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Tayters
19-04-2011, 10:58 PM
This particular pack runs all the chilled units in a department store restaurant. Loads of small fridges, butter wells, drinks coolers some turned off overnight. The pack (Hussman Enviropak) has 4 compressors, 2 cond. fans. A while back the main coldroom was taken off the system. I believe the last contractor (4+ years ago) had problems with oil return and apparently had to pump a fair bit of oil in. Elm themselves replaced the controller a couple of years ago. 1 cond. fan is wired from the NO terminal, not NC so it always runs.

Problem is (apart from leaks springing up every few weeks) the pack set up. Transducers appear to read absolute pressure and throughout the range they can be up to 5-8psi out, the setpoint is the default one (0.68bar) as are pretty much all but one of the settings. This means no compressor stages (each step shows all comps on), steps used is default (8), cond. fans set for 8 etc.. End result comps run and cycle on the LP switches.

So the transducers need calibrating, found the info for that on the elm data sheet, seems straightforward.
Pack needs re-commissioning for a HT system which is the bit I'm not too sure on.
Settings wise then I'd go for 3.5barg setpoint (R404A so -9*C), what dif and skip would be best?
Steps used would be 4 but how would the stages go? Logic says stage 1: 10000000, stage 2: 11000000 stage 3 :11100000 stage 4: 11110000. All the other stages set to 0 and then equalise the runtimes from the dip switch to spead it around the comps.
Likewise would the default cond. fan diff and skip be sufficient?
Last but not least what does Sticky Fans mean?

The pack seems to make its current setpoint quite easily (thankfully the LP switches are there) so making it higher would cause it to short cycle big stylee. This makes me wonder if the setpoint is low to help with previous oil return problems and fan was rewired to keep HP lower. Although the oil sep shows no oil in the lower sight glass, comp oil solenoids energise as required and I've never seen any out on oil faults. Yet.

Would be grateful for any Elm/Enviropack buffs out there who could advise bearing in mind the packs checkered history.


Many thanks,
Andy.<O:p</O:p
<O:p

Tayters
26-04-2011, 07:59 PM
Well I've programmed it according to Andylogic and all systems go.

In the words of Wilton Knight "Don't turn away in fear. One man can make a difference...."

Sticky Fans - never did find that one out.

Cheers,
Andy.

fowlie
27-04-2011, 06:58 PM
i think sticky fans was you could nominate say fan number one as sticky fan and that would mean it would always be first on and last off which would help maintain a constant head pressure and stop short cycling of fans.The stages part is spot on and the target set-point is up to you but the elm default setting ushally are quite close to what you need.

Tayters
27-04-2011, 09:39 PM
Hi Fowlie,

Thanks for the reply, the default settings for most things seem to work well as you say.

As no probe offset/span was configured the transducers were reading roughly absolute pressure. So a setpoint of 0.68bar meant into the realms of vacuum hence cycling on the LP switches. Because no stages were configured all 8 relays came on together. Only 4 compressors there so on they all go together and the main breaker in the store would trip. Took me ages to find it. 1 fan was wired on the NO contact so that never ran and the other ran constantly.

Sticky fans was later described to me for when there is a bank of fans and they come on in pairs. Your explanation makes more sense though.

All Elm technical support comes from Radford now. Although they tried their best, all they could really do was read through the documents they had on file so I never spoke to anyone who knew Elm stuff inside out. No matter, they sent me the info which cheered the wife up if you know what I mean.

Cheers,
Andy.

Silhouette
09-05-2011, 02:45 PM
Sticky fans is as advised earlier - nominate a fan to be first on and last off.
If you need any info I have most of the Elm documents in PDF format.

Tayters
09-05-2011, 09:19 PM
Hi Silhouette,

Thanks for the confirmation. If there's any info I can't get then I'll bear you in mind,
Not done loads of work on packs but it struck me early on it's all in the controls, and if it's a Hauser pack in Lidl then a command on the German lingo helps as well!

All the best,

Andy.