Wega Mininova EVD Help Please
I purchased a Wega Mininova recently as a non goer at a good price. I have spent a little time on it and made progress. I do have a question though.
When I arrived at work this morning (Monday, after the weekend), the machine was cold. At the moment, I feel that the mains water may be bypassing a valve or solenoid to cause an overfill situation that also cuts out the pressurestat.
I will include my log of work done so far as it may help diagnose the issue. I am an electrician by trade with other restricted tickets in gas fitting and A/C, so understanding basic principles of operation should not be an issue.
Here is my log so far, I usually do something like this so I can look back on the history later :-)
"Wega Mininova EVD
- Purchased July 2016
- Unit had been converted to mains by coffee shop (who?). No original level sensor for tank included though.
- Seller said that the vacuum breaker would need replacing, and that the tank pressure relief valve might too – spare relief valve was included.
- Burnt out wire inside.
- Replaced wire inside – wire to element, crimp connection was u/s. Resecured overtemp sensor to boiler with new thermal paste and double nut instead of single.
- Ordered and replaced vacuum breaker as original no longer sealed. Checked inside of tank, had a little scale but not too bad.
- Replaced boiler pressure relief valve as old one was tested and found to be corroded shut.
- Ran unit, found to be running OK but there was an apparent problem with boiler pressure – adjusted pressurestat but found water temp to be inconsistent. Checked and found scale inside capilliary to gauge, therefore gauge was reading incorrectly and inconsistently.
- Gauge removed and tested with low pressure compressed nitrogen and appears to work OK. Zeroes OK and moves OK, unlike when on machine. Capilliary pretty much completely blocked. Capilliary also corroded onto lower nut on tank, will need to free up some time.
- Pressurestat appeared to be working OK. Set pressure via group head temperature.
- Wet steam was noted.
- Water usually comes out of vacuum breaker when starting up.
- Worked OK for about a week. Came in on Monday morning, found no steam and boiler cold. A little water was on bench but not much.
- Checked pressurestat, was “off” i.e. up to pressure. Found tank had overfilled, allowing pressurestat to click off. Removed pressurestat pipework, flushed and tested – Pressurestat working OK. Reinstalled.
- Removed level probe – appeared to be fairly clean, but used sandpaper to clean surface. Measured length – 125mm overall. Checked level against element, reinstalled and set a little higher than before.
- Switched unit on, began heating OK. Opened steam valve to help reduce water level in boiler as unit has heat exchanger on both brew water and hot water outlets.
- Up to temp fine, steam appears dryer than usual.
- Disconnected level probe, began filling OK (usual slight delay). Reconnected, autofill stopped.
- Leaking valve on inlet? Filling up boiler over weekend/overnight? Causing wet steam? "
A copy of the hydraulic circuit is attached, any thoughts would be appreciated :-)
This is an amazing analysis of the coffee machine problem
I can't see anyone else responding to it though. How did you get it repaired as mine is doing the same thing now... )
Apologies for the late response.
In the end, the temperature problem was a simple issue; the microswitch on the pressurestat had burnt out, and was obviously working intermittently toward the end. It is a common "Mater" pressurestat with a micro switch screwed to the outside. Opening the switch up revealed badly burnt contacts. Finding an identical replacement micro switch was simple as it is a common type, RS Components happened to have what I was after.
The overfill/water level issue seems to have resolved itself, perhaps something was stuck in a fill valve? When it becomes a problem I will start looking again.
The unit is now doing full time active duty at the office :-)