Sage / Breville Dual Boiler - two problems

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

#1: Post by albionbrass » Oct 06, 2019, 4:29 pm

First problem is the easy one, I think. The hot water spout drips, more so when extracting espresso or using a blind filter. I think the needle valve is faulty - easy replacement, but the part is not so easy to get here in the UK. Any advice on how to repair the valve?

The second one, is the dreaded overheating problem, but not in the normal way. The machine only overheats when the boilers start off empty. What I think is going on is this, but, I may be wrong, so here goes...

When I first switch on (after a descale, for example) the smaller pump vibrates, the brew pump doesn't. The brew boiler doesn't seem to fill, the temperature rockets up very quickly. I switch the machine off, and on again, but the brew boiler still doesn't fill. It seems to be only after the temperature has gone over 93C, and I switch off then on again does the brew pump switch on, fill the brew boiler, and the temperature comes down, then it heats up normally. Once the boilers are full, everything behaves as it should (apart from the drippy hot water spout, of course).

Another way I can get the espresso boiler to fill from empty is to open the hot water spout. So, I do have workarounds, but I'd rather nail the problem and get it fixed.

A bit of history of the machine, it's about 5 years old, and the previous owner ditched it because it was tripping the house electrics. As covered elsewhere in these forums, changing the O-rings has cured this. But I'm wondering if at some point this has damaged something that could be causing the symptoms I'm experiencing. It's worth mentioning that I've replaced the brew pump, as the pre-infusion wasn't working, and I thought the odd behaviour might be related. It fixed the pre-infusion, but not the filling from empty problem.

Many thanks for any help.

Dave

pcrussell50

#2: Post by pcrussell50 » Oct 06, 2019, 6:02 pm

If anything it's the descaling that could be causing your problems. It is a disruptive process that other machines, especially high end machines, do not offer. The BDB has a classic high end machine water circuit and it's best if you just feed it with scale free water and not have to worry about scale for a very long time if ever.

Now to your hydraulic problem. You can pull one of the water tubes off the brew boiler and manually fill it with a tiny funnel or a gooseneck kettle or some means of precision pouring.

Each time you run the descale function run the risk of the vapor lock and purging issues you are experiencing, as well as possible burning of the steam boiler's thermal fuse which is a PITA repair.

-Peter
LMWDP #553

albionbrass

#3: Post by albionbrass » Oct 06, 2019, 6:26 pm

Thanks for your reply Peter. I have only just acquired the machine, and it's the 5th DB I've had, and restored. I've only ever managed to drain the boilers by removing a tube, so that's what I always do anyway. It seems that the brew pump just isn't starting to fill the boiler from empty. Am I right in thinking that both pumps should activate to fill both boilers from empty?

And re the hot water valve, shall I stop descaling it and hope a bit of limescale helps to plug the leak?!

pcrussell50

#4: Post by pcrussell50 » Oct 06, 2019, 7:15 pm

Ah good. You are handy with tools and understanding. I actually do not know about the full schedule for the brew boiler after draining because I have never drained it. But the brew pump does have standard blade connectors. With your skills you ought to do able to cobble up some wires with blade connectors and your own switch, pull the factory blades, and run the pump manually on your own directly from another 240V outlet.

This will allow you to run the pump on a cold boiler, with the drain cracked until you are certain you see flow.

Further, it will also give you the ability to do "soak and bloom" shots, in which you wet the puck with the pump on, then shut off the pump while the solenoid remains energized and let the puck soak for 30s or so before you hit it with pressure. For very light high acid beans, this often tames the acidity a little. Just a little extra flexibility over and above the already very capable, programmable pre infusion.

-Peter
LMWDP #553

albionbrass

#5: Post by albionbrass » Oct 07, 2019, 12:09 pm

Thanks again Peter. I like the idea of a separate switch to operate the pump, but I don't share your confidence in my abilities to fit it! And I'm looking to sell it on, so I shouldn't be tinkering with adding switches. But it's good to know it could be something as simple as an air lock. I'll keep running it for now and make sure it's all working properly before I do sell it.

Re the hot water valve, I saw your suggestion on a different thread about putting a sleeve over the needle. I'll give that a go. Is the way in to the needle via the nut at the end of the valve where the knob attaches?

And finally, I tried repositioning the knob of the hot water valve in an attempt to cure the drip, and in the process have managed to stumble on a position that activates the hot water spout, without activating the micro switch and thereby keeping the espresso flowing, to the extent that I can get the pressure to the head as low as around 1 bar. If you then turn it enough to activate the microswitch, it stops routing to the head and the water can be used as normal. So everything stays connected and usable, but with the flexibility of controlling the flow. This was all with a blind filter, haven't tried it with coffee yet, but would that pass a a way to get a Slayer-like shot? With the advantage of not rerouting tubes or removing microswitches.

Dave

pcrussell50

#6: Post by pcrussell50 » Oct 07, 2019, 12:52 pm

The switch: I probably wasn't clear. It's external to the machine no actual modification necessary. It connects to the pump with simple blade connectors that slip on and off the terminals on the pump and two wires to the wall. You can then turn the pump on and off at will to either prime the brew circuit or play with exotic extraction techniques. And when you're done, simply slip your blade connectors off the pump terminals and slip the stock ones back on.

By the way, I have little expertise in the matter of the stock water needle leaking. This is an area of long term BDB DIY maintenance that I still consider an "open" item. Meaning there is not yet a single particular known fix that the community has developed. It seems to be not a common item that afflicts all machines. I do know that it is easily removed and disassembled. And if it were I, I would disassemble and clear any obstructions like scale or see what I could make out of re establishing a needle and seat sealing relationship by sanding the needle or drilling the seat. Or putting a new brass plug in place of the seat and drilling that. Something along those lines.

Me? I have a completely different needle valve that I use for flow profiling. Though I should say that you can still flow profile perfectly well with the stock needle. Just mine gives more precise control.

I use a proper electric kettle for boiling water.

-Peter
LMWDP #553

albionbrass

#7: Post by albionbrass » Oct 08, 2019, 11:20 am

For the needle valve, I'm wondering if there is an option to put either a small dab of durable and adhesive silicone or similar on the end of the needle, or to glue a tiny rubber bung onto the end of it. Do either of these things exist?

Re sanding the needle, would you sand it to more of a point?

pcrussell50

#8: Post by pcrussell50 » Oct 08, 2019, 12:05 pm

albionbrass wrote: Re sanding the needle, would you sand it to more of a point?
I don't know. I haven't done it myself and don't know anyone who has. But if you put the needle and seat together and shine a light through from behind, you ought to be able to see where contact is not being made. You only need a contiguous ring/line of contact by the way. Not a whole surface area.

It may well be that merely re indexing by a spline or two will do it. Or putting some valve lapping compound or other abrasive paste on the needle and spinning it gently into the seat will re establish a sealing relationship. This would be my first thought.

-Peter
LMWDP #553

albionbrass

#9: Post by albionbrass » Oct 08, 2019, 1:11 pm

Great suggestions, I'll give those a go and report back.

pcrussell50

#10: Post by pcrussell50 » Oct 08, 2019, 1:39 pm

Yes please do. You would be doing the BDB community a favor. While not many people have this problem, it is not unheard of and a DIY solution would be most welcome.

-Peter
LMWDP #553