Can someone point what's wrong

Attached, you will find a schematic of something my apprentices did some weeks ago.
This was a part of a bigger project with a lot of other regulating devices in the synoptic panel.
The 3 Eliwells (220VAC supply) are each connected to solenoid valves. There commons are linked together and switched off by the defrost clock. On the on/off switch (DPDT), they had connected the supply to the Eliwell and the supply to a small fan.
The compressor shuts off in pump down.
Defrosting was done with one channel digital clock (ventilated defrost, room temperatures +/- 2°C)
Something very strange happened when there a defrost started .
What?
They searched almost two hours to locate the problem thinking that those who had layed the multicables (this was not done by us) to the different devices (sometimes far awy) had switched the connections, that they even had switched the cables (numbers on the cables fault?), lose connections, wrong supply voltage ....
They called me and als i didn't saw the fault just after one of them said something - on the 1st hand very stupid - which was the origin of the problem.
What?
See it as a sort of a technical riddle.

hi daliti
The compressor would stop on temperature satisfied/ pump down but not on defrost.Or the feed to the controllers/fans was switched when the single channel defrost timer changed over
is it a parallel circuit shown?.
regards mark:)

hi daliti,

the sketch is ok. if the main switch to the controlers and fans is part of the defrost timer, then the fans will stop working in defrost cycle!

chemi

No no,... the switches makes no part of the defrost timer.
The only contact opens whereby the common of only the solenoid valves are de-energized. The fans keeps turning.

daliti,
the sketch is ok , maybe there is something elsa missing from your question?

chemi

Hi Daliti:)
just goes to show you shouldn't switch neutrals as it adds to the confusion:confused:
If you use a separte neutral the circuit might just work.
Kind Regards. Andy:D :D

Hi,
I forgot to say that the supply comes from a 3 x 380 V +N circuit. We also still have 3 x 220 V +N in Belgium.
The only reason the technician did this was that with this one contact, we can switch off all the SV's at once and we don't need an aux. relay. Switching off the common is a common practice i've seen in US made installations (for example Liebert computer room controllers)
But this is really simple schematic and there can't be that lot of confusion.

Hi Daliti:)
well put it another way I would consider switching the neutral or common as poor practice, which will eventually see the culprit come un-stuck or some poor sod comming after him. Me I don't switch commons/neutrals, the same as I don't purge air from fridge systems, others can do as they see fit:( :o
You could also be having a partial suply voltage from the coil of the eliwell controllers, dependant on what internal protection they have to prevent this.
Safer wire in a relay or contactor to drop the suply voltage to the solinoides (tru a n/c contact)
Kind Regards. Andy:)

Well, I'm curious. I don't see anything beyond what Andy points out as problematic. Oh, the switch apears to be dpst not dpdt... anything there? It should work unless the diagram is actually wrong regarding the internals of the Eliwell.

I'm not sure what the function is of the top switches. Are these manual switches? Are they ganged together? Why not use one DPDT switch with eliwells on one pole and fans on the other? If one of the eliwells isn't getting power from its switch and the others are, then everything would backfeed through that eliwell.

Quote:

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Originally posted by Gary
I'm not sure what the function is of the top switches. Are these manual switches? Are they ganged together? Why not use one DPDT switch with eliwells on one pole and fans on the other? If one of the eliwells isn't getting power from its switch and the others are, then everything would backfeed through that eliwell.

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Manual switches on the synoptic panel, and they are ganged t
together. You pointed the problem Gary.

:) so peter what happened on defrost:confused: :eek:

The only problem I can see with this set up is that 3 evaporators are controlled by one single channel defrost timer. Assuming that the evaps are in different rooms this would not work very well and may affect pull down times. No matter what the state of each coil they will be forced into a defrost by the time clock. with a room temp of +/- 2C defrosts would be few and far between.

Quote:

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Originally posted by frank
The only problem I can see with this set up is that 3 evaporators are controlled by one single channel defrost timer. Assuming that the evaps are in different rooms this would not work very well and may affect pull down times. No matter what the state of each coil they will be forced into a defrost by the time clock. with a room temp of +/- 2C defrosts would be few and far between.

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This installation was placed in a (sorry if the word is not correct) hawking van. In Belgium, each city has on one day in the week a market where the fishmonger, the butcher, the cheesemonger ..., sells his wares in a big trailer (counters +/- 36 ft long ans some cold stores cabinets) They only sell from 07:00 till 13:00. Afterwards, they empty the counter and the stock in the cold stores at home. So defrosting is in most cases not really necessary.
In fact, those trailers are made of PU/wood panels with +/- 1 inch PU foam, so not that well insulated. We have to install +/- 200 W/m³ (normally 75 W/m³) to achieve the desired temperatures during summer operations whe nthe sun heats the panels. So pull down time is not that important.
We also must defrost the cold rooms at the same time -mostly before the market starts and after the end of the market when riding back home when the trailer is closed - because we can't defrost while selling the goods because we had to mutch trouble defrosting when there are unannounced controls of the public health services. Some of them don't understand that the temperature rises while defrosting.

Ditto with Markfiddy. Did we burn up some Eliwell's or did we fail to de-energize the solenoids?

As i replied to some, we changed the schematic. The defrost contact --> Aux. relay --> 3 contacts of Aux. Rel. switching off the live of each SV. I don't see - but I can be wrong - that there could have been a problem with overvoltage on the Eliwells because they are cut off on the live line.

I will give you the story what happened as already posted to those some who responded.
After the installation, our client called us some days later that he was unable to shut down his rooms for cleaning. A technician went to him and everything worked fine while the client was with him.
The other day, same story: now the technician checked if there were perhaps lose connections, or a short circuit in one of the switches. But again, everything was normal again when he arrived. Hee could switch off all the cold rooms.
3rd intervention with a rather strange explanation of the client" I think I found something which can maybe help. If I shut down the 1st switch, then the thermostat remains on, even with the switch in the off position. If I let the 1st in the off position and shut down the 2nd, both thermostats remains on, even with both switches in the off position. But... if I switch off the 3rd, then all the 3 shuts off at once. Putting them on one by one is no problem but you can't switch them off without switching all 3 of them."
I thought he was joking because I hadn't the schematic in front of me. Due to lot of work, the hand made schematic was even not ready to be drawn as build. I called two other technicians in the office, one of them had helped with the installation while the 1st one was searching at the client for the cause (where everything was again all normal)
One of them said: 'Hey, the 3 SV are fitted in a star point and when we defrost, we lose the connection with the common and the common gets floating (I don't know the exact English translation)
I didn't believe him 1st but anyhow, I called the technician on his mobile and asked him to set a manual defrost and tried it again (to simulate the problem which was gone again on that moment)and yes,...the phenomena was there again. We solved the problem by fitting an auxillary relay with the 3 different separated contacts for each SV (contact in the live line) and the problem was gone.
Strange but glad we finally could pinpoint the problem.
See it as a technical riddle.
I thought this story could be useful for others.
I have another story which I will post today:D :D

Mark,
As long as the contact of the defrost clock is closed, everything is normal. We have our live wires and everything is connected via the common (we call it the nuetral wire).
But if the contact opens, we lose our common. Thats why i said that the phenomena begins when the defrost starts (or when opening the contact)
It becomes then impossible to switch off one Eliwell at a time.
You switch Eliwell 1 off with the rocker switch in the live but it remains on. 1 off and now also two off--> 1 and 2 remain on even with an open live wire. As soon you switch off 3, then 1 and 2 go finally in the off position. I can assure you that on the 1st sight this sounds almost impossible for me.
When the contact is closed (normal cooling situation) you can switch each eliwell off independent of each other.
That's why I tried to explain (i'm doing my best) that this happens when a defrost start.
I hope this explantion was helpfull.

I haven't tried this - but it can be like you said - but isn't this dependend on the voltage drop we encounter over the different resistances (Eliwells and SV)? It is perhaps possible that the resistance has such a value where there is a voltage drop large enough to close the SV. Perhpas. As soon as I'm back at this client, i give it a try. eventually, i will rewire it like it was originally.
So the story can goes on. Anyhow, we changed it immediately after pinpointing the cause (aux. relay)
Went back this morning due to a faulty LP setting (client had turned on the knob of the LP. He tought that this was also 'a thermostat') and that the Eliwell was only a readout (I explained everything the 1st time to his son)

[QUOTE]Originally posted by Peter_1
[B]Mark,
As long as the contact of the defrost clock is closed, everything is normal. We have our live wires and everything is connected via the common (we call it the nuetral wire).
But if the contact opens, we lose our common. Thats why i said that the phenomena begins when the defrost starts (or when opening the contact)
It becomes then impossible to switch off one Eliwell at a time.
You switch Eliwell 1 off with the rocker switch in the live but it remains on. 1 off and now also two off--> 1 and 2 remain on even with an open live wire. As soon you switch off 3, then 1 and 2 go finally in the off position. I can assure you that on the 1st sight this sounds almost impossible for me.
When the contact is closed (normal cooling situation) you can switch each eliwell off independent of each other.
That's why I tried to explain (i'm doing my best) that this happens when a defrost start.

my point is that if it becomes impossible to switch off one eliwell at a time when the common breaks on defrost. Then the compressor would continue to cycle on thermostat as the eliwell would still be feeding the LLSV as it is still switched on.
see what i mean ??:confused: :)

To be sure, i will rewire it (as soon as I'm back at the client) to the 1st schematic and i will measure everything Then we will be shure.
OK?

I think it must have been " then we will be sure", isn't it?
Or in Zuidafrikaans something like "Dan sein wij seker, niewaar" "Pour être sur" en Français si tu plaît, oder in German "Wir sint dan sicher"

hi Mark,
i have seen such situation in the past, it happend when three different circuits of neon light went crazy and behaved the same.
there is something with the electricity which i can not explain. all i know is that if you supply three phase, each one to a different circuit and control it with the "0". thats what will happend.
it will not happend if you put the on/off switch on the phase.

chemi

I think that's the Law of Kirchoff you describe (long time i've learned that in school)

Same story for heating resistances in evaporators (each year, we find installations from our competitors with this fault) Situation: a lot of heaters in an evaporator + flexible drain heater and the starpoint isn’t connected to the common (neutral we say) on a 3 x 400V net. Suddenly, one heater fails and then the show begins. Always good for someone…. we in this case.

hi peter
Just out of interest what voltage was the eliwell thermostat
secondary supply voltage 12v to controller.via a step down transformer 220v primary input voltage.
control voltage 220v (ie switch wire) .
or
220v eliwell controller
220v switch wire.
regards mark:)

Everything is 220 VAC (220VAC power supply for the thermostat (Eliwell ID961), the SV's are also 220 VAC)
How old is your youngest?

Re-measured everything. Voltage on the 3 Eliwells 225V.

As soon as one thermostat reaches his setpoint and switches off his SV, then your able to switch off that specific thermostat.

Let's say 3 thermostat not already reached there setpoints: Switching off 1 thermostat, voltage dropped to 205 V on the remaining two, switching off the 2nd-->voltage dropped to 195 V.

I was at that moment not able to measure the voltage on the SV's. Client became unpatient.

The 5 January, the trailer comes in for some service works (greasing and some repainting, he already had a little accident on the market) I will then measure resistance and voltage over the SV's.

Peter

Posted some pictures of the van on http://users.skynet.be/sky71808/edelvis.htm

Is a large file +/- 1,7 MB.


Peter

Hi Peter

Just found this thread again, thanks for sharing the pictures with us.
A nice project.

With Kind regards
Mark

Nice pictures of the van.

Locked at the schematic a couple minutes. Figured out it would be impossible to switch off one thermostat when system in defrost. When in defrost, common for SV is/gets 240V if one or more thermostats calls for cooling. That 240V feeds the thermostat through the normal closed SV regulating contact when its switch is turned off. If that contact open due to cold enough, then thermostat momentarily looses its power when its switch is turned off. But then the normal closed contact in the thermostat closes and therby feed power to the regulator again. I guess the regulator has some sort of delay before it opens that contact again. So it will continue to restart so to speak as long as defrost is on and one of the other thermostats is calling for cooling or simply stay on if it is calling for cooling itself. If both other thermostats stopp calling for cooling, then the thermostat with its switch in off position will loose its power as normal as long as both other thermostats stay in off cooling position.