VBM Domobar Single Boiler - PID & thermostat questions

Need help with equipment usage or want to share your latest discovery?
_Ryan_
Posts: 183
Joined: 3 years ago

#1: Post by _Ryan_ »

G'day,

During lockdown (230+ days so far with another few months confirmed!) my passion for coffee has been reignited.
Rather, I can't visit my favorite coffee shops to try new beans as they're outside of a 5km radius from home so I have no choice other than to order different varieties to home.

My setup:
- Vibimme Domobar Piccolo (I believe the Piccolo name is only for the Australian market). It is a single boiler, e61 machine without a heat exchanger, purchased new in 2015 and maintained.
-- VST 20g ridgeless basket
-- Pullman Nexus 58.4mm tamper
-- Pesado naked portafilter - has highlighted uneven extractions which I appear to have corrected.
- Mazzer Mini Electronic type A, purchased new in 2015, new burrs replaced with OEM 64mm mini burrs in 2020. I appreciate this grinder is out of vogue these days due to retention and price, but it meets my needs, albeit clumps a little with some beans - these clumps are easily broken up and I'll be trying WDT because, why not? I have a friend 3d printing some distribution and WDT tools to addressing the clumping.
- Hario cold drip, Hario cold brew and a few other brewing methods such as pour over, percolator and press
- Hario scales, yes, not as fast as the Acaia scales but they're fit for purpose

I understand the basics of extracting espresso, ristretto and cold drip.
I drink espresso, ristretto and long blacks (americano?). Milk drinks are only prepared for guests.

One variable I don't have control of at the moment is temperature! To ensure I get the best out of some lighter roasts I'd like simpler temperature control.
I do not have access to a Scace thermofilter without making a trip to a coffee store that offers a calibration service. This would quickly prove expensive and is something I would do as a 'one-off' to calibrate a PID offset.

Ambient temperature isn't likely to vary by more than 5degC which I believe rules out significant fluctuations due to group head temperature.

I believe there are two options available to me to address temperature control:

- Option 1 - "Analogue"

Fit one of Eric's group-head thermometers and use this proxy/approximation of brew temperature to allow for tweaking of the standard Prodigy TR 86 thermostat.
Pros:
-- No wiring changes
Cons:
-- Aesthetics
-- Relies on the TR86 maintaining the desired temperature.
-- TR86 can be fiddly to adjust.
I appreciate that a GH thermometer is of high value to a HX machine due to the flushing process for temperature regulation- this isn't applicable to my machine.

- Option 2 - "Digital"

Fit an Auber PID with the appropriate RTD sensor mounted inside the boiler (links below). All the new Vibiemme dual boilers appear to come with PIDs, this should perform similarly just without a second boiler. PID offset would be calibrate with a Scace device by an expert.
Pros:
-- Once set, PID can be out of sight.
-- 1deg C incremental control.
-- Less temperature variation (assumption!).
-- Offset can be calibrated with Scace and remain accurate +/- 1degC due to ambient fluctuations.
Unknowns:
-- How will the temperature behave during a shot compared to now, and what will that mean for extraction?
-- How much better will temperature control actually be than the TR86?
Cons:
-- Still working with a 'proxy' temperature display, albeit calibrated.
-- Requires wiring.

Questions!
1-
a- How does a Prodigy TR86 thermostat behave?
b- How much of a drop does the TR86 need to see before it turns on the heating element? (i.e.: how much better will a PID be for temperature responsiveness)
2-
a- Is my assumption that the calibrated offset will be accurate for brew water temperature +/- 1degc, close enough to margin of error on an e61, correct? (i.e.: can I safety go from 91degC to 93degC when roasters recommendations change)
b- During the course of pulling a shot, will the change in temperature 'profile' compared to the TR86 (if any) be a problem?
c- Should I expect to see different numbers throughout pulling a shot relative to the behavior observed on the Scace?
d- Is a PID on an e61 machine worth it? knowing there's a lot of thermal inertia in these machines?

If you made it this far, thank you for reading and any light you can shed on my questions is appreciated. Apologies if the post is a little bit of a mess, 7:04am and can't sleep. :oops:

links:
OEM thermostat and probe https://nuovaricambi.net/en/product/106 ... 5x90mm-vbm
RTD I intend on using (adapter in the mail) https://www.auberins.com/index.php?main ... cts_id=107

Sources for boiler threads/adapters
--- note, this user didn't use the correct length RTD but the thread info is there https://coffeesnobs.com.au/forum/equipm ... post875336
-- The different threads and adapters used to fit the thermowells and thermostats and how they changed over generations
--- https://coffeesnobs.com.au/forum/equipm ... thermostat
-- A similar project on HB, albeit a different model
--- Install a PID on my Vibiemme Junior DB?

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cafeIKE
Posts: 4704
Joined: 18 years ago

#2: Post by cafeIKE »

To establish my creds, I've had PID on a Vibiemme HX for over 15 years, a DoubleDomo for 13 years and helped pals install Aubers in HX, so I'm pretty familiar. On either machine, I can pull back to back to back shots that vary less than ±1°C as measured with my Scace. The Scace is not mandatory as the EXCELLENT Espresso 101: How to Adjust Dose and Grind Setting by Taste is all we had for the first 100+ years of espresso

I run my DD boiler between about 105° [≈93°C shot] and 108°C [≈95°C shot] for coffee's I drink.

I'm not familiar with the Piccolo, but may be able to find out.

It's fairly straight forward to install a PID. They fit in a small project box and fit under the standard HX

Auber on a Super HX with higher feet for a bigger project box


The Auber's have a well proven track record and are Ezee-Pzee to program. You may want to have the PID accessible to adjust and for 'cool' factor.

You need an adequately sized SSR which should be well cooled with a heatsink, but many rely on the case which will function pretty well. It's imperative to have good contact with a good thermal grease.

IMO, it's very important to know the boiler internals
  • cold water injection point
  • heating element shape
  • locating TC probe to accommodate the above.
★ Helpful

_Ryan_ (original poster)
Posts: 183
Joined: 3 years ago

#3: Post by _Ryan_ (original poster) »

cafeIKE wrote:To establish my creds, I've had PID on a Vibiemme HX for over 15 years, a DoubleDomo for 13 years and helped pals install Aubers in HX, so I'm pretty familiar. On either machine, I can pull back to back to back shots that vary less than ±1°C as measured with my Scace. The Scace is not mandatory as the EXCELLENT Espresso 101: How to Adjust Dose and Grind Setting by Taste is all we had for the first 100+ years of espresso

I run my DD boiler between about 105° [≈93°C shot] and 108°C [≈95°C shot] for coffee's I drink.

I'm not familiar with the Piccolo, but may be able to find out.

<snip>

The Auber's have a well proven track record and are Ezee-Pzee to program. You may want to have the PID accessible to adjust and for 'cool' factor.

You need an adequately sized SSR which should be well cooled with a heatsink, but many rely on the case which will function pretty well. It's imperative to have good contact with a good thermal grease.

IMO, it's very important to know the boiler internals
  • cold water injection point
  • heating element shape
  • locating TC probe to accommodate the above.
Thanks Ian. Appreciate the reply, have come across some of your posts and your website.
Glad to hear your setup is running well! My end result should be similar to your DD but without the steam boiler. Great to hear of the consistency between shots.

I'm going to explore the boiler when I test fit the adapter, meaning check the cold water inlet point and element clearances for the 100mm probe. As the thermostat is using a 90mm thermocouple I'm reasonably confident that it should fit okay and location should be functional.

I intend on having the PID approx midway down one side of the machine, near my grinder so that it's accessible and legible but not "in my face" looks wise. I can't mount it under the machine as the Piccolo sits quite low.

The BOM I've come up with so far includes the below items:
- Case, friend can print it in black for <$1 https://www.thingiverse.com/thing:3671244
- PID, Auber suggested I get the Silvia kit which has a different PID to the universal PID they'd previously recommended, unclear on the differences. https://www.auberins.com/index.php?main ... ucts_id=14
- Relay https://www.auberins.com/index.php?main ... ducts_id=9
- RTD, which will mate to the adapter I found https://www.auberins.com/index.php?main ... cts_id=107
- M12 x 1mm Pitch x 1/4 NPT brass adapter
- Teflon tape
- I have thermal paste from CPUs which should be sufficient for the SSR to sit on the frame of the VBM. Otherwise will obtain a thermal pad suited to a relay.

What I'm still working through:
- Wire
- Spade terminals
- Piggy back method to connect to the water-level switch on the reservoir

A few questions you might be able to help me with:
1- What gauge wire did you use, 20?
2- Do you know the difference between the universal and Silvia kit PIDs from Auber?
3- Did you piggy back off of the water-level switch for PID power, if so, what kind of connector did you use?

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cafeIKE
Posts: 4704
Joined: 18 years ago

#4: Post by cafeIKE »

  1. I use 14ga internal wiring for the A/C, heater & SSR. Probably 18ga for the PID.
  2. The Silvia kit is preprogrammed for a Silvia boiler. Useless for your needs, but likely can be reset and reprogrammed if you find a good deal.
  3. This topic Pressure Perfect w Vibe Pump has schematics of what I did.
If you are electrically handy, do the Pressure Perfect mod while you are at it.

I'll have to find a picture of how I connected the PID power

_Ryan_ (original poster)
Posts: 183
Joined: 3 years ago

#5: Post by _Ryan_ (original poster) replying to cafeIKE »

2- Interesting, I wonder why they recommended it. I suspect the precut wires would be too short also.
3- I haven't notice a pressure drop when my heating element kicks in, is this something that is only observed on USA 120v power and not on the 240v we get here in AUS?

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cafeIKE
Posts: 4704
Joined: 18 years ago

#6: Post by cafeIKE »

18ga wire is rated for 16A for chassis wiring. 14ga for32A. 14ga gives a better mechanical connection and 2.5x the cross-sectional area, thus is just that much more robust. I've never had to fix anything where the wire was a bit over-size. Use a professional quality crimp tool and use top quality connectors.


The pump drop could be an issue of the Ulka 117v design and the machine internals. [Espresso machines are not the most elegant internally.] The line drops ≈3.8v with the HX heater engaged over the 54 foot run of 12ga. [I probably should reseat all the outlet terminals as we live on the coast.] I've observed the drop in the 5 locations where I've had the HX & DB in two homes and 3 industrial parks.

PID power take-off


SSR connection & PID neutral

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cafeIKE
Posts: 4704
Joined: 18 years ago

#7: Post by cafeIKE »

I'd recommend a thermocouple vs an RTD. Thermocouples react faster and a thin tube can be curved to the optimum boiler location.

_Ryan_ (original poster)
Posts: 183
Joined: 3 years ago

#8: Post by _Ryan_ (original poster) »

Regarding 12mm 1p to 1/4" NSP adapters, I found a third party one on UK eBay.
VBM also make one and the part number is 1349275, as seen here https://www.cafeparts.com/Bulb-Sheath-F ... TBULTERRID

Hope this helps anyone who is searching for the info in future.

_Ryan_ (original poster)
Posts: 183
Joined: 3 years ago

#9: Post by _Ryan_ (original poster) »

Slight change in direction.

I saw the Luminaire shot timer and thought "that would be super handy for when my housemate uses my machine" (I use the timer on my scales) as my grinder doses within about 0.2g, so if time is accurate the yield and extraction is generally pretty good.
In Australia, that shot timer is $AU140.
It doesn't work with a proper E61 group.
It looks rather simple to make and wire in.

The Auber PIDs only do a countDOWN shot timer, not count UP.
They also advise the firmware is different between the universal and coffee machine kits.

I have an old box of Particle Photons, Raspberry Pis etc. in the garage, so if I buy a display I can make the shot timer.
If I'm making the shot timer I might as well make the PID.

To make the shot timer and PID I'll be out of pocket:
- a small screen ($AU10),
- relay ($AU10),
- probably some wires ($10),
- a bag of beans to cover 3D printing an enclosure at a friends ($15)
- a temperature sensor that can be used with both a Particle based PID and also in future with the ITO based Leva! ($50-80)
Total: $AU125 + things I have lying around + maybe another PCB to neaten things up.

The Auber kit, for reference, even though it wouldn't meet my needs
- PID without shot timer $AU202
- PID with preinfusion (only way to get shot timer) $AU270
- Shipping $AU48
- Temp probe, if they won't swap it into the kit $AU43.50
So I'd be looking at $AU250 best case for the Auber PID, $293.50 if I need to buy the sensor. That still leaves me without a shot timer.


The ITO/Leva! kits look great but ordering appears near impossible with sporadic small batches available, so I intend on whipping up the PID and shot timer, but ensuring whatever wiring and temp sensor is put in place is re-usable for that project- if I can secure one.


Question
Is a temp probe in a compression fitting, directly fitted into the boiler (without a thermowell) considered secure?
From what I found of compression fitting on pipes, they can hold north of 300psi in the sizes I'd be working with.

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cafeIKE
Posts: 4704
Joined: 18 years ago

#10: Post by cafeIKE »

I used a compression fitting in a couple of HX [≈1.75 bar] back in 2007 & 2008. Still holding.



I have two of Eric's group adapters [≈10 bar] that were tightened around the same time, haven't been touched since and never leaked a drop.

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