Heat pump. Yes or no?

[manievanwyk]

Hi.

I'm looking at a good solution for water heating. I have a PV system, 8kw inverter, 12 panels and 3x 3,5kw batteries. 

I have a 200l geyser in place but removed the the 4kw element, installed a 2kw xtend element and a geyserwise. I'm running the geyser of the solar during the day but the 2kw element is really struggling to heat up the 200l water. Seems to only heat up the top layer but that quickly runs out.

Been looking at solar geysers and heat pumps. 

After properly diving into this rabbit hole I decided that the best option for me is to go for the 4.5 ITS super heat pump. Problem with PV is that even though you get free water during the day, if I need hot water in the morning I need to fall back to the element (back to the 2kw that takes too long). With the light load from the heat pump I will be running that from my PV during the day in anyway so still free hot water (unless it's a real crappy day but that will influence a solar geyser as well).  Also want to use my PV system and not have it idling after 11am when my batteries are full.

Any advice or input from the forum?

[Bobster.]

This depends on other stuff.

I usually have 60+ % of my 200aH battery left at 6 in the morning, and I run the heatpump then. The timer (pump's own) is set from 6 to 7, but it seldom uses the whole hour to get the water up to 55 degrees.

I would usually have 55 to 60% of the battery left in the battery when the heat pump is finished.

So if you have enough "in the bank" come early morning, you can try to warm the water then. Keep an eye on it and see how much battery you have when the heating cycle starts & finishes.

When I'm going into the office, I move everything forward an hour, so the pump starts at 5 am. This doesn't make a big difference in terms of nett battery use.

But this is for me, in my house, with my situation. I'm saying give it a try, but watch your system carefully to see if you're ending up or not with a remaining SOC that you're comfortable with.

[feoZA]

On 2022/12/02 at 1:53 PM, manievanwyk said:

Hi.

I'm looking at a good solution for water heating. I have a PV system, 8kw inverter, 12 panels and 3x 3,5kw batteries. 

I have a 200l geyser in place but removed the the 4kw element, installed a 2kw xtend element and a geyserwise. I'm running the geyser of the solar during the day but the 2kw element is really struggling to heat up the 200l water. Seems to only heat up the top layer but that quickly runs out.

Been looking at solar geysers and heat pumps. 

After properly diving into this rabbit hole I decided that the best option for me is to go for the 4.5 ITS super heat pump. Problem with PV is that even though you get free water during the day, if I need hot water in the morning I need to fall back to the element (back to the 2kw that takes too long). With the light load from the heat pump I will be running that from my PV during the day in anyway so still free hot water (unless it's a real crappy day but that will influence a solar geyser as well).  Also want to use my PV system and not have it idling after 11am when my batteries are full.

Any advice or input from the forum?

I just got the 4.5kW ITS Super installed a few days ago and it's pretty amazing.

You can leave the timer completely off on the heatpump and when it does eventually kick in, it won't really run for very long. And also, it will only draw 1-1.2kW or thereabouts.

So during the day, the PV will power the heatpump and then at night, it'll draw what it needs from the battery.

Eventually what I ended up doing is to set Timer 1 so that the heatpump doesn't run between 9pm and 3am i.e. when we don't need hot water. You can adjust according to your schedule.

Basically, as you said, free hot water during the day and then maybe one heating cycle at night that pulls from battery. (or worst case from grid if the battery is really low)

[dylan88]

I also faced the same struggle with heating water effectively. And after doing some research, I decided to go for a heat pump which has made a noticeable difference. Luckily, I found a reliable installer here in Edmond with a range of available options that suit my needs.

[Modina]

On 2022/12/02 at 2:30 PM, Bobster. said:

So if you have enough "in the bank" come early morning, you can try to warm the water then. Keep an eye on it and see how much battery you have when the heating cycle starts & finishes.

If you feel like a hot cup of coffee and use battery power to boil the kettle...  OK, fine.
But using battery power to heat en-mass (geyser water), with or without a heat-pump......  I am just speechless.
 

[Bobster.]

2 hours ago, Modina said:

If you feel like a hot cup of coffee and use battery power to boil the kettle...  OK, fine.
But using battery power to heat en-mass (geyser water), with or without a heat-pump......  I am just speechless.
 

I did say that if you had enough in hand THEN you can consider it. 

Here's my system this morning

You can see the heatpump kick in at 6:00. SOC then is 65%. Heatpump turns off just before 7:00 (when the timer would have turned it off anyway). SOC is 51%. The spike at 6:45 is the kettle. 

10kWh battery.

Temperature is set to 55 degrees.

But as I said, I got myself into this happy position by running the pump early in the morning and observing what happens. This may not work for everybody, but it's worth having a go.

Edited May 5, 2023 by Bobster.
"had" as in "had enough"

[Bobster.]

And when the day of the Zombies comes, or someother dread event, I won't have to worry about early morning showers, so I'll just kill that one program on the timer.

[Scorp007]

On 2023/05/05 at 11:06 AM, Modina said:

If you feel like a hot cup of coffee and use battery power to boil the kettle...  OK, fine.
But using battery power to heat en-mass (geyser water), with or without a heat-pump......  I am just speechless.
 

You can remain speechless at times. My 24V system CAN drive the heat pump from battery power for a splash and dash if needed but is mostly used with PV then only about 300-500W comes from the battery. 

So glad I installed it when we even got a subsidy from Eskom. It was at the time they gave out LED bulbs to replace filament bulbs. 

[Modina]

No problem doing bulk water heating from solar panels, but silly to burn batteries.  A hot water geyser has enough thermal mass to keep water warm enough for a quick morning shower, except for the Brady bunch, or 8-is-enough families.  

[Douw G. Gerber]

On 2022/12/05 at 4:04 PM, feoZA said:

I just got the 4.5kW ITS Super installed a few days ago and it's pretty amazing.

You can leave the timer completely off on the heatpump and when it does eventually kick in, it won't really run for very long. And also, it will only draw 1-1.2kW or thereabouts.

So during the day, the PV will power the heatpump and then at night, it'll draw what it needs from the battery.

Eventually what I ended up doing is to set Timer 1 so that the heatpump doesn't run between 9pm and 3am i.e. when we don't need hot water. You can adjust according to your schedule.

Basically, as you said, free hot water during the day and then maybe one heating cycle at night that pulls from battery. (or worst case from grid if the battery is really low)

I also have an ITS 5kw heatpump - first thing I installed a few years back to become more energy efficient.

Also have mine programmed to switch on at 5am-8:30am (4 adults who shower at different in the morning (3 ladies :-)), top up 12-1pm and 6-7pm (incase mamma wants to bath - happy wife happy life).  No cold-water problems at all.

[PicHopper]

For those of you who have Heat Pumps + PV and battery installed:

Where are you located to make use of the heat pump? I understand that in cold weather they still work, but not as effectively, and can even be prone to freezing. 
I am watching a house being built in Howick, KZN, where I know from experience it gets really cold in winter. How effective is the heat pump in winter, and what size does one need for a 150L geyser? 
It also appears that we will end up with 2 geysers: One for the kitchen / laundry and another for the two bathrooms. I am guessing that would mean 2 heat pumps as well? 

Your experience and advice is very much appreciated!

[manievanwyk]

I went with the heat pump and extremely happy with it (ITS 4.5hd). Heats the 200l geyser within 2 hours from 25 to 60 degrees and uses less than 2kw for that. The peak (1,25kw) usage I've seen is between 55 and 60. Works like a charm on my PV system. Sure it will take longer in the winter but still way more efficient than a geyser.

[PicHopper]

Hi Manie

Thanks for the feedback - could you perhaps indicate where this is installed? Climate appears to have a bit of an impact. 

Also the makes and model of geysers / Heat pumps? What should I consider? 

[tvic]

Heat pumps and extra water storage is a great combination for use with PV. I have 2 geysers in series - then you are sure that the hot water will last for the whole evening and morning. If I remember correctly the extra geyser in series is equivalent to a sizeable battery....and much much cheaper.

[Scorp007]

I also have a ITS 4.7 heat pump for nearly 10 years. Mine has an inverter start compressor. I am in Gauteng and have never connected the element. Even after this time it still uses less than 50% of the power of an element. Yes in winter during very cold nights it does run a long time and with the increased time it might use as much power as an element. In summer it uses less than 1.5hrs for heating a 150L geyser from about 27 to 55 degrees. 

My normal running times are 1hr early morning and 1hr latish in the afternoon. After running a bath I do over ride my timer to heat to 55 degrees. 

It is the 1st time I hear of freezing. Just ensure lagging is fitted on the outside pipes 

[Douw G. Gerber]

1 hour ago, Scorp007 said:

I also have a ITS 4.7 heat pump for nearly 10 years. Mine has an inverter start compressor. I am in Gauteng and have never connected the element. Even after this time it still uses less than 50% of the power of an element. Yes in winter during very cold nights it does run a long time and with the increased time it might use as much power as an element. In summer it uses less than 1.5hrs for heating a 150L geyser from about 27 to 55 degrees. 

My normal running times are 1hr early morning and 1hr latish in the afternoon. After running a bath I do over ride my timer to heat to 55 degrees. 

It is the 1st time I hear of freezing. Just ensure lagging is fitted on the outside pipes 

Same here - my unit has been running for 4 years no problems.  Run my timer from 5am-9am and 2pm-8pm.

[PicHopper]

Thank you - this is very interesting. I also don't understand how the refrigerant used in the Heat Pump pipes could freeze ? 

Many thanks! 

[Scorp007]

42 minutes ago, PicHopper said:

Thank you - this is very interesting. I also don't understand how the refrigerant used in the Heat Pump pipes could freeze ? 

Many thanks! 

I would think the water will rather freeze preventing operation/circulation. 

[PicHopper]

I see now what the issue with a heat pump freezing is: 

The cold water input to the Heat pump circulates to the heat pump and if the temp falls below zero, the water in the pipes (and the heat pump) might freeze, causing blockages of the system, or damage to the unit. 
Hmmmmmm. 

[iiznh]

On 2023/05/24 at 7:16 AM, PicHopper said:

I also don't understand how the refrigerant used in the Heat Pump pipes could freeze

There is a hot cycle and a cold cycle, the cold cycle goes through a heat exchanger/radiator to collect the energy/heat in the ambient air. The temperature on the cold cycle is generally below freezing point, so if there is enough moisture in the air it will freeze on the radiator causing a clump of ice and preventing the air to pass through. Most heatpumps detect this and go into a defrost cycle by running an electric element or reverse cycle for a couple of minutes till the ice melted. You will see water dripping from the heatpump radiator.

[Scorp007]

1 hour ago, iiznh said:

There is a hot cycle and a cold cycle, the cold cycle goes through a heat exchanger/radiator to collect the energy/heat in the ambient air. The temperature on the cold cycle is generally below freezing point, so if there is enough moisture in the air it will freeze on the radiator causing a clump of ice and preventing the air to pass through. Most heatpumps detect this and go into a defrost cycle by running an electric element or reverse cycle for a couple of minutes till the ice melted. You will see water dripping from the heatpump radiator.

Thanks a lot for explaining how it happens. Great to have this knowledge base right here. 

[PicHopper]

15 hours ago, iiznh said:

There is a hot cycle and a cold cycle, the cold cycle goes through a heat exchanger/radiator to collect the energy/heat in the ambient air. The temperature on the cold cycle is generally below freezing point, so if there is enough moisture in the air it will freeze on the radiator causing a clump of ice and preventing the air to pass through. Most heatpumps detect this and go into a defrost cycle by running an electric element or reverse cycle for a couple of minutes till the ice melted. You will see water dripping from the heatpump radiator.

Thank you for clarifying... 
Are there any specific makes of heat pump that are more effective than others?
What is the appropriate size for:

150litre geyser

100litre geyser

50 litre geyser 

I may need two geysers due to the layout of property. one small one for the kitchen / scullery and a larger one for two bathrooms. 

Thanks for your inputs

[Bobster.]

16 hours ago, iiznh said:

There is a hot cycle and a cold cycle, the cold cycle goes through a heat exchanger/radiator to collect the energy/heat in the ambient air. The temperature on the cold cycle is generally below freezing point, so if there is enough moisture in the air it will freeze on the radiator causing a clump of ice and preventing the air to pass through. Most heatpumps detect this and go into a defrost cycle by running an electric element or reverse cycle for a couple of minutes till the ice melted. You will see water dripping from the heatpump radiator.

This makes sense. Thanks. My heatpump has a defrost setting, but it can't be anything to do with the pipes because how can it "know" what's happening in the pipes, and what can it do about that? What it can know and then do something about is it's own radiator. 

[Scorp007]

4 hours ago, Bobster. said:

This makes sense. Thanks. My heatpump has a defrost setting, but it can't be anything to do with the pipes because how can it "know" what's happening in the pipes, and what can it do about that? What it can know and then do something about is it's own radiator. 

My answer to this will be using the ambient temp. This is the method used if you use the grid element for temps below about 5 degrees if I remember correctly. This function is just a low amp relay to bring in another relay to drive the grid element. 

This method is on the old 4.7 ITS. 

Edited May 29, 2023 by Scorp007

[Scorp007]

1 hour ago, Superfly said:

The plumbing in this diagram does not make sense.. but I assume we are diverting after the pressure control valve to the heat pump and return to the inlet (as hot rather than cold) 

Does the heat pump need an overflow to be teed with the geyser's overflow to the outside?

I'm thinking of installing the heat pump next to the geyser for ease of plumbing. The electrics seem pretty simple  - isolator to heat pump right? 

The heat pump has no overflow. It operates as a semi sealed unit and it cannot have a higher pressure than the geyser. Thus only the geyser has a expansion/overflow as you call it. 

Its normally only on elements where a thermostat gets stuck that the over pressure and expansion will operate. 

Not sure what is wrong with the basic picture. ITS do have their specific loading valve but others have followed with their own valve. 

This is how I see it.