15M pump required, one large Vs 2 small in series?

[Michael Groves]

I'm specifying a new system. It has a 15M head, I called Grundfos and they recommended Magna3 40-150 rrp £1,640. (using rrp for reference only)
A friend recommended 2 no. Grundfos Magna3 32-80 in series, rrp £628 (Total £1,256).
Running costs of 2no. 32-80 is a third of 40-150.
Grundfos technical advised they do not recommend running in series, nor do they recommend you do not run in series, they are mute on the subject.

This seems like a no brainer to me, what am I missing?

 

[ShaunCorbs]

no you cant sorry to say

 

[Michael Groves]

Why not, Grundfos confirmed it would work?

 

[ShaunCorbs]

Why not, Grundfos confirmed it would work?

will put undue load on them

 

[Michael Groves]

Grundfos advised 1st pump should be configured with autoAdapt, with second pump fixed rate. This way AutoAdapt will adjust accordingly.
But Grundfos said 2nd pump would always be running at 100% which would reduce life and ties in with your comment.

I've got some more realistic prices, difference is about £200

I'm still leaning towards 2 in series.

 

[ShaunCorbs]

Grundfos advised 1st pump should be configured with autoAdapt, with second pump fixed rate. This way AutoAdapt will adjust accordingly.
But Grundfos said 2nd pump would always be running at 100% which would reduce life and ties in with your comment.

I've got some more realistic prices, difference is about £200

I'm still leaning towards 2 in series.

have a look at dab pumps

 

[snowhead]

If running 2 pumps in series was so much more efficient then all manufacturers would offer twin inline pump sets.
Can't say I've seen any.

The final cost of the installed pumps will be about the same after allowing for mounting and connecting up 2 pumps against just mounting 1 at a slightly higher purchase price.

 

[Michael Groves]

If running 2 pumps in series was so much more efficient then all manufacturers would offer twin inline pump sets.
Can't say I've seen any.

The final cost of the installed pumps will be about the same after allowing for mounting and connecting up 2 pumps against just mounting 1 at a slightly higher purchase price.

Does not make commercial sense to sell pumps in series, when they can make more money selling one.

You have a valid point on extra time and vales, but if I allow £10 for valves and an extra hour work at £20, I'm still £170 better of running in series.

So technically I still see no reason not to run in series ?

 

[Michael Groves]

have a look at dab pumps

Seem good value, about half the price

 

[Chuck]

I'm specifying a new system. It has a 15M head,

This seems like a no brainer to me, what am I missing?

Why does the system require a 15 m head pump? It's an unusually high pressure.