Grundfos Bronze Pump

[Jack155Q4]

Hi,

We have a Grundfos Bronze Pump in our system which I think circulates the return cold water pipes for our flat. When we moved in 2.5 years ago to now I noticed it was always hot an extremely quiet. I thought this was normal.

We have just had a new boiler fitted and they re-wired it to only come on with the boiler. So now when the boiler is on the pump gets hot - I find this odd as it is on the cold water.

Also, even though the pump gets hot it seems to be silent (even with my ear to it I can't hear a thing) - I found the speed switch and it made no difference to the noise. I imagine it is broken but why would it get hot? Why does the cold need to be pumped and why would they wire it to come on with the boiler?

Sorry for so many questions!

Jack

 

[picasso]

I doubt its pumping the cold water, bronze pumps are normally used to circulate a hot water loop in big houses so you dont have to wait for the hot water to travel all the way from the hot water cylinder.

 

[simond]

I cannot think of a scenario where the bronze pump would want to come on whenever the boiler is on. Unless they have made a mistake....

I suggest you check with the installers you selected, we can't tell you from here.

 

[PlumbGas]

cold won't be pumped, it'll be a secondary return to keep hot water delivery at taps to as short a time as possible, feel the pipe work before and after the pump is it hot one side and cold the other ? if yes pump is not running and if not running it can be quiet as it ain't moving, if it is fitted to the cold (highly unlikely) then crap knows what sgoing on, Is it unvented cylinder ?, also secondary return pump will be running 24/7 not with boiler

 

[simond]

Some unventeds without secondary returns use the cold inlet for the secondary return....

Vaillant uniSTOR for instance - although theres a revised version coming with a secondary return tapping soon.

 

[Jack155Q4]

Sorry my mistake - yes it is the hot return - what threw me was it is connected via a t-piece to the tank and on the tank it says "Cold inlet". On the other part of the t-piece is the actual cold feed.

Obviously as it is the hot on a circuit both sides are hot and after the boiler has run. The circuit is tiny as it only goes to the bathroom and then next to the bathroom is the kitchen...that is all

There is hot water at the taps immediately if the boiler has just been on. However, if in the morning the boiler has not run since the previous day it does take a fair while for the hot water to arrive. The bathroom is in the room almost next to the boiler/tank room. I am talking here about when the bronze was hot 24/7 despite the boiler running or not.

It is an unvented Ultrasteel tank.

Should it be on 24/7 then? The plumbers said it was not a good idea and that's why they wired it with the boiler now.

Should I be able to hear it with my ear to it and should I be able to hear a change in speed if I turn it from 1 to 3? I certainly can with the Terrier Pegler they put in for the boiler!

I did query this right at the end of the job and he tried to undo the screw on the front but it was stuck solid. I think this was to get an idea of if it was spinning of stuck. He said you can sometimes knock them in to life again.

Thanks.

 

[muggles]

Sounds to me like it's working. Personally I'd wire it in on it's own time switch, that way you can run it independently of the boiler and at the times you want.

 

[Jack155Q4]

I can't believe the difference in noise. The blue Terrier Pegler so so audible when running but the bronze is absolutely silent at any speed and nor can it be felt spinning.

 

[mysteryman]

It sounds to me as if it is not working. The motor is hot because it is drawing electrical power, but not running. If you are happy with the performance of your hot water system with it not working, just turn it off and see if there's any difference.

The return pipe of a secondary circulation should return to near the top of the cylinder, and certainly not teed into the cold feed. This is essential on a solar cylinder.

 

[picasso]

The return pipe of a secondary circulation should return to near the top of the cylinder, and certainly not teed into the cold feed. This is essential on a solar cylinder.

bit difficult considering its an unvented cylinder

 

[mysteryman]

Why so?

 

[picasso]

a lot of unvented cylinders dont have a tapping for a secondary return.

 

[Jack155Q4]

The pipe off (flowing away) the bronze pump connects to the middle of a t-piece - the other parts of the T goes to the cylinder cold inlet (as part of the circuit) and the other part of the T is fed from the mains water.

Do these pumps have a hidden off switch?