Heat Pumps - Ground or Air

bifl

Hi,
I am wrestling with whether to go with a Ground source (horizontal/bore) or Air to Water as my type of heat pump.

I have dug through boards and the net in general, the reason I'm asking this question again is that the supposedly Air to Water have come 'along way in the last couple of years'. I have asked all the questions to suppliers around things that would have bothered me with Air such as defrost cycles, additional energy usage, COP calcs done different to Ground etc buts its still hard to really know

Coming into this process my head was saying Ground. I have dealt with two suppliers who I would say are generally regarded as respectable. Both suggesting Air is the way to go.

- company one is working out at 50% more for Ground excluding ground works & are (I suppose!!) recommend in Air
- company two priced for both types with the units being from the same manufacturer with the Air being 1K less AND then of course without any ground works to bother with. They did the estimated annual calculations and Air is actually €10 a year less to run.

The last point above really got me thinking, if the same company did my energy calculations with heats pumps from the same manufacturer is this getting into no-brainier territory ?????

So just wondering where peoples heads are at with Air vs Ground in 2014?
- what is that magic temp where Air begins to outperform Ground ?
Does anyone have Air installed in the last 12 months say who could give their thoughts particularly over the winter?

Molzer2

Hi bifl,
I'm not an expert bug have read widely on it as I'm thinking of buying off plans. I've spoken to a few people in the business but not overly connected with any supplier or system. I think if the building is designed for it the a2w is the way to go!
What one were you thinking of?

bifl

Molzer2 wrote: »

Hi bifl,
I'm not an expert bug have read widely on it as I'm thinking of buying off plans. I've spoken to a few people in the business but not overly connected with any supplier or system. I think if the building is designed for it the a2w is the way to go!What one were you thinking of?

Hi Molzer, thanks for the reply. I'm sure there are others out there who have wrestled with the same question .....newish a2w or Geo.
I really don't know but have to decide in the next few days so the model and COP goes into the provisional BER

If I thought that a2w worked as well with v similar costs as the analysis suggests from my original post then its surely a no brainer . This seems a fair comparison as the vendor did both analyses and sell both types.

The only thing holding me back is the thought Geo works better in the winter especially a hard one.....
The key question is what is the temperature that air becomes more efficient. Then you have to just compare against avg temps ??
To you point though for a well build house with a low heating demand then maybe a2w is enough.

Luimai

Hi! I'm currently in same position ATM with new build in progress. Just wondering if it's possible for you to send me on the details of info you have so far on a2w? We have committed to a2w here, but no idea yet of who or what we are getting! Went with a2w vs ground due to advice from engineer and family members who have the ground in and estimated cost of installing, it really came down to air or oil with Solar etc. recent convo with engineer leads us to believe that a2w for similar sized house to us should run at less than €3 per day on average. Any info on suppliers etc greatly appreciated! (By pm!)

bifl

Luimai wrote: »

Hi! I'm currently in same position ATM with new build in progress. Just wondering if it's possible for you to send me on the details of info you have so far on a2w? We have committed to a2w here, but no idea yet of who or what we are getting! Went with a2w vs ground due to advice from engineer and family members who have the ground in and estimated cost of installing, it really came down to air or oil with Solar etc. recent convo with engineer leads us to believe that a2w for similar sized house to us should run at less than €3 per day on average. Any info on suppliers etc greatly appreciated! (By pm!)

Pm sent

Mixupat

Would appreciate a PM also, not far from this decision!

Duffman1

If you could pm me the info as well, I'm trying to make a decision at the moment. Thanks.

bifl

Pm's sent with my 2 cents !!

Selfbuilder14

We to are thinking of going air to water. I know it is much cheaper to run than oil but say we have a very cold winter how do they perform. And what about hot water if we don't get solar panels?

To

blast06

In a new build since Aug 31st with A2W - 2650 sq ft. BER A2 (just about). Heating is off now for the summer and will almost certainly stay so until at least Aug 31st. I know my annual heating bull therefore to keep house at 20 degrees 24/7/365 and it come in at €431 (about another 100 for hot water).

Bear in mind though that heat pump is only 1 part of the overall jigsaw with each part complimenting the other. ...... air-tightness, insulation, MRHV and heat pump with UFH.
I would also strongly recommend Quinn lites on inside leaf of external walls plus on first line of all internal walls (to reduce thermal bridging)

Sandman777

blast06 wrote: »

In a new build since Aug 31st with A2W - 2650 sq ft. BER A2 (just about). Heating is off now for the summer and will almost certainly stay so until at least Aug 31st. I know my annual heating bull therefore to keep house at 20 degrees 24/7/365 and it come in at €431 (about another 100 for hot water).

Bear in mind though that heat pump is only 1 part of the overall jigsaw with each part complimenting the other. ...... air-tightness, insulation, MRHV and heat pump with UFH.
I would also strongly recommend Quinn lites on inside leaf of external walls plus on first line of all internal walls (to reduce thermal bridging)

I have gone down the Geothermal route myself but i agree with Blast06 that the Heat Pump is only one piece of the jigsaw!
Your heating bill sounds excellent....do you have solar to back this up or does HP provide the the lot?
Also do you mind me asking what levels of insulation you have?

blast06

Heat pump provides the lot.... no solar.

Insulation:
Floor: 2 x 80mm polyiso sheets running perpendicular to one another under the screed with sheet of polythene over the polyiso

Walls: very close to 7" cavity (pumped) with Quinn lites on inner leaf.

Ceilings: 2/3 of ground floor doesn't have an upstairs (if that makes sense) so for these parts i have 400mm wool.

Upstairs rooms (dormer): i have 100mm rafter lock for the walls and rafters fronted by 50mm insulated slab (air-tightness membrane between the 2). The ceiling parts of these rooms have 150mm rafter lock and 200mm wool

Sandman777

blast06 wrote: »

Heat pump provides the lot.... no solar.

Insulation:
Floor: 2 x 80mm polyiso sheets running perpendicular to one another under the screed with sheet of polythene over the polyiso

Walls: very close to 7" cavity (pumped) with Quinn lites on inner leaf.

Ceilings: 2/3 of ground floor doesn't have an upstairs (if that makes sense) so for these parts i have 400mm wool.

Upstairs rooms (dormer): i have 100mm rafter lock for the walls and rafters fronted by 50mm insulated slab (air-tightness membrane between the 2). The ceiling parts of these rooms have 150mm rafter lock and 200mm wool

Good to know, mine also will provide the lot. I have fairly similar levels of insuation also but just a regular block on inner leaf! I did however use quinlites for 1st course on all rising walls.
I'm putting a lot of work into airtightness and hoping to get a low result in blower test!

Thanks for the info.

dos30

I also have A2W in a new build since December. 2500sq ft, UFH downstairs, nothing upstairs.
During winter downstairs temp generally 21deg, upstairs 18-20deg.
Still have to get my BER done but my PHPP was estimating a heat demand of 19.5kW/m2/yr (Passive is 15kW/m2/yr)

Heating costs todate are

Jan €48.28
Feb €43.45
March €9.17
April -> Present €0.00

Hot water costs are
Jan €28.00
Feb €26.55
Mar €28.97
Apr €21.72

*Lit the stove most evenings in March and turned the heating down.

dos30

@blast06 Looks like my hot water costs are about 3 times yours.
I'm guessing you don't have any rainshowers? How many inhabitants in your house?

Sandman777

dos30 wrote: »

@blast06 Looks like my hot water costs are about 3 times yours.
I'm guessing you don't have any rainshowers? How many inhabitants in your house?

Thats interesting dos30! Ill take you have rainshowers then? Any Electric showers?

In my own build i am planning 2 rain showers run of the heat pump and no elec shower! It would be interesting to see the price difference between showers run off HP and elect showers!! I didnt see the point putting in Elect shower when we'll have constant hot water.

Any know the average cost of running an elect shower?

Duffman1

dos30 wrote: »

I also have A2W in a new build since December. 2500sq ft, UFH downstairs, nothing upstairs.
During winter downstairs temp generally 21deg, upstairs 18-20deg.
Still have to get my BER done but my PHPP was estimating a heat demand of 19.5kW/m2/yr (Passive is 15kW/m2/yr)

Heating costs todate are

Jan €48.28
Feb €43.45
March €9.17
April -> Present €0.00

Hot water costs are
Jan €28.00
Feb €26.55
Mar €28.97
Apr €21.72

*Lit the stove most evenings in March and turned the heating down.

Hi

What's the make and spec of the heat pump do you have. I'm trying to decide on A2W or geothermal setup at the minute

dos30

Duffman1 wrote: »

Hi

What's the make and spec of the heat pump do you have. I'm trying to decide on A2W or geothermal setup at the minute

Thermia Atec 11KW

dos30

Sandman777 wrote: »

Thats interesting dos30! Ill take you have rainshowers then? Any Electric showers?

In my own build i am planning 2 rain showers run of the heat pump and no elec shower! It would be interesting to see the price difference between showers run off HP and elect showers!! I didnt see the point putting in Elect shower when we'll have constant hot water.

Any know the average cost of running an elect shower?

We've 3 rain showers, and our toddler likes to play in the shower for about 1/2 an hour. Might have to put in the slow flow washer come January!
No point in getting an electric shower when the heat pump can generate the hot water at about 1/3 of the price.

Curious Geroge

blast06 and dos30; what are your hot water and cold water tank sizes. I was told a 150lt tank was all that was avail for an 11kw hp.. anything bigger was custom.

dos30

Curious Geroge wrote: »

blast06 and dos30; what are your hot water and cold water tank sizes. I was told a 150lt tank was all that was avail for an 11kw hp.. anything bigger was custom.

I've a fully pressurised cold water system with 2 cold water tanks.
An 800 litre tank in the garage with a pump pressurising from there into the house. And one in the attic of the house which is around 200 litres and is used for flushing toilets and provides a buffer in case the power goes and the pump stops working.

My hot water tank is built into the internal unit of the heat pump and has a 180 litre tank. See the total unit on the link below.

http://www.thermia.se/docroot/dokumentbank/Thermia-heatpumps-Atec-ENG.pdf

I was worried that 180 litres wouldn't be enough, but it's 180 litres at ~50 degrees which is something like 400litres of water at a usable temperature.
The main reason I went for the fully integrated unit is because of its small footprint. When you start adding expansion vessels etc to a normal hot water tank it could easily take up an entire small utility room.

Curious Geroge

dos30 wrote: »

I've a fully pressurised cold water system with 2 cold water tanks.
An 800 litre tank in the garage with a pump pressurising from there into the house. And one in the attic of the house which is around 200 litres and is used for flushing toilets and provides a buffer in case the power goes and the pump stops working.

My hot water tank is built into the internal unit of the heat pump and has a 180 litre tank. See the total unit on the link below.

http://www.thermia.se/docroot/dokumentbank/Thermia-heatpumps-Atec-ENG.pdf

I was worried that 180 litres wouldn't be enough, but it's 180 litres at ~50 degrees which is something like 400litres of water at a usable temperature.
The main reason I went for the fully integrated unit is because of its small footprint. When you start adding expansion vessels etc to a normal hot water tank it could easily take up an entire small utility room.

I think I'm looking at the same unit with the "other" badge on it. Build in 180lt tank.. I too was worried about that only having limited hot water but good too hear its ok. Cheers

BobMcBob

I'm looking at the same 2 HP, from what i can gather these are slightly older now and don't modulate. They do have good COP and can heat water to a higher temp than many units. While not the premier HP, there are a cut above the re-jigged air con units.
Saying that, looking at the figures above prob doesn't matter which unit you go for if the insulation and airtightness is done well, increasing the cost to run by 1/3 only means 20 euro month in winter and 10 in summer going by the figures above.

Had spent a long time thinking about with HP to go with, but not as worried now as it won't make that big a difference. Will go for the Danfoss / thermia now more because of the cooling facility - there will be an issue of overheating on those rare summer days in the west when the sun actually shines.

dos30
Interested in the plumbing was going to go for a 500L break tank plus submersible pump, i'd be very grateful if you post or pm me some details on your setup as this is what I want but my plumbing knowledge isn't up to scratch.

BmB

bifl

One problem I'm having with A2W is getting it to pass the BER/DEAP on its own without the need for some extra renewals such as solar/pv. One thing that attracted me to the heat pumps was the fact they seems to get you through the renewables part. I dont fancy adding in other elemets at extra cost

Not sure but there seems to be some debate between BER and Heat Pump retailers with the SEAI of late on how the direct hot water efficiencies should be calculated for a HP. Ultimatly some are giving it 0.5 while others would argue is gets 0.7 difference being a pass or a fail for me anyway. A lot seems to center around which clause G1.1(a) or (b) or G1.2. All depends on how you determine if there is an 'integral immersion' on the heat pump.

Not sure should if try a different A2W or go back to Geo as these seem to pass easier.
Are other people having problems with A2W an BER/DEAP

MOTM

bifl wrote: »

One problem I'm having with A2W is getting it to pass the BER/DEAP on its own without the need for some extra renewals such as solar/pv. One thing that attracted me to the heat pumps was the fact they seems to get you through the renewables part. I dont fancy adding in other elemets at extra cost

Not sure but there seems to be some debate between BER and Heat Pump retailers with the SEAI of late on how the direct hot water efficiencies should be calculated for a HP. Ultimatly some are giving it 0.5 while others would argue is gets 0.7 difference being a pass or a fail for me anyway. A lot seems to center around which clause G1.1(a) or (b) or G1.2. All depends on how you determine if there is an 'integral immersion' on the heat pump.

Not sure should if try a different A2W or go back to Geo as these seem to pass easier.
Are other people having problems with A2W an BER/DEAP

The guidance on this is here in the SEI FAQ and, as you’ve referenced, DEAP appendix G. Some more also in DEAP 4.6:
http://www.seai.ie/Your_Building/BER/BER_FAQ/FAQ_DEAP/Energy_Requirements/A_Heat_Pump_provides_space_and_domestic_hot_water_why_is_“Adjusted_Efficiency”_of_the_DHW_system_less_than_the_space_heating_system_.html
DEAP appendix G: “ Where the heat pump has an integral immersion or the heat pump is not designed to reach appropriate temperatures for water heating, G1.1 is followed.”
I’ve seen heat pumps consisting of an indoor and outdoor unit where the indoor unit includes an immersion and a hot water store. This is an integrated immersion. I’d say if in doubt about whether an immersion is integrated or not to check with the BER helpdesk (give them details of the system and let them make the call). You'll even see some systems where the immersion is optional so it depends on the system installed in the house you're looking at.

blast06

dos30 wrote: »

I've a fully pressurised cold water system with 2 cold water tanks.
An 800 litre tank in the garage with a pump pressurising from there into the house. And one in the attic of the house which is around 200 litres and is used for flushing toilets and provides a buffer in case the power goes and the pump stops working.

My hot water tank is built into the internal unit of the heat pump and has a 180 litre tank. See the total unit on the link below.

http://www.thermia.se/docroot/dokumentbank/Thermia-heatpumps-Atec-ENG.pdf

I was worried that 180 litres wouldn't be enough, but it's 180 litres at ~50 degrees which is something like 400litres of water at a usable temperature.
The main reason I went for the fully integrated unit is because of its small footprint. When you start adding expansion vessels etc to a normal hot water tank it could easily take up an entire small utility room.

Am pretty much the same but don't have the 200 litre tank in the attic.
Spend many hours deliberating on getting a custom made 300L hot water tank but thankfully never went with that cos have never once ran out of hot water (apart from a couple of times when i was trying to be too clever by having hot water heating during night hours only!)

Re some other questions on hot water use .... just checked a 3 month profile of use (i was monitoring daily for first few months) .... was averaging 80-90 kWh per month which would be €12-14 per which is slightly higher than i first indicated. Have 3 kids who are bathed ~twice per week. Daily rain shower for my wife and same for me plus all other domestic use.

dos30

blast06 Not a whole lot in the difference so, my hot water averaged 136 kWh per month from Jan - April. I was calculating cost @ €0.195 per kWh.
I have a pump that circulates the hot water from the tank around the pipes in the house on a regular timed basis. So get hot water straight away when turning on a tap.
I wonder if this is the difference as it would be dropping the temp in the tank and the heat pump would kick in more frequently.

blast06

dos30 wrote: »

blast06 Not a whole lot in the difference so, my hot water averaged 136 kWh per month from Jan - April. I was calculating cost @ €0.195 per kWh.
I have a pump that circulates the hot water from the tank around the pipes in the house on a regular timed basis. So get hot water straight away when turning on a tap.
I wonder if this is the difference as it would be dropping the temp in the tank and the heat pump would kick in more frequently.

Hmmm, you're paying a high rate at .195 ??
I don't have such a pump that you describe. All bar main en-suite are pretty close to hot water tank which is more or less in centre of house. I guess it has to add cost but have no clue if its pence or many pounds !

DragonPlumbing

HI Bifl

You should go for air source heat pump.

There is no difference in Ireland.
In Ireland we don't have very low temp as -10 or -20 in winter time and this is reason why you can use air source heat pump.

The other models for water or for bore hole are designed for places where winter is strong and air temp is to low.