CH pump - Variable or 3 speed?

[Twinlock]

Hi,

I’m looking for a central heating pump. It’s for a fairly conventional Y-Plan open vented system, condensing oil boiler, TRV’s (except for 1 rad). DHW.

I’ve come across the variable speed Grundfos Alpha 2L. This pump is a bit more expensive than the 3-speed types, but it is supposed to be more energy efficient and quieter due to its speed related to the load placed on it.

Is this all a bit of a gimmick, can it be used on a system such as mine and has anyone any idea of the drawbacks with this type of pump?

Much appreciate any advice on this.

Thanks and Cheers

 

[doitmyself]

I’ve come across the variable speed Grundfos Alpha 2L. This pump is a bit more expensive than the 3-speed types, but it is supposed to be more energy efficient and quieter due to its speed related to the load placed on it.

Is this all a bit of a gimmick

I can't imagine that Grundfos would be willing to spend £millions developing and patenting the system if it was just a gimmick. A typical 3 speed pump will consume about 275kWH of electricity a year. The Alpha2L will consume about 85kWH.

can it be used on a system such as mine and has anyone any idea of the drawbacks with this type of pump?

Which make and model boiler do you have?

 

[Twinlock]

Boiler type: Grant Vortex Eco Internal Wall Hung 12/16 kW -VTXWH1216


I like the energy saving bit and I'm sure it works fine on some boiler types but Grant don't recommend a modulating pump for their condensing boilers - so it looks like it's going to have to be conventional 3 speed job.


Cheers

 

[Jimbob]

hmmm wonder why grant wouldnt recommend one. Those modulating pump are a great idea, i suppose they just work off incoming temperture within the pump, or does it have an external sensor to measure return tempurture?

 

[doitmyself]

hmmm wonder why grant wouldnt recommend one. Those modulating pump are a great idea, i suppose they just work off incoming temperture within the pump, or does it have an external sensor to measure return tempurture?

They actually have three internal sensors which measure flow temperature, flow rate and pressure.

 

[migoplumber]

twinlock, you could quite easily install your modulating pump, would just need a t before and after pump with links to a pressure drop monitor. the pumps work by measuring the pressure drop off and keeping it constant through variable flow, as more rads are shut off the pump speed decreases keeping velocity through primaries constant.
temperature is not important!!

 

[Twinlock]

Thanks.

Grant technical dept. are generally very helpful but changeable when it comes down to modulating pump. The boiler manual says fit one if you can, technical then say you can’t but now say you can – the benefits are saying to me that it’s probably worth a go.

Hi Migoplumber. I’m fitting an automatic bypass valve (between flow/return after the pump) – is this what you mean by a pressure drop monitor, or am I missing something?

Cheers

Twinlock