Noisy Grundfoss 15-60 Central Heating Pump

[M1AYM]

Hello, My central heating seems to have a juddering sound that reverberates around the pipes in the house. I’m fairly convinced this is due to the pump as increasing the speed increases the noise level of the judder. My central heating service contractor advised it was due to hydrogen in the system. Since then I’ve added cleanser and drained it and refilled with no difference. The contractor will not change the pump for noise unless its faulty. I’m currently running without inhibitor until I resolve the issue as its likely I will have to drain again. I’m also running the pump at its lowest of the 3 speed settings to get some sleep.
As an electronic systems engineer, my feeling is that it could be an electrical winding in the pump motor that has gone open circuit and therefore a phase is missing and the motor is stalling in its rotation though I’ve not a lot of experience with AC motors. The other thing I am experiencing is that the when the pump has run for 5 minutes or so it switches off for 2-3 seconds then re-starts. I wondered if this was symptomatic of the same thing or if the boiler control to the pump was designed to do this?
If the capacitor has failed in the pump I would imagine the pump would not start or could this be the possible cause ? Has anyone come across these symptoms before?
The pump is a Grundfoss 15-60 fitted to a house built circa 2002. Having watched a plumber try and replace a pump in my old house, I’d rather not have to replace the entire pump unless its absolutely necessary.
There appear to be 4 alan bolts holding the motor body of the pump to the casting attached to the pipe. Does anyone have experience of separating and repairing/replacing the motor body its self in situ and is it possible ?. Is it possible to change the bearings by stripping in this manor ?
My fear at attempting this is that there will be some gasket behind the pump body which is probably not available as a replacement part and therefore if it leaks afterwards I would still have to replace the entire pump. Any ideas gratefully received…

 

[kevplumb]

you can get the pump head seperate

the o ring is included

 

[M1AYM]

you can get the pump head seperate

the o ring is included

Thanks very much - any ideas where from ?

 

[jtc21]

You won't be able to strip it without taking it off, don't know if replacing the bearings is possible. Best to just replace it. Can get them at all plumbing places. If you're fitting it yourself just drain the whole system to be on the safe side.

 

[RoyMacDonald]

My plumber did replace the motor by uscrewing the 4 allen headed bolts after closing the valves of course. All that you are left with is the back cast iron casing. It's a straight forward swap for the motor and bearings then. There are no moving parts in the back plate and there is no need to drain the system.

 

[M1AYM]

My plumber did replace the motor by uscrewing the 4 allen headed bolts after closing the valves of course. All that you are left with is the back cast iron casing. It's a straight forward swap for the motor and bearings then. There are no moving parts in the back plate and there is no need to drain the system.

Many thanks sir, I will try it. The drawing on the Grundfoss litterature looks to concur. My only worry is getting a good seel when it goes back together. [Im trying to avoid the plumbing replacement as Ive never seen one come out yet by opening the nuts on the valves above and below]. Did your plumer strip a new one to fit or did he get a seel from somewhere ?

 

[M1AYM]

You won't be able to strip it without taking it off, don't know if replacing the bearings is possible. Best to just replace it. Can get them at all plumbing places. If you're fitting it yourself just drain the whole system to be on the safe side.

Thanks but Im trying to avoid the plumbing job.

 

[mrgas]

If you have breakdown insurance then why not just break the pump and get it replaced by your contractor?

Hydrogen in the system my ar5e!

 

[oph]

My plumber did replace the motor by uscrewing the 4 allen headed bolts after closing the valves of course. All that you are left with is the back cast iron casing. It's a straight forward swap for the motor and bearings then. There are no moving parts in the back plate and there is no need to drain the system.

Assuming the pump unions truely lock the water out fully and then open back up again after....

 

[RoyMacDonald]

My plumber did replace the motor by uscrewing the 4 allen headed bolts after closing the valves of course. All that you are left with is the back cast iron casing. It's a straight forward swap for the motor and bearings then. There are no moving parts in the back plate and there is no need to drain the system.

Many thanks sir, I will try it. The drawing on the Grundfoss literature looks to concur. My only worry is getting a good seel when it goes back together. [Im trying to avoid the plumbing replacement as Ive never seen one come out yet by opening the nuts on the valves above and below]. Did your plumber strip a new one to fit or did he get a seel from somewhere ?

He used a new pump and took it apart. One of the nuts on the valve was seized solid an no amount of force with large spanners would shift it. So it would have been necessary to drain the system and cut the pipe otherwise.

Even if the valves let a little water by when closed it only takes seconds to do the swap.

The Gundfoss pump is designed to be removable from the back plate to allow it to be orientated for different situations anyway.

 

[M1AYM]

Many thanks to all of for all the responses - I will be exchanging the complete Grundfos pump by the sound of it. Can anyone recommend a quieter pump than a Grundfoss 15-60 or are they all par for the course ?

Also I have circulated Fernox cleanser before the drain down and then found a Sentinal inhibiter bottle left by the installer. Should I have the system flushed as well or is this mix of chemicals acceptable and should I use Fernox or Sentinal when replacing the water after the pump change ?

 

[oilhead]

You can take the head off a new pump, and use the 'o' ring from it, or change the whole pump. If the union nuts will not undo with pliers or spanners or wrench, then using an old chisel or large screwdriver on the nut wth a hammer, will unscrew them 99.9 times out of 100. Alternatively, hacksaw through the old nuts. Replacements are available from most plumbers merchants for a couple of quid.

 

[M1AYM]

Nice one - thanks. Just looked at the unions again and see what you mean now. Doesnt look too difficuly except slight problem since I made the original post is Ive broke my wrist. Local plummer wants £80 if I buy the pump. I think i might have to do that to get some sleep at the minute. Anyway thanks for the response.

You can take the head off a new pump, and use the 'o' ring from it, or change the whole pump. If the union nuts will not undo with pliers or spanners or wrench, then using an old chisel or large screwdriver on the nut wth a hammer, will unscrew them 99.9 times out of 100. Alternatively, hacksaw through the old nuts. Replacements are available from most plumbers merchants for a couple of quid.