Cold but no hot water from negative head pump to attic

Dono1975

I have a Grundfos negative head pressure pump feeding a shower sink and toilet in an attic which stopped working
I replaced the vessel on the hot side as it had burst internally
But I was only getting cold water so I replaced the pressure switch as well but I'm still only getting cold water
Is it possible that the propellor at the hot end of the pump isn't spinning ( I can't see as its against the wall) even though the cold end is
Has anyone any ideas as I'm running out of ideas at this stage

Thanks

PK27

It's possible it might just need to be bled after the works carried out on the pump, turn off the power to the pump, and turn the shower valve to fully hot. Disconnect the shower head from the hose, and if the connection cone will pull back onto the hose then pull it back a bit so you have just the hose top ready. Be careful not to lose the rubber washer!
Now suck the hose as hard as you can and the water should come through. If it does, let it run for a minute to clear any air from the pipes and pump. Once it runs steadily you can turn off shower and reconnect the head. Turn power back on to pump and check if it's working.

Dono1975

Thanks for that but what do you mean by ?

and if the connection come will pull back onto the hose then pull it back a bit so you have just the hose top ready

PK27

Sorry I meant cone, some hoses have a chrome cone that slips back onto the hose exposing the end of the hose. It just helps you get more suction because you can get your mouth tight around the hose!

Dono1975

PK27 wrote: »

Sorry I meant cone, some hoses have a chrome cone that slips back onto the hose exposing the end of the hose. It just helps you get more suction because you can get your mouth tight around the hose!

Ya I think it's badly air locked I can hear it gurgling but can't pull it thru
There might be a few bends on the way as well

PK27

Have you checked that there's no stopcock closed on the pump? Sometimes the flexible connectors onto pump have a built in screw valve, or the installer may have put stopcocks on. Just check that to be sure everything's open.
If all is open, try sucking again, you're trying to suck from the ground floor right up to attic so you need to suck damn hard. It's possible you might have got some water into the pump from the cylinder so if you've given up sucking turn power onto the pump and try a tap in the attic

PK27

Just thinking, with a negative head pump it should charge itself without effort and pump up, I'm thinking you do have a problem on the hot side of the pump

Dono1975

PK27 wrote: »

Just thinking, with a negative head pump it should charge itself without effort and pump up, I'm thinking you do have a problem on the hot side of the pump

Thats what im afraid of
Because of where its located against a wall I can't see it spinning
The propellor might have a problem think it happens with plastic pumps this is brass though
Ill email Grundfos tomorrow to see what they say