Ground Source Heat Pumps

Strummer22

Badger36 said:

I currently in the early stages of planning on building a house of around 200m2. I'm in Scotland.

Space isn't a concern and I understand that Ground Source is better if space allows. 

However I question the suitability for ourselves. 

• The house will be unoccupied for at least 10hrs most days
• With our business the house will frequently be unoccupied for days at a time during the midweek. 
• We are also keen climbers/trekkers - so weekends where the weather allows we pack the van and head off.

My concerns about the heat pump over an oil central heating systems are that my understanding of heat pumps are that they work best if on all of the time, which isn't efficient given the amount of time we spend not in our house.. They also don't heat a house up quickly if away for say 5 days with work. Whilst I do like the green credentials of the heat pump, I am unconvinced  that a heat pump is the correct option for our lifestyle. Our oil system just now will have the house, from cold, warm in 30 minutes - and that is in December temperatures. 

Also a lot of noise is being made in Scotland about these being made mandatory in future. 

Does anyone have any practical lived experience of how

If you don't have mains gas then a heat pump is unlikely to be mandatory, although renewable heat would help your planning application (assuming planning has not already been secured).

As it's a new build you can really spec the insulation properly and make sure there are no drafts, so no matter what heat source you use the heating costs will not be very high. Aim to design it to make the most of thermal gain from low sun in the winter (what little you get! Where in Scotland are you?).

Regarding operation of the heat pump, mine is not on all the time; at the moment it's on 4:30 am until 9:30 pm. The thermostat is in the hall and loses 1 - 2°C overnight, more if it's cold and windy, but my house is not great at retaining heat; yours could be if built right! It usually takes all day to make up that 1 - 2°C but I have the weather compensation curve set low (CH water is about 37°C today, it's 7°C outside), and as it's a retrofit we have somewhat undersized radiators, not underfloor heating. It is possible to get your heat pump to warm a house fairly fast, like 2-3 hours, but that's at the expense of efficiency because it means heating the water to a higher temperature. 

You would be best just making sure you have smart heating controls and keep it at maybe 13-14°C while you're away for days and set back to your preferred temperature 1 day before coming home. Near enough instant heat for at least part of the house could be provided by a wood burner (don't do this if you live in a town/village). 

If space is not a constraint a GSHP will always be a great option for a new build. Just be prepared to learn how to operate it properly and pay quite a lot more up front for installation than for an oil system.

Badger36

Hi there, my parents farm is towards (although not in) the Cairngorms - 20 minutes north of Blairgowrie. We have a 5 acre plot there, which we are just waiting on the lawyers to get everything signed over, but I don't anticipate any issues with getting planning. We currently live in a cottage on the outskirts of Blairgowrie with oil heating, and it works very well. 

Would you have any concerns about running it the way I would propose to? I am all for being green and sustainable, but if the system is going to cost lots to install, run and not do the job as well as an oil boiler, then I'm obviously concerned.

Strummer22

No, not got any concerns, but if you do go for a GSHP you must get the insulation and draft proofing up to spec, and size the emitters accordingly. Underfloor heating is best. Probably get triple glazed windows. It could easily be -20 there every few years. The GSHP would probably do ok even then if the house loses sufficiently little heat, but it would make sense to have a back up like the wood burner for those very cold nights or if you have a power cut.

Badger36

Strummer22 said:

No, not got any concerns, but if you do go for a GSHP you must get the insulation and draft proofing up to spec, and size the emitters accordingly. Underfloor heating is best. Probably get triple glazed windows. It could easily be -20 there every few years. The GSHP would probably do ok even then if the house loses sufficiently little heat, but it would make sense to have a back up like the wood burner for those very cold nights or if you have a power cut.

Thank you,

As said I just want to make the best choice for my needs, and that is balancing the moral obligation of being green versus the practicalities and costs of operating/installing such a system.

Whilst we aren't poor, we aren't in a position where we spend the sums making the house perfect from an insulation and green energy perspective - we can make it very good. Building a 200m2 house to a medium standard is the level of spending we are prepared to commit to - even at that 20-25m2 will be dedicated office space for the business.

The alternative of course is install oil heating but future proof the house for green heating in future. 

Strummer22

It’s probably also worth mentioning that running costs will differ. Obviously the relative prices of oil and electricity will mean the oil is sometimes cheaper than GSHP and vice versa, but right now it costs about 8p/kWh for oil heating. From 1 Jan 2024 electricity will be about 28.5p/kWh. So for GSHP to be cheaper to run than oil, your system would need an average coefficient of performance (COP) of 28.5/8 = 3.56. This is easily achievable, my system gets well over 4 and as a retrofit it’s less efficient - if I had UFH I would run the central heating flow temperature even lower. It’s quite likely that the GSHP running costs will be lower than the oil system over the lifetime of the system.

But installing the heat pump in the first place is a lot more expensive, even with the gov grant!

One last point, choose your installer carefully. 

Reed_Richards

Badger36 said:

I currently in the early stages of planning on building a house of around 200m2. I'm in Scotland.

Space isn't a concern and I understand that Ground Source is better if space allows. 

However I question the suitability for ourselves. 

• The house will be unoccupied for at least 10hrs most days
• With our business the house will frequently be unoccupied for days at a time during the midweek. 
• We are also keen climbers/trekkers - so weekends where the weather allows we pack the van and head off.

My concerns about the heat pump over an oil central heating systems are that my understanding of heat pumps are that they work best if on all of the time, which isn't efficient given the amount of time we spend not in our house.. They also don't heat a house up quickly if away for say 5 days with work. Whilst I do like the green credentials of the heat pump, I am unconvinced  that a heat pump is the correct option for our lifestyle. Our oil system just now will have the house, from cold, warm in 30 minutes - and that is in December temperatures. 

Also a lot of noise is being made in Scotland about these being made mandatory in future. 

Does anyone have any practical lived experience of how

Heat pumps do not need to be on all the time but the economics of having them off some of the time are not so good as for fossil fuel boilers. 

If you have underfloor heating then you will need your heat source to be on for long periods because underfloor heating with a big concrete slab acts like a giant storage heater and it takes a long time to bring this up to temperature (and then a long time for it to cool).  That applies with oil, gas or a heat pump. 

If you have radiators you can make your heat pump come on and heat your house within an hour or two but this would require a high water temperature, which is the least economical mode of operating a heat pump, so you save proportionately less by having it off some of the time than you would with an oil boiler.

Heat pumps may not become mandatory in future but oil boilers may become increasingly "unpopular" and expensive so your issue is not so much now but what you do in 10+ years time when you replace the oil boiler you install now.  You could make your heating system heat pump ready by installing suitably large radiators, suitably large bore pipes and a hot water cylinder with a suitably large area coil.

frslam

Badger36 said:

I currently in the early stages of planning on building a house of around 200m2. I'm in Scotland.

Space isn't a concern and I understand that Ground Source is better if space allows. 

However I question the suitability for ourselves. 

• The house will be unoccupied for at least 10hrs most days
• With our business the house will frequently be unoccupied for days at a time during the midweek. 
• We are also keen climbers/trekkers - so weekends where the weather allows we pack the van and head off.

My concerns about the heat pump over an oil central heating systems are that my understanding of heat pumps are that they work best if on all of the time, which isn't efficient given the amount of time we spend not in our house.. They also don't heat a house up quickly if away for say 5 days with work. Whilst I do like the green credentials of the heat pump, I am unconvinced  that a heat pump is the correct option for our lifestyle. Our oil system just now will have the house, from cold, warm in 30 minutes - and that is in December temperatures. 

Also a lot of noise is being made in Scotland about these being made mandatory in future. 

Does anyone have any practical lived experience of how

I have a self build 160m2 house in the Highlands, IVT HT Plus E7 (7kw) with 280lt Solar Coil Cylinder, underfloor heating on ground and first floor. My building warrant was pre 2010 regs, just made sure I over spec'd the insulation as much as I could. I don't know why anyone would go to oil or gas, especially with the higher spec these days. We do suffer from extreme temperature fluctuations. I think it's better for the house itself to remain at a constant temperature. Our Ground Source energy usage for Heat and Hot Water works out at around 6,000KW/Year. My house looks out to the Minch and quite exposed with 28 windows, more than half of them facing North West - we do get battered by storms. Some houses near me can have trouble in the winter trying to get oil or gas (transported). My heating system could use less energy but I prefer to have the inside temperature at 22-23c. I've run a spreadsheet since October 2010 when I moved into my house and the usage has been very constant. It would be a bit cheaper to run if I had the GSHP with internal cylinder, but the missus runs a B&B, the energy usage includes the hot water usage of 6-7 people having either baths/showers every day. Obviously underfloor heating on the ground floor keeps things cost effective with the average return temperatures at just over 30c. Even just now, the heating cycle comes on when the return temperature drops to between 26-28c, then heats up to 5c above that and stops. Most floor circuits on the ground floor only open every other day, reach temperature then close off.

Strummer22

My GSHP has a problem The external thermometer thinks it's 26C so it won't do central heating. I've forced the settings as much as possible and it will heat the water to 24C, so I have a very small amount of heat coming from my radiators. 

These things always happen on a Friday afternoon! 

Anyway, does anyone have any clue how I might turn weather compensation off or get it to ignore what it thinks the outside temperature is? It's an EcoForest EcoGeo if that helps. 

Edit: I've asked the installer but don't expect to hear back until Monday. Wood burner is stopping the house freezing until then.

Patrol

If this manual is for your GSHP it doesn't sound obvious https://ecoforest.co.uk/assets/files/2018_05_15__User_EN.pdf?rnd=

If it was me I'd try this bit on page 50 (assume you cannot disconnect the external sensor or doing so stops operation entirely)


Indoor room temperature: low in HEATING mode high in COOLING mode

• Outdoor temperature high / lower than the heating / active cooling / passive cooling cut-off temperature.
• Adjust the heating / active cooling / passive cooling cut-off temperature.

Strummer22

Patrol said:

If this manual is for your GSHP it doesn't sound obvious https://ecoforest.co.uk/assets/files/2018_05_15__User_EN.pdf?rnd=

If it was me I'd try this bit on page 50 (assume you cannot disconnect the external sensor or doing so stops operation entirely)


Indoor room temperature: low in HEATING mode high in COOLING mode

• Outdoor temperature high / lower than the heating / active cooling / passive cooling cut-off temperature.
• Adjust the heating / active cooling / passive cooling cut-off temperature.

Thanks Patrol, I don’t know how to disconnect the external sensor and not sure it’s a good idea anyway for kit still under warranty. I’ve adjusted the cut-off temperature so the heating is on, but the weather compensation means it won’t heat the water above 24C