variac help needed any sparkies out there?

[badbillybob]

Hello. 

I'm in the process of planning my next twin variac fan controller, but need some advice from someone who knows more about electrics than me (that's about 99% of you)

Right I was planning on building a twin variac, to control the input and output fans via a ATC 800 controller.....but I want to put 1 intake fan ( a RVK 200A1) 2 extraction fans ( both are RVK 315A)1 on it if possible?.

My reasons for putting 2 fans on the extract is for noise reduction, on the basis that 2 12 inch fans working away at 60% will be much quieter than one at 100%, and I have a spare 12 inch fan. I also want to downsize the extract ducting to 8 inch before it leaves the building.

 

So I have ordered a 10 amp DPDT relay and matching 8 pin DIN socket.

My plan was to have a trailing lead which would be cannibalised from an 4 socket extension lead. 

 

The spec on the fans is ;

8 inch = power 108watts, current 0.47 A

12 inch fan = power 176 watts, current 0.95 A (each fan).

 

Variacs will be 2 amp.

 

I attach a wiring diagram blagged from AN other site, to show how it would be wired for a 2 fan gig.. 

 

Question is, is it possible to run the 2 12 inchers on out take,

any help appreciated because, altho I can follow wiring diagrams and have made one of these twin variac controllers in the past,  (which even worked, before the pigs stole it, the c*nts), I don't know much about electrics

 

thanks in advance

[Joint hogger]

sorry pal but I'm afraid that if you wire three fans up then you'll overload the variacs & they'll fry themselves,

the main reasons being is that in effect, your 2A variacs can only supply a 2A draw for short periods of time

& will eventually overload, they're more realistic actual sweet spot is 1.8A for optimal use, ie 24/7 use.

 

so your two options are, only use the intake fan & one of the 12" outtake fans or get 3.5A variacs instead.

 

 

 

[badbillybob]

Quote

 

 

1 hour ago, Joint hogger said:

sorry pal but I'm afraid that if you wire three fans up then you'll overload the variacs & they'll fry themselves,

the main reasons being is that in effect, your 2A variacs can only supply a 2A draw for short periods of time

& will eventually overload, they're more realistic actual sweet spot is 1.8A for optimal use, ie 24/7 use.

 

so your two options are, only use the intake fan & one of the 12" outtake fans or get 3.5A variacs instead.

 

 

 

thanks for the quick answer, that's great.

So would I be right in thinking the 10 amp relay din and all the rest of the gubbins still be ok with the 3.5amp variacs, or would they need to be bigger too?

I'm thinking (dangerous I know) the amps drawn from the fans being less than the rating of the relay, the 10 amp relay will be ok, is that right mate?

I would really like to run both extract fans because on full pelt it sounds like a Eurofighter on afterburners.

 

edited to add, just checked, next size up is 6 amps, would they be ok?

Edited June 4, 2018 by badbillybob

[badbillybob]

thinking a bit more about this I think I might be better off with 2 separate controllers, one twin variac, and maybe a single variac for the other 12 incher.

what do u reckon? the 6 amp variac is massive, and dearer than 3 2 amp ones?

[zztopbudz]

Yes I think it would make more sense to do a standard 2 amp twin variac for the 8 and the 12 and then another much cheaper 1.5a for the 12 incher that could be wired to something like the atc 800s cheaper little brother or a Honeywell thermostat , so that it runs at a set idle speed depending on the time of the year and kicks in to full pelt once a max temp has been reached. 

I think two 3.5 amp variacs will be expensive . 

zz

[badbillybob]

Quote

 

Yeah mate, you are right they are almost twice the price, the 2a ones I can get for 42 quid and the 6's are 72 odd quid, so I will be cheaper getting 3 of the 2 amp ones.

 

I will have to wait a couple of months till they are back in stock, as they are on the slow boat from India, but I would rather wait than pay twice as much for the same thing from RS componennts

 

I have another stupid question for you. If I was to use the wiring diagram above for a single variac, would I just remove the connections from the relay points 1 & 2 to the variac and the neutral to the variac?

 

I told you I didn't know much about electrics didn't I?

[Laphroaig]

53 minutes ago, badbillybob said:

Yeah mate, you are right they are almost twice the price, the 2a ones I can get for 42 quid and the 6's are 72 odd quid, so I will be cheaper getting 3 of the 2 amp ones.

 

I will have to wait a couple of months till they are back in stock, as they are on the slow boat from India, but I would rather wait than pay twice as much for the same thing from RS componennts

 

I have another stupid question for you. If I was to use the wiring diagram above for a single variac, would I just remove the connections from the relay points 1 & 2 to the variac and the neutral to the variac?

 

I told you I didn't know much about electrics didn't I?

Just had someone ask about cheap variacs and the place I got mine seems to have shut down leaving only RS etc.  Would love to know where you found the cheap ones.  

[badbillybob]

hi, I got them from eastern transformers, but they dont have any in stock just now.  they trade on ebay under ETE. 

they are waiting for a delivery from India. when I spoke with them, he said the ship left last week, and it takes 3 months to get here, but I can wait, given that they are much cheaper, and I'm a tight   b*stard lol..

 

Do you fancy having a look at my wiring diagram and advising on the single variac use?

Do I just skip out the wires from the relay marked 1 and 2 and the blue wire?

 

cheers, I hope someone can give me an answer. 

[sinbad!]

On 6/4/2018 at 3:35 PM, badbillybob said:

Hello. 

I'm in the process of planning my next twin variac fan controller, but need some advice from someone who knows more about electrics than me (that's about 99% of you)

Right I was planning on building a twin variac, to control the input and output fans via a ATC 800 controller.....but I want to put 1 intake fan ( a RVK 200A1) 2 extraction fans ( both are RVK 315A)1 on it if possible?.

My reasons for putting 2 fans on the extract is for noise reduction, on the basis that 2 12 inch fans working away at 60% will be much quieter than one at 100%, and I have a spare 12 inch fan. I also want to downsize the extract ducting to 8 inch before it leaves the building.

 

So I have ordered a 10 amp DPDT relay and matching 8 pin DIN socket.

My plan was to have a trailing lead which would be cannibalised from an 4 socket extension lead. 

 

The spec on the fans is ;

8 inch = power 108watts, current 0.47 A

12 inch fan = power 176 watts, current 0.95 A (each fan).

 

Variacs will be 2 amp.

 

I attach a wiring diagram blagged from AN other site, to show how it would be wired for a 2 fan gig.. 

 

Question is, is it possible to run the 2 12 inchers on out take,

any help appreciated because, altho I can follow wiring diagrams and have made one of these twin variac controllers in the past,  (which even worked, before the pigs stole it, the c*nts), I don't know much about electrics

 

thanks in advance

you said about the 2 x fans running slower reduces the noise, I get that but how are you getting 2 x 315 rvk's out of your setup?  thats a lot of air flow ?  im struggling with a 250mm can fan split into  2 100mm's and a 150mm. (All in 1 box ) obviously it reduces the air flow., It doesnt matter in summer but as soon as there is snow about its essential else I have a glowing roof when everyone around me has a 2" thick layer of snow.

 

thanks for any tips

[badbillybob]

hello.

I did originally have a 8 inch intake and 12 inch out take  run off the twin variac controller.

I also had a single 12 inch out take run off a separate manually controlled variac controller, but I took it out as it isn't needed to be honest. I 

still have the 8 in 12 out set up and it idles at 30 %, but ramps up to about 80% depending on temps

I just twigged that your not asking about the controllers - doh, but the ducting out I presume.

right, well its 12 inch duct with 2 tees going to the soffits and the end restricted but allowing some of the air to remain in the building, to help intake temps.

here is a pic of my soffits, they have 4 No. 100mm diameter vents, for each teed outlet, if that makes sense

the ductwork is also insulated inside and around the outlets to stop any give away melted snow etc.

hope this helps

Edited October 20, 2018 by badbillybob

[badbillybob]

I would estimate that 80-90 % of exhausted air leaves the building. 

You don't really want to recirculate exhausted co2 laden air if you can help it.

 

[sinbad!]

cool, I get the soffit thing totally, I at the moment pull all my intake from one side of the house, ill try to explain but ive had a few beers,

 

On one side I have cut up some for sale signs and used expanding foam to seal them between each joist, and at the very last 600mm joist I built a box to pull all the air from the whole soffit as my intake, (250mm)

 

Im currently extracting back into the loft but am currently thinking of changing it all and putting in multiple tile vents for in and out but obviously they can be seen from outside and im not up for (at the moment) climbing on a roof.

 

do you use the soffits for in and out ?

[K-dawg]

2 hours ago, badbillybob said:

hello.

I did originally have a 8 inch intake and 12 inch out take  run off the twin variac controller.

I also had a single 12 inch out take run off a separate manually controlled variac controller, but I took it out as it isn't needed to be honest. I 

still have the 8 in 12 out set up and it idles at 30 %, but ramps up to about 80% depending on temps

I just twigged that your not asking about the controllers - doh, but the ducting out I presume.

right, well its 12 inch duct with 2 tees going to the soffits and the end restricted but allowing some of the air to remain in the building, to help intake temps.

here is a pic of my soffits, they have 4 No. 100mm diameter vents, for each teed outlet, if that makes sense

the ductwork is also insulated inside and around the outlets to stop any give away melted snow etc.

hope this helps

Can you see the hot air coming out those vents when its cold mate? I do like that idea, I currently just exhaust pointing my duct work to corner of my loft which is sealed off from rest of the room, i have a badly done loft conversion. But it doesn't work when its snowing, so i need to bring the ducting out through out loft hatch. Sends mrs k-dawg mental though i'm looking to fux it somehow before we get snow again.

[sinbad!]

No! same prob as I have and im doing the same, luckily there are lots of other houses on my estate that have rooms in their loft that are not insulated well so when it does snow im not the only one with clear patches on my roof, Unfortunately I can see what no one else seems to see. (as i know what im looking for)

 

I would like a good fix as this seems to be my weak spot at the mo, that and the high electricity usage

 

i did read a good post earlier with someone using cool tubes and putting the hot air back into the house, seems good but im so stealth my missus doesnt even know whats going on.

Edited October 21, 2018 by sinbad!

[badbillybob]

Well, I used to just exhaust into the attic when I grew indoors, and never had any problems, (that was 2 x 8 inchers and a 6 nch extract, but it was a big attic, you could stand up in it, and it had vented soffits, but my air just went into the actual attic. It worked great for years, with zero condensation in the attic, and no hot spots - as I checked regularly. I know the insulated duct helped against condensation

With my new set up, I think it might show up with hot air against cold outside air, that's pretty unavoidable, but mine goes out where no one can see from the street, and I will put something in front of the vents to disguise it if it happens.

If you want to be 100% certain of nothing showing up on the roof, you will have to insulate the underside of the roof, and vent into the attic, but if you do this, you also need to leave a gap between the underside of the sarking boards (the board you can see between the trusses inside) and the insulation, to allow for airflow.  It wont be cheap, because you would be using something like Kingspan, but it would show nothing.