Brew panel

[Mark Stewart]

I didn't buy the electric brewery relays because they are expensive with shipping .
[automerge]1586809571[/automerge]
Thanks for the link pc1966 I have ordered two LEWDEN - IC40/2

 

[pc1966]

Let us know how you get on when they arrive.

 

[marconi]

Power relay JQX-30F 20A HHC71A manufacturer from China Clion Electric Co., Ltd - http://clion.en.hisupplier.com/product-2103798-Power-relay-JQX-30F-20A.html

1-4sets Power Relay JQX-30F 2Z 30A HHC71A 12V 24V 110V 220V DPDT 8-Pin with Base | eBay - https://www.ebay.co.uk/i/123829966051?chn=ps&var=424527426383&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=424527426383_123829966051&targetid=876875609442&device=c&mktype=pla&googleloc=9045003&campaignid=9794971116&mkgroupid=98649235903&rlsatarget=pla-876875609442&abcId=1139126&merchantid=6995734&gclid=Cj0KCQjwm9D0BRCMARIsAIfvfIYw0kpVVKsmnokh06j_zZhxsQ9mIjRYubOQZAKpn7f8IbBThLWf4QsaAn0EEALw_wcB

I have been curious why the relay failed after the first power up.

I have been studying the underside of the relay around the power contacts. The damage looks remarkably like that produced by arcing and tracking. In this area between the two sets of power contacts here is line and neutral connected to the two Normally Open contacts - so full mains voltage over a short distance. The little hole suggests to me the final high current/energy arc which was cleared by the mcb operating. There does not seem to me to be much sign of the power relay pins getting too hot.

I reckon the OP did not plug in the relay fully home to ensure full surface contact between the relay power pins and the base contacts. This relay (see the links) has two plastic lugs on the side which open then close to snap secure the relay into its base - on the relay they are white with two rectangular slots on either side of the relay. Without a firm push home the relay would sit with a gap beneath it and the top of the base rendering the raised plastic fences and slots into which they fit ineffective as a shield - one can see this if you blow up the images under the relay on on top of the base respectively.

Not being fully inserted, the proper gripping of the relay power pins has not occurred and there may have been some misalignment. All in all an inadequate mating between base and relay contacts which were then stressed by the circa 25A current and mains emf. Heating, arcing, tracking ensued and eventually a short circuit between line and neutral.

So, I tend to think the relays may well not be the root cause of the problem rather their incorrect first placement into the base.

 

[Mark Stewart]

Thanks for everyone's help, you have all been great. I suspected that I may not have sat the relays correctly but I will never know now. Like I said before I have ordered two Lewden IC40/2's, could I be cheeky and ask how should wire into my existing diagram also should I fit an MCB (where and what Amp)? I have added a diagram.

Thanks again!

 

[marconi]

Might you open up a relay and take some photos of its innards so we can study any deterioration?

Did both relays fail and in the same way?

 

[Mark Stewart]

Sorry I'm at work at the moment but will take some photo's later. The one on the element side was burn more and I suspect that is the one that tripped the breaker. The other one the base was less melted and no deterioration on the relay.

 

[pc1966]

Thanks for everyone's help, you have all been great. I suspected that I may not have sat the relays correctly but I will never know now. Like I said before I have ordered two Lewden IC40/2's, could I be cheeky and ask how should wire into my existing diagram also should I fit an MCB (where and what Amp)? I have added a diagram.

Wiring the contactors is much as you show it, the coil connections are the A1/A2 terminals, etc, as shown on the front of the unit.

What do you want the MCB to cover? As this is taking something like 26A you must have some sort of feed from your consumer unit dedicated to it, is it hard wired from a cooker outlet? Or do you have a 32A "commando" (round blue) plug and socket?

Or do you want the MCB in place of the 7A fuse? There is nothing wrong with having a fuse there as it ought not to blow, but just in case you should make sure it is an HRC fuse.
[automerge]1586860458[/automerge]
Also to add, is there RCD protection on the feed to all of this? That should be the case, but just something to check.

 

[westward10]

I very much doubt that relay socket/base is rated for 26A in the first place.

 

[Mark Stewart]

Just wondering how to add extra protection to stop a repeat occurrence. I have a dedicated distribution box for my brew shed.

 

[pc1966]

Fitting a MCB won't in any simple sense stop overheating like this, it would only protect against over-current. The only real answer is adequate component rating and correct termination of cables, etc, so nothing overheats at the rated current.

If you are concerned about overheating then you could fit a thermal trip in to the enclosure to cut the coil circuit to the first (the "power") contactor to switch everything off if the temperature exceeds some reasonable limit, such as 60-80C or whatever you think is a bit more than the enclosure should get to normally.

You get bimetallic thermal switches but they self-reset, not good for a fire risk situation!

Instead you can get one-time thermal fuses that would be more appropriate here. Care is needed if you want to solder them in (obviously, they fuse only once on heat!) but if using screw terminals or spring loaded Wago terminals they are fine. For example:

SM 092 A0 2A | Limitor Thermal Fuse +97°C 2 A, 250V ac | RS

uk.rs-online.com

Thermal Fuse - 72 Degree Thermal Fuse | 72ºC Thermal Link

10 Amp and 15 Amp 72 Degree Thermal Fuse (Thermal Link), Non Resettable

sinolec.co.uk

 

[marconi]

I very much doubt that relay socket/base is rated for 26A in the first place.

The highest amperage base I can find from RS of that style is 16A. I bet this is for only one set of contacts and some downrating required when the other set are passing a sizeable current as in the OP's application =>A learning point for others.

 

[westward10]

I would say excess current just burnt them out.

 

[pc1966]

I have only ever seen 24A max for the 0.25" push-on style of terminal anyway, and that crimp terminal would be more metal than a typical relay base connection would use.

 

[Mark Stewart]

Marconi I will take some pictures soon, I'm leaving work soon. I have struggled with Microsoft paint and knocked a wiring diagram for my new LEWDEN - IC40/2 does it look ok?
[automerge]1586876142[/automerge]
Pictures of inside the relay, the relay that has no melting at all was fine. The melted relay on the element side here are some pictures with no internal damage, contractors are fine and no signs of burning.

 

[marconi]

Dear Mark Stewart - thank you so much for indulging my curiosity! My wife is one of those 'shielded' people as she is highly vulnerable, and I, because of that and also because I do not have a spleen, are both incarcerated at home - so I look for 'intellectual' escape from it all.

I am only interested in why your original set-up failed. The sage advice of pc1966 will set you right on the required modifications to your electric brewery to arrive at a reliable, safe and effective system.

The pristine condition of the innards of your relay(s) tell me the failure mode was something to do with the contacts of the relay and its base, and the insightful observation by westward10 that the base almost certainly does not have an adequate current handling rating. As an aside, the relay may well have coped if the leads had been connected to it directly - I can find no commentary on line which questions the current handling capability of the relay itself but as they say 'the absence of evidence is not evidence of absence'. The pins of the relay in contact with the base contacts has been inadequate to pass a steady state current of circa 25A for more than a short period.

The contactor pc1966 pointed you to is beefy enough to cope.

I strongly recommend you have your installation inspected and tested out by a competent electrician. I am sure there will be an EF member itching for a sample of your brew!

 

[pc1966]

The updated diagram looks fine.

In terms of using the contactors the main points are to fix them reliably (usually with a DIN rail bolted to the chassis, etc) and to take care in particular with the high current connections. They need to be well prepared and tight enough but not too tight!

The ideal solution to that is a torque screwdriver but medium single-hand torque is probably OK, and then wiggle the cables and check gain if the screws are as tight as you first applied. There are some handy points in this best-practice guide for replacing CU (please, don't try that at home!) which you might want to look over:

https://www.electricalsafetyfirst.org.uk/media/1258/consumer-unit-connections.pdf

Sadly there is no sign of a datasheet on the Lewden site (giving 404 page not found, doh!) but typically the screw torque for the larger cables is around 2Nm, smaller usually around the 0.8Nm region.

 

[Mark Stewart]

Can't believe how good you all have been! I will highly recommend the site to the brewing community. Once again thank you so much and will update my progress when I have fitted my new parts.

 

[Mark Stewart]

Hello again I'm back, I fitted my new contactors and seems to be no over heating. I am having an issue my PID is not switching my element off, the SSR is flashing on and off but the element is staying on. Have I got a wiring program?

Many thanks Mark

 

[pc1966]

It is the SSR that should do the functional switching, that is the operational cycling of the heater. There is nothing obviously wrong, but then there is no information about the pinout of the PID controller.

When you say "SSR is flashing on and off" do you mean the boil element light?

 

[Mark Stewart]

No the boiler light stays on, the light on the SSR it self flashes on and off. I tested the element and power is constant.