Geothermal Heating Effeciency

johnb25

This post may get long, but I want to share some experience of geothermal, and also get some feedback from others who have it installed.
The Experience
We have a direct evaporation geothermal heating system installed in a new house, using horizontal ground collectors. We moved in August, so it is still relatively new, but we find it very ineffecient. House is block-built bungalow, with standard cavity & attic insulation.
It takes a very long time of constant running of the system to get a good temperature in the house e.g. ran the system for 24 hours from 7.30 pm yesterday evening, and room temperature increased from 19 degrees to 20.7 degrees in that time. (Partly for the heat, and partly to get a baseline of performance). On a program running 10 hours overnight, the room temperature dropped from 20.1 on Sunday night to 19.0 degrees on Tuesday morning. Weather relatively mild just now also.
I had the company out last week to check system, and they could find no fault e.g. gas pressure ok etc. I was on to the installer again today, who is going to get them out again to try and resolve this. I will add some updates to this thread on progress.
I had some reservations about the suitability of our site. It is large enough, but we have a lot of limestone 3-4 ft down. I raised this with installer, and suggested vertical bore-holes. He assured me that ground was ok, and horizontal is preferrable to vertical if conditions permit.
At this stage our system is starting to look like an expensice failure.:mad:

Some feedback please
What flow temperatures should a direct expansion system produce, or what should be the differential between flow and return temperatures?
Any other experiences or advice?
Thanks for staying with me if you got this far:)

Qwerty?

Sorry to hear you having problems. Just wondering what temp your flow and return to the ground loop is coming in at?

Our flow and return inside is 30 -27, and the ground loop is coming in at 7deg.

yop

Not sure what the ground loop is coming in at in ours, the circulation temp is about 28.
What is happening is disgraceful, no way is that right, get them to sort it or take it out and give you your money back. 10 hours a day running is crazy!!

billy_beckham

"Our flow and return inside is 30 -27, and the ground loop is coming in at 7deg."

When you talk about flow and return temps, are you talking about the flow and return temp of the water in the underfloor heating circuits or the refridgerant temp's??

yop

I would suspect that is the UFH flow billy

CJhaughey

johnb25 wrote:

. House is block-built bungalow, with standard cavity & attic insulation.

What exactly are the insulation specs?What is the wall insulation, Aeroboard? What are you using in the Attic?
If the heat is escaping from the house through poor or insufficient attic insulation then no matter how powerful or efficient the system is it will have difficulty keeping the house warm.
Is there holes in the ceiling for recess halogens? are these allowing cold air to infiltrate?(posted this week)
I would go through and check to make sure that all the basic details are fully covered as well.

yop

Never thought of that CJ, with the "standard" of insulation that some builders use then it would take a ships steamroom to heat.

Is it Rads or UFH which is been used?

Are you sure that your UFH or rads are working right?

Qwerty?

billy_beckham wrote:

"Our flow and return inside is 30 -27, and the ground loop is coming in at 7deg."

When you talk about flow and return temps, are you talking about the flow and return temp of the water in the underfloor heating circuits or the refridgerant temp's??

Yeah, the flow and return of UFH in the house is around the 27-30 degrees mark. The flow and return to the ground loop outside is about 7 degress, depending on the days temp. Obviously it drops a bit (3 or 4 degrees) when the heat pump is on.

When you say the heating is on 10 hours, do you mean the compressor? That would be costing a lot to be running. One of the most important things with UFH is insulation. You don't want to be losing heat from your home.

We have had to switch off our heating a few times in the past year for a day or so, and didn't really notice large drop in temp for the first day, by the end of the second day, there was a noticible drop alright, but from what you are saying you are losing your heat in a matter of a few hours. Heat been lost somewhere. Have you stats in each room? what make of heatpump have you?

johnb25

Thanks for the comments.

Don't know the temp of the collectors, no gauge on that.
The water flow/return is typically 20-22 degrees, but not sure how accurate the gauges are.

Heat distribution is UFH.
The insulation is Xtratherm 50mm under the floor and in the wall cavity.
6" fibreglass wrap between ceiling joists. Attic is part floored. The void spaces have a further 4" or 6" wrap, and the floored area has 4" wrap under the membrane. Vertical divide between floored and void area has 6" wrap.
Due to rock on site, there is only foundation for outside wall and one down the middle. Precast slabs accross foundations, and floor/internal walls on top.

10 hours a day is the running time of the compressor, 11pm till 9am. I don't think heat loss is the cause of the problem. If it were, the house should at least be warm @ 9am! From the low temperatures of the water, I think the heat pump is only raising the water temp. very slowly.

We only have one stat/controller in the hall.
The heat pump is Neura, from Ecoheat.
I will chase them again tomorrow to get some action, and try to get the type of system their web site promises.

Thanks again.

Qwerty?

What kind of guarantee did you get off these guys? There website is a little vague...

This system is sounding a bit iffy imo. I'm no expert, but having to run your heatpump for 10 hrs solid is not right. What KW pump is it?

I think your flow and return need to be up nearer 30 deg to heat the rooms to a decent temp, but with no stats in the rooms, I don't understand how the installers are planning to let you regulate them.

My flow and return are automatically increased/decreased depending on the outdoor temp, just wondering do you have an outdoor temp guage, and is it working?

Do-more

johnb25 wrote:

Due to rock on site, there is only foundation for outside wall and one down the middle. Precast slabs accross foundations, and floor/internal walls on top.

This may well be more of your problem, if your site is rocky it may well not be suitable for a ground collector.

You will also have diminishing returns in running the sytem for long periods, as the heat in the soil around the collector will be extracted quite quickly. The heatpump will then have to work harder and harder to gain any further heat from the soil. This is compounded further by running at night when there is obviously no solar energy to add heat to the soil....

Wobs

Hi John,

What size is your house, what KW size is your heatpump and what area/size is your ground collector covering?

Wobs

yop

2" on the floor is very mimimum I suspect, I would have thought up to 4" is more the norm.

I think you maybe confusing running and room temp, if not the temp in the loop is at least 6 up to 20 degrees depending on your loops.

I am suprised that your sytem does not report the inlet temp.

To be honest I would be asking seriour questions, I wonder have they under sized your pump or is your UFH a shambles, this can also cause serious issues if not commissioned correctly.
Our heatpump also regulates the rooms, but Climate control also adjusted flow temp down on the rooms so that they would not be too uncomfortable, that with the fact we have room temp of 19 degrees keeps it very cosy.

As I said I would demand answers because from what I see the goods are not fit for their purpose.

johnb25

Thanks again for the comments.

Latest installment!!
I had a visit yesterday from the installer and the Ecoheat MD.
He still reckons system is performing ok, and blames heat loss and the way I was trying to over-regulate the heat.
The house has a stairs into the attic, and the storage heaters are not installed there yet.
There is a relatively small open area at the top of the stairs, and the rest of the attic space is insulated
and partitioned off. He says heating this space is more than the system was spec'ed for.
As for regulating, Ecoheat say that by trying to force the system to run on night rate, I was allowing
temperature to cool too much, and therefore leaving too much to do at night. Temperature should be kept within 1-2 degree range.
He has set the system to cut in if it falls below these temperatures at these times:
09:00 19 deg (Switch off night program)
15:00 20 deg (Day-time boost)
19:30 21 deg (Day-time boost)
23:00 23 deg (Switch on night program)
Theory is that if we maintain higher temp, it will find a balance, and run more efficiently.
I am sceptical, but will stick with it for now, at least until I have heating upstairs. (Hopefully this comming week)
Looks like a lot of day-time running to me.

Replies to your comments
The heat pump is 12 kW, with five 75M loops (2*37.5M). 2 years guarantee on all parts.
The house is 2,200 sq ft ground floor.
Honestly not sure about outside temp gauge.
The rooms are balanced by adjusting the flow rate on the return manifold. I have made some adjustments
and the balance is ok i.e. the whole house gets cold together! :rolleyes: I am ok with this method of balancing, as it is
something that should be permanent once the balance is found.
Yop, the only temperatures I can read are the flow/return gauges near the control panel, and
the gauges on the manifold. Not sure how accurate they are, but 22 degrees is typical.
I specifically asked when the system was comissioned about gas temp gauges, and was told there were none.

To be continued........

anon1

Increase the flow temperature to 45 degrees by changing settings on the boiler or upping the temperature on your room stats.
45 degrees would not be an excessive temperature for UFH.

Please list all the configurable settings from the HP manual here so we can have a look.

Does the manufacturer have a service desk so you can by pass the local rep for a second opinion?

Wobs

Hi Johnb25,

Any news on your heatpump? It looks to me that your collector bed may be a bit small for the size of your house. It should be at least the size of your house if not bigger, yours seems to be smaller.

keynesian

:eek: my thoughts exactly:eek:

jones085

Ground- The ground should be moist free draining soil. ie. on one end sand and shale are v free draining but hold very litlle moisture. The mechanism by wich heat is transfered into the pipe. At the other end bog or pure marl or clay hold moisture but tend not to be free draining. As most of the energy replacment for horizontal systems comes from the movmentment of moisture down through the soil. The system will not replenish. The key here is to look for the presence of marl or london clay. usually yellow to blue in color and looks like it should be on a potters wheel.
The size is the next essential part. DX or direct expansion systems base there princeple on the fact that by not using plate exchange and the natural circulation generated by the compressor they can derive more heat from the smaller parcell of ground and be more efficient on space and electricity draw. A brine closed loop system(water to water) would use around 8 loops of 150m for a 12kw system(an area roughly20m x 37). Much larger than DX. The question that has to be asked is. You may be able to get more heat from a smaller area with dx but when cooling such an area so aggressivly how does it regenerate its heat in time for the next heating cooling cycle?

On peak load (this time of year) a heat pump dx or not should be running for not much more than 10-12 hours a day. This would be fairly standard in the industry with the calcs used for heat load.

I would be concerned about the temps your getting on the heating side. This should be around 35-45 degrees to get a decent delta t for the underfloor.
This could be because of lack of collector energy or undersized system.

Hope this helps in some way.

Regards

Simon

finbarrk

Any more news on this?

feorais

johnb25 wrote:

This post may get long, but I want to share some experience of geothermal, and also get some feedback from others who have it installed.
The Experience
We have a direct evaporation geothermal heating system installed in a new house, using horizontal ground collectors. We moved in August, so it is still relatively new, but we find it very ineffecient. House is block-built bungalow, with standard cavity & attic insulation.
It takes a very long time of constant running of the system to get a good temperature in the house e.g. ran the system for 24 hours from 7.30 pm yesterday evening, and room temperature increased from 19 degrees to 20.7 degrees in that time. (Partly for the heat, and partly to get a baseline of performance). On a program running 10 hours overnight, the room temperature dropped from 20.1 on Sunday night to 19.0 degrees on Tuesday morning. Weather relatively mild just now also.
I had the company out last week to check system, and they could find no fault e.g. gas pressure ok etc. I was on to the installer again today, who is going to get them out again to try and resolve this. I will add some updates to this thread on progress.
I had some reservations about the suitability of our site. It is large enough, but we have a lot of limestone 3-4 ft down. I raised this with installer, and suggested vertical bore-holes. He assured me that ground was ok, and horizontal is preferrable to vertical if conditions permit.
At this stage our system is starting to look like an expensice failure.:mad:

Some feedback please
What flow temperatures should a direct expansion system produce, or what should be the differential between flow and return temperatures?
Any other experiences or advice?
Thanks for staying with me if you got this far:)

Sorry to hear this. I can offer a solution of sorts, it will increase your temperatures and cost less in the long run. You need to insulate your external walls with 62.5 mm Kingspan polyurethane 8 x 4 insulation board. The 12.5 plasterboard for skimming is an integral part of that board, so it is not as bad as it sounds. If not willing to lose the 62.5mm from the room dimensions, go for a 37.5 mm board, it will still make a huge difference. You will get payback within a couple of years and it will increase the comfort levels no end. You must have at least 14 inches of insulation in the attic. Make sure you have heavy curtains with thermal lining and close these every evening before darkness sets in. By selective dispersal of heat to prime area(s) and a combination of all of above you will compensate adequately for a lot of the deficiencies you may have in the system selection and installation. At least it will not be eating away at you all the time- the situation is salvagable.

Ronan 123

Mod edit.

Ronan, please open a new thread, this is eight years old