Ever wondered why cascades are so expensive.? Here's the breakdown.

[Dualist]

Hi guys,

Thought I'd give a bit of a write up on what makes up a cascade, what is needed to build, how much the parts are and what tooling is needed, as I've been pm'd loads about the subject so I'd thought I'd write it all here.

This is in no way a 'how to' follow step for step build, just a pricing up of an outlay to build for yourself, you still need to learn the basics of phase building via single stage systems, it's just to give you an insight on what is required to go further. You still have to do some maths and research here.

I and Benchtec.co.uk have no legal liabilty for you attempting this hobby and killing yourself, that is why there are no figures or specs mentioned for a finished unit.

Well legal crap out of the way and as you see below is the schematic of my old cascade, two old reciplicating compressors so nice and quiet.



So costs on the parts...

At the time of writing I'm working on a exchange rate of 1 GBP = 1.22778 EURO.
Sites I'm using for costings are...
http://www.kaeltetechnik-shop.at/
http://www.bes.co.uk/products/085a.asp

First stage..

Starting at the top is the first stage compressor, what ever you can pick up but remember this is the heart of the system so needs to be strong, depending on what temps you wish to achieve you really need to head towards the 13cc+ mark (rotary, 18cc+ recip). You can get these on Ebay cheap or buy new from Patrick still cheap for new but don't buy new from UK suppliers as refrigeration prices here are just nuts. So head for a 18cc recip and your looking at about £160... But if you want to go mental the get a 36cc rotary for... £202.

Condensors, you need to size this up with the best compressor you can afford and what load will be required on your unit. Luve are the smallest most effiecient condensors out there and come with motors and fans. Riva are good old skool condensors but you still need to buy a shroud, motor and fan. Luve prices.. 1kw... £67.52 2kw... £87... 3kw £141.75.

You'll need a reciever just as a liquid buffer on the high stage, doesn't need to be large, you can get these for about £20.

Sight glass, not really needed but when charging the system you just look and see when the system is full and that is it.... £11.80.

1/4" filter dryer, chunky and cheap, nowt fancy here. You can get these for ... £8.55.

Thermal Expansion Valve or TEV, best bet is an external equalising with an orifice within the working range of the system (what size is your condenser.?)....£44.79.. orifice.. £10.67.

Heat Exchangers. Best bet is ebay, plate heat exchangers are the best but make sure they are brazed not soft soldered as it needs to work in pressures of 300psi+ just as a safety margin. You can pick these up for £25-45 so shop around.

Second stage...

Well lets start off with the compressor, this needs to be either smaller or tha same size as your first stage compressor. So as before prices of what you can aquire.

After this you need your safety devices, a must have if you don't then you get what you desearve and please do not build for anyone else. You need a pressure cut off switch and also a pressure relief valve, cut off to kill the compressor and relief to let off any escalating pressure in the second stage. I'd rather have a flammable gas leak a little at high pressure than a second stage blow off an oil seperator or compressor at 500psi with the same flammable gas..!! Danfoss cut off £31.43.... relief valve plus adapter £15.63.

Oil seperators, I use Castel 5540's as they are large and have a floating valve and are huge ..!! Have a large working range too so you need nothing else. £69.12.

Depending on you capacity of your cascade (ie. watts) you may either need a small condensor or a copper coil for sub cooling here, small condensor (ND50F) is... £23.60.

This then enters the plate HX and then exits to the copper spun filter drier (20g.?) into a capillery tube. These filter driers are about £1.50 from Patrick (or RPW) but I've had my local refigeration engineer try to charge me £15+vat each for them.

Capillairy tube then of your tuned length enters your evap. You're on your own here, you can buy pre-made or make your own evap so I'll leave it at that. Evaps in kit form are about £30 plus enclosure. You can get suction line made up with evaps but quality is random between builders so go to guys recommended and expect to pay for a complete line for about £130-140.

Suction lines really need to be made of 3/8" stainless steel braided line. You can get a 4ft line with 10mm ends all tig welded up for you from Pirtek for about £70. Make sure that when you speak to them it can handle -200c @ 600psi minimum.! It should be hydraulic spec in the temperature range so should be able to handle 4000psi. Yes it's a specialist line.

Expansion tank, these are a must have, makes the whole start up pressure a big none event. Static pressures can be less than 100 psi and working will be around 200-250psi. It basically removes the shock at start up, so if you build for someone else there is no worry. You can use recivers as they are tested to 400psi+ working pressures, again about £20.

Odds and sods... If you want to get fancy then you can add guages on the high and low side of each stage so you can see what is happening at any time. The best guages I've found are Wigwam ML60/18C4FA/A8 and ML60/38C4FA/A8, both liquid damped and are £17.01 each.

Well you've now sourced you main parts so you thing you're nearly there, thing again, you're not even half way yet.!

You need copper tube, 1/4" a whole reel should sort you, about £18 from BES. Suction side of things 3/8" is good, not use a lot but more for your next build about £35. Capillary, I've got a sit load of 0.7mm great for small compressors or linking to guages but no good for rotaries, you'll need 0.9mm. Copper isn't cheap... £35.82.

One other thing Service Ports.! You'll need some 1/4" ISO shrader valves in the system so you can add the refigerant (always helps) these are £2.36 each.

Fittings, these are the main thing that catches you out. A small 1/4" equal tee will cost you about £2..!! And you'll use loads, joiners, tee's and adapters all mental money when you add it up, easy £50 plus per build then you need also flare nuts these are brass and will cost you about £50 per build too. Also you need to machine up some brass fittings for the oil seperator and the plate HX. Check out BES for best prices.

Hopefully that has covered all the build requirements for you. Now the tools..!!

Tools..

You need a set off manifold guages, Refco are the standard requirment. You can pick these up at about £60-70 with short charging lines. You can get extra lines but I recommend you get some ball valves for each line so you can vacuum your line set before you apply them to your system. Ball valves are about £10 a piece.

Tube cutters, large and small are always a help, pay £3-12 for these.

Tube benders, a good set of pipe benders that will do 1/4" to 3/8" or more, better sets will do 180degree bends. £10-25.

A good MAPP torch, MAPP heats really quick and has a swirl tip. Normally you go for around £40-50, extra gas is about £10.

I use only 55% silver rods now as it brazes all but you need silfow flux but the braze is strong and covers a range of mixed metals. Expect to pay about £2+ a rod. Flux leave it with me trying to find.

Flaring tools. You'll need a flaring tool either a cheap one from Halfords or a pukka refrigeration kit for £59.42.

Vacuum pumps. Now you can get getto on this and have a couple of rotaries working for you but I prefer not to. As a good small vacuum pump will cost you about £125+. Remember when you vacuum you will be running the pump for atleast nine hours per stage to get all the moister out.

Gases. Here's the biggie.

For purging you can either use small mig weld bottles of Argon and a guage to purge while brazing. I've used this and it's a beautiful clean finish in side the braze. Or you can use Nitrogen, you will need Nitrogen anyway to pressure test your system later on after you've completed brazing. You can pick up a small bottle from with guage for £150 but output pressure form that guage is only 2bar no good for pressure testing. I've just got a full size bottle off Ebay for £5.50.! But still need a pukka guage for it, a proper guage with an outlet pressure of 28 bar is £160+vat at cost (£224 + vat retail). You need to be able to pressure test at 300psi to make sure you've had no leaks.

Gases for charging the first stage..

You need to work out what gas you are going to use and what working temps it's going to be used in. Check out Toms guide on 'cool pak'.... for more info.
First stage gas on a cascade are normally R404, R507 or R290. Depending on budget or able to get your hands on. R404 is freely avaiable on Ebay at about £100 for 10kgs, R507 is anly available from BOC or some other gas suppliers but will need to know what you're up to and need a business account but you're looking at £96 +vat +bottle rental. R290 is pure propane, sort out your own regulator.
For R507 and R404 should be 1/4" SAE but if not then adapters are available from BES for about £20 but no regulators are needed.

Second stage gasses...

This depends on what you can get, Ethylene (R1150) is the gas of choice, mixed with a dash of R290 as an oil carrier. It also depends on the working range the system i tuned for. R1150 regulators are £124+vat at cost (£224 retail). R1150 is about £184 +vat +bottle rental.

As R1150 is extreamly hard to get hold off, then it's possible your cascade could be a CO2 cascade. With working temps of a max -78C you can use CO2 in the second stage. There is a danger though of dry ice forming in the suction line but tuning can make it work flawlessly

And I've not even mentioned cases, controllers or electrics yet..!!

Well now get your calculator out and see how much it all adds upto. Building one for yourself is at a mental cost but you can pay for stuff at your own pace and get the immense satisfaction of creating something of your own.... and also a shit load of stuff left over (tools, gas and copper) so you can build some more for a far less cost But spare a thought for the poor builder who has to size everything up so it all works right and together.

But builds are all about time aswell, if this was a commercial thing then just think you're be paying for a good nine hours vacuum time per stage, 18hrs @ £30ish = £540. In the end if you build for someone else there is nothing really in it for you except the pleasure of doing it so be patient or cough up, heh heh

A big thanks to unkle Tom for putting up with me and sharing the knowledge in the wonderful world of cascades, ta dude I owe you a shit load of favours

Dave.

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Edit..
As requested I've added up a build cost.......

Simple recip cascade like in the above schematic (as this is in my living room atm and just hums along while watching telly benching, he he)..

Danfoss 18cc Compressor.... £160.
Condensor (Riva) inc fan... £62.
Reciever... £20.
Sight glass... £11.80.
Filter dryer... £8.55.
TEV... £44.79.
Orifice... £10.67.
Plate HX... £36.
Danfoss 11cc Compressor.... £84.
Cut-off... £31.43
Relief and adapter... £15.63.
Oil seperator... £69.12.
Small condensor... £23.60
240v fan for above... £7.50.
Spun filter dryer...£1.50.
Complete suction line... £140.
3ltr expansion tank... £28.97.
One 15mtr reel of 1/4" copper pipe... £17.55.
One 15mtr reel of 3/8" copper tube... £30.39.
One reel of 0.7mm capillary tube... £32.64.
4x 1/4" tees... £8.00
2x 3/8" tees... £4.00
4x service ports... £9.44
5x 1/4" flare nuts... £2.80.
2x 3/8" flare nuts... £1.64
1x 1/2" flare nut... £1.07.
Compressors don't come with caps or relays so £35 for each compressor... £70.
1x real of 2.5mm three core, good for lots of amps... £30.
Dixel controller... £56.
4x guages... £68.04.
2x Themal probes... £14.
Random stab in the dark at about £100 for a case but more than likely a lot more.

Total.... 1201.13. JUST FOR PARTS..!!!!!!!
(and that doesn't include the shipping of parts to my gaff either....)


Building time though, that is a toughie.
But if your on it then I guess, you've got to take into account time machining brass adapters for the oil sep and also the plate HX as they are never right, 3hours there. Also brackets and stuff to make aswell.

But to build I guess you are looking at about 3-4 days (for a nice laid out build, planning takes time), then 1 day vacuuming both stages and charging the first if you really like working late (19hrs in that), then another charging and tuning the second stage. But charging and tuning may take a hell of a lot longer on a new spec'd build as everytime you want to alter the cap tube length you have to reclaim the gas, cut the cap tube and ditch the old filter drier for a new one with the newly shorted cap tube, re-braze and purge, and again vacuum but for only an hour or so this time then re-gas.
So call it six 10hr days (sorry no overtime rate).

60hrs @ £30+ = £1800..!!! If you got it done commercially. So that's a lot of love for your hobby.!

Then there is a percentage of gasses to pay for and maybe a couple of quid to help towards tools... mapp gas... silver rods...

[4Qman]

I brushed over it but it looks to be spot on mate. Some good info

[piotres]

so total cost is ?

even 2.0 kw condensor is still too small for powerful cascade ...for rotaries IMO 3.0kw is min.

Regards
Peter

[Dualist]

Ta Dave.

Hi Peter, thread wasn't set up to be a 'be all and end all' cost or even an order form dude. Just letting guys realise that when they work out their power requirements then they can work out the costs. And then realize what we as builders have have to go through to create what customers want.

Have you ever had a guy pm you asking for a cascade for £300 as there isn't that much to it.?

BTW, are your condensers Rivas.? Or another make.?

[Raja]

Add a total parts cost and projected labour charge to the bottom of the post and it'll make people think. I paid a lot of money for all 3 of my cascades - fully undertsanding the costs and effort that go into making them.

regards
Raja

[Pjalchemist]

Originally Posted by Dualist

Have you ever had a guy pm you asking for a cascade for £300 as there isn't that much to it.?

Least weekly people asking that. I can now send them to this topic and say read and weep! It's not just the parts or tools needed but it's the work load that goes into one i feel where the price really is justified! Peters units are amazing. I've never seen so manny cascades from one builder! Each one is different everytime! Same goes for Bazx.

Nice topic dude, really does highlight some important facts there than a lot of people do not know of or awear of at all what so ever!

[Dualist]

Thanks Raja and Pete, will total a mid-low range two stager price later tonight.

[Pjalchemist]

Infact Dualist may i quote your post and use it on Aqua PC's forum? I shall make not of full creditation to you

[Dualist]

Just updated the first post with a price just for parts and a realistic labour time too.
Enjoy.

Originally Posted by Pjalchemist

Infact Dualist may i quote your post and use it on Aqua PC's forum? I shall make not of full creditation to you

So long as you give me credit and possibly source link to this thread Pete then no problem at all mate.

[vento1]

Great thread Dave.
Having never built anything more chalenging than a triple decker cheese and piccalilli sandwich this has openend my eyes to how complex and expensive a cascade is.

[Pjalchemist]

Originally Posted by Dualist

So long as you give me credit and possibly source link to this thread Pete then no problem at all mate.

http://forum.aqua-pcs.co.uk/showthre...ted=1#post1545

If thats not okay then please let me know!

Thanks!

[Dualist]

Pete, that is more than perfect mate, thanks.!

[Raja]

That is an excellent breakdown. Too many folks out there nowadays that want everything for nothing.

regards
Raja

[Bustah]

Originally Posted by vento1

Having never built anything more chalenging than a triple decker cheese and piccalilli sandwich

That sounds complex enough let alone a cascade,

I can make beans on toast though.

[skull]

This is excellent, but you still haven't put me off getting one. Just need to save up first! Thanks Dualist. This helps clarify the workings of the Cascade, to some degree.