After coming back to my Faema Compact Hx after a few months in lever land, i'm experiencing what I diagnose as a cool and underextracted shot... slightly watery and on the sour side, fast pours despite a very tight grind compared to usual. I'm having no issues with the same beans and grinder on a Cremina.

The group is warming up nicely and too hot to touch so i'm ruling out thermosyphon stall, however after an hour of warm up time at 1.2 bar i'm not getting the initial flash boil during the cooling flush.

I have verified by brew pressure to be 9.5bar with a blind, however i've observed an unrestricted flow rate of 750ml/min. I have a FoT 1106 vibe pump installed.

So my question is... is my flow rate too high? Could this cause a cool shot by not allowing enough time for brew water to reach temperature as it passes through the HX? What flow rate should I be targeting and can I achieve this by regulating the mains pressure? (4 bar on the pf gauge with the solenoid open and the pump disconnected).

A 750 ml/minute flowrate with that pump leads me to believe that you are either missing a gicleur or the existing one has been drilled out to remove its intended effect.



That flowrate has no direct relationship to shot temperature.

Eric thanks for reposting that chart - I recall seeing it in another thread but coudn't put my finger on it. Am I correct that this graph indicates I should be targeting a flow rate of ~200ml/min for the 1106?

I recently replaced the gicleur with the OEM part while dignosing a bad pump a few months ago so i'm fairly sure this is not the issue unless I was shipped the wrong part in error. (it was the same size as the one in the machine when I recieved it)

I've been reviewing the parts diagram for the main water distribution valve which sits between the pump and the brew circut to direct water to the boiler during autofill. I've noticed the autofill is very slow to fill the boiler. Is it possible that the distribution valve is diverting too much flow to the brew circuit?

Back to my observations on temperature...my theory is that too much flow going through the HX is causing the thermosyphon to circulate so fast that the water inside never gets superheated. The group is very quick to heat up.

I am at a little disadvantage - never having seen this model - but, this link shows you to have a 0.50 mm gicleur: http://www.cafeparts.com/listCategoriesAndProducts.asp?CategoryID=2706&gclid=CPHU8PuR9aYCFQl_5QodmkVUCQ - pretty small at ~ 0.020".

The only way to get a good handle on brew pressure (live) would be to buy a spare plug for the grouphead (item 4 in the link) and drill/tap for a pressure fitting to be read during a normal shot.

Is it possible that the distribution valve is diverting too much flow to the brew circuit?

Even if it were, there's no place for the water to go in the brew circuit as the brew circuit only comes into play during brewing or flushing. But, back to your observations and assuming your flow is higher than design (for whatever reason), that would simply lessen your flushing time. Once the pump is operating, the thermosyphon flow inherently comes to a halt.

Unfortunately, those curves are really only valid for a pump taking suction under atmospheric pressure, i.e. a reservoir but I would say that the 200 ml/min figure with ~ 9.0 bar measured at the pump would be valid. Some of that 200 ml would head to the drip tray via the OPV in the water distribution assembly.

The only way to get a good handle on brew pressure (live) would be to buy a spare plug for the grouphead (item 4 in the link) and drill/tap for a pressure fitting to be read during a normal shot.

I had my eye on that plug to drill and tap in a thermocouple (or modify your adapter for this fitting.. any suggestions?). There is an unused fitting on the distribution valve I had intented for a pressure gauge but this is between the pump and the gicleur. I think you are suggesting measuring after the gicleur would be a more accurate location for a real live brew pressure.

My next steps are to draw from a bucket and measure the flow rate and brew pressure with the pf gauge. Perhaps this machine is simply unhappy when fed 4bar.

Thank you Eric for your help as always.

That's for sure that measuring the brew pressure downstream of the gicleur during actual brew conditions is optimal. The importance of brew pressure can be wildly debated but the information I have seen is that approaching numbers like 11.0 bar can be detrimental to your brew (not that you are close to this) and that real values a little less than 9.0 bar seem to be "just right".

What would be important is that my brew pressure is "x" in February and the same "x" in April - should I want to keep it that way.

While I think that you might have a bigger problem, I want to point out something. On my Compact, there is a screw on the water distribution valve that controls flow rate (there is also one for the expansion valve-dont adjust that). You might want to try adjusting this screw if you want to lower the flow rate.

Hi Frank; thanks for chiming in. If I recall, that screw controls how much pressure is diverted between HX and boiler circuits if the autofill happened to turn on during a brew cycle. I opened it as much as possible without it falling out and observed no change in flow rate, not surprising given the autofill was closed. When it is tightened down, all flow is cut off to the boiler during autofill.

It looks to me like as long as the autofill is off, this screw has no effect. Have you used this to regulate flow to the group when the autofill is OFF? Maybe i just need to find the perfect set point?

I can't remember whether the autofill was on or off while i was adjusting it. Also bear in mind that my water distribution valve is different than almost any other that I've seen on other Compacts. So it may work a little bit differently...

Hi Frank; thanks for chiming in.

Boy, do I concur with that. One thing you could do Frank, if you get the chance, is to measure your flushing flow rate and compare it to Michael's. A typical rate is 500 ml/min (or lower) for other machines I have measured and on those reported here on HB.

But, the autofill and the flushing rates are completely separate items which can only simultaneously occur when you have a streak of bad luck. Can it happen? - of course. Is there a way to avoid it? - of course - just hit the manual fill button for a second or two prior to pulling a shot. The water distribution assembly for this machine is complex and it is unique (and very interesting) in that the autofill rate is adjustable. The OPV in the water distribution assembly is very likely a "thermal" OPV designed to offload excess pressure that develops in the hx circuit due to water expansion. The pics that I have seen of this machine show a "hydraulic" OPV used to adjust pump discharge pressure by routing some water back to the pump's suction connection. This valve is most definitely designed for adjustment because of varying installations.

Here is the best source I have found for Faema technical info, including manuals and parts catalogs, should you not have those - http://www.faemasource.com/