Grundfos pumps

What's the difference between these two pumps. Guessing ones more of a 'smart' pump?

 

About £300 difference, I think.

 

Correct yes. Is it worth the extra money for the magna one?

 

This really depends on the system it is fitted too.

 

Could you elaborate please?

 

What is the system it is running?
Rads how many?
Zones?
Age?
There are many factors

 

Sealed system central heating

 

Heat only boiler 35 rads. No zones to the system.

 

Quiet an old system all copper 28/22mm with 15mm to the rads.

 

I take it the grundfos magna is a smart pump? That will adjust its pressure of its pump to the system demand?

 

Both pumps have been discontinued by Grundfos, so what you have found are end-of-line stock.

With 35 radiators, you have a very large system. Has anyone calculated the system index (max head and flow rate), so you know what size pump to buy?

 

Sadly not. The pump is the highest point of the system really. So not sure what this means with regards to max head. As its at the heightest point. Any help. Would be greatly appreciated. The pump on the old heat only boiler that was in was only a 15/50 60. Grundfos.

 

UPS15-50 is 130mm long.
Those two are 180mm long.
Be a tight squeeze!!

 

Google index circuit, the position and height of the system is irrelevant...head refers to frictional loss in the system when circulating the water at the maximum required rate. So a 6m Grundfos can create a 6m pressure drop across the system when the flowrate drops to zero...you'd never run the pump like that obviously.
What's the boiler make and model?

 

There's an inconsistency between the statements above as a "sealed system" normally means a system boiler boiler with integrated pump; while a "heat only boiler" is usually open vented with a external pump.

We need to know exactly which boiler is being fitted - make and exact model.

If the old system worked OK with a Grundfos 15-50/60 (which model?), you shouldn't need an 8m pump.