Ground Source Heat Pumps

lovesgshp

destry wrote: »

Many thanks, Lovegshp. I'll remember to ask about venting the pipes at the highest points. Does the pump use more energy because it has to push the fluid uphill?
The flow rate will determine what speed the pump needs to be set at, plus the loop pressure will help. It is normally set to 0.5-1.0 bar, albeit in many of the earlier discussions on here people have not got a pressure gauge on the loop, so have no idea. Also many have not got flow rate meters, another failing, as you have no check if the flow is too low or high.

I'm interested that you don't recommend slinkies, which most installers seem to suggest are just as efficient but cheaper to install. Apologies if you have covered this elsewhere, but what's the thinking here?
Slinkies are cheaper, but you do get heat loss with them, as against a normal install. In your case, I would be looking at 2x120 mtr excavations @ 1.2mtrs depth, 1.2mtrs wide and minimum 3 mtrs apart. 2 inlet and 2 return lines with 30cm seperation.

I have an advisor saying the feed from the manifold to the pump should go underground and will therefore just be picking up more heat from the ground (albeit less efficiently) as it travels the 35 metres to the house - and as such won't need to be insulated until it pops up to pass through the back wall. Does that make sense to you?

If it is at the design depth, then yes it will help. Where it gets to the approx 60cm depth to feed into the property, then you will need insulation to prevent heat loss in cold weather.

Finally (newbie question alert...) can you really get a steaming hot bath out of these critters in the height of summer?
Many pumps will give you DHW @ 65C if you want. The point is that you would be wasting energy, as you would need to cool the water down. The whole idea is to set a temperature that you don't really need to mess around with all the time. Average use for DHW here over the year is 20% of the pump usage. In the summer it operates for about 1 hr a day max.

Many thanks again!

Hope all those answers help.

destry

OK, add pressure gauge to checklist!

And just to check, your suggestion would be two 120m square trenches, at least 3 metres apart, each with four pipes, 2 inlet, and 2 return?

Thanks for your advice about the run to the house -- makes perfect sense.

Ref the DHW, I guess the point of very hot water is that you don't need so much of it to provide bath/shower water diluted to e.g. 40C. So, a trade-off between a big tank with water stored at the temperature you need, or a small tank with less water stored piping hot. I guess you advice is that a GSHP is better served by the former, right?

=========================

Cardew, the price of oil is at an historic low and you are brave to predict it will stay that way -- it is governed by a hugely complicated matrix of economic, political, environmental and geological factors which pretty much defy accurate forecasts. Even the geological surveys seem to produce a different set of results every few years. If the move away from oil gathers steam, that in time could push prices up as the economies of scale decrease.

Still, I it is not just a financial question for me. Oil is dirty stuff, and I'd prefer not to burn it if I have a choice. I feel the same about wood pellets. Of course, electricity has to be generated, but I can do some of that myself via solar pv; and if I'm prepared to pay more right now I can buy 'clean' electricity off the grid. In time, electricity generation will move away from coal/gas/oil and I'd like to participate in that. Waves/tides/wind and sun are there for the taking. Once the infrastructure investment is made, this energy will be both clean and cheap. Something to look forward to!

Many thanks to you both for your very helpful input.

lovesgshp

Hi Destry.
Yes the probes are in 2 excavations with 4 lines in each. If you want to PM me with a email address, then I can send you some pics of some installations.
With the DHW, then the default setting would normally be @ 50C, with a disinfection cycle @ 65C on a periodic basis. If you go to a higher temperature and use a lot of hot water, then disinfection is not required as often. Here we are at 30 day intervals.

peeta

hi all,
just looking for a recommendation.
we decided to use a GSHP and the shortlist is to go with either:
Option A - two NIBE 1245 machines, or
Option B the new Kensa 21kW hybrid machine

which manufacturer would you chose?
thanks

lovesgshp

peeta wrote: »

hi all,
just looking for a recommendation.
we decided to use a GSHP and the shortlist is to go with either:
Option A - two NIBE 1245 machines, or
Option B the new Kensa 21kW hybrid machine

which manufacturer would you chose?
thanks

Welcome to the forum.

You must have a very large or poorly insulated house, if you are looking at 21Kw output pumps.
Looking at the specs of the 2 units, then I would probably eliminate the Kensa, as it has no electrical heater backup. Reasons for this are, that if you have a compressor fault, then you cannot revert to the immersion heater. In many units as well, this will cut in to aid the heating after about 1hr of compressor operating time in very cold weather conditions.

peeta

thanks for your comment. yes the house is a new-build and on the larger side at 520 sq. metres including a heated basement of about 120 sq. metres.

I appreciate the Kensa has no backup heater. When I spoke to the manufacturer's they were very "enthusiastic" about their hybrid technology, and really emphasised that an immersion heater is a slippery slope towards making the system far less efficient. In other words the immersion would probably kick in more than anticipated and therefore increasing costs.

To be honest, I think I would rather go with the best quality system (NIBE offer a 7 year warranty and Kensa 5).

Of course, I also need to decide on the collector system. We have enough garden for 5 x 50m trenches for slinkies (about 1250m in total length). The other option is 4 x 110 boreholes for a vertical system. Clearly the boreholes are much more expensive, but are they worth it?

many thanks

lovesgshp

peeta wrote: »

thanks for your comment. yes the house is a new-build and on the larger side at 520 sq. metres including a heated basement of about 120 sq. metres.
Ok, can see the reason for the sizing.

I appreciate the Kensa has no backup heater. When I spoke to the manufacturer's they were very "enthusiastic" about their hybrid technology, and really emphasised that an immersion heater is a slippery slope towards making the system far less efficient. In other words the immersion would probably kick in more than anticipated and therefore increasing costs.
Not really a problem in normal operating conditions, it is there as a help, plus a emergency measure.

To be honest, I think I would rather go with the best quality system (NIBE offer a 7 year warranty and Kensa 5).

Of course, I also need to decide on the collector system. We have enough garden for 5 x 50m trenches for slinkies (about 1250m in total length). The other option is 4 x 110 boreholes for a vertical system. Clearly the boreholes are much more expensive, but are they worth it?
Forget boreholes if you can. We do not use slinkies, as they are not as efficient as a straight line installation.
One install a few years ago, with 2x11kw pumps, had 2 excavations of 160 mtrs each. if you can get to that, then i would advise it.

many thanks

Hope this helps.

poohbear59

Hi again, I am looking for some help please.

Our GSHP is in our cottage which we let next door to our house. I have just popped in to see the people in there and the hallway thermostat is flashing red. I have never, ever seen it lit up in 4.5 years of having the pump running every day. Does anyone know why the thermostat would flash red? It is steaming hot in there. We have a wood burning stove which is there more for a focal point than anything else and it was lit all day today!!!!

I hope someone can help please.

Patrol

Hi poohbear59
On my setup that light indicates there has been an alarm, and the pump was not operational on the one occasion my light went. More information can be found by accessing service mode; holding the rightmost button down for a few seconds. Then scrolling through to alarms and post any details back here as somebody may be able to help.

A reminder on what GSHP you have would be helpful too.

lovesgshp

poohbear59 wrote: »

Hi again, I am looking for some help please.

Our GSHP is in our cottage which we let next door to our house. I have just popped in to see the people in there and the hallway thermostat is flashing red. I have never, ever seen it lit up in 4.5 years of having the pump running every day. Does anyone know why the thermostat would flash red? It is steaming hot in there. We have a wood burning stove which is there more for a focal point than anything else and it was lit all day today!!!!

I hope someone can help please.

Hi Poohbear.

As Patrol has said, you need to access the alarm menu on the pump to see what it is, then we can look at a solution.