(Note, this problem was solved with the help of member erics (see the last posts in the thread). Yet another fine example of folks in this forum sharing knowledge and helping each other out -- Thanks!)

I am restoring a 1979 Elektra single group HX commercial machine (see the detailed post in the restoration section of the coffeegeeks forum for the details of my adventure with this project).

I have a problem I would like to address to the larger audience in this forum that has to do with a problem I'm having with restricted water flow to the grouphead when the brew circuit is engaged.

Here's what I know so far:
1. The pump seems to be working fine because it fills the boiler quickly even when it is under pressure (about 1 bar).
2. The plumbing from the HX to the grouphead seems to be flowing just fine because the grouphead heats up quickly when the boiler is heating up and stays hot -- so the convection heating plumbing (which also supplies pressurized water when the brew circuit is engaged) must be flowing freely.
3. Given the above 2 facts, the 4 areas that I can think of that might be involved in restricted flow are:
a. The solenoid that engages when the brew circuit is engaged that diverts water from the pump from the boiler to the HE.
b. The check-valve that is in the line from the solenoid mentioned in "a." to the HE might be clogged-up.
c. The pressure-relief valve for the HX might be leaking (although I don't seem to see much water flowing from the drain line when the brew circuit is engaged, so I doubt this is the culprit
d. There may be a clog or a partial blockage of the 3way valve in the grouphead causing the restriction

My question to you repair and maintenance gurus out there is which is most likely to be the culprit? Have I missed any possibilities?

The flow of water from the procon pump to the grouphead when the brew circuit is engaged is as follows:

1. The selector solenoid that determines where the water from the pump goes to is engaged to send the water to the heat exchanger (HX).
2. The water then flows through a check-valve
3. The water then goes into the bottom of the HX, where there is also a line going to a pressure-relief valve that is connected to the drain line.
4. The water line from the top of the HE goes to top port on the grouphead.
5. The water line from the bottom of the HE goes to the bottom port on the grouphead.
6. When the brew circuit is engaged, the 3way solenoid valve in the grouphead is activated and allows the water to flow to the filterscreen in the grouphead instead of recirculating through the channels in the grouphead.
7. When the brew circuit is turned off, the 3way solenoid valve in the grouphead closes off the flow the from the HX to the filterscreen in the grouphead and opens up the convection water flow through the grouphead from the HX.

That's the water circuit in this machine as I understand it.

I look forward to your replies and assistance.

Thanks,

Philip


PS added by moderator: Same question cross-posted on Coffeegeek.
PPS added by poster -- I got no response on Coffeegeek, so I posted the question here.

And you believe this flow is restricted because . . . ?

What is the discharge pressure of the pump, what is the measured flow out of the grouphead with an empty portafilter? This site has a pretty decent search function: http://www.home-barista.com/forums/search.php?keywords=elektra+flow&terms=all&author=&t=0&submit=Search&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300
A typical flowrate through an empty portafilter is about 500 ml/minute but, IIRC, Elektra's tend to be higher than that number.

Hi,

Thanks erics for responding!

In answer to erics response, the initial reason I thought there is restricted flow is that it just seemed way too slow -- no matter what coarseness or fineness of grind I used (or for that matter even with no grounds at all).

I took erics suggestion to heart and did a measurement of the flow with an empty portafilter. The result is that less than 30 ml is dispensed with an empty portafilter in 10 seconds. It looks to be about 25-28ml -- I don't have a way more accurately measure the flow than to use a shotglass that is marked at 1oz (30ml) and 1.5oz (44ml), and slightly less than 1oz is dispensed in 10 seconds.

As I mentioned in my first post, the pump has no trouble refilling the pressurized boiler (about 1 bar) when I draw a cup of water out of the hot water tap on the machine (which draws out of the boiler) -- it does so in just a few (3-4) seconds.

That's why I don't think the pump or supply is the issue.

I will be doing grouphead pressure test tomorrow, but I think that isn't the problem as I get quite a spray out of the 3way solenoid valve when a shot is completed. I've played with trying finer and coarser grinds, and the only thing I see that is different is the amount of pressure that seems to be released from the 3way solenoid valve when the shot completes -- the finer grind seems to have more backpressure when the valve opens up -- which makes sense as the finer grind restricts the flow through the puck more. However, neither coarser or finer grind seems to effect the overall low rate of flow, which was verified by the empty portafilter test.



Where do you folks suggest I start looking for the restriction -- the check-valve, the 3way solenoid, the orifice in the grouphead (I didn't realize there was one until I read some of the threads that erics suggested search brought up), or the overpressure relief valve?

Which seems the most likely to you folks?

Thanks for the help!

Philip
P.S. Yes, I also posted this question to the coffeegeeks.com forum, but the reason I did is that I got no replies, and so turned to both places hoping I could get some help.

phreich wrote:As I mentioned in my first post, the pump has no trouble refilling the pressurized boiler (about 1 bar) when I draw a cup of water out of the hot water tap on the machine (which draws out of the boiler) -- it does so in just a few (3-4) seconds.

Steam pressure pushes the hot water out. You can turn off your machine and it will still work, as long as its still hot (as in steam). The pump will refill it eventually, but its not related to output you see at the hot water tap. Because of this, your initial 2 facts aren't really facts, so does that change your gut feelings on probable causes?

Your flow rate is low. Are you plumbed in? If so, when you pull a shot, can you hear the pump running? You might be just running on line pressure.

Also re-run your flow test with no portafilter. Crappy old pfs could be well gunked up and distort the numbers.

Thanks gyro for responding.

What I meant when I talked about the pump refilling the boiler quickly was that, after I drain about a cup of water from the hot water tap, the pump comes on and refills the boiler fairly quickly -- replacing the 8 ounces of water that was dispensed from the hot, pressurized boiler. This seems to indicate that the pump is not the issue -- am I not correct in this?

The water test I ran was through a brand-new portafilter screen, so nothing was clogged. I get the same result without the portafilter in place (just capturing the output of the grouphead).

The machine is plumbed in, and the pump does come on when the brew circuit is engaged. The flow test I did had the pump running.

Any further thoughts?

Philip

Sure.

a. Inspect the gicleur and gicleur filter.

b. Disassemble/inspect/clean the brew solenoid valve.

When you are measuring flowrate, the better method would be to dispense into a pyrex measurer and time the delta between 2 ounces and 6 ounces or 4 ounces and 8 ounces, etc. etc.

Some X-rated pics of your machine would be helpful as I'm sure some listeners are wondering what an early Faema/Elektra looks like.

Thanks again erics!

I have just completed looking at the orifice/gicleur and found the following:

I took the large nut off the top of the grouphead and took out the orifice/gicleur -- it looks pretty small (I have no way to measure it), but it is not clogged. It is different from the current models that use a raised orifice with a slot on the top for a flat-bladed screw driver -- the orifice in my machine has threads on the bottom but then screws down flush to the inside of the grouphead -- showing only what looks like a 6-sided nut -- it looks a lot like some carburetor jets I've seen in the past. Also there is no filter or spring inside the opening -- just the orifice -- although there's lots of room that could accommodate a spring and filter. Maybe a past owner or servicer removed them for some unknown reason -- I plan to order and install them when I can.

According to what I read, it looks like the orifice should be about 0.9mm -- this one looks much smaller than that. Could the wrong orifice have been put in?

When I took the large nut off the grouphead, I discovered that water flowed out of the opening quite freely from just line pressure (the machine was turned off). Given this, it seems to remove the check-valve as an issue because water flows through it quite easily.

Water flowing from line pressure also would seem to eliminate the solenoid valve that controls whether the pump sends water to the boiler or the HE, because it looks like the HE is the default -- not the boiler. Am I correct in eliminating both of these as a potential cause of the problem?

I will disassemble the group-head the rest of the way and see if something is not right with the 3way solenoid. Since water doesn't flow out of the grouphead with just line pressure, I guess that I can assume that the 3way solenoid default is to close off the water from the orifice and open a path from the portafilter to the drain so that pressure is released from the portafilter when the brew cycle is done. The other solenoid position must be to allow water from the orifice/gicleur to flow to the portafilter when the solenoid is activated during the brew cycle. Am I correct on this?

I'll update this once I have disassembled and inspected the 3way solenoid on the bottom of the grouphead. I think I may try a test without the orifice/gicleur in place to see if water flows freely out of the grouphead. Maybe that would be an indicator that the wrong orifice/gicleur was installed.... I'm not saying that I would ever normally run without a orifice/gicleur -- but this test might eliminate some other possible culprits....

Thanks,

Philip

Update:

I did a quick test with the orifice/gicleur removed, and about 12 ounces of water flowed through the empty portafilter when the brew cycle was activated for 10 seconds. I think this probably eliminates any problem with the 3way solenoid, doesn't it?

I want to complete the pressure test (I have to get some fittings to connect a pressure gauge to the portafilter with a "t" and a needle valve in place to allow a small amount of water flow to simulate a shot being brewed.

If the pressure test comes in okay (about 9 bar), then does it seam that it could be the wrong orifice/gicleur was installed?

Of course if the pressure is too low, that would also explain a lot too -- but I kind of doubt it because of the evidence that I mentioned earlier that I saw when I ran a test with really fine ground coffee (when the 3way solenoid released the pressure from the portafilter it really shot out of the drain -- which would seem to indicate that quite a bit of pressure had built up behind the puck).

I'll update once I have run the pressure test.

As always, your opinions and thoughts are welcome.

Philip

What all of your numbers tell me is that your non-gicleur, unrestricted flowrate is ~ 2130 ml/minute which is sorta "off-the-charts" even for a single group commercial machine. And yes, the standard gicleur for later model Elektra's is 0.90 mm. You can size the existing gicleur fairly accurately, carefully using some numbered drill bits. Off-the-shelf gicleur's tend to be around 0.50 mm +/- 0.05 and the end user is expected to ream it to desired size. Maybe you have one of these in your machine?

All(?) espresso machine solenoid valves, both brew and boiler fill, have a built-in orifice which varies with the application. For example, Rancilio Silvia is 1.0 mm; LM GS3 is 1.20 mm. A typical size would be 1.0 mm and it does seem as though yours is OK. What is the nameplate information on the pump? IIRC, Elektra's tend to go with relatively high flow pumps.

Thanks erics,

Your comment about "on the shelf" orifices being drilled to 0.5mm was the clue that got the problem solved. I took it into a shop who had a set of orifice drills, drilled it out to a numbered drill size 65, which is just slightly under 0.90mm. I got the conversion from this chart (a very handy chart that shows the inches, mm, and numbered drill sizes):
http://www.keygas.com/tasks/sites/defau...hart-1.pdf

A number 65 drill is .0350 inches, and 0.9mm is .0354 inches so it is 4 thousandths of an inch undersized -- about 0.88mm. The next size larger drill, number 64 is .0360 inches, or 6 thousandths oversized. I think 4 thousandths under is close enough. I figure I'll try the slightly smaller hole first and see how it does. If I need to order a .9mm drill I will.

I got it reassembled and ran the brew circuit and WHAT A DIFFERENCE! It is now putting through a good amount of water (I haven't measured it yet). In the process of working on this the solenoid that diverts water from the pump to the boiler stuck open, causing the boiler to overfill and leak out of the safety check valve on the boiler, so I had to clean it out (some scale had built up in it). All seems to be working again. I have the boiler heating up and I'll try a shot later tonight (decaf).

I am working on building a pressure test setup with a spare portafilter, a T, a pressure gauge and a needle valve (to simulate a shot being done). I hope to have that tested tonight so I can dial-in the brew pressure right to 9 bar -- it may be there already, but I won't know until I test it.

Thanks again for the help!

Philip
P.S. If anyone is interested in reading about the restoration of this machine, you can view the post at the following URL:
http://www.coffeegeek.com/forums/espres...ods/499708