Rocket Cellini adding brew pressure gauge - Is it possible?

#1: Post by **mosheva** » June 12th, 2022, 6:50 am

Hi Guys,

So I've got a Rocket Cellini, the model with only a boiler pressure gauge.
I would like to know if it possible to add a fixed pump pressure gauge just like on the latest models.

I've been trying to figure out the schematics and compering the 2 models but I couldn't figure out where does the pump pressure gauge is connected to get a reading.

The reason I would like to add a fixed gauge is 1st to know that I'm brewing at the right pressure, 2nd - the looks, 3rd - to play around.
I know that I can add a pressure gauge to the E61 group but I don't like the look of it.

In addition and much more complicated I would like to know if it will be possible to replace the pressurestat with a PID?.

As far as I can tell the old and the new models are practically the same, even the new Appartamento shares the same enginering design ideas.. so I'm guessing that there's a way to make it happen.

I've been searching for modification but couldn't find any..

Hoping for your wisdom..

Thanks.

#2: Post by **Nunas** » June 12th, 2022, 10:47 am

Because your machine is a typical HX e61 box, adding a pump pressure gauge may not give you what you want. That said, you should be able to do it by adding a tee right after the pump and running some fine copper tubing to the new gauge, as one sees on many machines. I think it would fall short of your expectations, because you mention not wanting to add a manometer to the HX. The e61 group has a jet inside. A manometer added to the group on the little hole on the front reads the brew pressure because it's on the brew side of that jet. A manometer added to the pump will read pump pressure, which is not the same thing, as it's on the other side of the jet.

Similarly, I think you'll be disappointed if you add a PID to your machine to replace the pressurestat. While it's certainly possible, even fairly easy to do, for a reasonably talented DIYer, it won't make any discernible difference in the cup. A PID will probably regulate the temperature/pressure of the boiler a bit better than the pressurestat, but the temperature of the water in an HX boiler is only indirectly related to the temperature of the brewing water. You can't use it to regulate the temperature of the brewing water, because on a typical HX machine, that can only be done by flushing/waiting.

I've had HX machines similar to yours, and in my opinion, the single most useful addition would be a thermometer mounted on the e61, such as the one made popular by EricS.

#3: Post by **Giampiero** » June 13th, 2022, 8:15 am

Why don't you buy a pressure gauge suitable for the group head?
Ops...i just noted that Nunas already suggested you.

#4: Post by **cafeIKE** » June 13th, 2022, 9:54 am

Adding a PID could do a few things

allow walk up shots at the expense of waiting to steam
preclude ever needing to replace a pressure stat
free up the boiler gauge spot for a brew pressure gauge

Downside of [1]: requires running the PID up and down for steam if it is set low for walk-up brew temperature. Can be mitigated with a PS to engage for steam. See HX Heaven or 1½ Boiler

Brew pressure gauges in most e61 machines don't read puck pressure and puck pressure can be dialed by taste.

+1 to Nunas on the brew temp thermometer if only doing one thing.

#5: Post by **kris772** » June 13th, 2022, 7:01 pm

Having gone through 3 different E61s (and a couple Cimbali Juniors) a decade and a half ago I would suggest:

View Dan's short youtube video on flushing.

Practice and see what you can get - yes, the timing is an art based at least partially on the sound during the flush, as well as experience with your current boiler pressure setting.

Don't just flush it to flush it - when you stop a flush determines the temperature that will hit your grounds, whether for pre-infusion and/or brew and will determine the taste you get out of a pull. I can't stress that enough.

If you too often get sour, raise the pressurestat a tad and try some more. Be careful of following "someone else's rules about settings"! Find what works for you on your machine with your timings!
If you learn flush timing, you can achieve a whole range of tastes.

In my experience, trying to get the PID and Nose probe to tell you when it will taste good will not be easy - for me it was unsuccessful.

In short, just learn to surf.

EDIT: I will add a note here that will irritate some people. Sorry.
imho
There is a definite finite distance between the E61 nose and the boiler. (This is MUCH more pronounced on the Silvia.) But whatever, you need to take into account this lag between boiler temperature, and when I gets to the group head, and make that a part or your artistry. To ignore that, imho, is to be often confused by the tastes you are getting from your beautiful machines. (Note: I am of course not talking about machines like LMs and commercial Cimbalis etc because the design of those machines is such that the head is almost part of the boiler. That is quite intentional.)

June 14th, 2022, 7:30 am

Thanks for the information.
Actually a friend of mine have a Rocket R58 with the same gauge that I want to add to my Cellini and he also have added a brew group group pressure gauge and the reading are the same.. Both gauges showing the same result.

How would I know if my machine is brewing at the correct bar? how would I get indication of a pressure failure? how would I know if I tamper too hard or grind too fine?

I understand that I just need to play with it till I find my sweat spot but having said that I need to know that my equipment is working as it should.

Buying a brew pressure gauge will be the same price as getting a fixed pressure gauge so I rather have a fixed one and maybe adding a temperature gauge at the brew group. I wish I could add a digital fixed temp gauge as I don't like the look of the brew group gauges but that's just me.

Maybe adding a PID is over kill and the only reason I wish to add one is just to be sure that my brew group is at the right temp all the time without the need for a water flash before brewing.

as far as I can tell I need parts 16 & 17 in addition to the pump gauge..

can you guys confirm?

Thanks!

#7: Post by **JRising** » June 14th, 2022, 9:44 am

mosheva wrote:Thanks for the information.
Actually a friend of mine have a Rocket R58 with the same gauge that I want to add to my Cellini and he also have added a brew group group pressure gauge and the reading are the same.. Both gauges showing the same result.
How would I know if my machine is brewing at the correct bar? how would I get indication of a pressure failure? how would I know if I tamper too hard or grind too fine?
Maybe adding a PID is over kill and the only reason I wish to add one is just to be sure that my brew group is at the right temp all the time without the need for a water flash before brewing.

Okay, but your friend's machine is an R58. It has a brew boiler that is controlled by a PID.

Your machine doesn't have a brew boiler, it has a heat exchanger. The heat exchanger is heated by being immersed in the boiler. If you used a PID to keep the boiler at the proper temperature, it would make no difference to the temperature of the brew circuit in comparison to keeping it at that temp with a pressostat.
If you used a PID to keep the boiler at something like 100C to minimize cooling flushes, your brew circuit would take a very long time to heat up, and your brew water would get colder and colder if you brewed anything larger than a ristretto.

mosheva wrote:as far as I can tell I need parts 16 & 17 in addition to the pump gauge.
can you guys confirm?
Thanks!

What would work would be another Female Male Male tee like the one the Appartamento has between 16(check valve) and 14(expansion Valve) in the picture. Placed at whichever side of the check valve you want to read, and the pipette to the gauge would of course go on the tee.

Lastly: A better way to have a PID controlled brew circuit, a working steam boiler, a pump gauge and everything that an R58 has would be to actually have an R58. It's cheaper to buy a real 2 boiler machine than to convert a Heat Exchange machine into one.

Edit: Ian's post below this is from someone with real world experience operating a HX at "just above boiling". Trust his experience over my assumptions.

#8: Post by **cafeIKE** » June 14th, 2022, 12:13 pm

JRising wrote:If you used a PID to keep the boiler at something like 100C to minimize cooling flushes, your brew circuit would take a very long time to heat up, and your brew water would get colder and colder if you brewed anything larger than a ristretto.

I beg to differ. Having PID several e61 HX, the boiler is set to ≈227°F / 108°C, with actual values being machine / PID / sensor dependent. On full HX temp or walkup temp, machine takes about 45 minutes to reach brew temperature subject to environmental vagaries. Ditto e61 DB.

Typical shot profile is a slight droop mid shot. Repeated shots result in a slight overall brew temperature rise, provided one is fast enough and the machine is capable of handling the load.

Back to back shots are not an issue, provided the HX is well designed. No e61, HX or DB, is going to achieve saturated group precision, but definitely keeps the sweet spot for most coffees.

June 23rd, 2022, 5:43 am

Hi,

So I've opened up my machine to figure out the next steps.
As far as I understand if I will add anther T at the market (Red box) location the pipe which goes to the boiler will not fit..
I think that a T just before the boiler will fit.. (Green box)
Any ideas?

#10: Post by **JRising** » June 23rd, 2022, 9:45 am

Some re-bending of pipes would be needed. Maybe a little on the boiler fill pipe to move the whole assembly to the left, then a little on the HX fill pipe to connect to the new Tee.