20 and 21 blocking alarm help

[Madroaster]

Hi All,

A couple weeks ago I had a blocking alarm, 20 and 21 lit up (S1V2). I checked the manual for this and also on the forum, and it seemed the group temperature sensor was bad. I replaced it but it didn't fix the problem.

When I power up the machine the steam boiler doesn't heat up, but the heating lights flash to say it thinks it is. But there's no sound from it whatsoever and it never warms up. After the 5 minute time-out I get the blocking alarm. I checked the element and it reads fine; in spec with the new ones showing readings on the board here. Any ideas what could be wrong?

[chas]

As I read the manual, a bad group temperature sensor OR a bad group triac will cause 20-21 to blink. Since you ruled out the temperature sensor the hard way, it sounds like you have narrowed down the problem.

At first it may seem weird that the alarm is for a group boiler issue while the steam boiler isn't turning on. However, even in 20A mode, the group boiler heats up first before the steam boiler starts to heat up when the machine first turns on. This keeps the machine from drawing 20A for the extended period it takes for both boilers to heat up to nominal temperature.

Therefore, since the group boiler doesn't hit 60C within 5minute the machine turns off and the steam boiler never turns on since the group boiler never got up to temperature.

If you have an voltmeter capable of measuring AC voltage turn on the machine and check the voltage across the group element leads. It will probably be zero.

The fix depends on whether you have an older machines with a triac board or one of the new machines with a sealed SSR modules. In either case the one for the group boiler probably needs to be replaced.

[Madroaster]

Thanks for the insight. I hadn't noticed that there was more than one problem reported by the 20-21 alarm. I'll measure the voltage tomorrow and report back. Any idea what the triacs cost?

[Madroaster]

Also, where can I get a replacement triac? Seems like it's something I should be able to pick up locally. Does anyone know the part number? I'm assuming they're not terribly expensive, and I'd love to have some espresso this weekend.

ETA: I just checked out the parts catalog; it doesn't seem like I'll be picking this up locally.

[chas]

If you literally only want espresso this weekend you could swap the two identical triac boards so that the one for the steam boiler is used for the group boiler. Then you can have espresso but no hot water or milk drinks until you replace or repair the other board.

[Madroaster]

If you literally only want espresso this weekend you could swap the two identical triac boards so that the one for the steam boiler is used for the group boiler. Then you can have espresso but no hot water or milk drinks until you replace or repair the other board.

I was pretty excited about this until I checked the voltage across the boilers. The group boiler reads 120 but the steam boiler reads 0. But the steam boiler element tests fine. Any ideas what this could mean?

[chas]

As I stated in my earlier post, the group boiler is supposed to come up to temp BEFORE the steam boiler ever turns on, so the steam boiler voltage should be 0V. The fact that you see 120V at the group boiler element leads indicates that the group triac IS working. Since you have already changed out the group temp sensor, this brings us to the possibility that the group heat element has gone bad.

To see if this could be the problem, unplug the device, disconnect the power leads from the group heater element and ohm across the leads. I suspect the reading should be ~15-20ohms.

[Madroaster]

I misread the info about the boiler; was assuming it would still show voltage. Of course it wouldn't.

I checked the group element and it's dead; reads zero. Time to put in an order. Thanks for the help!

[chas]

By zero do you mean the group element is shorted and not open? If it's shorted I am surprised you were still seeing 120V across it and/or didn't blow a breaker.

[Madroaster]

To be honest, I don't know enough about circuitry to see contradictions. But with the machine powered up, it reads 120V across the group element. Powered down the ohmmeter reads 0. The steam boiler read 9.something when I tested it.

I just tested it again and the steam boiler reads 9.5 ohms, and the group reads open, 0.L. I didn't test the AC across the group again just now, but it definitely read 120V (or something waveringly close to it; I forget exactly).

[chas]

OK, as an electrical engineer your measurements now all make sense and completely jive with the theory that there's an internal break in the wire inside the group heater element. So you definitely need one of those. Hopefully, CCS will remind you that in order to R&R the cover on the rear of the group boiler you will also need to replace the circular gasket on that cover. Be sure you get one of those ordered as well.

I have never removed the group boiler cover myself but a number of those on the Forum have. As I recall there was a bit of a trick to it so while you are awaiting the part, you should search the forum and find some of those old posts. You may also want to obtain some Citric Acid for descaling if you don't have any lying around the house. You should always take advantage of the opportunity of having the cover off to descale.

BTW: If you purchased the machine about the same time you joined to group, didn't your two year warranty just run out???

[Madroaster]

Thanks. I'll get the gasket; I"m just waiting for an email from Mary on shipping.

Since I've had the machine apart to see what's wrong I've descaled the steam boiler. Wasn't bad but still needed it. I used citric acid and it worked great. I've also had to replace several wires and connectors; they were all heat damaged (though not fried like the steam element wires people have had problems with).

I actually bought my machine in '08, so there's no warranty left. I can't complain though; it's been on 24/7 since then with only a couple overnight/weekend shutdowns.