Replacing Wilo Gold-D pump with Grundfos Alpha 2

[jezcooke]

For a couple of months my central heating circulating pump (Wilo Gold-D) has started getting rather noisy, everything works fine (all radiators and hot water heat up as expected). I tried bleeding the pump in case any air had got in there but there was no sign of any and so this unsurprisingly made no difference. Therefore I guess the bearings in the pump are on the way out and would rather replace the pump now rather than wait for it to die completely – nicer to do it at my leisure rather than as a mad panic when we’ve got no heat or hot water (plus the sooner I shut the thing up the better).

I figure if I'm going to go to the cost and effort of replacing the pump I may as well put something decent in, reading this and other forums Grundfos seem to have the best reputation so I was looking at the Alpha 2 as it looks like it should be very quiet and be able to save a few quid on the leccy bill too. Is this a good choice?

The whole system is original and as installed when the house was built in 1998 and consists of: Ideal Classic FF240 conventional boiler, 10 rads (all with TRVs) plumbed with microbore tails, hot water cylinder (via mid position valve), Wilo Gold-D circulator (for now). There is a manual bypass valve installed (or at least I assume that is what the manual valve in the 15mm pipe that appears to 'short-circuit' the primary circuit is? - see pic below). Last weekend I put Sentinel X400 in the system to give it a bit of a clean and will drain it down fully in a week or two, fit the pump then refill including X100.

If I go with the Alpha 2 would the factory set 'Auto-adapt' setting be the correct one for my system?

Since the Wilo-D doesn't seem to be a current model finding specs on it is a little tricky but I did find one reference to it being rated for 5m head. I can get the Alpha 2 15-50 or 15-60 at about the same price (from different places) I guess either would work but would there be any advantage of either one over the other in my scenario?

I'm curious as to the point of the 'night set-back' function of the Alpha 2 which apparently runs it slower if the feed pipe temperature drops (e.g. at night), but surely the pump is controlled by the boiler or the mid-position valve (which in turn is controlled by the room stat, cylinder stat and programmer) so what's the point in it (i.e. if the hot water/rads are off at night then the pump will be off anyway)? Also it says that this setting is disabled in the event of power loss - again surely power will be cut to the pump repeatedly throughout the day each time demand is satisfied? Do some systems therefore pump constantly (even when there is no demand for heat or water) or am I just being thick?

A picture paints a thousand words as they say so here's the setup in my airing cupboard (I think it's pretty bog standard):

By the way what's the round grey junction box at the top of the image called and what goes on inside it? The pipes go up to the F&E cistern in the loft so I suppose it’s the equivalent of an 'H' join between the fill land expansion pipes, just curious.

Sorry for the long post, I seem to have rambled on a bit but any comments greatly appreciated, thanks

Jez

 

[Hugh Jaleak]

Grundfos have a reputation for being the best, having said that my pump is a Wilo and has been happily running my system since 1999. (it'll break down now....) Id say a Grundfos 15/50 would be more than adequate, the 15/50 is a 5m head, 15/60 6m, only difference i'm aware of other than the price.... Think most modern boilers now control the pump, with a low water content they keep the pump running after the burners have shut down to dissipate the heat. Unsure about the 'night set back' feature, but if the heating/water is timed there will be no power to the system unless timed to be on, so pump wont run anyway as you've said. If the system is pumping constantly i'd assume a fault, its a waste of energy and would likely serve to shorten lifespan of the pump.

That is a manual bypass, with lockshield valve, should have been set when system was commisioned. The 'round grey junction box' is an air seperator, as said, does the job of the 'H' where the feed and expansion pipes connect to the system.

 

[Agile]

If you have added X400 then you need to wait FOUR weeks before you remove it !

I dont see any great point in fitting an alpha pump in your case!

Just put a 15-50.

Tony

 

[jezcooke]

Hi,

Thanks to both of you for your replies.

Tony,

If you have added X400 then you need to wait FOUR weeks before you remove it !

The instructions seemed to recommend between 2 hours and four weeks so I was aiming for the middle ground of around 2-3 weeks. No problem, I can wait an extra week or two and give it the full four weeks if that's best then.

I dont see any great point in fitting an alpha pump in your case!

Could you elaborate on that a little? I thought that since the system has all TRVs that it would benefit from the modulating pump (from a noise and electricity consumption point of view) or have I just been taken in by all the marketing claims? Obviously I wouldn't want to waste money on a fancy pump if it's not gonna gain anything.

Thanks again, I appreciate you taking your time to help.

Jez

 

[Agile]

I appreciate that a DIYer does not have experience and reads the instructions.

In the case of X400 they try to make it look user friendly. In reality it needs 4-5 weeks to have maximum effect.

Its far better to use X800 which does the job in 2-4 hours at a similar price!

The main purpose of the Alpha pump is to reduce the pump pressure when the flow is restricted for example as TRVs close.

In your case you have microbore! We dont know what size, but regardless, my view is that the smart pump would not give any great benefit and to get it to work might have to be on a setting which would not give the advantages your instructions may claim.

The Wilo RS50 is 51w on setting "2" and 35w on setting"1" although with microbore you will almost certainly need to run it on "2" if not "3".

Tony

 

[Statia]

I have a similar setup to yourself Jez. 10mm microbore, Y-plan system.

I had a noisy pump and problems with hammering of the TRV's due to the pressure in the system when they were closing. I fitted a Grundfos Alpha 2 and don't regret it. Perfectly quiet, no more hammering and more energy effiecient.

Takes about a week to settle down and "learn", so leave it a week on auto before messing about with it.

I can't comment on the night function as we don't have the heating on at night. We have a good duck down duvet so no need.

Best of luck.

 

[jezcooke]

Hi Tony,

Thanks for the further info, I'll bow to your experience and leave the X400 in for the four weeks, and duly noted about X800 for future reference.

In your case you have microbore! We dont know what size, but regardless, my view is that the smart pump would not give any great benefit and to get it to work might have to be on a setting which would not give the advantages your instructions may claim.

Thanks for the explanation, the current pump has always been set to setting 3 and I've never changed it (other than briefly when investigating the pump noise!). Looks like you've saved me the cost of the more expensive smart pump. I'm now thinking that if there's no point in 'upgrading' the pump and I'm to replace like with like would the simplest way be to simply swap the Wilo head and leave the existing body? Would the current Wilo RS50 head fit on the current Gold-D body (they look pretty similar apart from the colour)? Otherwise there's a new Gold-D on eBay that I could go for.

 

[jezcooke]

I have a similar setup to yourself Jez. 10mm microbore, Y-plan system.

I had a noisy pump and problems with hammering of the TRV's due to the pressure in the system when they were closing. I fitted a Grundfos Alpha 2 and don't regret it. Perfectly quiet, no more hammering and more energy effiecient.

Takes about a week to settle down and "learn", so leave it a week on auto before messing about with it.

I can't comment on the night function as we don't have the heating on at night. We have a good duck down duvet so no need.

Best of luck.

Hi Statia, thanks for the info interesting to hear from someone who's tried it in a similar situation but darn now I've got conflicting advice oh well at least I've got a couple more weeks of the system cleaning itself to decide in!

Likewise, I don't need the night function I was just curious that this and some other bits of information in the Alpha 2 literature seemed to imply that the pump should be on 24-7 which didn't make sense to me.

Jez

 

[Agile]

You still have not told us what size microbore you have.

If its 10 mm and the house not too big then an Alpha would not be too bad. In that case your old pump setting of "2" would probably have been adequate.

Its not a question of the Alpha not being suitable, it will work, but whether its going to give any significant advantage for the increased cost.

If its 8mm then my advice would be to use a standard pump which are currently all lower energy models now anyway.

You seem to have the old "long shaft" Wilo pump!

I think these are now obsolete and you CANNOT just change the pump head with the current ones! You need to replace the whole pump!

The current Wilo is different from the earlier ones to make it more efficient and has a colour bar graph on the box showing a "C" energy rating.

The bearings on the Grunfoss are harder than the plastic ones on the Wilo but then the Grunfoss is about twice the cost!

I would say a cheaper Wilo is the best cost effective solution as, after cleaning the system, it should last another 10 years at least.

Tony

 

[jezcooke]

You still have not told us what size microbore you have.

Sorry, not sure and I'm at work at the moment so can't go and measure them right now.

You seem to have the old "long shaft" Wilo pump!

I think these are now obsolete and you CANNOT just change the pump head!

You need to replace the whole pump!

OK, thanks for clearing that up. I'll check the microbore size and look into a standard Wilo or Grunfos pump.

Jez

 

[jezcooke]

You still have not told us what size microbore you have.

Sorry, not sure and I'm at work at the moment so can't go and measure them right now.

OK home now, callipers say that it's 10mm pipe to the rads. So I guess the Alpha 2 may still be in the running.

If its 10 mm and the house not too big then an Alpha would not be too bad. In that case your old pump setting of "2" would probably have been adequate.

House is 3 bed detached approx 6m x 6.5m (i.e. about 78 m2 or 840 sq ft)

I have a similar setup to yourself Jez. 10mm microbore, Y-plan system.

Hi Statia (if you're still reading this), since the pump displays its current power, what sort of values does your seem to run at? I guess this would give an idea of how much the pump actually throttles back in reality in a similar scenario to mine.

Jez

 

[Agile]

Is each floor supplied from a central(ish) manifold or a 22/15 distribution with the last part to each rad in 10 mm?

Could I suggest you turn your existing pump back to setting "2" and see what effect that has on the performanance?

If you can measure the flow and return temperatures at the boiler with heating only on and stabilised that will give an inverse indication of the flow rate.

Tony

 

[jezcooke]

Hi Tony,

Is each floor supplied from a central(ish) manifold or a 22/15 distribution with the last part to each rad in 10 mm?

From what I can gather (not ripped the whole floor up but there's a couple of places that I can peak through in the en-suite I'm working on that's next to the airing cupboard) it seems be distributed around the house between the two floors in 22mm and 15mm pipe, then 10mm tails take it up or down to each of the rads.

Could I suggest you turn your existing pump back to setting "2" and see what effect that has on the performanance?

OK will try that, what effect should I expect see if it doesn't perform well (e.g. would all rads warm up more slowly?, some rads not get hot at all? etc).

If you can measure the flow and return temperatures at the boiler with heating only on and stabilised that will give an inverse indication of the flow rate.

Will see if I can get hold of a suitable thermometer (not sure if the kids' forehead one has a high enough range!)

 

[Statia]

Hi Statia (if you're still reading this), since the pump displays its current power, what sort of values does your seem to run at? I guess this would give an idea of how much the pump actually throttles back in reality in a similar scenario to mine.

Hi Jez,

When the rads are stone cold, the pump reads 15w. With most of the TRV's closed, it drops to about 8w. The pump is so quiet, only aural indication that the heating is on is from the flue fan in my Glow Worm Micron boiler, which I think has bearings which are on their way out.

I know the Alpha 2's are an expensive piece of kit, but I do a lot of DIY and the way I see it is that I save so much money by not using tradesmen, that I could afford to buy the best pump. I got mine off the 'net for ~£100 delivered. You can buy a cheap pump, but as my missus always says ... "Buy cheap, buy twice", and she's quite right. Personally, I would't touch a wilo pump, but that's just my opinion. I suppose it all depends on available funds etc.

Also, the Alpha 2 is the only pump I know of on the market which has an "A" energy rating.

Finally, spend a couple of quid and get some quality fibre washers from B&Q when fitting a new pump. The rubber ones which come with pumps perish over time.

 

[jezcooke]

Hi Statia,

Thanks for the info, very interesting, those readings are lower than I would have expected (of course that doesn't necessarily mean that I would see the same low readings).

I fully agree about buying quality, and it'll take just as much effort to install a cheapie pump as a decent one. I have no problem spending the money on the Alpha but of course I wouldn't want to waste money if it's not going to be any more effective than a standard pump in my situation. I also like to do quite a bit of DIY (although fitting it in between work and kids can be an issue) and it certainly saves a lot of money but equally it also means that I get the satisfaction of achieving something rather than just paying someone else to do it for me. On top of that I gain a much better understanding of how everything within my house works so I'm in a much better position to deal with things when they stop working as they should.

Funny that you should mention the fan's on the way out on your boiler, think the same is true of my Ideal, it started making a right racquet for a couple of days in December but then seemed to settle down again by itself (although I think it's still noisier than it should be). In that case though, despite it looking very straightforward to change, I think I'll employ someone qualified to fit it (I’m rather more paranoid when it comes to the gas side of things!).

Jez