The New Load Tester

[Gray Mole]

Before I start, I want to give a big shout out to Timo Minx and Froudeg for supplying the block and Housing for this. Was a great gift and I haven't been able to set it up until now. A few years later, but I never let it go. Thanks guys

So this is custom made for load testing. They had some made up with power supplies and resistors, and their setup was pretty cool. Froudeg was some kinda genius with the electronics and while my setup won't be nearly as cool, I'm hoping to get it pretty accurate.

The load testing system I have now is ok, and pretty accurate, but it's bulky and ugly.

The 'station' is ok, with the Power Meter and variable voltage, it's always been the block design that i hated. Awkward and just didn't look professional.

So some pics of where I'm at.


The housing...


The block with locations for resistor/heating element...



the mounting plate...


The base of the block is 1.5" and the face is reduced to 1.3" with a location for the K probe, drilled right to the center of the mass.

The base has a location that will currently fit an 5/16" (8mm) bore, 1.5" (40mm) length load resistor or heating element (same difference)

That plate is an old backplate from a Kayl mount so thanks to you too Kayl! I didn't have to touch it, it's the ideal size square cutout for this setup.

I just had to measure and drill the holes to bolt the plate down, and I countersunk the holes so that the screws are just under flush.



Once I have a heater to stick in there, I'm good to go. I'll be using expanding foam for the fill behind, along with some fine tuning of the plate.

I need to grind just a tiny bit off the plate so that it has enough clearance for some foam tape to insulate from the heater block. that way it should give as true a reading on heatload as it can.

Before it was just the housing and block but now that I finally got around to making the plate work, I'm pretty stoked to give it a try.

Just need to make a couple calls tomorrow, I've been reading the catalogues for a few suppliers, but the variety is way too huge. Besides, ideally it'd be great to find a copper or brass style of element if I can. If I can match the size, or go to a very slight interference fit, I should be able to get the best heat transfer I can with minimal need for paste.


Otherwise I'll fit something in that's very close to size, and use a thermal epoxy. Not as good, but I'll do what I need.

As long as I can get it well insulated so the heat can only go to the evaporator it should get me the accuracy I'm hoping for.

I'll run a K probe on the face where it is, and I'm going to run 2 more, one on the resistor, and one on the rear of the block as well. Bit more infomation on heat and where it's going.


I'm going to see if I can find a decent control, or even just a heat sensor and relay to cut the tester off if it's over 70c or so. I think that should do, though I don't know what the plastic is so I may go slightly lower.

At least then it'll be safer against failure in cooling, or if it's left on after testing.

Just a few little things, and it'll be ready to roll. Just need to find something in a 200w or better rated, 20 to 25 ohm (or close) resistor of the right size.



Oh, that's the variable power and power meter station I made up, works pretty well, and goes up to around 400w at the moment. Hoping work it to 600w max when I'm done. We'll see what resistor I can find

So that's the project, hope I can find that last thing soon. The test block I have now works really well, but this should give me a bit more data when I'm testing, and let me do even more with respect to tuning, and assessing evap effectiveness.


Gray

[Gray Mole]

So I know what I should need to fit and do the load I'm after.

Turns out a company named 'Watlow' makes heat cartridges (probably common knowledge, but I don't buy them very often) and there's an 8mm version that this was probably designed for.

So if I get a 500w one in the 8mm x 35mm package (I think that's the size this one comes in) then with the reduction in the Dimmer I'm using, should net around 400w again on the tester.

Anyone know a company stocks Watlow? Can't seem to spot one yet, and they say 3 weeks to order one custom :p


Gray

[wdrzal]

You can start here:

http://www.chromalox.com/productcata...ils.aspx?p=241

DetroitAC had a nice heater for his load tester. Either search for the thread or pm him he may have a extra one sitting around.

[Gray Mole]

Sweet, thanks Walt

I'll shoot a PM over and see if he's still around. Haven't seen him for ages.

Looking through that site now, see if they stock anything that'll fit.

I can bore it out to a 3/8 if I have to, but the 8mm size on the Watlow's was right for length, so I'm hoping to get one that's a decent match.

[wdrzal]

Some of those heaters @ cromolox come in and out of stock as production runs start and stop. I'll look in the catalog or you can call chromolox. They are worldwide but HQ is based close to me ,Pittsburg,Pa.

A quick first look didn't see any 5/16" or even a 3/8"x1.5" @120v/400watt.

I'll look around over the holiday.

[Gray Mole]

Wow, my eyes are bleeding.

Wish now I could find these that are rated for 48v or something, since I can easily run them cold at higher than rated wattages, but whatever.

http://www.omega.ca/shop/pptsc.asp?r...D=CSS_CSH&Nav=

Best price I've found so far, though I'd be looking at drilling and installing 3 if I want the wattage I'm after.

Size is tough. To stay at 1.5" or less, you can't get the wattage. The block and housing are small.

Unless I can email and request something, and of course pay double for custom, I'll have to think about options here.

They seem pretty reasonable though. Still ends up at 75 bucks for 3 cartridges, but that would be 600w at 120v.

So working out the math, it's 120v and 600w total.

My power meter is reading 116v, but I'll estimate for 115v.

So 115 should give 575w

my original tester gave 520w with full wall voltage, but only gives 400w with the dimmer. Dimmers 'steal' voltage from the start, at least every one I've used. It's why Variacs are better, but Dimmers are about 1/10 the price unless you're really lucky.

So, that's roughly 440w max load using the 3 cartridges with the variable station.

Unfortunately it's either 200w carts, or 150w carts if I use these guys, since that's what they sell, and the 150's are only 1 dollar less each, so not a lot of reason for dropping that.

If it's 3 x 150w carts for 450w total, I get 435w at 115v, blah blah blah ending up with 330w max with the station.

I only save 3 bucks. I do like having the 400+ max wattage for testing.

Edit, just checked. Same price.

So I have room to drill to 3/8", and room to use 3 carts.

Looks like an expensive hit, but I do like the tester.

Thinking about the mod on it, it'll decrease the mass of the copper and replace it with faster heatup and cooldown on load testing, which would be pretty nice.

So that's that I guess, unless I get lucky and I can find 'em cheap or fast somehow, I'll be looking at ordering them. Site says a week to order, not in stock, but at least they're available.

Now I remember why I hadn't bought the cartridges before 100 bucks by the time I pay the shipping, but at least I'll have a nicer tester and still be able to do the range I want.

Edit again.

If I get a Variac, I can probably use just 2 carts and get the wattage I want. Variacs usually push the volts to 140v (at least what I've seen) but I can't see one for 2-3 amps under a hundred bucks anyways. So I can't see any real benefit there, other than getting a bit smoother curve on the station, but with a Variac being pretty gigantic, I'm not that inclined.


Gray

[Gray Mole]

Some of those heaters @ cromolox come in and out of stock as production runs start and stop. I'll look in the catalog or you can call chromolox. They are worldwide but HQ is based close to me ,Pittsburg,Pa.

A quick first look didn't see any 5/16" or even a 3/8"x1.5" @120v/400watt.

I'll look around over the holiday.

Cheers Walt, if you can find anything more ideal it'd be great!

I'm noticing the length is going to limit the wattage, and I noticed the the RS UK site was the same. The Omega site actually has a few more choices in the 1.5" stuff. That's my limit, and I'll still be doing a bit of playing to make that a nice fit. Not sure what the length of the part that sticks out (unheated portion) but I'll make it work.

the block is 1.5" exactly in the base area so the heater'll be a perfect fit on the heated portion of it.

Nothing over 200w in 1.5" length at all.

I think I could 'get' one if I start calling, but it'd be custom, take a month or 2, and cost more than the 3 standard ones I think (unless I sleep with the rep, and he's probably not pretty)

So thanks been a huge help

Wouldn't have found the links so easy without you

[wdrzal]

Nothing over 200w in 1.5" length at all.

Yep two 1/4" x 1.5" 200 watt would work but I know your trying not to drill it full of holes.


400 watt is a high energy density for 1.5"

A variac will provide you with 140 volt so they will be a bit more than rated with the variac.

240 volt is a option but I would try to stay @ 140 volt.

That came from Europe????? so it's probably a standard metric size. Re-drilling with a bit wouldn't give the best fit. Just guessing but probably done on a mill.

[Gray Mole]

Yep two 1/4" x 1.5" 200 watt would work but I know your trying not to drill it full of holes.


400 watt is a high energy density for 1.5"

A variac will provide you with 140 volt so they will be a bit more than rated with the variac.

240 volt is a option but I would try to stay @ 140 volt.

That came from Europe????? so it's probably a standard metric size. Re-drilling with a bit wouldn't give the best fit. Just guessing but probably done on a mill.

yeah, well it'll be pretty thin when i'm done if I up it to 3/8" x 3

Oh yeah, it was made there, so using the 240v and probably a 200 or 300w cartridge with a variac was more than enough back then.

But if I could do the 1/4's on the sides and up to 3/8 on the middle one, that's cool too.

I have a drill press here, just have to take it real slow and up the sizes very gradually. Sucks though, copper is a pain to drill nice. If I take a few hours to work up to the size, should end up with a fairly true hole.

I don't know if I saw the 1/4 in a 150w that wasn't 240v, but if you were looking as the CIR ones, then maybe it was there.

Just those were 40 to 50 dollars each, and if I'm stuck at using 3 total to get what I need, then it's just as good to get the 3 and mod this block.

I'd really like to drill .01 undersize give or take, and have to heat the block to press them in (minimal force of course) and use a thermal paste as a 'lubricant' of sorts.

I think if I could get a mild interference fit, the heat transfer would be just about perfect. Don't want much, hate to crack the cartridge, but it looks like a metal casing so i don't know if there's a ceramic in there to damage or not.

Will have to look, but it's late and I can't see that well now after reading the 'fine print'

Hard work, was hoping to find local suppliers too but this is a bit different, and it seems like most of the shops here don't do 'different' at all.

Can't even find a PT1000 probe local. PITA.

I guess as long as I get a relatively snug pushfit it's ok, and the option of thermal epoxy is there, though i'd rather not if I can help it, be nice to be able to swap them out if one breaks.

Bit crazy though, all this work and I already have a tester that works.

I just hate the look of it, and the fact that the alu resistor casings are built for heatsinking and it's hard to say if 100% of the heat is going to the tester. I insulated mine pretty well, but they have losses and I'd like to be a lot more sure of the load. this should be well over 99% by the time it's insulated, since the entire surface will have solid copper transfer. The thinner areas may leak a bit, but insulated and sealed, I'm hoping to see a more accurate unit.

But I've got this one until I get the new one done, so it's all good

Hey Walt, I know why I'm still up but don't you ever sleep?

[wdrzal]

I may take a nap every third or fourth day......Just waiting for the sun to come up.

There's some in the catalog that I didn't see on the net like 3/8"x1.5" 250watt @120 volt. I look tomorrow.

I think Omega is expensive.

[wdrzal]

To assemble throw the Cartridge in the freezer and heat the copper block. A tight fit is most important. You can sleeve a smaller size to a larger with no penality since you'll be using the cartridge in "steady state".

[Buckeye]

Hey Gary check out this thread
http://www.xtremesystems.org/forums/...t=99979&page=4

Ron and I used two 200watt cartridges for ours and we have a thermostat to protect it in case it over heats.

I would really have to dig up info on these parts as its been awhile that we built these things.

[wdrzal]

^^^^^^^ Forgot about those, Real nice,I think the thermal protection in mandatory with all the melted blocks we seen over the years.

[Gray Mole]

Perfect guys thanks

I actually have a few of those here, I'll have a look at the size but as with most of the things I've been doing lately, this housing is small and space is an issue.

I also have some of the heat sensor cutouts that the old Prometeia units had on the discharge line, and I know they'd fit (would have to run a relay for those) but I need to see if anything I have here will work.

Can always pick on up in a heat range that'll work.

It's all going to be 'in the new year' now though, not much action is going to happen on new year's weekend.

Appreciate all the feedback. Got a full plan now, should have the load test 'upgrade' done pretty soon


Gray