Grundfos pump advice

[shaggie16]

Hello all, I hope you can help.
I have a Gledhill Boilermate III thermal store (I know most of you hate them, but it is what it is.)

This system is fitted with two pumps. Once circulates water from the store to boiler (via the rads if CH is on) and the other circulates hot store water into a plate heat exchanger when there is a hot tap open.

I want to replace the circulation pump that pumps the water to the boiler as it has become very noisy.
The pump is marked as a Grundfos 15-50 X18 whereas the hot water heat exchanger pump is marked as a standard 15-50.

I spoke to the Geldhill technical line, and he told me these are the wrong way around as the X18 was a modulating pump and should be used for the heat exchanger pump, leaving the standard 15-50 for the so called system pump (to boiler via rads if called for.)

My understanding of the Boilermate system was that YES the plate heat exhanger pump for the hot water is indeed modulated, but NOT by the pump itself, rather its speed is controlled by the electronics of the Boilermate. Am I right? If so, that should indeed be a standard pump?

So that brings me to the real question - what does the X18 suffix on the pump label mean - is there any difference between the 15-50 and the 15-50 X18 and if so what is it?

I was going to simply replace the system pump with a 15-50 until I noticed the existing one had the X18 suffix, so thought I should ask you brainy people first.

Thanks in advance.
Mike

 

[Agile]

I dont know what the X18 means but obviously it is somehow modified to make it modulate.

We dont know what your standard pump is doing in the wrong place! Or if it still modulates.

The Gledhill spares are very expensive an unique to their products so a single source where they can charge what they like.

The obvious advice is to use a standard pump to replace the boiler one and buy the X18 for the hot water.

However, as the X18 is probably very expensive and you probably think the 15-50 is working you will probably choose to leave it as it is!

Tony

 

[shaggie16]

Thanks for the reply.
I have no complaints regarding the hot water, so the standard 15-50 is doing its job there - which I guess isn't surprising if the control circuitry of the Boilermate itself modulates the pump.

I assume I am right in thinking that just because a pump is not a modulating pump, doesn't mean that an external controller cannot modulate it?

Even if the X18 is a modulating pump, I assume I wouldn't need / want a modulating pump to circulate the water to the boiler and the rads?

Thanks

 

[Agile]

A standard pump is whats needed for the boiler flow.

The PCB sends a modulating supply to the pump and we dont know how the pump responds to the varying supply.

Being a sceptic I wonder what little difference there is in the X18 pump but its not for me to reason why.

Tony