Fuse keeps blowing on SS

[POGE]

Question #1
I have an modified cooler express 2011 SS and I have it set up on a circuit I built that controls whether the compressor gets power via a relay. Whenever the machine is powered on and off too quickly, (as in I press the power button to turn it on then turn it off within a second or two, or I turn it off and then on in one motion, the fuse blows.

Question #2
Another thing I am concerned about is if it hurts the hermetically sealed compressor to be started and stopped frequently at short intervals. The way my circuit works, when the "master" switch is turned on, a 12v coil relay (lets call it the compressor relay) gets power and the compressor gets cold for a couple minutes, then the PC is turned on and the compressor relay gets power from a different source, a molex connector off the PC's power supply. This is done using another 12v coil relay that when in the normally open position sends power to the compressor relay from the PC power supply molex, and when in the normally closed position sends power to the compressor relay from my circuit's power supply. This is done using a second relay In between for about a 10th of a second there is a period where the compressor does not recieve power from either source, so it "stutters". Is this okay? This happens whenever the computer has to cold boot. This is a 24/7 system that is on most of the time, used for scientific research.

I know this might be hard to understand, I will add a diagram soon, help really appreciated.

[n00b 0f l337]

It would say you need to add a delay-on-start timer to your system to delay reboots. It's something I used for years on single stages set to 3-5 minutes.
Or switch to a slow-blow fuse.

[POGE]

Thanks for your reply! I need the system to be user friendly for people who don't understand there is a compressor in the PC. I'm not quite sure what you mean by "delay on start timer" to delay reboots. Slow blow fuse I have considered a lot but I'm not sure what rating or if it would still serve its purpose. Currently 10A quick blow.

Also still worried about compressor cycling on and off too quickly causing damage?

[Buckeye]

Just a question... why are you shutting the SS on and off so fast ?

If you are just doing a computer reboot you don'r need to shut the SS off, just leave it running. The only time you need to turn the SS off is when you are done with the computer and shut down the SS last.

I am not sure how many times you would need to cycle the compressor real fast to cause any damage, but generally its not a good thing to do. I believe it can cause pressure to spike very high which in turn can cause damage to the comp itself. Just guessing here.

From the limited time that I used a controller board it was something like ~5 minutes after you shut off the SS before it would allow you to turn it back on again.

I think the reason why you keep blowing fuses after quick restarts is the pressure inside the system is to high casuing a higher charge from the start cap to make it startup again.

I have used many of these Cooler Express units and they are designed to be run continuous, meaning turn them on and leave them on. If you have to shut it off and then need to start it back up just wait a few minutes before doing so.

How was this unit modified ?

[POGE]

Why am I switching the SS on and off so fast... well the relay does that in my circuit, and also when I'm troubleshooting, its probably a terrible thing to do though.

Okay, I see what is meant by delay timer for being able to reboot now. Makes perfect sense, I will add it too my circuit. However I am still confused/worried about the time in between power sources where my relay is switching where the compressor doesnt recieve power for a millisecond, and stutters, vibrating the entire computer case. :/

Just to be clear:
Compressor ON 3 minutes ---> Compressor OFF .01 seconds ----> Compressor ON hours/days

Is this okay? I've read some sources that say its okay to turn a compressor off and then back on quickly but not okay to turn it on for only a few seconds, and that it has to do with oil in the compressor. If this is true I think I may be safe as I don't go from off(long) to on(short) to off(long) quickly, but instead on(long) to off(very short) to on(long). If not could switching from a coil relay to a solid state eliminate this stutter?

[Buckeye]

Well there should be no delay or power off for a simple reboot of the computer, its only on shut downs that you need to delay.
I would also say that your delay after its been on for 3 minutes before turn back on should be a few minutes, not .01 seconds.

Depending on why you have it on for 3 minutes then shutting it off, you can skip the compressor off completely. The only time you should cycle the SS or shut it off is when you done with your computer and shut the whole thing down.

Your short cycles is what causes the pressure to spike up and making it hard on the unit to do restarts.

Hopefully a builder can come in here and make sugestions.

[POGE]

Depending on why you have it on for 3 minutes then shutting it off, you can skip the compressor off completely. The only time you should cycle the SS or shut it off is when you done with your computer and shut the whole thing down.

Its because my circuit uses a relay to switch where the compressor gets power. During startup during the compressor cooldown period, the compressor gets power from my controller circuit's power supply. After that, a relay switches its power source to my PC's molex. This is so if the PC turns off, loses power, or crashes, the compressor turns off automatically. At the time the PC turns on and the relay switches, there is an almost instantaneous period where the compressor recieves no power.

[Buckeye]

Understood

That is what I am trying to say. If your PC turns off for what ever reason controllers I have used shut down everything, then have a delay for the SS of a few minutes before it can startup again. The controller then watches SS Evap temps and when they reach a set temp it will then startup the computer. If for what ever reason the SS does not cool down to the set temp, say the SS broke, it will not allow the computer to start back up.

[POGE]

So I should have the compressor cool down for a few minutes, turn off for a few minutes, then start again with the PC? Thanks for your responses btw, very helpful.

[Buckeye]

Yes, it should start up first before the PC. Then when it reaches a set temp of what ever, say -40c, then start the computer back up.

[POGE]

Your not understanding I don't think. I'm not understanding... when I start my PC, the compressor will not be getting power momentarily, because at this time, a relay flips, and for a moment the reed in the relay isnt touching anything, and the compressor loses power. I could change my circuit so that the compressor runs for a few minutes, turns off for a few minutes, then starts again with the PC, but wouldnt the evap just warm back up during the few minutes it is off, defeating the purpose?

[Buckeye]

Yes I understand.

When you start your PC the very first thing that SHOULD get power is the SS, then delay until temps get to preset, THEN start the PC.

You should change your circuit so when you hit the power button it starts the SS first and do not turn it off before starting the PC, leave the SS running. Wait a few minutes then start the PC.

Do not cycle the SS

[POGE]

Hmm okay, I think I'll try a solid state relay to switch power source for the compressor relay if thats the only option. I really want to use the molex to drive the compressor while the PC is on.
Thanks again.

[n00b 0f l337]

Or if you want to keep the molex drive. Install a "reboot button" on your SS. A switch you can hold (preferably a momentary switch) that bypasses the controller and keeps the power going to the unit.

[Buckeye]

noob there is no controller on the Cooler Express units, I believe he is trying to make one of his own.

[n00b 0f l337]

It sounds like he already has one in place though. So adding a momentary that connects around it could solve his reboot issue.
The point is that the compressor CANNOT reboot when the computer does.

So you have to keep it giving power.

So either change your controller, add a switch you can press or flip to bypass controller, or go to higher fuses and not be protect and in short term burn out compressor.

[POGE]

The bypass switch is a great idea, I will use a electronic switch (relay) instead though. I will wire a coil relay parallel to the compressor relay that bypasses it for a few seconds keeping the compressor running during the time the compressor relay is momentarily off. I should have just made 2 relays in parallel from the start and had them overlap to avoid the momentarily off compressor. but Ive finallized the circuit I have now so I'll just add the bypass relay. Once I do this and add a delay on start timer my compressor will see no more hard times. Just hope the damage hasnt been done, been running it constantly for a couple months now with daily "dirty" bootups with cycling on the compressor. As for the fuse I think I'll try slow burn as sometimes it even blows for apparently no good reason when I power off the machine after its been running for hours.

[wdrzal]

After a compressor shuts off it Must have 2 to 3 minuites of Off time to allow the high side to equilize with the low side or the differential pressure will prevent the compressor from starting. Essentially a Locked Rotor condition. Most of the time the thermal protector opens ,but if the fuse is blowing it may be undersized. You do not use the thermal protector opening as a replacement for a compressor delay.

A slow blow fuse will not work. You either need a contactor with a time delay (usually a adjustable delay time),as noob said , or you need to build the delay into the controller or the solid state circiurty.