Grundfos ups3 15-50/65 130 fails as replacement for old Grundfos UPS-15-50 Selectric

[ngate]

Hi all,

My trusty Grundfos UPS-15-50 Selectric was looking a bit sorry for itself because the ball valve on one of its pump fittings had been leaking. Since it was now 20 years old I thought it might be a good idea to fit a replacement before next winter sets in (probably around end July given the current state of "summer" 2024)

I plugged the pump's spec into the Grundfos site and was advised to buy a UPS3 15-50/65 130. There was an online manual and everything things looked good so I went ahead and bought one.

Things went well initially. DImensions-wise the pump was a perfect replacement and it certainly looked the part with its matt black finish and rinky-dink led control panel. My problems began when I turned it on.

I've got a fairly demanding system and used to run the old UPS Selectric on its maximum speed setting. I've tried all 7 of the UPS3's speed settings and not one of them seems capable of shifting water through the boiler fast enough to stop the boiler turning off due to over-heating.

I thought that maybe I'd got an airlock or something, but I've now gone through exactly the same procedure to reinstall/uninstall the old pump (ie twice). This still does the job perfectly, despite its horrible, corroded appearance.

Has anybody else had problems with the UPS3? My feeling is that it's under-powered. Can anyone suggest where I might have gone wrong?

Regards, MartinJ

 

[danfre]

Pump valve's fully open?

 

[ngate]

Oh yes - I've been down that bear trap too. Both(!) fully open.

 

[danfre]

Pump in the correct direction

 

[ngate]

Oh yes - there too

 

[danfre]

Air lock, try turning gas off at boiler,
Turn system on and alternate pump speed settings to shift air away from the boiler

 

[ngate]

I could play that game forever. Refit old Gfs- everything fine. Refit new Gfs - burner gives up after 10 min with rads still lukewarm.

 

[Rodders53]

What does Grundfos Technical suggest? Could the new one be faulty out of the box?

Mind, with the old one off, a good clean up and a few coats of paint may have it looking like almost new.

 

[danfre]

Did you try increasing pump speed on new one?

 

[ngate]

@Rodders. I think you've called it right. I need a break from this! Thanks, everybody, for your input. MJ

 

[ngate]

Postscript: I'd recovered enough this morning to give the new pump one last try. It worked!

I now think my problems were indeed down to air lodged somewhere in my pipework (must remember to fit a few more air valves next time I play this game).

I'm still not confident that the new Grundfos delivers the same "welly" as the old one: max input power 60w as against 105w. But it works well enough, and is probably saving the planet.

So I'm keeping it (though I'll still be hanging onto the old one ...)