Central heating pump sizing

[John.g]

I can certainly suggest a 6m Wilo Yonos Pico that I installed 2 years ago in my 10 rad system like your own and it works perfectly, Grundfos or DAB is often the preferred choice of some, I will suggest one later.

Because you have chemically cleaned you system regularly, I would install the pump first and see how your system performs, if performing exactly the same, I would immediately remove it and re install the old pump until the power wash or whatever is carried out.
But if you are handy yourself, it only takes less than a hour to remove the existing pump head, inspect. clean and replace, the impeller may just be full of crap.

The pump head is the differential pressure (head) measured in meters between the pump suction and discharge and the chosen pump differential head required depends on the frictional resistances in the systems piping, radiator & fittings, boiler Hx resistance etc. at the required flow rate. A 6M pump will be quite adequate for most domestic systems but its very rarely that the pump would have to run on speed3 as a much lower head of say 2.5 to 3.5M is only needed to give the required flow rate.

 

[SJB060685]

If we had an idea of extension and existing pipework sizes and runs we could guesstimate a bit further.
Furthermore I just want to thank you again John. I've never really dived into the exacts of pump characteristics, partly because I've never needed to and partly because of laziness maybe but my understanding now is better.

 

[Reddwarf4ever]

I can certainly suggest a 6m Wilo Yonos Pico that I installed 2 years ago in my 10 rad system like your own and it works perfectly, Grundfos or DAB is often the preferred choice of some, I will suggest one later.

Because you have chemically cleaned you system regularly, I would install the pump first and see how your system performs, if performing exactly the same, I would immediately remove it and re install the old pump until the power wash or whatever is carried out.
But if you are handy yourself, it only takes less than a hour to remove the existing pump head, inspect. clean and replace, the impeller may just be full of crap.

The pump head is the differential pressure (head) measured in meters between the pump suction and discharge and the chosen pump differential head required depends on the frictional resistances in the systems piping, radiator & fittings, boiler Hx resistance etc. at the required flow rate. A 6M pump will be quite adequate for most domestic systems but its very rarely that the pump would have to run on speed3 as a much lower head of say 2.5 to 3.5M is only needed to give the required flow rate.

I can certainly remove the pump for cleaning. The Pico you have is 6m, does that mean 6m head ? So when you refer to a pump size by head, is this a different way of saying differential pressure ?
I will check the pump first and if clean, will replace with one as suggested..the restriction is as. See it...1 - the pump 2 - sludge build up in the pipework and or HX 3 - pipework modifications
FYI the extension added 6 extra rooms and a 30% increase to the lounge......

looking forward to seeing suggestions of pumps, Amazon links would help, pump numbering could be an issue in searching

is this the one you have ? https://smile.amazon.co.uk/Wilo-421...ords=6m+Wilo+Yonos+Pico&qid=1609116976&sr=8-3

whats the numbering mean ? There are so many similar models are greatly different prices

 

[John.g]

Yes, that's my pump, 6M or whatever always refers to the differential pressure head.

Referring to these numbers.

Wilo 4215516 YONOS PICO 25/1-6-130-(Row), Green​

the 4215516 is probably the Wilo model number.
25 is the diameter of the pump ports in MM.
1-6 is the operating range in meters.
130 is the distance in MM between the pump end connections and is very important as some pumps are "longer" so measure this on your own pump, if not 130mm then you will have to crop and remake one compression fitting which would mean system drain down.
Don't know what ROW means.

Am I correct in assuming that your house with extension has 10 rads?.

Here is a link to a DAB Evosta 3 which is a 7M pump (which you may prefer) which displays power, flow rate and pump head, just make sure before purchase that you are getting this exact model with that display. It also seems exceptional value for money and I would have no hesitation in recommending it.

https://www.stuartplumbing.co.uk/dab-evosta-circulating-central-heating-pump-replacement-grundfos-pump/

 

[SJB060685]

6 extra rooms and a 30% increase to the longe will add quite a lot of resistance to the circuit, on top of what was already there.

 

[Reddwarf4ever]

Yes, that's my pump, 6M or whatever always refers to the differential pressure head.

Referring to these numbers.

Wilo 4215516 YONOS PICO 25/1-6-130-(Row), Green​

the 4215516 is probably the Wilo model number.
25 is the diameter of the pump ports in MM.
1-6 is the operating range in meters.
130 is the distance in MM between the pump end connections and is very important as some pumps are "longer" so measure this on your own pump, if not 130mm then you will have to crop and remake one compression fitting which would mean system drain down.
Don't know what ROW means.

Am I correct in assuming that your house with extension has 10 rads?.

Here is a link to a DAB Evosta 3 which is a 7M pump (which you may prefer) which displays power, flow rate and pump head, just make sure before purchase that you are getting this exact model with that display. It also seems exceptional value for money and I would have no hesitation in recommending it.

https://www.stuartplumbing.co.uk/dab-evosta-circulating-central-heating-pump-replacement-grundfos-pump/

Thanks for the numbering info, mine is a 130mm a Wilo Gold, the link you gave shows a 5m pump, However the specs say up to 6.9m, bit confusing unless incorrectly listed....also

MPN	60161174 doesn’t mention the on pump displays you mention, unless it’s a different model ?

Certainly sounds good, DAB also come with a 3 year guarantee.

P.S. I have 12 radiators includes 3 towel rads

 

[John.g]

The Wilo is a 6M pump (your link). The DAB (my link) is a 7M (6.9) pump.

• "Operating range: from 0.4 to 3.3 m3/h with head up to 6.9 meters."

Don't have any code but the description should be enough ie DAB Evosta 3 but check with your supplier.

 

[Reddwarf4ever]

The Wilo is a 6M pump (your link). The DAB (my link) is a 7M (6.9) pump.

• "Operating range: from 0.4 to 3.3 m3/h with head up to 6.9 meters."

Don't have any code but the description should be enough ie DAB Evosta 3 but check with your supplier.

Hi
the link you gave shows a 5m pump but specs say 6.9m also no mention of the display options, have emailed them and also DAB evosta, their email address is not on their website, but on the very last page of the downloadable [email protected]
sounds very promising, as you say, need to get the right one.....Amazon have loads of V3 various prices....

the DAB pump has 40 as the connection size, my Wilo Gold is 25mm will that be an issue ?

 

[John.g]

The "normal" connection size is 1.25 ins which is the internal dia of the threaded part, I measured the OD of the threaded part at ~ 47.6mm, measurement across the flats on the isol valve(s) attaching nuts is 2 ins. (51 mm)

 

[Reddwarf4ever]

The "normal" connection size is 1.25 ins which is the internal dia of the threaded part, I measured the OD of the threaded part at ~ 47.6mm, measurement across the flats on the isol valve(s) attaching nuts is 2 ins. (51 mm)

Wilo 4215516 YONOS PICO 25/1-6-130-(Row), Green​

the 4215516 is probably the Wilo model number.
25 is the diameter of the pump ports in MM.
My Wilo Gold is also quoted as 25, just confused why the DAB has a 40 at the beginning of the number ???

The Wilo is a 6M pump (your link). The DAB (my link) is a 7M (6.9) pump.

• "Operating range: from 0.4 to 3.3 m3/h with head up to 6.9 meters."

Don't have any code but the description should be enough ie DAB Evosta 3 but check with your supplier.