Replacement Central Heating Pump

silvasava

Morning all. I'm hoping that someone on the MSE collective can help. Our central heating pump started making nasty groaning noises this morning. DH reckons the bearings have gone so he'll replace it. 
Problem is the WS Gold pump he put in over 20 years ago is discontinued. We're looking at a Danfoss,  would this likely to be compatible to the fittings? We have 11 radiators and 7 of them are doubles.
Any info appreciated.

Section62

silvasava said:

Morning all. I'm hoping that someone on the MSE collective can help. Our central heating pump started making nasty groaning noises this morning. DH reckons the bearings have gone so he'll replace it. 
Problem is the WS Gold pump he put in over 20 years ago is discontinued. We're looking at a Danfoss,  would this likely to be compatible to the fittings? We have 11 radiators and 7 of them are doubles.
Any info appreciated.

A 'groaning' noise can just be air in the system.  Are all the radiators fully bled?

Also the pump itself should have a bleed screw on the end, slackening that off should result in drips of water rather than air.  The rotor in many CH pumps is 'wet' - meaning the rotating parts are all running in water rather than sealed.  Being 'wet' helps with cooling and lubrication. The bleed screw on the pump makes sure that the rotor is running in water rather than air.

If you do change the pump then the connecting threads are standard, but there can be variations in the distance between the faces of the 'flanges' (the flat surfaces on the outside faces of the pump connection ports).  To minimise the amount of work needed to fit the pump, just make sure this dimension is the same on the new one as the old.  You'll also need to make sure you/he uses new sealing washers, which are standard, but may not be supplied with the pump.

silvasava

Thanks for your info. Much appreciated. DH has measured the space available for the pump, the Danfoss will fit in size and the fittings are the same size. DH is an ex hydraulics guy so washers are always replaced    As we've had the original pump well over 20 years I think a new one is the best option regardless!

Section62

silvasava said:

As we've had the original pump well over 20 years I think a new one is the best option regardless!

As this is MSE I feel duty bound to mention that replacement pumps are not cheap, and on the old ones there's not a lot to go wrong with them.  My own Gold is approaching it's 30th birthday and still working fine.

Ganga

You say it is a Danfoss pump? do you not mean a Grunfos pump ,a much better item.

Bendy_House

I'm guessing the old 'Gold' has a three-speed selector switch? Note what setting it's on.

Your call, but these days you can get 'smart' pumps (in fact it might be the only option...?) which can be set to 'auto'. These will adjust their flow to suit the demand of the system, so if more rads are open, the pump will provide more flow. As rads shut off their TRVs, the pump will ease back to suit.

Terrific in theory, and quite possibly in practice too. Obviously a lot more to go wrong, tho'...

The last one I fitted even had a 'watt' display to tell you how much power it was using at any time - it was certainly a lot less than the old manual pump was rated at, so theoretically saved some energy cost.

coffeehound

Bendy_House said:
. . these days you can get 'smart' pumps (in fact it might be the only option...?) which can be set to 'auto'. These will adjust their flow to suit the demand of the system, so if more rads are open, the pump will provide more flow. As rads shut off their TRVs, the pump will ease back to suit.  

How does that work, Bendy, can they detect back pressure or something?

FreeBear

coffeehound said:

Bendy_House said:
. . these days you can get 'smart' pumps (in fact it might be the only option...?) which can be set to 'auto'. These will adjust their flow to suit the demand of the system, so if more rads are open, the pump will provide more flow. As rads shut off their TRVs, the pump will ease back to suit.  

How does that work, Bendy, can they detect back pressure or something?

As the back pressure increases, so will the energy consumption. I would imagine that there is some little internal widget that will throttle back the pump to limit the energy consumption to a preset level.

Bendy_House

No idea, Coffee, but I suspect it's as FB says.

Trying to recall which model it was, but it was certainly a Grundfos* - the pump body looked ID to the standard GF's.

* Cough, it was definitely not a GF - it was a Wilo Yonos, having done a Google... :-( (I had flash-backs to it being literally green, so had to check...)

The other one I replaced around the same time was a Grundfos, also 'smart' but only had LED 'bars' to indicate performance.

Bendy_House

How interesting that Grundfos's new models are seemingly around half the price of their 'traditional' range'.

https://www.screwfix.com/c/heating-plumbing/central-heating-pumps/cat831036?brand=grundfos

Is this an example of pressuring a change towards 'eco'? If so, fair do's.

Section62

Bendy_House said:

How interesting that Grundfos's new models are seemingly around half the price of their 'traditional' range'.

https://www.screwfix.com/c/heating-plumbing/central-heating-pumps/cat831036?brand=grundfos

Is this an example of pressuring a change towards 'eco'? If so, fair do's.

It could be, or could be something to do with volume production.

On the other hand, when the rules started changing the cost of 'eco' CH pumps typically tripled (or a lot more'd) compared to the cost of 'traditional' pumps (which IIRC were typically around the £40 mark).


Curiously, CH pumps are still available for around that amount though -
https://www.amazon.co.uk/Central-Circulation-Circulator-Replacement-KBD20-6S-130/dp/B07F8P9ZQJ

So what is that Grundfos one being sold by Screwfix giving you for £259, which the £45 one isn't?