Roof Fan Power Consumption

[wildebus]

Something that I have wondered about is how much power the fan I have uses.
I've noticed in the recent weather that my power consumption has increased noticeably. It might be thought this is mainly due to the fridge having to work harder, but actually the fridge has not had to do much extra at all (surprising but true) and because I log the power consumption on a literal minute-by-minute basis, I can see the pattern is not fridge-related.
The other obvious 'culprit' is the fan, being put into use more with the hotter temperatures of course.

I have a MaxxAir 7000 Deluxe Fan (the 7500 is the exact same model but with a Smoked cover instead of the White cover - I mention this due to a typo in the graph later in the post) and that has an AUTO mode that changes the fan speed automatically depending on delta between Ambient vs Target temp, and also turns itself on and off. Becuase of this automatic mode, you can't tell for sure how the fan is running when away from the vehicle and so what power is being used.
So me being me, I decided to log it specifically
NOTE: The specific data is for the MaxxAir Fan I have installed. Other Fans will have different characteristics, but another Fan with the same CFM value is likely to draw the same power.

Test Environment:
Power taken from Leisure Battery reduced to minimum - So VSR disabled; both Inverters OFF )but there is a tiny residual draw as both can be turn on and off remotely); 3 x USB Dual Sockets powered up (nothing plugged in); Raspberry Pi powered up via a USB 3A PSU; Fridge Fan Temp Controller on (fan off); Water Pump on (not being used).
All the above results in a constant 3W draw on the battery - so that is our baseline without the Fan in use.

I then turned the fan on using manual mode only, setting it to the lowest setting - 10%. Approximately every 15 minutes I used the remote control to step up the speed to the next setting (so 20%, 30%, 40% etc. up to 100%). Finally hit the stop button and the fan turned off and the motorised cover closed.

The following graph shows the difference in power drawn for each speed, the value adjusted to remove the baseline power draw.

Maxxair Power Consumption by David, on Flickr

It is interesting that the first few steps are not that different from each other (and in use, the audible difference between 10% and 20% for example is very hard to hear) but as you get faster, the power differences widens.
I had previously noted that my fridge draws an average of about 1.2A/hour in use inc the Inverter O/H - If you compare that to the fan use, it is around the same as the fan running at 60% - this might surprise some folk?

The fan is great and I would recommend the MaxxAir 7000/7500 100% and without hesitation, but it is a powerful beast at the higher speeds and you would need a decent battery capacity or Solar charging if running the whole day.
PLUS - if using on AUTO mode, the fan may kick into higher speeds when the temp goes up and if the target temp set is not achievable, then you may be away from your van for the day, with the fan consuming 37Wh/Hr - which would be well over half the typical (100Ah) Leisure Batteries usable power (600W) used up in under half a day.

 

[Byronic]

But the proof of the pudding is, how efficient is it
at various speeds in displacing air, (or smoke!)
For instance @ 10% setting it consumes 3W.
Then @ 100% it consumes 37W.

So does it shift roughly 12 times as much air at the
!00% setting as compared to the 10% setting.
You'll have purchase a flow capacity meter now
and run it asnear the optimum speed commensurate
with simultaneous best comfort condition!

 

[Bigusdickus]

Can't you just open a window?

 

[wildebus]

Can't you just open a window?

No.

(my windows are fixed)

 

[Tezza33]

I have a Fiamma Turbo Vent fitted, I don't know how much power it uses but I have noticed if I turn it up to full speed when my batteries are full my solar panels go into overdrive to top the batteries up so obviously it is a lot of power

 

[Bigusdickus]

No.

(my windows are fixed)

err....was that intentional or an oversight?

 

[Wissel]

Interesting thread as I have a Maxxfan Deluxe fitted. I've not moved the van for about a month and had the fan running continuously.

I usually have it on quite low (maybe 30 - 50%) and had briefly looked to see what consumption was being used including laptop and phone charging etc. The total draw was only a couple of amps so I didn't give it anymore thought. The last few nights I've had it on full power as its been really sticky here, and noticed this morning my batteries were lower than I've seen them to date. If using 3A per hour this explains it

It is probably my favourite upgrade in the vans rebuild. My van already kept nice and cool as it was initially designed and built for my dog to always be at a comfortable temperature. In fact it was this reason that got us self-building as our "off the shelf" vans were always like ovens. But even with the recent heatwave (was in direct sunlight in Cornwall for most of that) the Maxxfan kept the van cool. I usually have the windows open in the vent position and the fan on extract. This shifts enough air to feel an inward breeze from the windows which is lovely. If it gets hot and horrible during the night I flick it over to blow as it's above our bed (we have the clear version). During the heatwave I had a screen cover on all the time as well.

I've not really used auto, apart from to test it.

PS - for anyone thinking about going for one of these, they are very quiet up to about 40-50% power. Quiet enough to get a good nights sleep. When I was researching roof fans I saw a lot of YT videos from the States where people had swapped from a Fantastic to the Maxxfan because of noise. Plus, this fan can be open in the rain as the vents are on underside. No more coming back to a wet bed after the pub

 

[wildebus]

err....was that intentional or an oversight?

Minibus conversion of a PVC conversion, so all windows are almost all fixed glass in those. I do actually have one small sliding window but as it slides across and not hinges from the top, it needs to be closed in the rain - so I have to assume worst case scenario ...

.....
It is probably my favourite upgrade in the vans rebuild. My van already kept nice and cool as it was initially designed and built for my dog to always be at a comfortable temperature. In fact it was this reason that got us self-building as our "off the shelf" vans were always like ovens. But even with the recent heatwave (was in direct sunlight in Cornwall for most of that) the Maxxfan kept the van cool. I usually have the windows open in the vent position and the fan on extract. This shifts enough air to feel an inward breeze from the windows which is lovely. If it gets hot and horrible during the night I flick it over to blow as it's above our bed (we have the clear version). During the heatwave I had a screen cover on all the time as well.

This is my 3rd van conversion and the other two were also self-builds with fixed windows all round and got very hot in the sun. I didn't fit any roof ventilation in them, and when it came to build #3, a roof fan was on the "must have" list and in fact the MaxxAir fan was the only fan I considered after looking at all the options.
I chose the white cover version as it blocked more light (though not opaque). the smoked grey ones looks cooler though

... PS - for anyone thinking about going for one of these, they are very quiet up to about 40-50% power. Quiet enough to get a good nights sleep. When I was researching roof fans I saw a lot of YT videos from the States where people had swapped from a Fantastic to the Maxxfan because of noise. Plus, this fan can be open in the rain as the vents are on underside. No more coming back to a wet bed after the pub

Fully Agree. When on the lower settings you really cannot hear the fan going unless you specifically listen out for it.
A key aspect of this fan was also the fact you can use in the rain (useful in the UK generally and essential up here in Scotland; plus you can safely drive with the top cover open - very useful in a van with no opening rear windows and no cab air conditioning.

I've not really used auto, apart from to test it.

I tend to use the Auto setting much more than the manual actually. I like the way it adjusts the speed by itself and turns itself off overnight and back on early morning as the sun warms the interior. I think of the Maxxair Fan as the closest thing it is possible to get to A/C without actually getting A/C