• Welcome to PlumbersForums.net - The international free plumbing advice forum. Professional plumbers sharing advice with fellow plumbers and DIY alike. Register for free today! - Checkout the Plumbing Advice forum and then our Plumbing Videos area which still needs populating.

Discuss Boiler pump speed wrong? in the Central Heating Forum area at PlumbersForums.net

Messages
8
I had my boiler pump replaced yesterday as the other one had stopped working. The guy said he had one on the van that would fit and the boiler started working again. Now I'm finding the radiators that are furthest away from the boiler arent getting quite as hot as they were before. The pump he put on has 3 speed which are 35 45 50 and he set it to 3 and the one he took off was 40 65 95 and was set to position 2. Its a grundfos pump & it's a fairly large house. Is this just coincidence or do you think I should call him back?
 
Messages
2,162
Your old pump was probably a selectric, has the "new" one got LEDs on it or is it a used old type pump?, if it is then there will be a fairly large reduction in the circulation flow, the impeller may also be partially blocked with deposits.
 
Messages
8
no it was a new pump that he fitted and both the old & new are the same red selectric red ones, only difference seems to be the flow rate, I was just interested in if the lesser flow ratings would make the new pump less powerful than the old
 
Messages
2,162
Can't find any reference to a 35/45/50 watt 5m selectric which would be as rare as a hen's tooth now anyway as they have been superseded a number of times, of course there might be one or two lying around somewhere, unused.
I have referenced a 5M 35/45/50W model but this actually was/is more powerful than your old model, its B energy rated with speeds of 1700/2100/2300 RPM vs yours at 800/1200/1900 RPM so even speed 1 @ 1700RPM is/should be more powerful than speed 2 @ 1200RPM on the old model, so speed 2 or 3 should be "overkill" on the new one. The pump curves bear this out as well. So that pump should be OK except something silly like installed wrong way round or pump isolation valves partially closed. If you still have the old pump note the speeds on this as well.

Can you post a photo of the new pump or jot down the label data, especially the 3 speed settings etc.
All the older, selectric and possibly later Grundfos pumps have a date stamp on them, PC: year&manufacturing week, ie PC:9704 will be a pump manufactured in week4 of year 1997.
 
Messages
2,162
You can see that the replacement pump is almost 12 years old (week2 2010), the old pump was 18 years old (week36 2003).
As you have no idea what condition that replacement pump is in and it's not performing then I wouldn't waste any more time on it and get your plumber to install a new pump, would suggest a DAB Evosta 3 (owned by Grundfos) and a far better choice than the Grundfos UPS 3 as it gives better settings and also displays the Pumps Head, Flow and Power.
 
Messages
7
Incredible. What a shoddy service and a con. The previous pump is a 15-60 (6m head) and the plumber has replaced with an "old" 15-50 (5m head). No wonder the radiators are not that hot. I wonder how much he charged...
 
Messages
7
Yes. If the old pump was set to speed II and the new is set also to speed II, it will be slightly less powerful. So, even a 15-50 in 1990s used more power than a 15-50 made in 2010 and despite what manufacturers say, there is a difference.

I had the same situation in my home. I originally had a 15-60 which I personally replaced with a new 15-50 some years ago thinking that I would not need a 15-60 as my main flow and return pipes are 22m and clean and I only have 10 radiators total. Also, remember that these pumps are using less power now than before. Whilst it's almost the same, I did notice that the radiators were not as hot. Anyway, I am still living with the 15-50 - I have got used to slightly less hot temperature.

I would take take John.g guidance above.
 
Messages
2,162
The selectrics had weird pump curve settings. Have a look at the pump curves.

!5 60 130 Super selectric
1637925134857.png

15 50 130 Selectric
1637925164364.png
The old pump was running on speed 2 and assuming a required flow rate of 15 LPM then that pump will/would deliver that at 2.2M and so will/should the old one on speed 1. The only speed where the old pump is more powerful than the new one is on speed 3. So IF the old pump was set to speed 2 then the new one should have no problem whatsoever on speed 2 or speed 3.

So, IMO, its just not performing, probably because the impeller is blocked up but only worth looking at it if you are handy yourself, just shut the pump isolating valves, remove the 4 bolts and remove the head, replace. Also clean the pump ports. Take a photo first of impeller.
If your plumber is known to you then he should just replace it with a new DAB Evosta 3 for the cost of the pump.
 

Reply to Boiler pump speed wrong? in the Central Heating Forum area at PlumbersForums.net

Top