Wega Atlas Water Level Probe Circuit

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scrimshanker
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#1: Post by scrimshanker »

I am restoring a Wega Atlas EVD ./2-AT machine.
In all of the electrical schematics shown in the service manual for this machine, a single wire is shown running from the 'Gicar' dosiatura to the Water Level Probe.
On my machine, an additional circuit exists which includes the Finder relay shown. The relay is activated from the heating element, and switches an additional wire - running to the water level probe - to ground.
This relay is burned on my machine. I have a new relay - but I'm not sure that this circuit is needed.
I haven't been able to get a response from Wega.
Can anyone identify and explain this circuity to me?


ira
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#2: Post by ira »

I'm not at all familiar with that machine, but from your explanation I can't figure out where that relay is located. A picture or a scetch of how it's wired would likely go a long way to helping us better understand the question.

If the pins on the end with 2 pins are connected one to the Gicar and one to ground it's possible it's an external relay added to control the heater to either replace the one in the Gicar that burned or to insure it doesn't. No clue, but that's the only reason I can see for a relay like that being mounted external and the fact it looks burnt out would indicate it's controlling something that uses a lot of power, most likely the heater.

JRising
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#3: Post by JRising »

scrimshanker wrote: On my machine, an additional circuit exists which includes the Finder relay shown. The relay is activated from the heating element, and switches an additional wire - running to the water level probe - to ground.
Do you mean "Activated by the Gicar's 'heating element' pin"? If so, it's a sacrificial relay, it is controlled by the Gicar to turn the element on and off, burning its own contacts rather than letting the Gicar burn the contacts of its own internal relay. The sacrificial relay is much cheaper to replace that the Gicar.

A photo of the Gicar's "Pin Out" diagram/sticker would help, if you have it. It sounds really fishy that any part of that relay is connected to ground. Neutral maybe, on the other side of the coil, but ground is odd.

scrimshanker (original poster)
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#4: Post by scrimshanker (original poster) »

I'm fairly sure the relay circuit was part of the original wiring. I've included a couple of images of the relay mounted in situ. The coil side of the relay is wired to the line and neutral terminals of the heating element. It appears that, when the heating element is activated, the relay is activated in turn, and switches the wire running to the water level probe to ground.
Why this happens is a mystery to me. It's also confusing that the relay is a 'CO' - crossover - relay....instead of the more common 'NO'- normally open - relay, which would achieve the same result.

I've rewired the machine and tested it without the additional circuit. Everything seems to operate normally. The pump fills the boiler, and the probe (I assume) turns off the pump when the fill level is reached. The boiler heats up to the set pressure. All functions controlled by the 'Gicar' controller seem to work normally. The groups can be activated with the manual switches, or the doser keypad units which appear to work normally.

The schematic I've included shows a slightly different setup to mine. My machine is single phase 230V. I've sketched in the additional circuit which includes the 'Finder' relay shown above.

I've included four images:
#1 - The relay in situ
#2. The coil control wires from the relay that are connected to L and N on the heating element
#3. Shows the wire wiring from the switched terminal of the relay which was connected to the water level probe
#4. Shows a simplified schematic of the actual wiring





scrimshanker (original poster)
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#5: Post by scrimshanker (original poster) »

This is my Gicar controller: #WY18090030


ira
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#6: Post by ira »

Unless I'm completely off my rocker, that should mean that whenever the heater is on, the boiler should not be filling. That seems like a recipe for disaster.

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homeburrero
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#7: Post by homeburrero »

I think that what the OP said:
scrimshanker wrote:The coil side of the relay is wired to the line and neutral terminals of the heating element.
Does not agree at all with his drawing if I'm looking at it correctly:

Note that the drawing does not show the relay in parallel with the element, but instead is powered by one pin of a connector or perhaps a rotary switch. When powered it would close a contact between the probe and ground, which is consistent with the unusual situation where one wire of a relay contact is a ground wire. When the coil is powered it would essentially ground the fill probe which would signal the Gicar that the boiler is full, stopping/preventing an autofill.
Pat
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ira
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#8: Post by ira »

You're correct in that I got how the probe works backwards. I'll go edit my post, but that drawing makes sense for a 3 phase heating element wired for single phase. That's what my 3 phase machine looks like wired for single phase.

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homeburrero
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#9: Post by homeburrero »

I stand corrected, after digging up an online set of Wega Atlas diagrams I see that the thing I thought was a connector or rotary switch is actually a depiction of the 400V three phase element, just as Ira said. The thing I thought was the element (SCT) is just the cup warming element.

So I have to agree with Ira that this setup, with the relay actually in parallel with the element looks a little screwy. With a normally open relay it would disable autofill whenever the element is powered.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

scrimshanker (original poster)
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#10: Post by scrimshanker (original poster) »

Thank you all for taking the time to try to help me understand this odd piece of circuitry.
As my machine seems to work normally without the additional relay, and as Wega doesn't show it in any schematic I can find online, I'm going to disregard it for now.
My concern all along has been that, when the 'Finder' relay is activated (when the boiler element is on), the relay will signal the Cigar that the boiler is full by grounding the water level probe. I am admittedly a naif on the subject, but to me, that does seem to be a 'recipe for disaster'.

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