Grundfos Home Booster not going above 3.6 bar

[ln1234]

I have a Grundfos Home Booster fitted (the inbuilt pump and tank solution), and if I put the high pressure above 3.6bar the pump keeps going, almost as if it's trying hard to increase the pressure. If I keep it at 3.5 bar with a 2 bar differential then it behaves correctly. I'd like to increase the pressure to hopefully get a bit more flow rate to a shower which is quite far.

Do I have it set up correctly with these settings, or should it indeed be able to get above 3.6bar? I can't see any leaks in the pipework

thanks

 

[Biggles..]

It Should run upto 5bar from memory,the outlet of the unit should have a pressure reducing valve fitted normally are around 2-2.5 bar.this is because the unit is an accumalator based product rather than a constant pressure pump.
The idea is the unit charges to the set pressure,your pipework runs at what you set the pressure reducing valve to,as the homebooster loses it charge it kicks in at the minimum which should bthr same as your reducing valve pressure.
This means the pump should only run in short burst not continuously.

If your pump is trying to get above 3.5 and can't then you either have a leak,a prv discharging somewhere(possibly invented cylinder etc) or the pumps duff(unlikely).

 

[ln1234]

thanks for that!

There is a prv in line between the pump and the unvented cylinder so it might be that. You've given some good ideas, and I might try and isolate the outlet of the pump and see if the pressure increases then. There is a brass tap just before the prv so might try closing that and seeing if the pressure can be increased.

Cheers

 

[croydoncorgi]

If you raise the working pressure on these, what about the preload in the internal accumulator? I'd have thought that ought to be raised to...?

 

[Technotim]

I thought that it used a 8 liter pressure vessel not an accumulator as such?

I think the max pressure you will get is 3.6 bar as a closed head situation and you can only adjust the cut in pressure on these transducers so you are not adjusting the pressure you are adjusting the point at which the pump will turn on, so when you think you are adjusting the pressure you are in fact only adjusting the cut in point therefore the pump will not turn off.

 

[Biggles..]

you can set the max pressure (5bar) and the differential(cut in) the reducing valve stops constant pump running by having it set just below the cut in pressure.

i see the new ones say 3.7bar,we fitted them over 2 years ago and it deffinately went above 4.5bar.

View media item 19282

 

[Technotim]

Cor thats a nice work of art!

I am not too sure about what you are saying as to the max static pressure they will produce when they first released them I did not think they have changed apart from the cover made more modern, not that I do not believe you.

As it stands with the current model we have a pressure vessel that is just a buffer to reduce to on offs, and its max static head is 3.6 bar so running pressure is going to be much reduced.

So the transducer should be set to say 3.4 bar to stop the pump from just running all the time, I guess that the next issue is the valve in front of the cylinder, is it one of those with a balanced cold outlet and what is the pressure on that.

Another question is what is the max flow rate of the cylinder itself as that might be a restricting factor as well.