Cascade Start-Up Circuits

[mytekcontrols]

Hopefully this hasn't been covered elsewhere on this forum, but I thought it would be an important topic to discuss none the less.

I don't have any direct knowledge of working with a Cascade System (only Autocascades). Apparently from what I gather (and it makes perfect sense to me) there is a delayed start-up sequence that must be observed. Where each individual compressor, starting with the warmer first stage, must be allowed to run for a period of time before allowing the subsequent stages to kick in. This is to allow each stage to cool down to an operational temperature, before taking on the load of the next stage that follows.

This has been done with thermostatic switches, but can be problematic when dealing with 3-stage cascades, due to colder temperature requirements, thereby necessitating a more expensive sensing device. It would also seem that time delays could be used instead, since the system time-to-temperature characteristics should be fairly well understood. Below I present such a possibility, showing both a common power supply, and a distributed power scheme where the amperage requirements exceed the capability of a single power circuit. I also know of, but have to relocate a rather inexpensive solid state ON-Delay Timer that is wired inline with either 115 or 230 VAC power just like a switch, and is programmable in minutes (I will provide details on this later).

[Jack]

Looks pretty straight forward :)

As far as I know, it is currently done electronically...
Like with a G-Froster cascade controller:
http://www.xtremesystems.org/forums/showthread.php?t=49823

Or manually, by adding gauges to the high side of each stage and then watching the pressure go down below a curtain point.

[[XC] gomeler]

Great concept Mytek :up: In general this would work like a charm but sometimes the user has to turn the 2nd or 3rd stage off and on to get the CPUs to boot. Tossing in a manual switch after the final stage relay would be great for this as it'd let the user cut power when a desired evap temp is reached, boot the CPU and get it stable, then continue the pull down.

[mytekcontrols]

I found the time delay relay I was looking for at Newark.com Part Number 88K1409 (http://www.newark.com/88K1409/electromechanical-industrial-control/product.us0?sku=ARTISAN-CONTROLS-438USA-4) (Artisan Controls P/N 438USA-4) $28.59 each.

Specs:

Time Range:2 - 2048s (0-34 minutes)
Timing Function: Delay-On-Make
Leaded Process Compatible:Yes
Supply Voltage Max: 288V
Supply Voltage Min: 19V
Output Current Rating: 1 Amp Inductive
RoHS Compliant: Yes


PDF Datasheet (http://www.artisancontrols.com/pdf/438usa-x.pdf)


In general this would work like a charm but sometimes the user has to turn the 2nd or 3rd stage off and on to get the CPUs to boot. Tossing in a manual switch after the final stage relay would be great for this as it'd let the user cut power when a desired evap temp is reached, boot the CPU and get it stable, then continue the pull down.
Yes I was unfamiliar with this procedure, but your addition would seem to be a simple solution.

Photo of Timer:

[august123]

It's much more comfortable to use temperature controllers to start each stage when temperature is low enough. And you have more safety, because Controllers turn off the lower stage when temperatures becomes too high.
Plus they give you full automatic start up, whole system starts when pushing one button :D You don`t have to plug in various plugs when you do a litte bit of wiring like mytekcontrols showed in first post.


The timers only once start the stage, but never stop it when something is wrong. Not the perfekt thing for multi-stage cascades i think :rolleyes:
And trusting in safety cut off devices is not the right way in this case. You should use at least two devices which give you safety.


For example, this controllers:

http://www.extremecooling.net/index/e107_files/public/1206549054_119_FT31681_dsc_4926.jpg

they display temperatures till -200°C and can switch load at progammed temperature. Like Dixel, but better & cheaper :D Uses PT-100 Sensors, which are quite cheap, too.
The perfect controller for our systems :D

[jinu117]

it also uses k-type, etc :) I've used them a lot on many builds. Also can program it so it cuts power off to other stages until previous stage is ready with additional relay :)
Nice things.

[[XC] gomeler]

Can we get some info on product numbers and manufacturers on those thermal displays/cutouts? Would save me half an hour searching through my product catalogs and possibly not finding it :up:

[Dualist]

We use something similar at work, they were made by Omron, can't remember the price though.

[august123]

called XMT7100, no special manufactor. I get mine from a guy here in germany.

[mytekcontrols]

It's much more comfortable to use temperature controllers to start each stage when temperature is low enough. And you have more safety, because Controllers turn off the lower stage when temperatures becomes too high.
You'll get no arguments from me. Safety should definitely come first.

I didn't see a price on the XMT7100 Display/Controller. However I did find these at: AutomationDirect.com (http://web1.automationdirect.com/adc/Home/Home), and they looked very reasonable for what you get.

SL4824-RR (http://web1.automationdirect.com/adc/Shopping/Catalog/Process_Controls/Temperature_-z-_Process_Controllers/1-z-32_DIN_Size_(SL4824_Series)/SL4824-RR)

SOLO (tm) dual-output process controller, 1/32 DIN, with two 3A SPST mechanical relays (one can be used as an alarm output). Universal inputs include T/C, RTD and analog (0-5V, 0-10V, 0-20mA, 4-20mA, 0-50mV), accepts 100-240 VAC operational power. PID, ON/OFF and manual control plus 64-segment Ramp/Soak profile, standard RS-485 communications (Modbus ASCII and RTU). Mounting clip included.

Although the 3 Amp contacts might fall a little short if you don't want to use an external relay (could parallel them for 6 Amps).

The Price is reasonable at $89.00

This one looks offers a bit higher amperage, and more relays:

SL4848-RR (http://web1.automationdirect.com/adc/Shopping/Catalog/Process_Controls/Temperature_-z-_Process_Controllers/1-z-16_DIN_Size_(SL4848_-z-_PM_-z-_TC_-z-_PC_Series)/SL4848-RR)

SOLO (tm) dual-output process controller, 1/16 DIN, with two 5A SPST mechanical relays and two 3A SPST alarm relays (with a shared common). Universal inputs include T/C, RTD and analog (0-5V, 0-10V, 0-20mA, 4-20mA, 0-50mV), accepts 100-240 VAC operational power. PID, ON/OFF and manual control plus 64-segment Ramp/Soak profile, standard RS-485 communications (Modbus ASCII and RTU). Mounting clips are included.

Price is $10 more: $99.00

Photos of SL4824-RR and SL4848-RR:

[august123]

You'll get no arguments from me. Safety should definitely come first.



As i said, two safety devices are better than one. I never said that temperature controller can recplace an pressure-cut off switch.

Price for XMT7100 Controller is about 60€, depending on amount.
It's right that they are not listed at electronic dealers. Some kind of OEM.

[n00b 0f l337]

PID's are great aren't they?
Still a bit pricey though in comparison to the price of builds though.

[august123]

hmm i don`t think that 100-200€ in an cascade for temperature controllers are too much. These builds are over 1500€, it`s peanuts in my optinion.

[mytekcontrols]

As i said, two safety devices are better than one. I never said that temperature controller can recplace an pressure-cut off switch.
Agreed! A purely electro-mechanical device should be your primary electrical cut-off, and in the case of a refrigeration system using high pressure gases, a PRV is also highly recommended.


Price for XMT7100 Controller is about 60€, depending on amount.
About $94.00 US Dollars. Pretty close in price to the controllers that I listed. How about the rating of the relay contacts, do you have any info on that?

Edit:

Still a bit pricey though in comparison to the price of builds though.
Hmmm... Yes and No. If you are building a unit for profit (to sell to someone else), then you just need to factor in the extra cost of materials and labor. After all, this is the way most businesses work. It also isn't safe from a personal liability standpoint not to make the system safe, and fool proof. This last part becomes even more important if you are not doing business under the protection of a corporation or LLC, especially if you have significant amount of personal assets.

Of course if your market wont support a higher price, then this does pose a problem (I for one would look for a market and/or product that does allow for this).

Building as a hobby does allow you to ignore some of this, but only if you can insure that you are the only one that is put at risk.

[n00b 0f l337]

Heh maybe over there, I charge less than that! ;)

[godmod]

No need for PIDs in our applications, unless you have a frequency inverter. But that would be sweet !

[A/\/\/\C]

Heres a great little device that has a potentiometer and a "NClosed , COMMON, NOpen" switch relay on it with a thermister it an be used for Single Stage or on each stage of a cascade
its powered by 12volts you can also hook this up to control a 12v to 120ac or 12v to 240ac switching relay
this thermostatic switching device is only £5.99 from maplins UK http://www.maplin.co.uk/Module.aspx?ModuleNo=220003&criteria=temprature&doy=7m4
http://homepage.ntlworld.com/roberts0n/maplins/maplins.jpg

it has other uses like i have one gaurding my watercooling setup should my graphics cards get too hot i lost 2 8800 gtx due to pump failure when i was out costing me £500 now with one of these sensing my GPU water block temps should there be a problem it shuts my pc down or you can use it to stop your pc powering up until your phase unit hits a certain temprature and also use it to shut your pc down should your single stage or cascade fail :)

[runmc]

nice find A/\/\C - now it's time for conversion

whoops that was for the cards - how much for the controller?

[A/\/\/\C]

£5.99GBP thats around 11.9380 USD for the controller

but i lost £500GBP thats 994.987 USD on two 8800gtx before i had one of these controllers

[killermiller]

Temperature Activated Switch Kit

Manufacturer: TR

• A universal temperature sensitive switch with adjustable sensitivity
• Single pole changeover relay rated at 24V 10A (not suitable for direct switching of mains voltages)
• Requires a 12V power supply

That thermoswitch is only rated for 240w. The only way I see useful would be to use this with a relay to the 120/240v. The relay would carry current for the mains which is accutated by the thermoswitch itself.

[A/\/\/\C]

That thermoswitch is only rated for 240w. The only way I see useful would be to use this with a relay to the 120/240v. The relay would carry current for the mains which is accutated by the thermoswitch itself.




hook this up to control a 12v to 120ac or 12v to 240ac switching relay


I already wrote that if you look at my post i put you can hook it up to a 240v switching relay obviously to handle a greater mains load using the switch to activate the relay :up:

[Xeon th MG Pony]

Or add a Optoisolated Traic and go right up to 400A @ 240

[killermiller]

I already wrote that if you look at my post i put you can hook it up to a 240v switching relay obviously to handle a greater mains load using the switch to activate the relay :up:

Whoops, I missed that. Good thinking.:)

[mytekcontrols]

Or add a Optoisolated Traic and go right up to 400A @ 240
What Kind of system are we talking about :eek: Something to cool an entire room full of PC's? (Wow what a Monster :D )

How about Crydom D4825 (http://www.surplussales.com/Relays/RESSPlug-1.html) (25 Amps @ 240 VAC) for $19 instead.