difference in pump sizes

[holty]

hope the non return valve aint going on the vent pipe.

 

[D_Hailsham]

I would have thought that if your installer has sized your system at 40KW like your boiler

It must be a very large house if it needs a 40kW boiler for heating. Makes you wonder if the installer did any sizing.

Even with 22 rads at a minimum of 1KW your getting to the borders of your pump,

They would have to average 1.8kW to justify a 40kW boiler; which is another reason for thinking the system has not been sized properly.

The Grundfos sizing calculator suggest a 15/60 or a Magna 25/60, depending on the head.

 

[Biggles..]

Thats what makes me laugh about the Grundfos web calculator.

those 2 pumps couldnt be further apart in spec and price.

UPS15/60 fixed speed circulator 130mm generally suitable to 30kw due to 15mm port size.£50

UPE25/60 electronic variable speed pump 180mm.Priced at between £200 and £400 dependant on your terms.

Both pumps are the same head so i dont fully understand your statement. difference being port size therefore differing flowrates at compartible resistances.

Cant wait to hear the results of the NRV going on the open vent.

 

[D_Hailsham]

Both pumps are the same head so i dont fully understand your statement.

But the pump curves are completely different. I used the following assumptions:
Boiler =40kW
Temp diff = 20C
Flow rate 1.8m³/hr
Head 3m or 4m

The UPS15/60 is suitable for a 3m head but not 4m, which needs a Magna; see graphs below

UPS Pump Curve

• D_Hailsham
• 22 Dec 2009
• 1

Magna Pump Curve

• D_Hailsham
• 22 Dec 2009
• 1

 

[Agile]

Hm - I got a Gas Safe engineer to install the boiler. He was recommended to me and was cheaper than another quote I got.

Its not surprising that he was cheaper!

Because he was going to undersize the gas supply and not power flush the system or balance tyhe rads!

As always said, you get what you pay for!

Have you told the person who recommended him?

Where abouts in the UK are you?

Tony