Inverter Temperature Derating

[Gavin A]

The Power One Aurora family of inverters are roughly as follows:

Air temperature / output

35-40'C: no loss of output (cooling fan gradually increases its speed to cool the internals).
40-45'C: 5-10% loss of output
45-50'C: 15-20% loss of output
50-55'C: 30-40% loss of output
>55'C: major power reduction and risk of shutdown due to overheating

It is also recommended to avoid mounting in direct sunlight as the inverter casing will absorb sun/heat and get hotter than if the inverter is in shade or in a loft/garage/utility room etc.

do you know if that's true for both the indoor and outdoor versions?

useful to know that they start derating 10 degrees lower than the TL series sunny boy inverters, and so aren't as good for loft mounting.

 

[rgf1]

Gavin, can you tell me more about the Power One Aurora family of inverters. I am also finding the maximum power is far less than I expected. I now have learned from the forum that this is inevitable in very how ambient temperatures.

I can find nothing on the 3.6 Kw Aurora about cooling fans - I have also found an advert by them saying there is not fan. Who is right?

 

[FB.]

do you know if that's true for both the indoor and outdoor versions?

useful to know that they start derating 10 degrees lower than the TL series sunny boy inverters, and so aren't as good for loft mounting.

Yes, the indoor (fan cooled) and outdoor (heat-sink/fin-cooled) versions may see a reduction in output from 40'C air temperature.

But I suspect that it would be somewhat modified by the amount of DC power being processed at any given time, since that is also heat-generative within the inverter.

Knowing the manufacturers and the need to put a positive sales spin on their products, I would suspect that the >40'C temperature-induced power derating occurs at relatively low power throughput, and probably the inverter could de-rate at 35'C ambient temperature if it was running close to full capacity and therefore generating a lot of heat within itself.

 

[FB.]

Gavin, can you tell me more about the Power One Aurora family of inverters. I am also finding the maximum power is far less than I expected. I now have learned from the forum that this is inevitable in very how ambient temperatures.

I can find nothing on the 3.6 Kw Aurora about cooling fans - I have also found an advert by them saying there is not fan. Who is right?

The PVI-3600 and PVI-2000 indoor models use a cooling fan.

The PVI-3600-OUTD (outdoor) models use cooling fins/heat sinks; more suitable for dusty places like lofts, or, apparently, mounting in shady locations on the exterior of a building, since without a cooling fan they don't get clogged-up with dust (although the cooling fins may need occasional wipe with a duster).

 

[FB.]

do you know if that's true for both the indoor and outdoor versions?

useful to know that they start derating 10 degrees lower than the TL series sunny boy inverters, and so aren't as good for loft mounting.

For info, though, my PVI-3600 indoor model had the following performance efficiency at different ambient temperatures:

Indoor utility room temperature about 15'C (early April, mid-morning at peak generation)
Power in: 3.90kW
Power out: 3.66kW
Efficiency: 93.8%

Indoor utility room temperature about 25'C (in recent days, early afternoon, after peak generation but as temperatures are rising after mid-day)
Power coming into inverter: 2.90kW
Power going out of inverter: 2.71kW
Inverter efficiency: 93.4%

So no noticeable de-rating at 25'C air temperature (in the room where the inverter is located) when running at 80% capacity.

The 0.4% difference is probably merely down to inverters tending to run more efficiently the closer they get to their maximum rating.

 

[rgf1]

Thanks to FB for his quick and cogent reply.

My Aurora 3.6 OUTD is clearly is an outdoor model, installed in a completely dry, fairly dustproof stables - in the tackroom where the saddles, horse tack is installed. There is little evidence of any of the fins being clogged be contaminated by dust. My question is, how do I clean the finned heatsink if it needs it. Can I remove the outer case? or is there a simple method using a nozzle on a vacuum cleaner. (Has anyone fitted the fan off the indoor model and, can it actually be fitted, or has anyone fitted a simple external fan - like a computer fan and does this work enough to compensate its losses?)

The temperature of the heatsink does run about 60 degrees C - this is the temperature displayed on the screen. Is this the temperature used to measure and therefore control the derating or is the derating temperature at the measured at the internals of the unit?. In my manual it says - page 83 - full power is guaranteed up to ambient temperature of 55 degrees C.

Also, another question for the gurus of the forum to get their teeth into. Maybe this is another thread, or there already is a thread on this - please redirect me if so.

Page 81 of my manual - which is PVI-3.0/3.6/4.2-OUTD-UK Rev 1.0 states that the maximum recommended output is 4150 W - the absolute maximum I have ever recorded is a consistent 3984 W - this must be a clipped output as in the winter I get this value every sunny cold day.

Questions:

1. Why can I not get 4150 W
2. Is the inverter clipped to this to meet the UK regs.
3. If so how can the clipping be removed.

Many thanks to all replies

rgf1

 

[FB.]

Curious.

On the copy of the manual I'm looking at, page 83 has no temperature data.

But on page 90, the OUTD manual says:

"....

AURORA ensures top power up to 40°C ambient temperature, as faras it is not directly exposed to the sun......"

But on page 25 it says:

Temperatures exceeding 45°C for the PVI-4.2, 55°C for PVI-3.6
and 55°C per PVI-3.0, may result in power derating.
Output power derating is more likely to occur in case of high output
power and high ambient temperature.

 

[FB.]

Thanks to FB for his quick and cogent reply.

My Aurora 3.6 OUTD is clearly is an outdoor model, installed in a completely dry, fairly dustproof stables - in the tackroom where the saddles, horse tack is installed. There is little evidence of any of the fins being clogged be contaminated by dust. My question is, how do I clean the finned heatsink if it needs it. Can I remove the outer case? or is there a simple method using a nozzle on a vacuum cleaner. (Has anyone fitted the fan off the indoor model and, can it actually be fitted, or has anyone fitted a simple external fan - like a computer fan and does this work enough to compensate its losses?)

The temperature of the heatsink does run about 60 degrees C - this is the temperature displayed on the screen. Is this the temperature used to measure and therefore control the derating or is the derating temperature at the measured at the internals of the unit?. In my manual it says - page 83 - full power is guaranteed up to ambient temperature of 55 degrees C.

Also, another question for the gurus of the forum to get their teeth into. Maybe this is another thread, or there already is a thread on this - please redirect me if so.

Page 81 of my manual - which is PVI-3.0/3.6/4.2-OUTD-UK Rev 1.0 states that the maximum recommended output is 4150 W - the absolute maximum I have ever recorded is a consistent 3984 W - this must be a clipped output as in the winter I get this value every sunny cold day.

Questions:

1. Why can I not get 4150 W
2. Is the inverter clipped to this to meet the UK regs.
3. If so how can the clipping be removed.

Many thanks to all replies

rgf1

My 3.6kW Aurora indoor model is reporting internal temperature of 45'C with the air temperature around the inverter at 25'C and with 3kW of power going through it.
It is not de-rating at those temperatures and outputs - proven by the efficiency remaining in the 93-94% range just as it was a couple of months ago with the air around the inverter at about 15'C.

 

[moggy1968]

both the SB series and power one indoor inverter are less efficient than the TL, HF or outdoor versions.
They are older designs of inverter, some might say obsolete

 

[Gary K]

both the SB series and power one indoor inverter are less efficient than the TL, HF or outdoor versions.
They are older designs of inverter, some might say obsolete

I wish I had specced a 4000tl rather than the 3800 I have got, When I checked the info linked above ,I was surprised to see not only is it more efficient in general as to be expected but the 3800 drops off even more approaching max output and is most efficient at 30-50% of max knowing what I know now, and after checking the max outputs on PVoutput,I now believe the inverter could be equally if not more important than the panel choice

 

[moggy1968]

oh yes, to have a good quality system, you need a good quality system, not just decent panels. The components need to be properly matched.

You wouldn't put bicycle tyres on a ferrari!

 

[FB.]

I've had a max/min thermometer in the loft for the last few days, to see what the temperature variation has been.

Days have been sunny - sometimes a little haze or a thin cloud - with outdoor temperatures peaking around 26'C.
The loft has been peaking at 33'C; 7'C above ambient.

It should be borne in mind that about three-quarters of one roof aspect has now been covered by solar panels which will be blocking the sun's heat from that direction (but that would be the case with most solar arrays; it covers part of the roof and keeps the roof cooler).

If the roof hadn't been part-covered by panels then I suspect it would have added about 11'C to the loft temperature, taking it up to about 37'C in recent days (taking into account the additional unshaded roof and its likely ability to absorb the sun's heat).

I remember having to change the ball and float on the water tank in my old house on a hot sunny day about ten years ago and it was probably 40'C in the loft.

 

[babba]

I've had a max/min thermometer in the loft for the last few days, to see what the temperature variation has been.

Days have been sunny - sometimes a little haze or a thin cloud - with outdoor temperatures peaking around 26'C.
The loft has been peaking at 33'C; 7'C above ambient.

It should be borne in mind that about three-quarters of one roof aspect has now been covered by solar panels which will be blocking the sun's heat from that direction (but that would be the case with most solar arrays; it covers part of the roof and keeps the roof cooler).

If the roof hadn't been part-covered by panels then I suspect it would have added about 11'C to the loft temperature, taking it up to about 37'C in recent days (taking into account the additional unshaded roof and its likely ability to absorb the sun's heat).

I remember having to change the ball and float on the water tank in my old house on a hot sunny day about ten years ago and it was probably 40'C in the loft.

So you should not put inverters in lofts ?

 

[Earthstore]

So you should not put inverters in lofts ?

This has been covered before, but just a little refresher; Most installs differ, and it can be a case of saftey over performance, DC cables have no mechanical protection, no trips, nothing. So if you feel it is safe to route DC cables through a house with 600V+ maybe to gain a little performance on a hot day, then that is your decision, As FB stated the temperature in his loft was 33 degrees, so he was way below the 40 advised for the SMA, the biggest loses come from the panel temperature and not the inverter.

 

[FB.]

This has been covered before, but just a little refresher; Most installs differ, and it can be a case of saftey over performance, DC cables have no mechanical protection, no trips, nothing. So if you feel it is safe to route DC cables through a house with 600V+ maybe to gain a little performance on a hot day, then that is your decision, As FB stated the temperature in his loft was 33 degrees, so he was way below the 40 advised for the SMA, the biggest loses come from the panel temperature and not the inverter.

I agree. The panel output is about 20% lower in this weather, so the inverter won't be running as hot, so may cope with a slightly higher temperature than expected.

I have a P1 Aurora indoor model in a downstairs utility, which hasn't exceeded the outdoor 26' temperature in recent days, whereas it would have been 33'C in the loft (perhaps another degree or two warmer in the loft due to the inverter's own heat generation; the inverter adds a few degrees of heat to my cool downstairs utility room), but even if it was in the loft, it should still be within its 40'C de-rating.
Mine runs two strings, running down the outside of the house in a conduit on the wall between mine and the neighbours house, so out of view. Cables come back into the house next to the inverter, into two DC isolators. The DC voltages are about the same as mains voltages (200-300V DC, 7-8A current at full power).

I find the inverter's location convenient for taking a look at what it's doing without needing a desktop monitoring device (costing £100+ and which may only last a few years like most electronics) - the screen on the indoor model is more useful than certain other inverters - pic below:

 

[babba]

DC cable can be protected, I think the inverter will be working its socks of in tempetures stated by FB and is sure to shorten its life

 

[moggy1968]

DC cable can be protected, I think the inverter will be working its socks of in tempetures stated by FB and is sure to shorten its life

All things being equal we will mount the inverter somewhere other than the loft, but sometimes it's inevitable. SMA HF and TL inverters are rated to 60C so typical loft temperatures are well within it's operating range.