# Help wiring fans to a relay to cool amp



## Blistered1 (Jan 6, 2018)

Hi there, I recently upgraded my sub woofers and now it has been causing my amp to overheat, so i've decided to build an amp cooling rack to keep it cool.

I'm going make an enclosed rack made out of MDF with a plexi-glass lid with 4 80mm fans, 2 on either end, one side pushing the other pulling. 

Since I don't have much experience with wiring and such I did bit of research on how to wire all of this together and have it turn on and off with a remote source. I found that I needed a relay for all of this to work. So I made a diagram for myself on what information I was able to find but none of the information I came across was really specific about the wiring.

Because I am not sure if the diagram I created is 100% accurate I would like anyone on here to take a look at it and correct me on anything that is wrong so I don't burn my car down or fry something.

Thanks in advance!


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## Horsemanwill (Jun 1, 2008)

This book should help with anything that you need.

http://www.davebarton.com/pdf/RelayGuide.pdf

with that said make sure since you plan on having the fans run constant that you get some really quiet ones. i've always wanted to use a temp controlled fan type system. something like you see in PC rigs.


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## Blistered1 (Jan 6, 2018)

These are the fans i'll be getting for the application. By design they should be pretty quite. 









I plan on adding an on/off switch at some point so I can just flip the fans and amp on when ever I feel like jamming.


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## Blistered1 (Jan 6, 2018)

After reading through the PDF you sent I can see that nothing in my diagram is wrong but it also doesn't show enough to confirm everything on my diagram should be right. Can you or anyone tell by the diagram I have made if this will work? 

Also, after reading your post I decided that it would be essential to add and on/off switch for the fans so I have updated the diagram picture on the original post to reflect that.


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## Horsemanwill (Jun 1, 2008)

if you're adding a switch you don't really need the relay just make sure your main power wire to the switch is fused and don't use the remote wire.

but the correct diagram in the guide is on page 31 the first diagram


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## FordEscape (Nov 23, 2014)

I'd not switch both power and ground to the fan. I'd use a simple SPST switch on the power to the fan and run the fan ground to constant chassis ground. A cheap SPST switch with a built-in indicator light showing when the fan is 'on' might be preferable.

IMHO all grounds should always be constant to chassis, never 'switched'.

The rare exception being ground-switched circuits where the power is constant - not at all a common situation and not what you have/need here.


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## Blistered1 (Jan 6, 2018)

Alright, I think I have the confidence to do this project now. So I should give everything its own constant chassis ground. 

I think I still might keep the relay even though i'm going to be adding a toggle switch for the fans just in case I forget to turn the fans off and run the battery dead.

I have updated the diagram in the original post hopefully for the last time. haha

Thanks for the help, wish me luck.

EDIT: Also, should 16g wire work for this application? Or should I get something a little bigger?


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## Locomotive Tech (May 23, 2016)

Just curious, why not upgrade the amp too?


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## trahilaloid (Jan 7, 2018)

Lol that's so wrong head unit goes to 85 86 goes to amp then the amp has a ground completes that circuit then batt 12v then fuse then goes to 30 87a goes to fan then ground fan all grounds don't have to go to the same place either so that's key on then the fan kicks on same way I just wired my trailer brakes and you don't have to use the head unit wire you can use a key on 12 v wire 

Sent from my XT1609 using Tapatalk


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## trahilaloid (Jan 7, 2018)

The relay is the whole point on not having a switch it turns of when you turn the key off

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## trahilaloid (Jan 7, 2018)

I'd use an auto reset breaker 30 amp instead of a fuse also

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## Theslaking (Oct 8, 2013)

You may not want to use the relays acc. output to power the remote on the amps. A lot of amps are very sensitive to remote input amperage. .5 is enough for most amps and 5 amps can damage some. Just split the remote wire directly from the HU. The HU will have no problem turning on two things.


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## trahilaloid (Jan 7, 2018)

Just use a key on hot wire why would you split the wire or even use it

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## Theslaking (Oct 8, 2013)

Because the remote is already run to where the amp is. Why would you run an extra wire when you have one there already?


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## Blistered1 (Jan 6, 2018)

Locomotive Tech said:


> Just curious, why not upgrade the amp too?


Well, because there would be no gain besides having an amp that doesn't overheat. A new amp would cost double if not more then what it would cost to build a cooling rack. The amp I have already give my subs all the rms they need.


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## Blistered1 (Jan 6, 2018)

trahilaloid said:


> Lol that's so wrong head unit goes to 85 86 goes to amp then the amp has a ground completes that circuit then batt 12v then fuse then goes to 30 87a goes to fan then ground fan all grounds don't have to go to the same place either so that's key on then the fan kicks on same way I just wired my trailer brakes and you don't have to use the head unit wire you can use a key on 12 v wire
> 
> Sent from my XT1609 using Tapatalk


From what I understand with relays is that you can invert 85/86 and 87/30 and it mostly depends on personal opinion. Also why would it matter if i gave the relay its own dedicated ground or grounded it to the amps ground, wouldn't it better if it had its own dedicated ground?

EDIT: Also, i'm pretty sure that 87A has no use in my application.


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## Blistered1 (Jan 6, 2018)

Theslaking said:


> You may not want to use the relays acc. output to power the remote on the amps. A lot of amps are very sensitive to remote input amperage. .5 is enough for most amps and 5 amps can damage some. Just split the remote wire directly from the HU. The HU will have no problem turning on two things.


Okay, I have no problem doing that which is actually what i preferred but i read somewhere that it can damage your head unit over time if you use it to trigger to many devices.


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## Theslaking (Oct 8, 2013)

If your amp is giving your sub all the power it's needs then it shouldn't be overheating. Are you running it at the correct load? Amps that are not broken or overworked don't typically overheat. How do know it's overheating? Is going in to protect? Some amps run to hot to touch.


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## Blistered1 (Jan 6, 2018)

Theslaking said:


> If your amp is giving your sub all the power it's needs then it shouldn't be overheating. Are you running it at the correct load? Amps that are not broken or overworked don't typically overheat. How do know it's overheating? Is going in to protect? Some amps run to hot to touch.


Well it has only cut out on me once since the install of the new sub woofers, all at once the bass just cut off as if the amp shutdown. By the time i pulled over to check it it had already recovered and was working again but that sucker was HOT i could barley touch it.

It's a type a/b 900W 2 channel amp, it is rated at 225W RMS x2 at 2ohms which is what i have it wired as. The sub woofers i have are 2ohm rated at 250W RMS. So i suppose the subs aren't quite maxed out but a new amp would still not offer enough to justify the cost.


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## Theslaking (Oct 8, 2013)

Just making sure. The wrong load can overheat amps quickly. To many things on a remote wire can surely damage an HU. The amp and relay is not to much. A dedicated ground for individual items is not best. Ideally all things would be grounded to the same point. Obviously not feasible in most situations.


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## Theslaking (Oct 8, 2013)

And really many amps run to hot to touch. But if it's shutting off even once, you should turn that gain down a little. Adding fans is never a bad thing.


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## Blistered1 (Jan 6, 2018)

I did turn it down a little bit since the incident, and it hasn't happened again since. But maybe if i get this cooling rack i will have peace of mind while jamming and maybe turn it back up.


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## Locomotive Tech (May 23, 2016)

Theslaking said:


> And really many amps run to hot to touch. But if it's shutting off even once, you should turn that gain down a little. Adding fans is never a bad thing.


I agree, adding fans is not a bad thing. My concern would be, is this a thermal protect or clipping. OP did not give the amp brand, that would help.

I am not sure I would go through the trouble of adding fans before I knew exacly what was going on. I was worried about adding fans to a JL HD600 that was driving 2 15" subs bridged to 300 watts @ 2 ohms to each sub. The amp got crazy hot but never shut down. I could get the thermal to kick in with the HU Sub output all the way up and the gains all the way up. So after setting the gains back correctly , I never had an issue


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## Locomotive Tech (May 23, 2016)

Just my 2 cents, but turning the gains up to increase output is not usually the best way to gain output. Adding fans to compensate for this may have you running on the ragged edge of the capabilities of the amp. Could lead to premature failure of the amp.


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## Maxim7 (Nov 23, 2013)

ditch the switch, use your amp remote wire to power them on/off.
what amp, are we taking about?
had the same issue with my alpine PDX- and adding a cooling fan.


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## Blistered1 (Jan 6, 2018)

This is the amp i amp using. 
https://www.pioneerelectronics.com/PUSA/Car/Amplifiers/GM+Series/GM-A5602#specs

These are the speakers I am using. 2 of them.
Punch 10" P1 2-Ohm SVC Subwoofer | Rockford Fosgate ®

And the sub woofers are wired like this. 
https://images.crutchfieldonline.com/ca/learningcenter/car/subwoofer_wiring/2SVC_2-ohm_2ch.jpg

Nothing to special.


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## FordEscape (Nov 23, 2014)

Blistered1 said:


> ... I have updated the diagram in the original post hopefully for the last time. haha


*NO*

*1.* DO NOT GROUND THE SWITCH You don't indicate the switch type - depending on what it is and your wiring you risk building-in a 'switch-to-short-to-ground'. YOU DO NOT WANT THAT FOR CERTAIN.

The sole purpose of the switch is to interrupt the power to the fans; that doesn't involve the ground-side of the circuit at all.

*2.* Look at the spec for the fans (go to Cooler Master Website); _they pull a fraction of an amp each_. 

18 or even 20ga wire is fine for the wire from the fan fuse to the relay, switch and fans. 

You should fuse the fan wire accordingly - 1, 2 or 5A inline fuse will work great depending on how many fans. You don't need and don't want a huge over-capacity (in terms of fuse or wire) for this very low-current fan load circuit.

*3.* You can use a _much lower current rated relay_ (20A probably lowest commonly available); the lower rated relay will likely have a lower "coil current" demand, placing less stress on you HU Rem Out. Remember, relay current rating is for the load it is switching - you are switching a very low-amp load (sum of the current demand of the fans).

My diagram shows the 'internals' of the relay and switch so you can hopefully understand what is actually going on in the circuit. I'm just trying to show you an electrically safe arrangement for you and your equipment that meets your requirements for 'auto fan operation' with a switch that you can use to 'over-ride' the automatic operation if you want. 

Not commenting on the other OT stuff, just sticking with your OP question.


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## Locomotive Tech (May 23, 2016)

I think you are underpowering those subs.

That amp doesn't seem to be a rockstar of any sort. From the overview I see this statement "Pioneer's Gain Control Caution feature will automatically reduce the amplifier's output until the headunit volume is decreased to acceptable levels".

I can go look in the basement and see what I got laying around, I am sure I have something a little better and cheaper thatn a 150 bucks.....if you want? or keep the gains down and ditch the cooling fans idea.


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## Locomotive Tech (May 23, 2016)

I also see that there is a bass boost level control......where do you have that set?


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## Locomotive Tech (May 23, 2016)

FordEscape said:


> *NO*
> 
> *1.* DO NOT GROUND THE SWITCH You don't indicate the switch type - depending on what it is and your wiring you risk building-in a 'switch-to-short-to-ground'. YOU DO NOT WANT THAT FOR CERTAIN.
> 
> ...


Good stuff right there!..................READ AND HEED!!!!!!


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## Blistered1 (Jan 6, 2018)

FordEscape said:


> *NO*
> 
> *1.* DO NOT GROUND THE SWITCH You don't indicate the switch type - depending on what it is and your wiring you risk building-in a 'switch-to-short-to-ground'. YOU DO NOT WANT THAT FOR CERTAIN.
> 
> ...


Ok, so grounding the switch is big no. Also, sorry I forgot to add that that the switch I planned on using was a SPST type switch. I also will use the 20A relay instead of the 40A as to not put to much strain on the HU. Thanks for setting up a diagram for me! Really helped.


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## Blistered1 (Jan 6, 2018)

Locomotive Tech said:


> I think you are underpowering those subs.
> 
> That amp doesn't seem to be a rockstar of any sort. From the overview I see this statement "Pioneer's Gain Control Caution feature will automatically reduce the amplifier's output until the headunit volume is decreased to acceptable levels".
> 
> I can go look in the basement and see what I got laying around, I am sure I have something a little better and cheaper thatn a 150 bucks.....if you want? or keep the gains down and ditch the cooling fans idea.


I meen, I knew i was going to be under powering them slightly. But would that really cause this problem? To me it seems my amp just doesn't have the cooling capability's to keep itself cool under its max rms. I never heard any distortion or clipping before the amp shut off. Also $150 is the amps retail price, you can find it for around $80-$100.

To the question you asked about the bass boost, I have it set to 6Db.


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## FordEscape (Nov 23, 2014)

Blistered1 said:


> Ok, so grounding the switch is big no. Also, sorry I forgot to add that that the switch I planned on using was a SPST type switch. .....


Well, I overstepped :blush:

*IF* you are using an *SPST* switch *AND* it has an internal indicator lamp, then it *will* have 3 connectors and it *WILL* need a connection to ground for the indicator lamp to operate:










For this you can use any ground conveniently near the switch; no reason whatsoever to run this ground back to near the amps/fans.

Sorry, from your drawing I was afraid you might be using other than an SPST switch since it showed 3 connectors with no mention of an indicator.

No worries, carry on.


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## neuspeedescort (Feb 23, 2010)

just use the relay or just use a switch.
i wouldn't be using the amp as a distribution block.


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## Blistered1 (Jan 6, 2018)

FordEscape said:


> Well, I overstepped :blush:
> 
> *IF* you are using an *SPST* switch *AND* it has an internal indicator lamp, then it *will* have 3 connectors and it *WILL* need a connection to ground for the indicator lamp to operate:
> 
> ...


Ohh ok, I see. Sorry I should have added that it was a SPST switch with an led earlier.


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## Blistered1 (Jan 6, 2018)

neuspeedescort said:


> i wouldn't be using the amp as a distribution block.


I planned on running a 16g wire alongside the wire I have for the amp from the battery. I don't have a distribution block but the only connections i'm using on the amp is its ground.


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## FordEscape (Nov 23, 2014)

Blistered1 said:


> I planned on running a 16g wire alongside the wire I have for the amp from the battery. I don't have a distribution block but the only connections i'm using on the amp is its ground.


In that case be sure to put a fuse on that 16ga very near the battery. _Never_ run _any_ wire directly from the battery without having a fuse very near the battery (certainly in the engine compartment, before the wire goes through any firewall penetration) that is sized appropriate to protect the wire.

Even a small ga wire will carry enough current for a brief time to start a fire if it is shorted. The appropriately sized fuse near the battery is to prevent that tragedy.

And now that you're showing a 5-pin relay in your OP diagram rev x, be sure to insulate blade 87A, it'll be 12VDC hot whenever your HU is off even when the car is off.

I'm with @neuspeedescort, I wouldn't use the amp for distro of ground or power. Using the amp REM IN for a 'jumper connection' is my limit for that sort of thing.

IMHO there's nothing wrong with the concept of an auto-fan relay and even an over-ride switch, but this is looking more and more 'cobbled' as the details come out .... IMHO there's good reasons for 'best practices' like single feeds to amp bays, distro blocks, etc, etc.

Sorry, but I'm out on this one.


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## Blistered1 (Jan 6, 2018)

Hey, i'm here for guidance. I want this to be as clean and safe as possible and I don't have a lot of experience doing this sort of thing, that's why i'm here asking. I have no problem creating a dedicated ground for the relay and fans and not jumping off the amps ground, I was under the impression that it would be fine. 

Also, I forgot to remove the 87A off the image, i just needed the picture to use with my diagram. I still plan on using a 4-pin relay. I have updated my diagram to reflect that. As of right now this is just a concept as I work out the kinks. 

If it is highly recommended to get a power distribution block then i'll get one of those as well.


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## Theslaking (Oct 8, 2013)

Like I said earlier. Single ground point (distribution block). You get a good chance of noise when adding stuff like lights. I never thought you were running a separate power wire for the relay. That's kinda silly when you have a big ol' power wire there already. Get some type of distribution. To me disto blocks and insulated wires is a given wether it be heat shrink or tape. I personally only use connectors with 3m heat shrink and adhesive. The adhesive holds better then the crimps and helps keep moisture out. 

Think of risk vs reward when doing anything in this hobby. Powering the amp with a 12v acc from a relay could damage the amp = not worth it.

Jumping wires between high power and low power items could start a fire = not worth it

Running fans off a remote wire if fan motors blow and short will damage the hu = not worth it. 

Turning up amp to get just a bit louder and over pushing amp = not worth it

Yes many have done these types of things with out damage but I'm not risking my hard earned money repairing/replacing equipment if all I had to do is buy a distribution block and an extra piece of wire.


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## Locomotive Tech (May 23, 2016)

Blistered1 said:


> I meen, I knew i was going to be under powering them slightly. But would that really cause this problem? To me it seems my amp just doesn't have the cooling capability's to keep itself cool under its max rms. I never heard any distortion or clipping before the amp shut off. Also $150 is the amps retail price, you can find it for around $80-$100.
> 
> To the question you asked about the bass boost, I have it set to 6Db.


I would be t that you are underpowering those subs more than you think. The rated power that is shown in the specs is based on 14.8 volts. I am sure that your alt doesn't put that voltage out constantly. 225 is a stretch.


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## DeltaB (Jun 17, 2017)

If you are going to use your amp "on" signal lead from your HU, make sure you measure at the HU the amount of current you are loading this with various amps and relays as not to exceed it's current rating, or you can run the risk of damaging your HU. This generally is as little as 300mA. See your HU docs for this rating. A single amp can utilize more than half of the rating, and many relays can be well over 150mA for the coil. Multiple amps with multiple relays need to be addressed by a single reed relay providing a single 12v source as the buffer circuit for providing 12v to all of the devices like amps and secondary relays for fans or illumination.

It is much better to utilize the model shown and illustrated at the lower end of this page under the "Proper Fuse and Wire Selection" section;

Relays


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## Gadget01 (Oct 20, 2008)

Curious why most HU remote turnons are not fused. The current is magnitudes lower than that of your amp's power wire from the battery, but still... if it gets shorted, it will likely draw more than what is considered safe and might damage the HU. The good news is, it's easy to wire an inline fuse at the HU for the turnon remote.

As for the relay use... the 30A automotive relay I assume you plan on using is epic overkill for a set of less than 1A fans, but spade connectors or a relay socket makes is easier to work with vs a surface-mount breadboard and project enclosure, so... no judgement.

Relays function by an electromagnetic coil (85 & 86) to actuate a switch (30- common, 87A- NC or normally closed, 87- NO or normally open). "Normally" being at rest or un-actuated. This electromagnet coil, since it's a coil, also acts like an inductor and stores a high voltage charge (1,500v is possible) while it's actuated/powered.

What happens when you deactivate the relay coil is this stored HV charge takes the path of least resistance, and if your HU is that path, then your HU will take the 1,000v spike. Maybe it will take a joke and not care for the first few hundred times. All you need to do to avoid this is wire a diode in parallel with the relay coil (85 / 86), also known as a spike suppressor or flyback diode. The anode should be connected to the ground side. The cathode side of a diode is indicated by the "|" symbol. If you get it backwards, the diode will be forward biased when the HU turnon is active and the relay will not trigger nor will your amps turn on. If you get it right, the diode will only be forward biased when the HU turnon is deactivated and absorb the HV spike.











It's pretty easy to implement, esp if you use a socket for the relay:









The only thing I would do differently here is use clear shrink tubing over the diode as a function of my OCD.


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## Electricalartist (May 30, 2021)

Blistered1 said:


> Hi there, I recently upgraded my sub woofers and now it has been causing my amp to overheat, so i've decided to build an amp cooling rack to keep it cool.
> 
> I'm going make an enclosed rack made out of MDF with a plexi-glass lid with 4 80mm fans, 2 on either end, one side pushing the other pulling.
> 
> ...


I think you


Blistered1 said:


> Hi there, I recently upgraded my sub woofers and now it has been causing my amp to overheat, so i've decided to build an amp cooling rack to keep it cool.
> 
> I'm going make an enclosed rack made out of MDF with a plexi-glass lid with 4 80mm fans, 2 on either end, one side pushing the other pulling.
> 
> ...


Might be better to add separate relays protected by separate fuses for each fan, in case there's a short on one device the others are okay and protected.


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## magmun (Feb 17, 2021)

Although this thread is over 3 years old it s relevant to my current build. I m have a builder make an enclosure for all my gear, and incorporate 2 fans. I think the builder is going to re arrange stuff, but it will be similar to image.


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## Ayrton (Jan 17, 2006)

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## cerrone (Jan 28, 2010)

Hello guys.

I am using the old discussion in order to ask your opinion about my installation plan.
Could I use 1 x relay for delivering +12V to 2x amps REM In, 4 x fans and optional LED strip in my amp rack as in the photo? Or, could I use it just for the amps and the fans? LED strip is not planned to be installed now anyway.

I decided to use barrier terminal blocks in the sake of the easy serviceability of the system (huge fan of SIS masterpieces works, where they are using them frequently).

If there is a need to install a switch in order to turn on/off the fans, where should I plan to install it on the scheme? Would it be on the positive 12V wire between the "12v terminal block" and the fans?


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## Ayrton (Jan 17, 2006)

Why not just run a small sub panel with or without a relay? You can then run your fans (with or without a controller), your LEDs, etc. Everything can be fused separately as well.









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## cerrone (Jan 28, 2010)

Ayrton said:


> Why not just run a small sub panel with or without a relay? You can then run your fans (with or without a controller), your LEDs, etc. Everything can be fused separately as well.
> 
> 
> 
> ...


Thanks for the advise. After I browsed the forum I found out a common opinion that since I will be using a DSP it negates the use of a relay especially since when I'm only powering up two amps after that. Mine goes from the Pioneer player remote out to DSP. Then DSP remote out to amps. And I think that the Zapco DSP-Z8 IV II has some signal delay applied to the REM OUT to the amps. 

Adding a small fuse block might give me the ability to run the remote signal through the DSP and +12V to the fans and/or LEDs.


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## cerrone (Jan 28, 2010)

Hey guys,
I am still debating over the relay/no relay question.
Would this relay work for the fan circuit? 
It comes with 30A fuse, which I intend to replace with 10A.


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