11 minutes ago, iiznh said:

I was thinking about adding in a calculation to prove the point... but it is way too early and my coffee hasn't kicked in yet and (my wife also told me that math is not for everyone)

So I just opted to add my voice to the choir and hope for the best. Some people want to discover the principles of physics by experimentation, and some of us google the formulas and calculate the values (so we can sound clever).  

You will never know until you do the math. Currently you are also just guessing. Don't forget most garages are very leaky and many have windows that can be opened. If my massive aircon can hardly keep my living room cool unless in "Turbo" mode, I doubt a geyser HP will be able to freeze my garage over.

1 hour ago, HendrikBigChief said:

You will never know until you do the math.

The heat capacity of water is 4.183 kJ/kg.
Arguments sake lets take a small geyser that holds 150 liters and lets heat it from 30 to 60

So you will need approx 
150 * 4.183 * 30
= 18 MJ   (and divided by 3600 is approx 5Kwh), sounds about right

The heat capacity of air is 1.005 kJ/kg
The mass of air is approximately 1.2 to 1.3 kg/m^3

So lets assume a large double garage with a high ceiling
5m x 5m x 4m = 100 m^3
so at best case about 130kg of air

Lets assume the garage is 30 degrees and we take it down to freezing so 30 degree delta
130 * 1.005 * 30 grees
=6.5MJ (about 2KWh of energy) 

It appears our garage is too small 

Someone please check my numbers (because I asked ChatGPT and it made the same mistake over and over, even pointing out the mistake was not enough,  unless I got it wrong...)

Edited June 29, 20233 yr by iiznh

4 minutes ago, iiznh said:

The heat capacity of water is 4.183 kJ/kg.
Arguments sake lets take a small geyser that holds 150 liters and lets heat it from 30 to 60

So you will need approx 
150 * 4.183 * 30
= 18 MJ   (and divided by 3600 is approx 5Kwh), sounds about right

The heat capacity of air is 1.005 kJ/kg
The mass of air is approximately 1.2 to 1.3 kg/m^3

So lets assume a large double garage with a high ceiling
5m x 5m x 4m = 100 m^3
so at best case about 130kg of air

Lets assume the garage is 30 degrees and we take it down to freezing so 30 degree delta
130 * 1.005 * 30 grees
=6.5MJ (about 2KWh of energy) 

It appears our garage is too small 

Someone please check my numbers

Are you taking into account the garage is north facing and the sun is baking the metal door? The roof of the garage is also absorbing heat and radiating it into the garage.

I will personally not be installing any heat pumps inside an enclosed space as they are designed to be outdoors and our weather here in SA is very good for heat pumps with our relatively mild winters. Most will get a COP of 4 or above with a modern unit if mounted outside.

While we're talking about heat pumps, maybe somebody can explain something that's puzzling me: Why does my heat pump use more power at middday than in the morning.

EG today HP kicked in at 8:00. I was already busy on the computer to work, but no big appliances running. Total load was in the order of 1.6kW.

Then at 12:00 two things happened: Loadshedding and HP started up again. Now the total load is 1.9kw. OK, so maybe there's something else running that I'm not aware of. I turn off the HP, consumption drops to 250W. So this morning with all that was running at the time, total load was 1.6. Now HP is taking 1.65 to 1.7 all by itself.

This seems to not be a fluke. Sometimes it is no so apparent because we haven't had a lot of loadshedding recently, and usually not at midday. But Tuesday something similar happened. Early AM (7:00) total draw was 1.4. Then just before 12:00 the load (with pool pump running) was 970ish W. HP starts up at 12:00 and draw whilst it's running is 2.1kW on startup, then 2.7ish. So again, 1.65 to 1.7 kW just for the HP, whilst total load when it was running earlier in the morning was less than that.

But not every day. Sunday it makes about 1.5kW difference at midday. Friday last week total load for the early run is about 1.5kW, midday HP seems to make about 1.2kW difference.

OK... so the question is why isn't the draw fairly constant? Why do I see these variations? I understand that sometimes it might need to defrost, but that would be a short spike on the graph, not sustained for 45m to an hour.
 

I have never used a heat pump before but the comments in this thread led me to to the following question - if the pump is blowing cold air, can it be used as an air con for a living room in summer? E.g. redirect the cold air to the room via a duct and close the duct in winter. 

1 hour ago, PowerUser said:

I have never used a heat pump before but the comments in this thread led me to to the following question - if the pump is blowing cold air, can it be used as an air con for a living room in summer? E.g. redirect the cold air to the room via a duct and close the duct in winter. 

I would think so. You could make a very efficient system where in summer, when the sun is shining at max in the middle of the day, you redirect the cold air from it to your house to help with cooling if the HP is on a timer. Would also help if the whole system is on solar panels. The cold air could be redirected using one of those ducted fans. Might not look very nice however.

1 hour ago, PowerUser said:

I have never used a heat pump before but the comments in this thread led me to to the following question - if the pump is blowing cold air, can it be used as an air con for a living room in summer? E.g. redirect the cold air to the room via a duct and close the duct in winter. 

Yes you can direct the exit cold air via a duct. One must just ensure you don't impede the air flow via restrictions and reduce the volume pushed out by the fan 

@Bobster.

I think you need to measure the actual power used by the HP as it seems you have smaller like 50W loads which might not be detected if you work from the total load in the inverter. I have never found it on mine but I don't watch it that closely. If the higher draw was in the morning there might be some explanation but only for I guess about 5-10W.

13 minutes ago, HendrikBigChief said:

I would think so. You could make a very efficient system where in summer, when the sun is shining at max in the middle of the day, you redirect the cold air from it to your house to help with cooling if the HP is on a timer. Would also help if the whole system is on solar panels. The cold air could be redirected using one of those ducted fans. Might not look very nice however.

Did some googling and these articles suggest that a Heat Pump is a viable aircon solution:

https://www.ahi-carriersa.co.za/advantages-of-a-heat-pump-air-con/

https://www.daikin-ce.com/en_us/daikin-blog/can-heat-pumps-cool.html

https://www.nrdc.org/bio/alejandra-mejia-cunningham/thinking-buying-air-conditioner-consider-heat-pump

 

@Scorp007 How difficult would it be to use my aircon in summer to heat my swimming pool?

Was thinking that it might also improve my aircon efficiency, especially on those hot days.

35 minutes ago, Sc00bs said:

@Scorp007 How difficult would it be to use my aircon in summer to heat my swimming pool?

Was thinking that it might also improve my aircon efficiency, especially on those hot days.

Just looking at the great calculation of @iiznh I think he will be the best guy to weigh in on this.

For me drivers would be the quick heat loss from aircon due to ambient temp causing the heat to reduce. Air with a 4 times lower SHC might battle to heat the water. Just a big guess. 

Any guys that have tried a oil burning heater to heat the pool. Source of old oil from a car workshop. 

 

2 hours ago, Sc00bs said:

@Scorp007 How difficult would it be to use my aircon in summer to heat my swimming pool?

Was thinking that it might also improve my aircon efficiency, especially on those hot days.

My guess is very very difficult. heating a pool takes a lot of heat, just looking around on the internet, for a 45000 liter pool you will need a 13kW dedicated heat pump, so massive energy needed.

Edited June 30, 20233 yr by HendrikBigChief

8 minutes ago, HendrikBigChief said:

 

My guess is very very difficult. heating a pool takes a lot of heat, just looking around on the internet, for a 45000 liter pool you will need a 13kW dedicated heat pump, so massive energy needed. With a COP of 4, that means the effective heating is like 54kW.

Here are some results using a dedicated heat pump for pool. Results are for a 8 degree increase in 60 hrs initially. 

49 minutes ago, HendrikBigChief said:

My guess is very very difficult. heating a pool takes a lot of heat, just looking around on the internet, for a 45000 liter pool you will need a 13kW dedicated heat pump, so massive energy needed. With a COP of 4, that means the effective heating is like 54kW.

No, the 13kW is the energy output. A heatpump like that will have a compressor of 2kW or less.

21 minutes ago, P1000 said:

No, the 13kW is the energy output. A heatpump like that will have a compressor of 2kW or less.

Good point

2 hours ago, Scorp007 said:

For me drivers would be the quick heat loss from aircon due to ambient temp causing the heat to reduce. Air with a 4 times lower SHC might battle to heat the water. Just a big guess. 

Absolutely right. The reason I made the post as simple as possible so that anyone can plug in the numbers and understand

 

If you have a 45 000 liter pool and you wish to raise it by 1 degree then you will need to dump this much energy into it

45000 * 4.183 * 1 = 188235 kJ = 188MJ (and converter to kWh / 3600) = 52kWh

Pool heatpumps will very likely run at lower pressure and have a much bigger heat exchanger + fan that needs to cycle more air to achieve a higher COP but the temps they will achieve is much lower compared to a heatpump meant for geyser heating. I am sure the enigeers tweak the variables for the desired applications. 

If you take the cold air and feed it to your aircon it will work much better in the summmer but I suspect the amount of savings calculated in rands will not be a lot. You are better off buying another solar panel

 

3 hours ago, Sc00bs said:

How difficult would it be to use my aircon in summer to heat my swimming pool

Plug your numbers in the formula, you need to calculate the area that you are cooling in your house and see how much energy your aircon needs to dump outside.

Then calculate the energy needed for your size pool. I suspect this will be a fraction of a degree unfortunately

 

 

 

 

47 minutes ago, iiznh said:

Absolutely right. The reason I made the post as simple as possible so that anyone can plug in the numbers and understand

 

If you have a 45 000 liter pool and you wish to raise it by 1 degree then you will need to dump this much energy into it

45000 * 4.183 * 1 = 188235 kJ = 188MJ (and converter to kWh / 3600) = 52kWh

Pool heatpumps will very likely run at lower pressure and have a much bigger heat exchanger + fan that needs to cycle more air to achieve a higher COP but the temps they will achieve is much lower compared to a heatpump meant for geyser heating. I am sure the enigeers tweak the variables for the desired applications. 

If you take the cold air and feed it to your aircon it will work much better in the summmer but I suspect the amount of savings calculated in rands will not be a lot. You are better off buying another solar panel

 

Plug your numbers in the formula, you need to calculate the area that you are cooling in your house and see how much energy your aircon needs to dump outside.

Then calculate the energy needed for your size pool. I suspect this will be a fraction of a degree unfortunately

 

 

 

 

Great. I take it the heat loss due to large area is also a killer? 

2 hours ago, iiznh said:

Absolutely right. The reason I made the post as simple as possible so that anyone can plug in the numbers and understand

 

If you have a 45 000 liter pool and you wish to raise it by 1 degree then you will need to dump this much energy into it

45000 * 4.183 * 1 = 188235 kJ = 188MJ (and converter to kWh / 3600) = 52kWh

Pool heatpumps will very likely run at lower pressure and have a much bigger heat exchanger + fan that needs to cycle more air to achieve a higher COP but the temps they will achieve is much lower compared to a heatpump meant for geyser heating. I am sure the enigeers tweak the variables for the desired applications. 

If you take the cold air and feed it to your aircon it will work much better in the summmer but I suspect the amount of savings calculated in rands will not be a lot. You are better off buying another solar panel

 

Plug your numbers in the formula, you need to calculate the area that you are cooling in your house and see how much energy your aircon needs to dump outside.

Then calculate the energy needed for your size pool. I suspect this will be a fraction of a degree unfortunately

 

 

 

 

So even that 13kW heat pump AC direct is recommending for a 45000 liter swimming pool is going to battle uphill to heat the swimming pool.

16 minutes ago, HendrikBigChief said:

So even that 13kW heat pump AC direct is recommending for a 45000 liter swimming pool is going to battle uphill to heat the swimming pool.

Surface area exposed to air will be enemy number one. Running that pump for almost 4 hours to gain one degree Celsius (assuming no losses). You probably need more pumps

 

 

3 hours ago, iiznh said:

Surface area exposed to air will be enemy number one. Running that pump for almost 4 hours to gain one degree Celsius (assuming no losses). You probably need more pumps

 

 

You really need to have a blanket on the pool if you want to heat it.

I have a 13kw heatpump (+-45,000ltr ) that pulls about 2kw AC power.

Takes about 40rs of heating to go from 20C-30c , heating for 10hrs a day on nice warm days.

1 hour ago, Sc00bs said:

You really need to have a blanket on the pool if you want to heat it.

I have a 13kw heatpump (+-45,000ltr ) that pulls about 2kw AC power.

Takes about 40rs of heating to go from 20C-30c , heating for 10hrs a day on nice warm days.

Good to hear you already have a HP for the pool. Not much to gain by using the aircon to help with heating. 

What pool HP have you got as it has a very high COP? Geyser type are normally around 3-4.5.

Hi guys, I have recently installed a Kwikot/ Electrolux 300l integrated heat pump which sits outside our bathroom area . It's heating capacity is 3.6kw but only draws around 900w of power from the solar system. I'm trying to ascertain if it is working as efficiently as advertised. At the current ambient temperatures in Johannesburg it increases the water temperature in the tank by about 4.5° C per hour. I'm told the in summer it would increase the water temperature by around 10° per hour. It seems that the heating capacity is so much lower during winter at around 20° C ambient temperature...can this be correct? I've got the heat pump on a timer from 12 midday to 3 pm, and measured these heating parameters without using any hot water. Any one have a similar set up? 

1 hour ago, Markprop said:

At the current ambient temperatures in Johannesburg it increases the water temperature in the tank by about 4.5° C per hour. I'm told the in summer it would increase the water temperature by around 10° per hour.

The amount of water you are heating makes a big difference, maybe state that first. Edit: Sorry misread 300 liters

My 13 year old ITS heatpump has a heating output of 4.5kW and heats 150liter geyser from 20 degrees to 53 degrees in just under 2 hours. In summer it takes 45 minutes. It is still roughly 2-3 times more power efficient than a heating element even when the ambient temps are around 4 degrees

 

The heat capacity of water is 4.183 kJ/kg.
300 liters and lets heat it 10 degrees

So you will need approx 
300 * 4.183 * 10 
= 12 MJ   (and divided by 3600 to convert joules to kWh is approx 3.5 Kwh)

So I would agree with it taking an hour to heat with an effective 3.6kW output (10 degree delta)

 

Now clearly the states figure is for summer output

 

Edited July 18, 20233 yr by iiznh

Hi all, I just bought a 2nd hand Eze heat pump. Fault reading is PP 01.  I’ve googled and it seems to mean the incoming temperature sensor, it’s also displaying 99 degrees C n incoming temp sensor reading. Would anyone know who stocks spare sensors in Gauteng? 

20 hours ago, KeithC said:

 I’ve googled and it seems to mean the incoming temperature sensor, it’s also displaying 99 degrees C n incoming temp sensor reading.

My ITS heatpump uses a 10K NTC.  Inexpensive component and easy to source. I would assume other heat pumps use them too

On 2024/08/11 at 12:33 PM, KeithC said:

Hi all, I just bought a 2nd hand Eze heat pump. Fault reading is PP 01.  I’ve googled and it seems to mean the incoming temperature sensor, it’s also displaying 99 degrees C n incoming temp sensor reading. Would anyone know who stocks spare sensors in Gauteng? 

This error code is also the same on the ITS 4.7kW.