My geothermal heating system experience

Wearb

shane0007 wrote: »

This is simply not true. Heat cannot open & close doors after it! By having different zones at differing temperatures is a useful way of saving energy.
For example, bedrooms would be comfortable at a consistent temp of 18c, whilst living areas would be 20c, but bathrooms would be 22c. Why, because of the level of clothing we wear in those rooms, living areas we hopefully wear normally attire, bathrooms we have nothing on & bedrooms we are wrapped up in cosy duvets!
By having the varying temps in each zone, heat loss is based on the outside temp relative to the internal design temp for that zone. We base calculations on -3 outside temp so for a living area that would be a design delta T of 23c but a bathroom would be a delta T of 25c.
With this in mind, each room can be calculated upon its own merits, i.e. u value of walls, floors, ceilings, windows, external doors, etc.
This room having a differing delta T will have a direct impact upon the overall demand of the system & ultimately the running costs of said system.

This is as I thought. Common sense tells me this, but a few times over the years my common sense wasn't up to scratch and needed a good talking to.

cuculainn

I would agree that you will notice a temp difference in teh different zones, but if you have air in a bedroom at 18 degs and air in a bathroom beside it at 22 degs, doors or not there will be movement of the warm air to the colder air. A closed door will slow this down. but added to this a HRV extract in the bathroom and a inlet in the room, well then this will accelerate the movement of heat to the bed room.....

What I dont know is the rate of heat transfer but there has be be some.....meaning that the bathroom zone is heating the bedroom. therefore you will get bathroom calling more for heat than the bedroom...........The rate of heat loss from the building will determine how significant this is


This is how i understand it anyway.......

Wearb

cuculainn wrote: »

I would agree that you will notice a temp difference in teh different zones, but if you have air in a bedroom at 18 degs and air in a bathroom beside it at 22 degs, doors or not there will be movement of the warm air to the colder air. A closed door will slow this down. but added to this a HRV extract in the bathroom and a inlet in the room, well then this will accelerate the movement of heat to the bed room.....

What I dont know is the rate of heat transfer but there has be be some.....meaning that the bathroom zone is heating the bedroom. therefore you will get bathroom calling more for heat than the bedroom...........The rate of heat loss from the building will determine how significant this is


This is how i understand it anyway.......

Yes, but I think we are now starting to talk about "angels on the tip of a pin". Yes a warmer area will always heat an adjacent cold area. In the same way that a warm house will lose heat to colder outside air. But I still think that with the temperature difference between zones being so small that the transfer will be minimal.

cuculainn

agreed.....

Condenser

shane0007 wrote: »

This is simply not true. Heat cannot open & close doors after it! By having different zones at differing temperatures is a useful way of saving energy.
For example, bedrooms would be comfortable at a consistent temp of 18c, whilst living areas would be 20c, but bathrooms would be 22c. Why, because of the level of clothing we wear in those rooms, living areas we hopefully wear normally attire, bathrooms we have nothing on & bedrooms we are wrapped up in cosy duvets!
By having the varying temps in each zone, heat loss is based on the outside temp relative to the internal design temp for that zone. We base calculations on -3 outside temp so for a living area that would be a design delta T of 23c but a bathroom would be a delta T of 25c.
With this in mind, each room can be calculated upon its own merits, i.e. u value of walls, floors, ceilings, windows, external doors, etc.
This room having a differing delta T will have a direct impact upon the overall demand of the system & ultimately the running costs of said system.

And what exactly is the u-value of a panel door and the 5-10mm gap underneath it?
Is the door opened at all? Maybe the HRV unit will confine the heat you produce in the living room by sending it back to the living room only?
Bathrooms attached directly to bedroom maintaining a different temp for no extra cost?
Please have a rethink about the situation you suggest as it goes against the laws of thermodynamics. Theres a reason a house is insulated at the extremities.

shane0007

Condenser wrote: »

And what exactly is the u-value of a panel door and the 5-10mm gap underneath it?
Is the door opened at all? Maybe the HRV unit will confine the heat you produce in the living room by sending it back to the living room only?
Bathrooms attached directly to bedroom maintaining a different temp for no extra cost?
Please have a rethink about the situation you suggest as it goes against the laws of thermodynamics. Theres a reason a house is insulated at the extremities.

U value of air is 0.025. U value of a timber door will depend upon what material it is made of and then the exact U value can be determined based on its thickness. You could then do a calculation on the size of the wall even down to the 3mm skim coat of plaster U value, work out the size of the door, calculate the delta T between the 22c desired temp of the bathroom & the 18c of the bedroom.
You could further calculate a different U value based upon the door being left open or being left closed.
But then again, that would be just silly now that you have asked me to think about it, which I have and based upon that pondering thought, I deduced that you are still wrong. Furthermore, it still take energy to heat a bedroom from 18c to 22c just because it has an en suite!

Tommyboy08

shane0007 wrote: »

U value of air is 0.025. U value of a timber door will depend upon what material it is made of and then the exact U value can be determined based on its thickness. You could then do a calculation on the size of the wall even down to the 3mm skim coat of plaster U value, work out the size of the door, calculate the delta T between the 22c desired temp of the bathroom & the 18c of the bedroom.
You could further calculate a different U value based upon the door being left open or being left closed.
But then again, that would be just silly now that you have asked me to think about it, which I have and based upon that pondering thought, I deduced that you are still wrong. Furthermore, it still take energy to heat a bedroom from 18c to 22c just because it has an en suite!

Lads, lads, lads has anyone looked at the figures, you can't compare running costs of different systems by saying well my brother used this much oil, etc etc
The bottom line is jp used 3400 units of electricity (I'm not even gonna take the circ pump out of the equation) giving him 20400kwhrs of heating to his house,
To deliver the same amount of heat to his house to heat it to the level he likes it would cost €2422 in LPG and €2040 in fuel oil

TPM

Tommyboy08 wrote: »

Lads, lads, lads has anyone looked at the figures, you can't compare running costs of different systems by saying well my brother used this much oil, etc etc
The bottom line is jp used 3400 units of electricity (I'm not even gonna take the circ pump out of the equation) giving him 20400kwhrs of heating to his house,
To deliver the same amount of heat to his house to heat it to the level he likes it would cost €2422 in LPG and €2040 in fuel oil

Just out of interest what figures are you using to work that out, IMO they seem a bit off?
would 3400 units not realistic give around 15300 kwhrs of heat, costing more like €1530 in oil?

Tommyboy08

TPM wrote: »

Just out of interest what figures are you using to work that out, IMO they seem a bit off?
would 3400 units not realistic give around 15300 kwhrs of heat, costing more like €1530 in oil?

It would with a standard heat pump, but jp did say that the heat pump he fitted was a heliotherm which has a much higher cop of 5.8 at a flow temp of 35 so it's more than likely even higher than a cop of 6 which is what I based my figures on, the fuel oil ang LPG figures were taken from the seai website and I gave the gas boiler an 86% efficiency and 95 for the oil

shane0007

Tommyboy08 wrote: »

It would with a standard heat pump, but jp did say that the heat pump he fitted was a heliotherm which has a much higher cop of 5.8 at a flow temp of 35 so it's more than likely even higher than a cop of 6 which is what I based my figures on, the fuel oil ang LPG figures were taken from the seai website and I gave the gas boiler an 86% efficiency and 95 for the oil

SEAI's figures on LPG are way off the scale. A client of mine just signed a contract with Calor for 63 cent per litre. Nearly all Band A gas boilers are SEDBUK/HARP 90.2%.
The flow temperature you have used is extremely low for UFH. More like 45c.
What water temperature are you achieving for DHW in your calculations?
To bring the water DHW temperature to 55c, I presume it is done by means of a 3kw immersion. Is this cost in your heating calculations or is it thrown into the lighting/socket side of the electricity consumption calculations?

Tommyboy08

shane0007 wrote: »

SEAI's figures on LPG are way off the scale. A client of mine just signed a contract with Calor for 63 cent per litre. Nearly all Band A gas boilers are SEDBUK/HARP 90.2%.
The flow temperature you have used is extremely low for UFH. More like 45c.
What water temperature are you achieving for DHW in your calculations?
To bring the water DHW temperature to 55c, I presume it is done by means of a 3kw immersion. Is this cost in your heating calculations or is it thrown into the lighting/socket side of the electricity consumption calculations?

Flow temps in a proper underfloor system shouldn't need to be above 32 degrees unless its below zero outside or your underfloor was fitted by muppets using typical layouts and 150mm or greater spacing and this old craic of one loop per room no matter how big or small it is, also with good weather compensated controls you can limit your flow temps on quite a lot of days throughout the heating season saving you a good of money in the process and improving overall system efficiency,

Tommyboy08

Tommyboy08 wrote: »

Flow temps in a proper underfloor system shouldn't need to be above 32 degrees unless its below zero outside or your underfloor was fitted by muppets using typical layouts and 150mm or greater spacing and this old craic of one loop per room no matter how big or small it is, also with good weather compensated controls you can limit your flow temps on quite a lot of days throughout the heating season saving you a good oefficient boiler @ 63 cent per liter that's still €2010 for the gas against €580 at 17 cents per unit of electricity as he is not on a nightrate meter and paying the daytime premium, still a huge difference almost €1500 per year, and if you use a fresh water system to heat dhw you only ever need to heat your tank to about 45 and never need immersion not even for legionella, it's a much better system

Wearb

Originally Posted by Tommyboy08 View Post
Lads, lads, lads has anyone looked at the figures, you can't compare running costs of different systems by saying well my brother used this much oil, etc etc
The bottom line is jp used 3400 units of electricity (I'm not even gonna take the circ pump out of the equation) giving him 20400kwhrs of heating to his house,
To deliver the same amount of heat to his house to heat it to the level he likes it would cost €2422 in LPG and €2040 in fuel oil

---

A point is being left of these equations; 21 degrees all over 24/7 might be practical on the geothermal system, in fact might be necessary giving its response time. On a gas or oil system, the amount of time that it would be heating would be perhaps about a third of that (depending on circumstances). I do understand that the same level of comfort would not be achieved, but those 24/7 temperatures are not necessary for nice comfort. I offer this contribution only to help thread followers, who may be trying to decide on what system to use and comparing one system with the other in this way is a little like comparing apples and oranges.

Condenser

Wearb wrote: »

Originally Posted by Tommyboy08 View Post
Lads, lads, lads has anyone looked at the figures, you can't compare running costs of different systems by saying well my brother used this much oil, etc etc
The bottom line is jp used 3400 units of electricity (I'm not even gonna take the circ pump out of the equation) giving him 20400kwhrs of heating to his house,
To deliver the same amount of heat to his house to heat it to the level he likes it would cost €2422 in LPG and €2040 in fuel oil

---

A point is being left of these equations; 21 degrees all over 24/7 might be practical on the geothermal system, in fact might be necessary giving its response time. On a gas or oil system, the amount of time that it would be heating would be perhaps about a third of that (depending on circumstances). I do understand that the same level of comfort would not be achieved, but those 24/7 temperatures are not necessary for nice comfort. I offer this contribution only to help thread followers, who may be trying to decide on what system to use and comparing one system with the other in this way is a little like comparing apples and oranges.

It wouldn't be 24/7. A well designed geothermal system would drop temp by 3C at night so it would be comfortable to sleep. I don't understand the thinking behind dropping bedroom temp below living temp all the time. Personally when I leave my shower and head into the bedroom I want the room to be warm. Set backs should only be employed in sleep times or inoccupancy. The real comfort of properly installed heat pumps is that you never worry about minding it in fear of running up a bill, you'll never need to worry about topping up, you'll never have your fuel stolen and you're future proofed as no matter what happens to fuels on the world market you can always create a good portion of your electricty from wind or PV.

TPM

It is going to be almost impossible to get a direct comparison unless someone decided to install an oil/or gas boiler to heat their efficent house which is currently been heated by a heat pump, even then the comparison isnt realy much use because even though the insulation levels would be constant, heating systems should be designed, installed and "tweeked" according to the specified heat source.

IMO there is no question about the fact that a properly installed heatpump and heating system will heat a house very cheaply.
The question is the feasibility of installing one based on the install costs and payback time of each system.
If the yearly saving equates to a 20 year payback time is it going to make sense

Wearb

Condenser wrote: »

It wouldn't be 24/7. A well designed geothermal system would drop temp by 3C at night so it would be comfortable to sleep. I don't understand the thinking behind dropping bedroom temp below living temp all the time. Personally when I leave my shower and head into the bedroom I want the room to be warm. Set backs should only be employed in sleep times or inoccupancy. The real comfort of properly installed heat pumps is that you never worry about minding it in fear of running up a bill, you'll never need to worry about topping up, you'll never have your fuel stolen and you're future proofed as no matter what happens to fuels on the world market you can always create a good portion of your electricty from wind or PV.

So were you comparing JPL's system or not; "Since then the house has been at a constant 21 degrees, day and night. "

---

"The bottom line is jp used 3400 units of electricity" Last one is your quote.

I am not trying to score points here, but keep the goalposts in the same place so as not to confuse everybody.

Wearb

TPM wrote: »

It is going to be almost impossible to get a direct comparison unless someone decided to install an oil/or gas boiler to heat their efficent house which is currently been heated by a heat pump, even then the comparison isnt realy much use because even though the insulation levels would be constant, heating systems should be designed, installed and "tweeked" according to the specified heat source.

IMO there is no question about the fact that a properly installed heatpump and heating system will heat a house very cheaply.
The question is the feasibility of installing one based on the install costs and payback time of each system.
If the yearly saving equates to a 20 year payback time is it going to make sense

Yes that is what is trying to be teased out here. I think that with all the contributions, I for one have a better understanding of it now.

Condenser

TPM wrote: »

It is going to be almost impossible to get a direct comparison unless someone decided to install an oil/or gas boiler to heat their efficent house which is currently been heated by a heat pump, even then the comparison isnt realy much use because even though the insulation levels would be constant, heating systems should be designed, installed and "tweeked" according to the specified heat source.

IMO there is no question about the fact that a properly installed heatpump and heating system will heat a house very cheaply.
The question is the feasibility of installing one based on the install costs and payback time of each system.
If the yearly saving equates to a 20 year payback time is it going to make sense

A retrofit will illustrate the point quite nicely. We've installed a number of retrofits down through the years and with people burning €2500-3000 per year on oil and ufh we managed to bring them down to about €700-850. Rads would be different but if low temp forced air rads were fitted the results would be similar. The payback is nowhere near 20yrs, more like 6 and 8 at the outside.

Tommyboy08

Wearb wrote: »

Originally Posted by Tommyboy08 View Post
Lads, lads, lads has anyone looked at the figures, you can't compare running costs of different systems by saying well my brother used this much oil, etc etc
The bottom line is jp used 3400 units of electricity (I'm not even gonna take the circ pump out of the equation) giving him 20400kwhrs of heating to his house,
To deliver the same amount of heat to his house to heat it to the level he likes it would cost €2422 in LPG and €2040 in fuel oil

---

A point is being left of these equations; 21 degrees all over 24/7 might be practical on the geothermal system, in fact might be necessary giving its response time. On a gas or oil system, the amount of time that it would be heating would be perhaps about a third of that (depending on circumstances). I do understand that the same level of comfort would not be achieved, but those 24/7 temperatures are not necessary for nice comfort. I offer this contribution only to help thread followers, who may be trying to decide on what system to use and comparing one system with the other in this way is a little like comparing apples and oranges.

Well the heat losses on the house are the same no matter what system you use, you can turn down the temp on a heat pump too you know, if that's the temp he wants and I don't blame him, who wants to be getting out of the shower and have to do a dance around the bedroom to keep warm till you get your clothes warm, is that not the point of building houses the way we do nowadays, I remember what it was like growing up seeing the fog coming off your breath in the morning in the bedroom, I'm glad we don't live like that anymore!
Or maybe some of us do?
My point with those calculations was to create that same amount of heat energy would cost that amount with a gas boiler and thems the facts
I was trying to offer those who are deciding on a system the same help, to get themselves out of the dark ages and future proof themselves from the inevitable oil and gas price hikes( and don't start another one of those electricity will rise too debates as we all know it will but very little in comparison) and be able to live in an extremely comfortable house and not have it cost them an arm and a leg every year to run

Tommyboy08

TPM wrote: »

It is going to be almost impossible to get a direct comparison unless someone decided to install an oil/or gas boiler to heat their efficent house which is currently been heated by a heat pump, even then the comparison isnt realy much use because even though the insulation levels would be constant, heating systems should be designed, installed and "tweeked" according to the specified heat source.

IMO there is no question about the fact that a properly installed heatpump and heating system will heat a house very cheaply.
The question is the feasibility of installing one based on the install costs and payback time of each system.
If the yearly saving equates to a 20 year payback time is it going to make sense

I thought I gave you a comparison for the same house already

shane0007

Tommyboy08 wrote: »

Tommyboy08 wrote: »

Flow temps in a proper underfloor system shouldn't need to be above 32 degrees unless its below zero outside or your underfloor was fitted by muppets using typical layouts and 150mm or greater spacing and this old craic of one loop per room no matter how big or small it is, also with good weather compensated controls you can limit your flow temps on quite a lot of days throughout the heating season saving you a good oefficient boiler @ 63 cent per liter that's still €2010 for the gas against €580 at 17 cents per unit of electricity as he is not on a nightrate meter and paying the daytime premium, still a huge difference almost €1500 per year, and if you use a fresh water system to heat dhw you only ever need to heat your tank to about 45 and never need immersion not even for legionella, it's a much better system

Perhaps you could post your information that legionella does not survive at 45c. It can survive upto 55c, not many albeit, but some can. This is the reason regs state 60C to 100% eliminate them. Legionella is similar to asbestos. It only takes one to kill.

With regard to 32c flow rate, could you also post your proof of this as all manufacturers/designers I have come across specify 45C. 32C taking into account system losses will be a lot lower than 32c. Return temps will then be as low as 21c, I would really like to see performance sheets/calculations based upon your set up.

oikster

I think the use of a fresh water system makes a difference here Shane with regards to legionella.

Condenser

shane0007 wrote: »

Tommyboy08 wrote: »

Perhaps you could post your information that legionella does not survive at 45c. It can survive upto 55c, not many albeit, but some can. This is the reason regs state 60C to 100% eliminate them. Legionella is similar to asbestos. It only takes one to kill.

With regard to 32c flow rate, could you also post your proof of this as all manufacturers/designers I have come across specify 45C. 32C taking into account system losses will be a lot lower than 32c. Return temps will then be as low as 21c, I would really like to see performance sheets/calculations based upon your set up.

45C flow rates are antiquated and the domain of oil boilers and gas boilers. A properly designed ufh system will rarely top 30C due to higher densities of pipe work and shorter loop lengths. Not one of the 280 heat pumps I have installed would require a flow temp of more than 35. And return temps would not drop as much as you state as the system should be designed with a 5k differential across the loop.

He never stated that legionella does not survive at 45C he merely stated that with a fresh water system he need not exceed it.
Fresh water systems do not need to exceed 45C as the stored heated water never leaves the tank, its merely used to heat fresh cold water instantaneously. The OP discussed all of this and how it works earlier in the thread.

shane0007

When you say a fresh water system, what do you mean exactly by this? A standard domestic hot water cylinder fed by a cwst is a fresh water system. All stored hot water must be brought to 60C at least once a week otherwise legionella can be present. 35C is the ideal temperature for them to multiply, so cylinder stored at 45C will most likely be in the 35c range extremely often as once any hot water is used, it replaced by colder water, thus cooling the system.

Tommyboy08

shane0007 wrote: »

When you say a fresh water system, what do you mean exactly by this? A standard domestic hot water cylinder fed by a cwst is a fresh water system. All stored hot water must be brought to 60C at least once a week otherwise legionella can be present. 35C is the ideal temperature for them to multiply, so cylinder stored at 45C will most likely be in the 35c range extremely often as once any hot water is used, it replaced by colder water, thus cooling the system.

The water in the holding tank is heated to 45 degrees, this tank has a stainless steel heat exchanger on the side of it with flow switch and small circulator, when the fresh cold water starts to flow after a hot tap is opened the flow switch turns on the circulating pump and this drives hot water through the heat exchanger to heat the water going to the tap, it is pretty instantaneous and will bring the hot water to one degree of the water in the tank, 44 degree should be well hot enough for any body to wash in.
So no need for costly immersion heaters

jlptheman

Condenser wrote: »

shane0007 wrote: »

45C flow rates are antiquated and the domain of oil boilers and gas boilers. A properly designed ufh system will rarely top 30C due to higher densities of pipe work and shorter loop lengths. Not one of the 280 heat pumps I have installed would require a flow temp of more than 35. And return temps would not drop as much as you state as the system should be designed with a 5k differential across the loop.

He never stated that legionella does not survive at 45C he merely stated that with a fresh water system he need not exceed it.
Fresh water systems do not need to exceed 45C as the stored heated water never leaves the tank, its merely used to heat fresh cold water instantaneously. The OP discussed all of this and how it works earlier in the thread.

The inlet manifold for my UFH demands heat when the temp falls below 20degrees and stops demanding heat when it gets up to 24 or 25 degrees. My installer said that his aim was a temperature drop of 1 degree for each loop. This is why loop length and screed depth had to be precise AFAIK.

My DHW tank demands heat when it drops below 35 or 36 degrees and stops demanding heat when it reaches 44 degrees.

Until now, I have not died of Legionnaires' disease:D

shane0007

jlptheman wrote: »

Condenser wrote: »

The inlet manifold for my UFH demands heat when the temp falls below 20degrees and stops demanding heat when it gets up to 24 or 25 degrees. My installer said that his aim was a temperature drop of 1 degree for each loop. This is why loop length and screed depth had to be precise AFAIK.

My DHW tank demands heat when it drops below 35 or 36 degrees and stops demanding heat when it reaches 44 degrees.

Until now, I have not died of Legionnaires' disease:D

Lets hope they are not famous last words!

jlptheman

shane0007 wrote: »

jlptheman wrote: »

Lets hope they are not famous last words!

True!

Na, from what I've read it seems to be a pretty safe and well proven system. If I'm out of the house for more than a few days or a week, we let the taps run for a few mins when we get back. I know Legionnaires can be airborne but I just think it might help.

shane0007

jlptheman wrote: »

The inlet manifold for my UFH demands heat when the temp falls below 20degrees and stops demanding heat when it gets up to 24 or 25 degrees. My installer said that his aim was a temperature drop of 1 degree for each loop. This is why loop length and screed depth had to be precise AFAIK.

Just read this properly. A 1C drop. What a load of nonsense! The flow rates will have to be set to absolute max. Ideal UFH delta T is 11C not 1C.

corkgsxr

Showers are also the worst thing for transmission of legionnaires.