DIY Temperature Controlled Cooling Solution (For SolarInverter)

[nero44]

Hello everyone,

in these warm sunny days I noticed that my solar inverter reached an internal temperature of 50 degrees celsius. This is when running full whack with about 26 degrees outside temperature. Whilst the inverter is rated at an operating temperature up to 60 degrees, the inverter will start to derate beyond 45, so I am looking to add a simple cooling solution. The inverter has a passive system, i.e. metal cooling fins but no fans. I've read in a another forum that someone managed to successfully implement this, keeping their inverter at 35 degrees even with scorching hot outside temperatures. With the added bonus that it automatically switches on only when needed, i.e. at night it stays nice and quiet.

So my idea is to get a couple of 12v DC fans, mount them to the fins, connect them to a programmable temperature controller (which has a temperature sensor), and this connected to mains via transformer. The temperature would measure the temperature of the fins and switch on once it reaches 45 degrees and then switches off again once the temp drops down to 35. I have a lighting circuit very close to the inverter, which the installer also used to power the heat alarm. So that would be my power source.

Mechanically, I think this is quite easy to wire up and it appears these temperature controllers are also quite easy to use. I plan to use:
Fans
Temperature Controller with sensor
Transformer

Could this work/anything blatantly wrong with the basic setup?
The transformer is actually a LED driver with 30w/2.5a rating, but with 3 watts per fan I should be easily able to operate 3-4 fans?
Same for temperature controller, which can take up to 120w, so running anything lower should be no problem?

 

[ericmark]

I would use a simple desk fan connected to some thing like this the InkBird 308 I have these got before the Inkbird came out, there are others but keep it simple. Not sure why is should be getting that hot now? I made up mine to brew beer, but have used them for all sorts, using a small freezer as a fridge, and turning on room fans in hot weather, what you show will work, but seems a lot of work to go to.

I when fitting solar was told the inverter would go in the loft, with the batteries, I did not like that idea so had the inverter down stairs in the flat, which is just as well as now not permitted to have batteries in the loft, not because of batteries going on fire, but the problem if the house goes on fire the batteries exploding.

 

[Harry Bloomfield]

KISS - Mount a simple thermal preset switch, set for 40C, onto the heatsink, to power one or perhaps two, 240v 5" old server fans. If necessary, the second fan could have it's own switch, set at 45C. Alternatively, connect the fans in series, and they will run super quiet.

One of these - https://www.ebay.co.uk/itm/18467350...fUrb6yDSPNAilrdXPMTUg2Cw==|tkp:BlBMUNqL9vXsYw

 

[nero44]

I when fitting solar was told the inverter would go in the loft, with the batteries, I did not like that idea so had the inverter down stairs in the flat, which is just as well as now not permitted to have batteries in the loft, not because of batteries going on fire, but the problem if the house goes on fire the batteries exploding.

yup, mine is in the loft of the rear extension of my victorian terrace. I had no other options and was struggling to find an installer who would even take a look at it. In the end it all worked out and I am quite happy with everything. Whilst I understand the new recommendation, it will make it so much more difficult for this country to come closer to net zero, especially in urban areas. Same with heat pumps etc.. but that is a topic for a different thread.

I like the idea of keeping things simple and these inkbird controllers look literally plug and play. If I really wanted to be lazy I could just buy these two and be done with hit?
triple fan with transformer and speed settings
inkbird-308s

the fan "set" is already wired together in series and even has different speed settings, so I can adjust to minimum effective speed. I'd just use the fan cable and plug it into the cooling socket of the inkbird. I do not have any sockets in my loft, so I'd need to cut the plug off and connect it manually to the lighting circuit. I would lose the fuse from the inkbird, but the fan plug would still have a fuse.

 

[Harry Bloomfield]

I'd just use the fan cable and plug it into the cooling socket of the inkbird. I do not have any sockets in my loft, so I'd need to cut the plug off and connect it manually to the lighting circuit. I would lose the fuse from the inkbird, but the fan plug would still have a fuse.

You can quite legally add a 13amp socket, to the lighting circuit..

 

[nero44]

You can quite legally add a 13amp socket, to the lighting circuit..

Mhm really? My lighting circuit is rcbo protected at 6 amps. I plan to retire in my house, but if some future owner sees a socket there and plugs in a 13a rated heater, it will trip the entire lighting circuit, no? And they will wonder why. If I wire via JB then its quite clear that there is no socket available to use for any other purpose?

 

[Harry Bloomfield]

Mhm really?

Really!

It has been discussed at length in this very forum, and the concensus is that you can quite legally connect a 13amp socket, to a lighting circuit.

My lighting circuit is rcbo protected at 6 amps. I plan to retire in my house, but if some future owner sees a socket there and plugs in a 13a rated heater, it will trip the entire lighting circuit, no?

Why would anyone plug a 3Kw heater, into a socket in the loft? It would be prudent to add a label to the socket, such as '6amp max load'. In fact, if your lighting circuit is wired in 1.5mm, there is nothing to prevent you changing the 6amp, to a 16amp MCB.

 

[nero44]

Ok thanks that’s very helpful.

 

[ericmark]

Using a fused connection unit (FCU) one can fuse to 1 amp, or maybe better with grid switch like I did here. However "The PAS 63100: 2024 was published by the BSI in March 2024. Section 6.5. 5 states that batteries shall not be installed in 'voids, roof spaces, or lofts. '4 Apr 2024" but reading on here it seems not that cut and dried.

The picture they show there is a roof window with ventilation and clearly a large loft. With the work bench it seems more like a room.

I can't really advise, it seems there is some upset in the industry, but I would keep it simple, then easy to modify latter.

 

[nero44]

It's all done now. Installed a new socket, went with the Inkbird-308, a simple DC transformer (with different speed settings) and this gpu fan, which perfectly fit over the fins. Setup and applicability of the Inkbird is super easy, great recommendation! Looks like a fairly sunny day ahead, so inverter should be running at full speed at some point, so will keep an eye temp development.

reading on here it seems not that cut and dried.

Yes definitely not clear, other than the fact that it is a recommendation only at the moment. For me personally I feel quiet happy with the location, I have mains wired heat detector, linked to the others in the house, use LiFePO4 batteries, got access to the loft. Also it's under the roof space where most of my panels sit. So I'd argue that the panels themselves actually dissipate a good amount of heat, as the roof is effectively now shaded for 80% of the surface. Tbf, I don't really have any other option if it became law... but as is the case with many aspects of old victorian terraced houses >> it appears quite rare for regulator to force costly change to an existing setup that was legal at the time it was installed.

Anyhow, according to this link, the working group will meet again in July to hopefully refine the standard and give some leeway/guidance for batteries in lofts, e.g. acceptable subject to some common sense additions (LiFePO4 only, access, smoke/heat detector etc). In this aged housing stock in London you already have to be lucky to have enough roof space, the correct orientation of that roof space, no trees covering that roof space, etc... for most of my neighbours in a 100m radius it rules them out and that is a good amount of properties.

 

[ericmark]

Orientation of the sloping roof it seems does not matter to much now, mine is East/West and the installers did some calculations to decide if it needed two sets of panels or one, so they went for one, so it is slow to start charging in the morning, but until 5 am the battery is charged from grid, so the gap between battery coming off grid charge to getting solar is not enough for the battery to hit 10% as which it stops discharging (10% for UPS use) in fact rarely drops below 70% in the morning, it is the evening use where we may not bridge the gap and solar reduces before we are into off peak tariff.

Yesterday midnight down to 24%, but many days we have run out of battery before off peak starts. But if we stop using heavy users by 4 pm to 7 pm depending on the sun that day, the use of peak rate electric is minimal.

OK not everyone has a roof which can take 14 panels on one side. I think mine could have another 4 panels if we wanted there is enough space, but south west it seems is better than north east due to when we use electric and when off peak is available.

There was a discussion on if batteries can pay without any solar, not so sure about that, as still need the inverter.

 

[nero44]

OK not everyone has a roof which can take 14 panels on one side. I think mine could have another 4 panels if we wanted there is enough space, but south west it seems is better than north east due to when we use electric and when off peak is available.

Amazing, yes I wish I had that roof space. I have 9 x 430w panels spread across south and south east sloping roofs. This is my roof. N.b. I did not move any velux windows. 3 on top roof and 6 on the lower roof. It's slightly south east so I get most in the early part of the day and then once afternoon sun comes from the west the output is greatly reduced and most of the power comes from the top pure south facing roof. We don't consume much, so these days I export 3x as much as I use and the grid is only used at 2am for an hour or two. So far the battery covers our usage even during winter.

But you can imagine with this type of terraced house solar is very difficult. North side is no point so none of my neighbours on the other side of the street can get any meaningful solar.