Breville Dual Boiler Rebuild - Page 3

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#21: Post by grufromtheloo »

I am now starting to prepare to re-assemble the steam path and test it out before cleaning up the rest of the machine. Came across an interesting find. The steam boiler had these weird little washers between the metal washers and the boiler housing. I thought they were for thermal insulation, but they are actually for electrical insulation. I verified this with a multi meter on my working BDB; no connection between the boiler housing and boiler. That is, the steam boiler body is _not_ grounded whereas the brew boiler body is. If you are disassembling save those insulating washers and put them back! Mine mostly came apart so I am looking for new ones.


#22: Post by grufromtheloo »

I only have 4 mica insulating washers on my project BDB. On my primary BDB it looks like I have 2 per screw, as expected. Not sure what happened to the rest on the project. Maybe just disintegrated with all the rust and corrosion or came apart on disassembly.

Pick of the steam boiler mounts on my primary bdb.


#23: Post by grufromtheloo »

BDB faithful.

The link below is a great resource on how liquid level sensors work in espresso machines. I believe the brew boiler is type-b (two probe) and steam boiler is type-c (3 probe). Other non Breville machines, from what I have seen, mostly use the single probe to grounded boiler approach. Why Breville uses a two probe vs one on the brew boiler is a mystery. Maybe because the brew boiler is only grounded by wire instead of through a More solid connection to a metal frame metal frame (plastic frame on the BDB)?

As per my last post...This means it actually doesn't matter if the steam boiler is grounded or insulated as long as the ground/common probe is grounded. ... y-sensors/


#24: Post by grufromtheloo »

Finally starting a rebuild. If I haven't mentioned it my plan is to rebuild the steam path to determine if this BDB can be saved. Steam boiler was dead when I got it so I have no idea if the element actually works (tests ok) or if the sealed element silicone is good (looks ok) or if some other issue exists.

Reassembled the boiler and housing. Used a stainless zip tie to secure the thermal fuse. Still need to trim it.

The mica washers that provide thermal insulation disintegrated while disassembling so I have temporarily wedged some old silicone o-rings in there for now.

Replaced the washers on the drain, boiler and drain valve side. Both were 010. Replaced with silicone as AFLAS is damn near $1/ washer here. All dabbed with food grade silicone before re-assembly.


#25: Post by grufromtheloo »

Steam valve is going to be hit or miss. The ball was fairly heavily corroded on one side, to the point where the surface is not smooth. In addition the centre screw had to be drilled out as it was heavily rusted leaving no good way to make a solid connection.

After reassembly the steam valve is holding up to a quick blow test will have to see if it survives steam boiler pressure.


#26: Post by grufromtheloo »

Replaced the steam valve mount. The base that connects to the plastic chassis has 4 tabs that push into the chassis then have to be twisted.

The tabs sticking through, still need to be twister properly. Bent a bare min to dry fit.

Steam valve connecting screw was drilled out and the plastic knob took some damage.

My end goal is to epoxy the black metal piece on to the end of the knob. For the dry fit using some silicone grease to temporality stick it on. Decided I would try holding the knob in with a screw drilled into the knob's shaft. Delighted to say it works!

Despite no screw from the knob to the valve the pressure of keeping the knob in place and steam valve mount holding the valve in place is enough to provide a reliable mating.

With the steam knob lever attached I can say that 3/4 of the turn feels great. That last quarter there is more friction than a stock machine but still completely usable.