Replacing Grundfos 15-60 selectric pump

[donkeeboy]

Hi,

My worcester bosch boiler CDI 40 (not combi) keeps going on a E9 fault code every week or two - I reset the boiler and everything works fine until the next time. E9 means 'Safety temperature circuit has tripped'. Been like this for 2 or 3 months now.

I phoned worcester bosch, he said take the bleed nut out the pump (Grundfos 15-60 selectric - on speed setting 3), force a screw driver in the hole and see if I can stop it - if I can then I have a weak pump. Well I did that, and I could stop the pump with screw driver pretty easy. So it looks like I need a new pump.

Firstly - is it a forgone conclusion that the pump is dying? Is it worth me taking the pump out and cleaning it in a situation like this?

Secondly - Grundfos have a good name - but this pump is only 3 years old. Surely I should expect it to last longer than that. Whats the typical lifetime of a 15-60 pump? It was all installed with my new boiler by a corgi guy 3 years ago.

Thirdly - I'm looking at the replacement bare pump, I can pull this off myself, however all the product pages state the pumps are OK for systems up to 35KW. Well my boiler is 40.8 KW. Maybe this is why it only lasted 3 years, is this a problem? I cant see no bigger pumps, should I get another 15-60 or something else do you think? My system is big - 19 rads + normal style hotwater cylinder. Its a sealed system.

Thanks in advance everybody.

 

[AllyBongo]

If all your rads are heating ok, its probably not your pump

 

[donkeeboy]

Thanks for the reply.

What about this test that Worcester bosch told be to do - by pushing a screw driver into pump hand and see if it will stop? I did that and stopped it - they reckon that means I got a weak pump. Anyone got an opinion on that?

When I get the E9 fault code, nothing works, boiler shuts off. Once reset it will indeed work and get rads hot for a few days, or may a couple of weeks before the next E9 fault.

Its either a blockage, the pump, or the boiler sensors or something. I really dont thnks its a blockage, else prob would stil be there after boiler reset. Only drained the system a few months ago, water was pretty clear.

I have actually witnessed the boiler do this by chance one time when I was stood next to it - it starts making a lot of noise - like it was overheating. Sounds likes its taking off. So I dont thinks its boiler sensors tripping out by mistake - there really is something happening to it. Im no expert, but I think it prob well could be the pump.

I dont want to get a new one tho if I really dont need one, or its gonna die after 3 years again though like this one.

Thanks

 

[cdodds2004]

many things can lower the life off your pump, for instance if its a old system and is pumping aload of crap around that can lower life exspectency of the system drastically, do u no if the system was power flushed before the boiler was installed? does it have inhibitor in? usually a sign of a a well maintained system,

 

[donkeeboy]

Yes it was all 3 years ago - new boiler + pump. Yes it was all power flushed at that time. Its had inhibitor in it, and I drained it a few months ago water still pretty clear. I put new inhibitor in it then too. Its all pretty new and in good nick in other words.

I just wonder about the adverts for the Grundfos 15-60 pump - saying for use on systems up to 35KW. Mine is 40.8KW.

 

[AllyBongo]

What temp does the boiler get to when it starts boiling? Could be the primary sensor playing up, think cdi's should shut off about 88 degrees. Check the burner light to see when it goes off.

 

[donkeeboy]

Under normal operation, it never gets hotter that 80/81 degrees. When it saw it go crazy that time, it went into the 90's and was going up VERY fast. I turned it off in the hi 90's quick.

Basically it seems to act very much like it is air locked - but I am SURE it is not an airlock, I have been bleeding the pump for air a 100 times since this started happinging and no air - well only small amounts of air. It was airlocked after I drained it in the summer, and that time you could really hear loads of air spurting out, not like now.

Cheers.

 

[cdodds2004]

how many radiators do u have on your system, i would hedge my bets and say that your pump is fine on that system, so u have ruled out dirty system, and air, could be a bad pump or possibly a faulty temp sensor causing intermitent cut out, also dont rule out faulty circuit board but would explore all other avenues first, first port of call would be to replace pump, rule that out first, maybe try the new modulating pumps

 

[tamz]

It sounds like there may still be a pocket of air in the system which gets trapped in the boiler from time to time.

You can stop any pump with a screwdriver and it does not take much to hold it.
The 35kw you mention is a bit of a generalisation. Pumps should be selected to suit the load which can be calculated.

 

[donkeeboy]

Thats interesting what you say about being able to stop any pump like that. Now im not sure what to think, im thinking more towards a fault in the boiler now, but thats just a guess.

By the way its just done it again (E9) 30 mins ago. This time I removed the bleed screw from pump completely, reset the boiler, waited 20 mins while it did its initialisation tests, and watched it. When it fired up 20 mins later, there was NO air emitted from the pump (bleed screw completely removed). I was thinking this may be a good idea as the airilock (if that what it is) should be right there, in the boiler directly before the pump at that point in time.

Interestingly, when i found the boiler in its E9 state just a while ago, I noticed the pump was still running. I took off the bleed screw then too, no gush of air, and pump was definitely spinning, I poker a screw driver in there.

This is starting to happen ever more frequently now. Im more confused now tamz has contradicting what Worcester Bosch told be about the pump (ie being able to stop it with a screw driver means its no good).

Any tips on removing an airlock? Previously I just been loosening it off and often it fizzes a bit buit nothing much then stops, I tighten it back up. Should I take off the bleed nut totally, and leave it running like that for an hour or two or something? I want to try and find the airlock, or to be able to rule it out.

Cheers guys.