 1L of oil is worth 7kWh of heat energy at best.
Now 6 months = 180 days, 2000L of oil/180 days=11.1L per day on average. 11.1L=111kWh at 70% it is 77.7kWh and that's you average heat loss per day, 2331 per month, 13986 per 6 months that you heat your house. If you want to know how much it would be per 1 sqm just divide the number by 280. All the numbers are examples and you need to use your own.

From here you can calculate how much it would cost you to heat your house on any kind of fuel/boiler.
All you need to know is kWh/unit of fuel and "engine" efficiency. All can be googled.
The colder the water feeding the radiators the bigger area surface of them you need. But that you already know.

You can be even more accurate and figure out using the same method how much oil you need for your domestic hot water during the months that you don't use your heating and deduct it from the previous number. I'm quite confident this method in your case is far more accurate than any BER assessment and it's free. That's because you know how much oil you use right now. It is your real life number that has all included. Thermal bridging, lifestyle, air tightness and anything else we or best BER specialist my not even think of.

I'm not heating specialist of any kind so feel free to criticize what I just wrote. I simply used my own common sense.

I would like to add a concern that I would have about sizing your heat pump using the above method. Because of its quick reaction time, oil/gas heating using rads will not be turned on all of the time. there will be night time setback or even off. There will be times when all are at work, when zones are off etc. So maybe you are just keeping the house at 21C for half the time that you would with a heat pump.

A heat pump needs to be on 24/7 or very close to that. So sizing a heat pump depending on oil usage could leave you very much undersized.

Latro

Wearb wrote: »

I would like to add a concern that I would have about sizing your heat pump using the above method...

What better method would you use to asses HP size requirement? If average real life heat loss right now would be 77kWh there would be colder days when you need somewhere around 100kWh per day and that would be basis for me to pick the heat pump size.
If you pick 9-10kW HP it should cover your heat loss within 10h theoretically. Perhaps even 7kW is safe bet.
There is still large margin for efficiency drop during extra cold snap.
But you should never design heating system around those 3-4 odd cold days that we have here once every 2-3 years.

I'd be more concerned about sizing the heat pump from BER by someone who never saw nor inspected the house.
I'm actually very interested in BER rating vs real life heat loss. Is there any interesting discussion on the forums about that?

If according to BER I should burn 1000L of oil at constant 20C temperature but for some reason I burn 2000L who would be right? BER or me?

If some elderly lady has good BER and then she lets electrician into the attic to do some work for her and he sweeps all the insulation to the side and is not bothered to put it properly back resulting in huge heat loss will BER rating take it into the consideration? Between design and construction there could be hundreds of problems like that but the guy at the desk saw loads of insulation on the house plans resulting in excellent rating.

Often fuel is wasted due to installation defects which can lead to a massive difference between heat required and heat used.

Heat pumps work very well when fitted by experts but until the industry is policed with forced good work standards and accountability home owners are in the same position as they were with wood pellets, solar etc... where bad men pretending to be tradesmen take their money and ride off in to the night leaving mayhem in the homes behind them.

Wearb

Latro wrote: »

What better method would you use to asses HP size requirement? If average real life heat loss right now would be 77kWh there would be colder days when you need somewhere around 100kWh per day and that would be basis for me to pick the heat pump size.
If you pick 9-10kW HP it should cover your heat loss within 10h theoretically. Perhaps even 7kW is safe bet.
There is still large margin for efficiency drop during extra cold snap.
But you should never design heating system around those 3-4 odd cold days that we have here once every 2-3 years.

There are good heat loss calculators used by architects and BER accessors. Bur you will have temperature below 0°C often enough to design for it, or have other top up methods such as a stove.

I'd be more concerned about sizing the heat pump from BER by someone who never saw nor inspected the house.
I'm actually very interested in BER rating vs real life heat loss. Is there any interesting discussion on the forums about that?

Do people provide BER off plans without checking? That's not my (limited) experience. I know architects have a ber in mind when designing and from the few houses that I have recently had reason to be interested, they were bang on when compared to the eventual physical BER.

If according to BER I should burn 1000L of oil at constant 20C temperature but for some reason I burn 2000L who would be right? BER or me?

That depends greatly on the cause. But if every thing is as it should be, then the BER would have been way off. But you cannot design a heating system on the off chance that most BER's are that bad.

If some elderly lady has good BER and then she lets electrician into the attic to do some work for her and he sweeps all the insulation to the side and is not bothered to put it properly back resulting in huge heat loss will BER rating take it into the consideration? Between design and construction there could be hundreds of problems like that but the guy at the desk saw loads of insulation on the house plans resulting in excellent rating.

Of course those sort of things will upset heat loss, but once again you cant design around those things. They have to be sorted out when they arise.

I still maintain that oil or gas usage isn't a good measure to use when calculating heat loss for a heat pump installation. My reasons as stated above.

Outkast_IRE

Latro wrote: »

What better method would you use to asses HP size requirement? If average real life heat loss right now would be 77kWh there would be colder days when you need somewhere around 100kWh per day and that would be basis for me to pick the heat pump size.
If you pick 9-10kW HP it should cover your heat loss within 10h theoretically. Perhaps even 7kW is safe bet.
There is still large margin for efficiency drop during extra cold snap.
But you should never design heating system around those 3-4 odd cold days that we have here once every 2-3 years.

I'd be more concerned about sizing the heat pump from BER by someone who never saw nor inspected the house.
I'm actually very interested in BER rating vs real life heat loss. Is there any interesting discussion on the forums about that?

If according to BER I should burn 1000L of oil at constant 20C temperature but for some reason I burn 2000L who would be right? BER or me?

If some elderly lady has good BER and then she lets electrician into the attic to do some work for her and he sweeps all the insulation to the side and is not bothered to put it properly back resulting in huge heat loss will BER rating take it into the consideration? Between design and construction there could be hundreds of problems like that but the guy at the desk saw loads of insulation on the house plans resulting in excellent rating.

The winter design temp for sizing heating loads in buildings in Ireland is taken as -5 Deg c. We do a lot of IES modelling and that's the recommend for this country based on the perecentile it's occurs each year. If you use anything lower you will be let down by the heating plant when you need it most.

As suggested later in your post if you are trying to select a smaller boiler or heat pump improving insulation and airtightness is how to achieve it .