Wilo Rs50 to Grundfos Alpha 2l problems!

[Patrick Hutchinson]

hi, my Wilo gold RS50 started to get really noisy, ran ok and all 14 radiators heated without a problem but could be heard all round the house. I ran it on setting 2 without any boiler or flow problems.
So I replaced it with a Grundfos alpha 2l and immediately had flow errors f25 on my glow worm hx24 boiler. I have run the pump in all modes and still get the fault.
It is an open vented 2 valve arrangement with separate time clock and thermostats for heat and hot water. TRVs on all radiator but hallway which is fully open.
Some time it starts no problem then when hot water valve opens it faults out then other times it faults out as soon as hot water or heat is called for.
Incidentally I stripped the Wilo pump and found the impeller to be totally choaked up so can't understand how it was never faulty out on low flow!

What am I missing here? Cheers

 

[Patrick Hutchinson]

Should have said the Grundfos is a alph2 L 15-60

 

[Gas2Air]

You're not missing anything. F25 on this boiler is very common and a pain. It's so sensitive to and flow/return temp or restriction issues it's a nightmare. Did you drain to replace the pump? Pump valves open ok? I'd suggest running it and resetting the f25 as long as you can, it should settle down barring something else.

 

[Patrick Hutchinson]

I didn't drain, just isolated, swapped over the pumps and restarted, I followed the pump instruction for airlock, ran at setting III then powered off with both valves in the forced open position there was then a few large surges but when I do it now I get nothing.
I ran it on Pp2 which is default and I got f22!
It ran ok for a day then faulted out now it is running for a couple of hrs

 

[Gas2Air]

Like I said just continue with it, it will settle. I see these 2-3 times a week and just looking at them throws f22 and f25.

 

[Patrick Hutchinson]

Any idea what the best pump setting would be, there are 7 setting on a alpha2l, currently I have it set at II for a fixed medium flow?

 

[Phill Peck]

how is the pump fitted
Orientation wise??

 

[matgriff]

In fixed speed mode II or III that pump will have the same performance as the Wilo Gold 50 (or better)

SO basically as long as you haven't selected one of the variable speed/pressure modes, that don't work well with modulating boilers then you should be good to go.

Make sure you don't have the pump circulating in the wrong direction. Have you changed the balance of the system by altering the setting of the cylinder balancing valve ? If you say that you get low flow alarm when it calls for hot water.. is that hot water only or hot water + CH ?

When your system calls for HW only, then the system pressure drop will be lower than CH or both, so if anything you would get much higher flow through the boiler for a given pump speed


Thx

 

[Patrick Hutchinson]

the hot water feed from the boiler rises into the hot press to both overflow vent and header tank then the pump is mounted vertically pumping down to the 2 valves and pressure relief

 

[Patrick Hutchinson]

Photo

 

[Patrick Hutchinson]

I have noticed that when all the radiators are hot the pipe from the relief valve to the return is too hot to touch, I would guess this is because the TRVs are closed, what setting should the valve be set at? Could this cause hot water to return to the boiler so it thinks it is heating too fast? Kind of makes sense that I take out a knackered pump then the new one performs so well that the relief loop causes issues?

 

[ianmcd]

Photo

I think that you have fitted the pump the wrong way round according to these instructions your pump is pumping upwards also the manufacturer doesent advise fitting the pump vertically if for use with HW, on the side of the pump there will be a small arrow showing you which way it is pumping, I tried to send you the link to the instructions but for some reason it wont attach, but according to the instructions I have then the flow is from the end where the cord entry is so in your case its upside down

 

[Phill Peck]

Based on the colour of the bolts. I'd say he's rotated the head. Which is what I was asking previously

 

[ianmcd]

Based on the colour of the bolts. I'd say he's rotated the head. Which is what I was asking previously

Yes I knew what you were getting at mate unfortunately I am on my phone and the pic isnt great. OP here is a link to the installation instructions.

https://www.google.co.uk/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=grundfos alpha 2l installation

I was just wondering Gass if he has made the mistake that many engineers do and not just customers and has assumed that if you change the head around then the pump will pump the other way but we both know it doesnt the op will have to go with the directional arrow on the pump body, moving pump head orientation is fine to accomodate existing wiring but if the motor turns clock wise no matter how many times you turn it the motor will still pump clockwise its the base that decides the direction of flow

 

[Patrick Hutchinson]

FYI i rotated the head 180 degrees before fitting so the the plug was from the bottom as per the manual, flow is downward.
PRV setting anyone?