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Author Topic: PV system in Tandem with a ASHP system need advice please  (Read 546 times)
mpooley
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« on: April 15, 2018, 12:10:49 PM »

HI all
I am trying to help my Nephew understand a system installed into a house he has just bought.
He has been left with very very little info on how it was installed.
He has a daikin altherma  high temperature heat pump and about 15 solar panels installed by a company that is now folded so can't get any info from them.

My first question is regarding a "Solar Cache" system that is installed I believe this a Diverter which diverts excess power to an immersion heater.
Why would you need that? I would have thought that excess power would naturally flow to the ASHP which heats the water anyway and would be more efficient ?
Or would the ASHP take all the power it needs and only then would the power be diverted to the immersion? .......Have I just answered my own question?  banghead

Thanks

Mike
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RIT
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« Reply #1 on: April 15, 2018, 02:26:55 PM »

The diverter should be monitoring the main's cable at the main meter, if it see the house export electricity to the national grid it will instead 'divert' the energy to the immersion heater.

The aim of the device is to allow a PV owner to gain the most benefit possible from the electricity generated after all other loads (such as the ASHP) in the house have had their demand meet.


The reason why a diverter is normally connected to an immersion heater is due to the fact that the immersion heater is little more than a large resistor and so can feed any level of current. So the diverter can operate even if the amount of energy being export is just a few 100 watts. So just about all the energy from the PV gets used in the home and the ASHP does not need to operate for as long to heat the water.
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M
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« Reply #2 on: April 15, 2018, 05:19:05 PM »

This is a question, not an answer, but thinking back to what the clever people have posted on Navitron in the past, don't ASHP's that heat water lose efficiency as the temperature of the water goes higher. So perhaps the HP takes the water to a certain temp, but the diverter can then store some extra energy by topping it up?

This would seem similar to the idea of dialing the water temp thermostat from a gas boiler down a bit, and the immersion temp up a bit, when using a PV diverter, so the gas does the minimum to ensure there's just enough, or doesn't even cycle on if the tank temp is above minimum, whilst the diverter tries to shove as much PV in as possible (when spare).
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
Tinbum
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« Reply #3 on: April 15, 2018, 06:30:38 PM »

http://www.solarcache.co.uk/index.php/solarcache

Add one or more Switch Modules to switch an air source heat pump, air conditioning unit, or other plant or equipment, either when the solar generation reaches a given value, or during timed periods. (The switch module must be fitted by a competent electrician, and is suitable only for use with a resistive load. Maximum load 10A rms.)
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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
mpooley
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« Reply #4 on: April 16, 2018, 04:21:27 PM »

Thanks for your replies .
I might get on to SolarCache for some manuals etc

thanks again

Mike
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It's not easy having a good time. Even smiling makes my face ache.

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Tinbum
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« Reply #5 on: April 16, 2018, 08:37:01 PM »

Thanks for your replies .
I might get on to SolarCache for some manuals etc

thanks again

Mike

May be difficult because they are in administration. http://www.solarcache.co.uk/
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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
mpooley
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« Reply #6 on: April 16, 2018, 09:17:44 PM »

Oh Dear  banghead
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It's not easy having a good time. Even smiling makes my face ache.

“Science is the belief in the ignorance of experts.” Richard Feynman
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« Reply #7 on: April 17, 2018, 12:36:32 AM »

Good Evening All,

The manuals are still there to download at least?

Regards

Richard
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