My Grundfos 15-50 that I use for my solar thermal system makes a rattley/cavitating kind of noise when in position 1. Its silent when in position 2 or 3.
Ive bled it a number of times but it wont stay quiet.
Am I doing something wrong? will it be the set up? The gate valves are fully open, changing them doesnt seem to help. Or is it just the symptoms of an old s/h pump?
Oh, I see. As you were. Carry on.
Sounds as though the pump driveshaft bearings might be on their way out.
If so you'll need a replacement pump head, about £70 inc vat.
Prob about £30 to fit (unless you can DIY).
If it isn't the bearings it'll be something else. 😳
I was told (*by an appropriately skilled person) that cleaning them could help.
already had this one open for a clean when it was initially binding after I got it (eBay, s/h). Cant get the impeller/drive shaft out, needs a special tool I think.
Ah well, didnt cost much. When it gives up the ghost then Ill just get a new one and swap it in.
In our old house we had this problem with the central heating pump. Occasionally it would bind too. I posted about it on here ages ago.
I think that would run fine at position 2 & 3, but was quite noisy.
We bought a pump to replace it, but never fitted it as the isolation valves either side were borked too and I couldn't be bothered to sort it.
I'll have to check, but I think we still have the one we didn't fit in the garage.
Think it's one of these:
http://www.screwfix.com/p/grundfos-ups15-50-5-metre-circulating-pump/50183
I was going to say you could have it for a reduced price, but I imagine that postage would be quite hefty & looking on eBay there are people selling new ones for £40 including delivery! I think we paid £70 or so for ours....