Replacing a central heating pump

I need to replace our ailing CH pump, a Grundfos UPS 15-50. The CH system is a straightforward Y-plan set-up in a 4 bed house, with TRVs.
Grundfos literature recommends either their Alpha 2L 15-50 or UPS2 15-50/60 models.
Which is the better choice for performance, economy, reliability? Any benefits/gotchas re installation[1] of one product versus the other? Other brands worth considering?
[1] I'm aware of the horror stories re stuck isolation valves etc that can afflict any pump replacement project :-(
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wrote:

When we had the CH installed just over 3 decades ago, the CH firm fitted a Grundfos pump. Since this was our first experience with CH, we just assumed that the low frequency vibration in the pipework was 'normal' (it wasn't exactly loud).
When it packed up 4 or 5 years later, I was rather put off fitting another Grundfos and bodged a replacement from a similar sized recirculation pump that my dad, bless him, had rescued from going into the works skip (may have been part of the cooling system for the innards of a water cooled IBM mainframe - he had a plum job of maintaining the air conditioning plant at a major finance house).
These pumps were of the split dry electrical side / wet iron rotor running in water lubed ceramic bearings, seperated by a thin aluminium sheet. I only mention this in case anyone recognises the design as being specific to a particulr brand or model range since I no longer have them to hand to check for any maker's markings which, I'm now unable to recall other than it most definitely wasn't a Grundfos pump.
Anyhoo, this type had the unfortunate habit of seizing up every other year or thereabouts so it became a regular routine to swap out with the other refurbed pump (my dad had managed to liberate another one of these pumps). At first, the pump isolator valves 'worked as advertised' but there did come a time, maybe 10 or 12 years later when the isolator valves started to leak past the o ring seal on the actuator spindle (screwdriver slotted ball valve type) and exhibited leakage in the shut off position when I next had to fix the pump.
At this stage, I'd had enough of those 'cast offs' so, with some reluctance I bought myself a replacement Grundfos UPS 15-60 130, along with a pair of gate type isolator valves. After successfully installing the new pump, I was staggered by the almost total absence of vibration. The pump is still quietly beavering away over a decade later, still just as quiet as the day I first powered it up.
I don't know why the first Grundfos pump had been less than silent, and had finally failed after only 4 or 5 years of service, perhaps a "Friday Afternoon" job in the factory or just possibly, the CH installers had fitted a secondhand pump or maybe that second Grundfoss was just an exceptionally well made example.
If my only experience with Grundfos had been just the replacement I bought over a decade back, I'd have to say Grundfos can make a high quality and reliable pump. My experience with the original rather spoils things a little but I suppose I could assume that it was either an exceptionally bad example or else had been a secondhand pump to start with.
All I can say with any certainty about the Grundfos UPS 15-60 130 pump is that they can make a high quality pump. The only question is whether they can do this consistently or only one in fifty times.
I think you'll need a consensus of opinion by a reasonable sample size of DIYers or else the opinion of a CH engineer who's dealt with a few hundred of these pumps in his time.
Incidentally, those other pumps I bodged up were about the same as the original in terms of noise and vibration. This is why I was (and remain) so impressed by that replacement Grundfos.
HTH &HAND
--
J B Good

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On Wed, 10 Sep 2014 01:48:45 +0100, Johny B Good wrote:

The stupid feckers didn't bleed it. None of the three pumps here were bleed after the refurb. Two were reused from the old system so didn't get much air out of them. The new one, in the solar thermal circuit, was decidedly noisey until I bled it.
All three are quiet, though one mounted in some vertical pipe work with a solid pipe clip where the pipe turns 90 deg to follow the floor does transmit a bit of hum. I expect a thin bit of rubbery stuff in the clip will stop that.
--
Cheers
Dave.
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On 09/09/2014 13:44, nemo wrote:

Just found this document that compares the two models. Page 6 is interesting, discussing the 'clever' features of the Alpha 2L. What does the panel think?
<http://assets.grahamplumbersmerchant.co.uk/product-docs/12276/12276.pdf
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nemo wrote:

I had to strip ours down a few weeks ago, because a flake of magnetite made it seize up. Easy fix, but having two sets of waterpump pliers is handy. Big tray and old towels underneath, too. Our valves weren't exactly stuck, but I couldn't stop them dripping copiously. Lots of black sludge, too.
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On 09/09/2014 13:44, nemo wrote:

Update: I had a Grundfos Alpha 2L 15-50 pump fitted - I chickened out of DIY and was glad I'd done so, given the struggle the plumber had with removing the old one.
I was swayed to that model mainly by the promise of reduced noise through the pump's electronics modulating pressure according to demand. A secondary consideration was economy: between 5 and 24 W electrickery consumed versus 7-48W for the alternative. The purchase price difference of only about £5 helped as well. BTW the old one gobbled 70W on its medium setting.
It has certainly delivered on the noise front - it's *very* quiet. We've had to retrain ourselves not to worry that the heating isn't working just because we can't hear the pump running.
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