Hi all,

Just a quick question really. I bought my variac from my friend who built it but doesnt use it anymore. He is quite good with electrics and he assured me when I bought it that it is fully safe etc. Anyway, it works a treat and I currently have my 2 6inch Ruck fans plugged into it on about 70% power.

Now the question, just how many fans is it safe to control with these variacs? Mine has a 4 way extension plug on but the variac gets hot at 70% (Not burn the hand hot like the ballasts). The reason I am asking is because I have an old 6 inch fan which is too powerful for my mother/clone tent which only has a couple of flouros in it but if I could have that plugged into the variac aswell on 70% this will save me buying a smaller Ruck for the vegging tent. (Hope that makes sense)

I dont want to cut corners obviously but just wanted to know how much these variacs can take? I am guessing I am running about maximum and it would be safer to build another one (or buy a smaller fan) but thought I would check before I do anything silly

Thanks in advance

666

forgive me I'm no electrician,
but:-

i always figured it depends what the amp rating is on the variac, as long as the amp ratings on the fans dont add up to more than the rated amps for the controller.

but dont quote me on that

3 amps will handle up to 800 watts

A RVK150L1 is rated at 85/115 watts that uses 660m3/ moves that amount of air

Find out how many watts each one of your fans is and then check that that the variac is of sufficient amps to be able to handle it.


Hope that helps

SS

Thanks for the replies, really appreciated.

So if he built it correctly there is a good chance I could run all 3? I will give him a ring and see if he remembers how many amps it is.

If he cant remember how can I check the amps on the variac?

Sorry for the "simple" questions but I really no nothing about electrics. I can barely wire a plug!

Hmm, I have just spoken to him and it is a 0.75 amp Variac. I have just seen it on the Maplin website.

Maybe 3 fans is pushing it what do you think?

I will add that the 3rd fan is only the 6inch A1 fan so not the high powered version like the other 2.

My friend said he had 3 running fine on it at about 80% but I really want to avoid anything dodgy!

Thanks again in advance

ill just mention something here.

i had one of them 0.75 maplin variacs & run a ruck150L on it, & the variac got realy realy realy HOT
i couldnt touch the thing.

now i got one off that auction site, used 3amp variac & this things not hot at all. not even warm.

so ild say if your going to be running 3 fans, get a bigger amp variac, as itll be cooler.

one 150L is about all that thing can handle, with two on it, it's not gonna last long until insulation failure, and the thing will just put out 240v (or some random figure between 0 and 240v) it may burn out a coil and stop working altogther

Im scared now! Is running 2 ruck fans on this a fire risk then? Thanks for the great advice all.

Hmmm, I will buy a better one straight away. To be honest I havent plugged my 3rd fan in yet but it is making a right racket going at full speed so after lastnight I decided I was going to buy another variac to run that seperately but if you think that 2 fans on that my current variac is too much I will just bite the bullet and buy a variac with a bigger amp.

I am sure my friend will wire it up for me if I look at the pinned thread and buy the parts but maybe I will invest it a good Speed Controller from Greens that will do what I want. Any ideas of one?

Thanks again for your help. I am sure without the help of UK420 I would have burnt my house down twice already

i doubt it will set anything alight.... massive lumps of iron don't burn, might make the enclosure melt a bit if it gets really hot, but most likely it'll just short a few coils and you wont have any speed control. but yeah, not good. i'll just go check the systemair site, and see exactlyhow much current they pull, i'd imagine you're right on the edge

oh, sorry, your fans are rucks aren't they...... got a model number? a high powered 150mm rvk is 0.5A i'd imagine the rucks are pretty similar, so overloading it a bit. if you can manage with only slowing one fan, i'd do that, if not keep it cool until you can get a new one, get a fan blowing on the transformer, put some vent holes/slots in the enclosure if it doesn't already have them

eeek, yeah they are both high powered Rucks that are running on it at the moment

The enclosure has got holes in it but it does get hot. Like I said though, not hot like the ballasts, I can actually pick it up and hold it but I appreciate now that I am pushing it to its full capacity and it probably wont last long like this. To be honest one of the fans is on a timer and only comes on during lights on so the variac is operating 2 fans for 12 hours and 1 fan for 24 hours (If that makes sense - I dont need them both on during lights off). Maybe why it is operating ok/hot at the moment?

I have spoken to my friend today and he will build me a new variac with a bigger capacity as such, I just need to order the bits now. I have seen a 2 amp one on a popular auction website for about £45 which I think will handle both fans fine. Or would it still be better to go for the 4 amp one instead which will stay cooler? I am now planning on running the 2 high powered 6 inch ruck fans on the new 2 amp variac my friend will build for me and use my 0.75 amp variac for my 6 inch RVK fan pulling from my vegging tent. It would just be easier for me to have 2 seperate controllers as oppose to all 3 fans in the same one what with wires etc (and the fact that it is cheaper as I already have the 0.75 one )

Thanks again for the information scraglor, it is really appreciated. My friend said for the short term to have a fan blowing through the enclosure aswell but honestly I would rather just do things properly and if that means buying a new variac then that is what I will do Nice to know it "probably" wont set anything alight, it is sat on kingspan which is better than the carpet but I still dont want it to stop working on me so I will definately get it sorted sooner rather than later.

Now to order the parts

just go for the two amp one, a 4 amp one will be effin massive!

Noted mate cheers Any ideas how big the 2 amp is? I had a look on the site and even the site they linked to but no dimensions available Is it much bigger than the 0.75 amp one?

depends really, but about twice the size