Nuova pump problem

#1: Post by **340valnt** » February 15th, 2010, 8:59 pm

I have a 9 bar pressure with my machine off, It is plumbed direct to water softener It also seems to overfill;.I've checked the boiler ground and needle Checked the solenoid valve and its working correctly.I noticed the pump output is t'd to group head, gauge and bottom of boiler. Do the rotary pumps supposed to have that much pressure flowing thru them without being on
thanx for the help I',m just about lost. Oh by the way I just descaled the machine w citric acid using the pump to draw from a 5gal bucket It didn't do this before
ps do pumps have a bypass or some sort of built in check valve?

#2: Post by HB » February 15th, 2010, 10:16 pm

Sounds like your inlet pressure is too high; the boiler is probably overfilling because the fill solenoid is failing to close (IIRC, they're rated around 70 PSI). Anyway, assuming your machine's pump is like Procon rotary pumps, you should find a pressure adjusting screw similar to the one shown below:

From Procon exploded view; also see Adjusting espresso machine's rotary pump brew pressure?

Counter-clockwise = more water passes from outlet to inlet through the bypass valve = lower pressure. Clockwise = less water passes from outlet to inlet = higher pressure. Barring more specific instructions from the manufacturer, the inlet pressure should be regulated to ~25 PSI.

PS: See Water pressure and the effect(s) it may have on rotary pump for more details and the FAQs and Favorites for related topics under Rotary Pumps.

http://users.rcn.com/erics/ · #3: Post by **erics** » February 15th, 2010, 11:30 pm

I noticed the pump output is t'd to group head, gauge and bottom of boiler.

I don't understand why the pump output (in part) is directed to the grouphead. Are you sure of this? Normally the pump has a check valve in the line leading to the heat exchanger (typically in the bottom area of the boiler). Another part of the pump discharge will lead to the boiler fill solenoid.

Did you need to rearrange any ball valves on the machine to perform this descaling and neglect to return them to their original position?

ps do pumps have a bypass or some sort of built in check valve?

They do have a bypass as Dan explained. This serves to pass ABOUT 80% of the pump's flow from the internal discharge port back to the suction port. No rotary pump is equipped with a built-in check valve as far as I know.

Given the point at which your pressure gage is sensing, it seems to me that your check valve is leaking.

February 16th, 2010, 12:31 am

Is your water softener an RO unit with an auxiliary pump? Or is your water mains pressure too high, for instance, if you live in a high rise with auxiliary pumps? If this is the problem, you need a pressure regulating valve on the line coming into the machine and pump, so the water line pressure is down to 3 bar max.

February 16th, 2010, 1:05 am

it is a 12 liter regenerating type I also have a pressure regulator on house set at 65psi

the green braided hose goes to back to valve then t's off and comes to the front to t boiler, pressure gauge, and up to head

http://users.rcn.com/erics/ · #6: Post by **erics** » February 16th, 2010, 10:39 am

The valve that the steel braided pump discharge hose connects to is the check valve, yes?

It would be nice, of course, to have a hydraulics diagram as the best I have found is here - which has a copy of your posted image: http://www.nuovadistribution.com/images ... s_book.pdf

February 16th, 2010, 2:28 pm

yes there is a check valve attached to a 3 way: 1 braided pump line, checkvalve, rt side to fill solenoid, left to front 3 way: 1 to boiler the other to group bottom thanx i was just looking at the pump diagram and noticed it says 25psi at intake I've never had this problem before. I had to have done something when descaling not sure what. I just spent the morning taking pump off and blowing it out to make sure nothing lodged inside

http://users.rcn.com/erics/ · #8: Post by **erics** » February 16th, 2010, 3:59 pm

Some X-rated pics of your machine's internals, especially the rear would be nice. Someone is going to have the same problem you have or another and anything to enrichen this thread (especially your solution when it turns up) would be useful to them.

February 16th, 2010, 5:36 pm

i found this page of someone doing a restoration
http://www.espresso-restorations.com/NSMAC.html

http://users.rcn.com/erics/ · #10: Post by **erics** » February 16th, 2010, 6:53 pm

Yes, that is work done by a recognized expert. I would save every pic and word for future use.