Swapping a central heating pump.

Paradigm

My c/h pump has died & I'm going to swap it with the same type (Grundfos Alpha 2l) so it should be relatively sraightforward.

There are shut off valves directly above & below the pump so, hopefully, I can avoid draining the system but...

Swapping will obviously introduce air, Grundfos reckon the pump is "self venting".. what does this mean? Where does the air go?

Am I in for weeks of radiator bleeding?

27col

Why does it matter where the air goes, just as long as it leaves the system. I would have thought that the name "self venting" would have been self explanatory.

Paradigm

27col wrote: »

Why does it matter where the air goes, just as long as it leaves the system. I would have thought that the name "self venting" would have been self explanatory.

As you might have guessed, I'm not a plumber/heating engineer so... the pump itself might "self vent" but does it actually leave the system? Or does the pump merely vent/push the air into the system?

Ruski

The pump will remove the air from the pump itself and it will find it's way to other parts (normally the highest point) of the system.

As the pump itself only hold a small amount of water anyway, there will be very little air introduced assuming that your isolation valves work correctly... which is in the lap of the gods somethimes!!

HTH
Russ

Plumber90

You will be lucky to get pump valves that actually shut off properly. I would be willing to put money on it that you will need to drain it down to change the pump.

marlot

Plumber90 wrote: »

You will be lucky to get pump valves that actually shut off properly. I would be willing to put money on it that you will need to drain it down to change the pump.

That's my experience too!

cyclonebri1

27col wrote: »

Why does it matter where the air goes, just as long as it leaves the system. I would have thought that the name "self venting" would have been self explanatory.

That's not helping this chap, he has a better grasp than you realise.
The pump is self venting, his system won't be.

You are right OP, the pump clears it's self, self vents if you like, but as you surmise the air has to go somewhere.
It will settle in the top of the 1st rad it comes accross and that may not be exactly where you expect it to be.

In short it won't be an awful lot of air, so give it a week then simply bleed all rads in turn. should be an end to it.

Paradigm

Cheers bri, that's what I thought & looking at it now it was a bit of a dumb question

Plumber90 wrote: »

You will be lucky to get pump valves that actually shut off properly. I would be willing to put money on it that you will need to drain it down to change the pump.

That's cheered me up no end

Will have to wait & see I suppose.

Paradigm

Well it went far better than I expected

The two isolator valves shut off perfectly & everything undid without any effort, as it was the exactly the same pump it was an easy swap... works nicely.

But, I don't know if it's because the system has been shut down for a few days.... now the 3 port valve is making lots of noise & I can only get hot water (better than nothing) so I'm guessing I need a new one of them

Looking on the web it's a drain down to fit...hey ho!

southcoastrgi

what valve is it ? most new ones you just change the head with no draining, or you can fit a new motor (although that's normally a PITA), a pic or two would help

Paradigm

southcoastrgi wrote: »

what valve is it ? most new ones you just change the head with no draining, a pic or two would help

Honeywell (I think) but I can't get at the head, that was my first thought. (Can't you tell I've been on youtube :rotfl: )

It's low down in the airing cupboard but horizontal... away from me towards the wall. There's no way I can get in to get the head off!

I'd have to take it off to dismantle it.