Ebac/DH unit for dummies

[JoshNZ]

I finally got some spare time to put the ebac DH unit up on the bench and have a look at it today. Looks old and neglected. I pulled all the panels off and cleaned everything out, figured out the wiring and fixed up anything looking not so good.

Anyway... The compressor is a danfoss sc21g. I have no idea what to expect of it in terms of performance, how quickly should the coils get cold? How evenly should they get cold with no air movement? How hot should the compressor get? How even should the temp be between the pair of coils?

I plugged it in and went inside for dinner, figured I'd check up on it a half hour later or so then sat down and got reading in the data sheet about cooling requirements of which I had zero, so I unplugged it. About 15 minutes running, I pretty much couldn't touch the compressor, must've been 60C/140F or so, is this normal?
The beginning of the RH coil was icing up, but none of the rest of it. The LH coil had no ice on it at all, but was cold to the touch. This seems quite bizarre to me as they appear to share a common supply. The only thing I could think was the thinner copper pipe was kinked on the LH coil but no such luck.

Is there anything I can do in terms of regassing myself, to give it a birthday? I would like to get a refrigerant expert to look at it but I doubt I could for months. A starting point would be great, regardless!



 

 

[YellowHammer]

I am not familiar with the Ebac but the compressor should not be scalding hot.  If it gets hot too many times, there is a risk of burning it up.     

There should be a sticker or something that tells the type of refrigerant used, as well as the weight to put in.  There may be a high and low pressure operating rating, if so you can use gauges for that.

Many of these small units require a weighed in charge, so pressure gauges won't help much, except to see if there is a leak.

The classic way to check these is to bleed the refrigerant and put in some nitrogen, and use gauges to see if the system holds pressure.

If so then weigh in the charge through the low pressure side.

There should be frost on the low pressure side, but no ice.

  

[JoshNZ]

It is r134a refrigerant, there are little kits with a gauge and 400g charge at auto store I might give that a go.

Will see if that improves the coil temps, I'd say the LH one is not going to be removing any water as it is now.

It seems I could sub in any old fridge/freezer compressor with the appropriate duty cycle if it did burn up? Nothing overly complex here, Silver solder joints?

[JoshNZ]

I got on the phone to a technician at a local refrigeration company and ended up chewing his ear for a while he was really good. He ended up offering to look at it and I picked it up 45min later, he'd leak tested and added another 800 grams of rf (out of 1300 full charge) all of both coils frosting up nicely now.

Me and my partner got busy painting the container today, didn't think it was possible but think we managed to make it look worse xD. Looks like it might have a nuclear reactor inside it.

Will fit out the header/fans and put a roof on it the next couple of days.



 

[YellowHammer]

That's good, an overheating compressor is a classic symptom of low freon charge.  Does the Ebac not have a low pressure cutoff?

Did he find any leaks?  Losing half the charge, even after a number of years, is not normal.  If he found the leak, all is well, if he didn't then it will de pressurize again even if it takes months.  So I would note exactly where the frost line on the coils stop, generally at a bulkhead or fitting, and if you see it ever move, then you will know it's losing refrigerant, even if its just a little bit, and can trace the leak before the unit loses efficiency.

Most small compressor units are very common, and when I burned out a unit, I was able to get a replacement compressor quite cheaply from Grainger.  

Yes, silver solder joints is fine, some people (manufacturers) use Silfloss, but it will degrade in the kiln environment over many years.  That's what happened in one of my kilns, all the Silfloss eventually evaporated and it seemed like every joint started leaking.  

I once tried putting UV tracer in a leaking unit, but it didn't work very well.  I even bought a freon detector but its wasn't a commercial unit so was a boat anchor.  The best I've used is still the classic old fashioned HVAC leak finder super bubble solution, which bubbles more than soap.  



 

[K-Guy]

The best I've used is still the classic fashioned HVAC leak finder super bubble solution, which bubbles more than soap.  

Sometimes the old ways are best. ;D

If you unit has silicon used for sealing it, it can cause false reads from leak detectors.

[JoshNZ]

He didn't find a leak, the only thing he could put it down to is the little schrader valves might've been weeping. Who knows what the last owner did with it and what's been happening while it sat for 15 years. Might run into trouble again will have to see

[K-Guy]

the little schrader valves might've been weeping

If he didn't replace them and recharge it, he should have. Over time the rubber/plastic can degrade and allow the leakage.

[YellowHammer]

That's what I was thinking.  I would think, hope anyway, that they were replaced, as most times a system is leak checked and recharged, the schraders are removed and replaced as a matter of routine.

[JoshNZ]

I've got the container looking pretty kilny. Has taken me a while, I've only had 20 min every now and then over the last week to work on it. After I clad it I'll be ready to put the DH unit in and start running wiring etc.

I suppose it's on the same topic so I won't start a new thread - I essentially want to end up being able to monitor and control the kiln remotely, I have a reasonable idea of how I'd do it but I'd be interested to hear how it's been done before? Which microcontroller/computer or anything off the shelf, which sensors hold up inside the kiln etc?

One thing that has me a bit stumped is the humidity sensors I find, accurate to +/-3% (is that any good?) Definitely not a wet/dry bulb setup inside the little module, do they work ok for a kiln?



 

 

[JoshNZ]

I've got the panels all back on the ebac unit, fans heaters and compressor all running together draw ~13A so I won't be able to run this thing off an extension cord to start with, will have to get trenching.

With everything running, the coils are still getting frosty. They got wet in the first few minutes then frosty, I don't know what defines icey/frosty, but they stayed white. I left it on for ten minutes or so, and no drops of water forming anywhere, just more frost.

Would this unit be tuned to run at an air temp of 100F or so? I can imagine that would make the difference to frost/water droplets? I'll trudge on but would be nice to know if I'm going to need to change something.
It seems if this were the case I would only run the heater/fans for day 1 until the kiln was up to temp then start the compressor. How long does a 20ft container take to come up to temp with ~3kW being pumped into it?

[YellowHammer]

Doesn't it have the copper pipes going into a section with heat exchanger fins that the moist kiln air is forced over?  Surely the kiln air doesn't just flow over the bare copper wires?  If it did, ir would be very inefficient.  

Typically, the bare copper line can stay frosty as long as the fin exchanger pack is no more than cool.  On my Nyle, the copper stays frosty until the fin pack, and then the fins are cool but not ice cold, to keep frost from forming in the fins.  The moist air flows through the finned exchanger, and condenses out into a drip pan and exits the kiln.  I've not seen an Ebac in detail, is this how it works?

I would doubt that these have reverser valves and a so don't have a defrost cycle.  The Nyle compressors won't turn on until 80F, but certainly 100F is in their sweet spot.  I would think, but don't know, the Ebac would be similar?  Did it come with some sort of owner service manual?  Something seems missing, I can't get my head around it.
 

Here are a a couple pics of my small kiln operating correctly after a recharge and compressor replacement.  You can see the frost line on the copper pipe, and see the water condensing on the cool fins.


 

 

The chamber should heat up within a day, anyway, I would expect with a full load.

[JoshNZ]

Thanks for the pic yellow hammer nope old-school here, just bare copper coils. I've got two ebac units (one given to me free as a parts donor in the deal) and in both units the evaporator is a length of say ~3/8" copper tube. Metred by a capillary tube. Maybe 20ft of tube per coil if you were to unroll it.

The condenser is certainly a finned heat exchanger.

There is no controlling circuitry in the unit. just a heater, fans and compressor all wired to a terminal block, I'll provide the controller circuitry outside of the kiln, it'll eventually go to a server based microcontroller board but to start with just a humidstat and thermostat.

Here is a photo of the donor unit, I haven't got one handy of the one I'm using but in essence exactly the same thing, different configuration.