UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

John_Pierpoint

grahamc2003 wrote: »

MTBF - these days, does it matter? They are hardly worth repairing imv - any repair would cost at least 1/3rd of a new machine where I usually try to get a new 5 year guarantee. I'm afraid we're forced into a very wasteful world - although I still have my previous one which only needs new rollers for the drum, which I intend to fit one day.

It is a bit like the argument on when to replace a gas boiler with a condensing one, thus getting a heat exchanger that lasts 10 years if you are lucky.
The replacement market for gas boilers is nearly 1,000,000 a year but will you save enough gas to make it worthwhile?
What is the extra value of the saved carbon - beyond price if you live in Hull or Canvey Island or North Blyth?
What is the embedded carbon and additional costs of recycling an increasingly complex box of processed raw materials.
It kind of reminds me of the joys of "mini" ownership in the 1960s, I could change the exhaust system without even jacking the car off the ground - mind you the nuts were not rusted on, because I had done it before only 24 months earlier :eek:

I just hate the impotence of being unable or forbidden to fix something, where a trivial component has failed.
Built in obsolescence should be a capital offence. [that has killed off the female fashion industry:rotfl:]

So has anyone got mean time to failure figures for air source heat pumps?

nande2000

nande2000 wrote: »

Anyone had any problems with ASHPs causing "islanding" problems with PV inverters ?
My PV inverter shut down this morning at the same time that my DHW cycle started on my Ecodan. I spoke to the the inverter company and they said it is possible that the compressor turning on caused a spike that the inverter thought was an issue with the grid and so it turned itself off and back on. Is there a way of smoothing the startup of the heatpump ?

I have an update on my 'Islanding' problem. Seems the Immersun unit I have fitted is the cause. 4ECO are currently trialing prototype units with a fix. It seems to be common to users who are in rural environments with long cable runs to the nearest transformer.

John_Pierpoint

I'm not even sure what you mean by "islanding" or rather why the PV inverter stopping generation momentarily is called "islanding".

Can you explain more clearly what is supposedly happening?

An "immersun" is a gizmo that not only turns the immersion heater on and off, but some how modulates the current (volts and amps) into the immersion to prevent mains juice needing to being "sucked" in to make up any deficit?

[This isn't just idle curiosity as I might fill your definition of "[I]user in rural environment with long cable runs to the nearest transformer[/I]".]

nande2000

John_Pierpoint wrote: »

I'm not even sure what you mean by "islanding" or rather why the PV inverter stopping generation momentarily is called "islanding".

Can you explain more clearly what is supposedly happening?

An "immersun" is a gizmo that not only turns the immersion heater on and off, but some how modulates the current (volts and amps) into the immersion to prevent mains juice needing to being "sucked" in to make up any deficit?

[This isn't just idle curiosity as I might fill your definition of "[I]user in rural environment with long cable runs to the nearest transformer[/I]".]

Islanding protection has to be in all inverters so that if the grid is off then the inverter (the island) doesnt continue to put electric into the grid and potentially electrocute someone working to fix the grid. Also if the grid voltage is too high the inverter shuts itself off to protect itself.

I dont know exactly why the Immersun is causing a false positive for 'Islanding' but I suspect that on sunny days with large fluctuating peaks in PV the immersun is causing spikes in grid voltage usage which momentarily effects voltage at the end of the line which the inverter interprets as a grid fault.

As luck would have it 4ECO have just confirmed they are sending me a new Immersun with new firmware to address the problem.

John_Pierpoint

Good luck,

The trace of my generation suggests that I sometimes get a shut off for no apparent reason (it only samples every 5 - 10 minutes so the length of the shut down is not obvious and I have never "caught" my "Aurora" inverter in the act).

According to the inverter I do suffer regular high voltage often 250+.

"My" transformer, only about 150 meters away, feeds me and one other "workshop" by two overhead wires (TT system) . The transformer is fed in turn by a fat underground cable and appears to break that down into 3 one phase feeds - one to me overland and the other two used to light a dual carriageway road . This means that I have little local opportunity to share spare electricity with any other consumers.

I also know from experience that I am the last customer fed from the West, as the nearest house some 200 meters to my east; suffers a completely different set of power cuts (or more accurately almost never has a power cut as the first major building in that direction is a regional hospital complete with A&E department.)

nande2000 wrote: »

I dont know exactly why the Immersun is causing a false positive for 'Islanding' but I suspect that on sunny days with large fluctuating peaks in PV the immersun is causing spikes in grid voltage usage which momentarily effects voltage at the end of the line which the inverter interprets as a grid fault.

Just my 35 year old chest freezer can flicker my lights, or rather could when they were tungsten. It has some sort of "soft" start as it does not come in with a complete "bang",
however a modern heat pump is a seriously powerful compressor and even with soft start and even an inverter motor must give the mains a shock when it turns on.
Persuading the local electricity supplier that the pump is not going to cycle frequently and that it won't upset the neighbours, can be a stumbling block for those wanting to install heat pump technology - there is something to be said for having "prime mover advantage".;)

[My neighbour the "workshop" installed a compressor (spray painting blowing up tyres.......) without checking the quality of the earth return on the overhead supply - it drove me nuts working out why my earth circuit leakage breaker would trigger apparently at random - until I noticed a never on a Sunday and 08:15 on other days pattern, which tied in with the combine harvester scraping the earth connection off a pole in the field.]

What make and model is the Heat Pump?

richardc1983

On start up the compressor pulls about 3amp it really is soft start no shock to the mains at all. Max it pulls when ramped up slowly is about 11amp so well within limits. So despite being powerful they start up slowly and current draw is minimum. In the old days before inverter technology that shock and large voltage draw was to get the compressor started in motion.

John_Pierpoint

Has nande2000 got the same kit as you ?

richardc1983

John_Pierpoint wrote: »

Has nande2000 got the same kit as you ?

I was refering to inverter compressor in the heat pump I think nande2000 was reffering to an electrical power supply inverter that puts electricity back into the mains grid network.

nande2000

richardc1983 wrote: »

I was refering to inverter compressor in the heat pump I think nande2000 was reffering to an electrical power supply inverter that puts electricity back into the mains grid network.

That's correct. Its a fault I initially thought was caused by the heat pump, but that has been ruled out.

John_Pierpoint

Yes, but do we really know HOW and Exactly WHY and WHEN the "Immersun" upsets the PV Inverter. At the moment we know WERE and we think we know WHO (Immersun) is responsible.
From many years in systems analysis I know the really nasty ones to solve are where two manufacturers' equipment are both interacting to contribute to the problem, So could the problem be unique to the particular model of inverter?
If I was Immersun's ceo I would make sure this problem was fully explained PDQ. He/she would not want to feature in a thread like this
https://forums.moneysavingexpert.com/discussion/comment/43205962#Comment_43205962
or this:
https://forums.moneysavingexpert.com/discussion/2959648

In both cases the management appeared as candidates for bone head of the year.