How to select the prober size of Geothermal HeatPump

anthger

Hello
I am building an new house with underfloor heating and fun coils for heating and cooling the house.

The house is 300 square meters and a mechanical engineer made calculations on the house and tolds me that the house needs 25kw heating system and for using a heatpump would be best to use a 20kw heatpump with 5 or more borehols.

An installer (thermia) told me that my best solution was using 16kw heatpump. Of course we cold also use a 20kw heatpump he told me.

So i would ask you will it be better to use the 20kw or it will be more energy efficient if i will use the 16kw?

Thank you in advanced,
Antonis

The Hurricane

Hi Antonis,

My House is over 300 square meters and I have a 12 Kilowatt Alpha Innotec Heatpump( borehole system not groundloops) and its working well and can deal effectively with the heat requirements for the house we also have solar panels two which work well in summer but only partially in winter. My total esb bill last year for 1 year for everything heat light appliances etc was 1400euro. If you install a bigger Heat pump you use more units mine a 12 Kw used 3 per hour at night but it has a COP of 4:1 which means for every unit you use to power the heatpump it delivers 4 units of heat per unit of energy thats the therory anyway.

Im no engineer but you may be oversized with a 20KW heatpump and not sure about 16 too. Basically the most important this is to insullate your house as well as you can make sure the underfloor pipes are covering the area sufficiently your plumber installer knows the system and heatpump they are installing well and that they set it up to do the bulk of its work at night on the cheap rate electricity and you install an ESB nightmeter.

Feel free to PM me if you have any queries would be glad to help I had some teething problems and had a few high bills as the system was not set up properly. One more thing when your supplier installs it make sure they take your through the ststem how the heatpump controls work and be sure you have a working knowledge yourself of what to do if there is a problem by consulting the manual.

Regards
Hurricane.

Hello
I am building an new house with underfloor heating and fun coils for heating and cooling the house.

The house is 300 square meters and a mechanical engineer made calculations on the house and tolds me that the house needs 25kw heating system and for using a heatpump would be best to use a 20kw heatpump with 5 or more borehols.

An installer (thermia) told me that my best solution was using 16kw heatpump. Of course we cold also use a 20kw heatpump he told me.

So i would ask you will it be better to use the 20kw or it will be more energy efficient if i will use the 16kw?

Thank you in advanced,
Antonis

Condenser

anthger wrote: »

Hello
I am building an new house with underfloor heating and fun coils for heating and cooling the house.

The house is 300 square meters and a mechanical engineer made calculations on the house and tolds me that the house needs 25kw heating system and for using a heatpump would be best to use a 20kw heatpump with 5 or more borehols.

An installer (thermia) told me that my best solution was using 16kw heatpump. Of course we cold also use a 20kw heatpump he told me.

So i would ask you will it be better to use the 20kw or it will be more energy efficient if i will use the 16kw?

Thank you in advanced,
Antonis

Hi Antonis,

The size you require will depend on the heat losses of your house. The greater the level of insulation the smaller the heat losses, the smaller the heatpump. Unless you're building a Wendyhouse 25kw is ridiculous for a 300sqm house and I suggest you forget getting any further info from your enginneer.

If you give me some info on the type of insulation level you plan on installing, I'll give you a fairly accurate idea of what size heatpump you'll require. Whether its an Air to Water or a ground source will also affect your sizing

anthger

Hello,
My house will have 25cm brick with all the outsite of the house covered with polystyrene and then finish with a mixture that has the paint in it. So there will be a shell outsite of the hole house.
Also i will have thermal aluminium windows and low emmisions double glass on them.

That will be my insulation level.
The heatpump will be ground source.

Condenser wrote: »

Hi Antonis,

The size you require will depend on the heat losses of your house. The greater the level of insulation the smaller the heat losses, the smaller the heatpump. Unless you're building a Wendyhouse 25kw is ridiculous for a 300sqm house and I suggest you forget getting any further info from your enginneer.

If you give me some info on the type of insulation level you plan on installing, I'll give you a fairly accurate idea of what size heatpump you'll require. Whether its an Air to Water or a ground source will also affect your sizing

Condenser

anthger wrote: »

Hello,
My house will have 25cm brick with all the outsite of the house covered with polystyrene and then finish with a mixture that has the paint in it. So there will be a shell outsite of the hole house.
Also i will have thermal aluminium windows and low emmisions double glass on them.

That will be my insulation level.
The heatpump will be ground source.

So you're using external insulation. Does that include the roof? How thick is the insulation and what are you planning for under the underfloor. 125mm of kingspan or similar is the recommended level

Sorry for all the questions but in order to get an accurate answer i'll need those specs

anthger

The outsite shell of the house will be 6mm Styrofoam of DOW (blue Polystyrene ). And after it, its finnish with the paint. The total wall size including the outside shell will be 33mm.
Also there will be sth similar in the roof.
Under the underfloor pip in pip (PexA) there will be 30mm sth like polystyrene b;ue again). Under that there will be power foam.

Thank you in advanced,
Antonis
P.S What is 125mm kingspan?

Condenser wrote: »

So you're using external insulation. Does that include the roof? How thick is the insulation and what are you planning for under the underfloor. 125mm of kingspan or similar is the recommended level

Sorry for all the questions but in order to get an accurate answer i'll need those specs

Condenser

anthger wrote: »

The outsite shell of the house will be 6mm Styrofoam of DOW (blue Polystyrene ). And after it, its finnish with the paint. The total wall size including the outside shell will be 33mm.
Also there will be sth similar in the roof.
Under the underfloor pip in pip (PexA) there will be 30mm sth like polystyrene b;ue again). Under that there will be power foam.

Thank you in advanced,
Antonis
P.S What is 125mm kingspan?

Maybe I'm picking you up wrong but that seems a very small amount of insulation. 6mm is a very thin layer of any insulation to use. Can you send me a link to the product or a spec for the house that the engineer has provided you with.

Kingspan is a PU panel with an aluminium foil backing on both sides. Kingspan is the brand name same as we would refer to a vaccuum as a hoover

anthger

Ok
Here is what i mean
i will use the following thermal brick

the size of it is 250mm x 200mm x 300mm (250) and the hole wall will be like this one


So the the grey part (no 1) is from DOW the Xenergy system and that is the one that is 6mm.
I hope i explained you what i mean now

Condenser wrote: »

Maybe I'm picking you up wrong but that seems a very small amount of insulation. 6mm is a very thin layer of any insulation to use. Can you send me a link to the product or a spec for the house that the engineer has provided you with.

Kingspan is a PU panel with an aluminium foil backing on both sides. Kingspan is the brand name same as we would refer to a vaccuum as a hoover

Condenser

anthger wrote: »

Ok
Here is what i mean
i will use the following thermal brick

the size of it is 250mm x 200mm x 300mm (250) and the hole wall will be like this one


So the the grey part (no 1) is from DOW the Xenergy system and that is the one that is 6mm.
I hope i explained you what i mean now

Had a look at the exenergy website there. The smallest insulation they were quoting was a 60mm so I assume this is what you'll be using.
Looks like a great system. Based on the heatlosses you would incur in a house with that build type I would suggest you should be looking at a heatpump of around about 10kw.

Hope this is off help to you

Remember, your heatpump will only give you its rated output at 35C, go higher than that and it drops efficiency, lower and it increases. So any UFH or fan coils you install should be designed to run at 35C or below

anthger

Ooops
Yes i should say 6cm not 6mm

What every plumper here told me was that the underfloor heating works with 40c - 42c will it work with 35c or it will need more underfloor pipes in meters in order to work with 35c ?

Condenser

anthger wrote: »

Ooops
Yes i should say 6cm not 6mm

What every plumper here told me was that the underfloor heating works with 40c - 42c will it work with 35c or it will need more underfloor pipes in meters in order to work with 35c ?

You can't design UFH for a heatpump in the same way as you do for an oil boiler. 42C doesn't matter for an oil or gas system because you're usually bringing the temperature down from about 60C anyway.

The lower temp you design your UFH to operate at the more efficient the HP will be. You should really be aiming for water temps of around 30C. That will maximise performance and reduce the size of HP you need to install. In order to do that you will need to install more piping.

Also avoid HP's with immersion backups, they are just covering up design flaws.

anthger

Well ,
I would like to thank you for all the help regarding my question.
You answer me more of what i first ask.

Best regards,
Antonis

P.S I will let you know what will be the results when i will finnish the house and install the HeatPump.

Condenser wrote: »

You can't design UFH for a heatpump in the same way as you do for an oil boiler. 42C doesn't matter for an oil or gas system because you're usually bringing the temperature down from about 60C anyway.

The lower temp you design your UFH to operate at the more efficient the HP will be. You should really be aiming for water temps of around 30C. That will maximise performance and reduce the size of HP you need to install. In order to do that you will need to install more piping.

Also avoid HP's with immersion backups, they are just covering up design flaws.

Condenser

anthger wrote: »

Well ,
I would like to thank you for all the help regarding my question.
You answer me more of what i first ask.

Best regards,
Antonis

P.S I will let you know what will be the results when i will finnish the house and install the HeatPump.

No bother, best of luck with the build