new radiator has got me beaten!

[chriselevate]

It's one of these that I've had about 7 years now: www.screwfix.com/p/grundfos-15-60-domestic-circulating-pump/67637

Annoyingly I've always had to run it on III as any lower and it doesn't get the rads furthest away hot enough. The pump itself is absolutely boiling hot but the radiators are not as hot as it is.

 

[footprints]

Unless the pump is screaming or rumbling badly with luck it still works.

You either have as others have said one or more large air locks, "drop systems" where the pipes run down to radiators are famous for them, or the pump has caused cavitation resulting in the problem I described.

Either you need to find the air locks and release them or get the maximum pressure from your pump and hope that does it.

If I am right the pump cannot get a good push to move any air.

No guarantees but I have spent hours trying to clear air and finally told the customer (who has that Oh yea! what a load of BS look in their eyes) to leave it off till the morning and when I turn up it's worked

 

[chriselevate]

Thanks for that. I agree that the fault might be down to an air lock somewhere but I have a funny feeling it's not as I've drained down the system lots of times before to do work and replace rads but never had this problem before. The problem started yesterday when I finished the work and filled the system and it's still here today when I'm having another go. If there was an air lock in the system it would surely mean that the last radiators in the system wouldn't get warm all rather than slightly warm (which is what it's doing now). I have a funny feeling that if the pump is hot and pipes around it hot then it's a pump issue because it's simply not able to push the water around the house.

 

[chriselevate]

Also... the radiator that it staying slightly warm has a drain valve on it. I've opened this valve in a bucket/tray and the water doesn't get any hotter after running it for a couple of minutes. I would surely expect it to run nice and hot if it was pumping the water properly?

The HW is nice and hot and all the rads have water coming out of them when I bleed them. Surely it can't be air in the system?

 

[Galoka]

Pumps generally either work or they don't (though I suppose, as suggested above, you might have a some horrible noises before it seizes up.).

You can either hear it, or feel the vibrations with your hand when it is running. and the pipe after the pump should rapidly get hot once the boiler fires up.

Pumps have a a slot in the end of the shaft maybe under a pop off cap etc.) which you can use a screwdriver on the turn the shaft if it is stuck, this can sometimes free it up.

 

[longdogs]

Have you bled the pump?

 

[BARNY78BG]

How old is your pump

 

[chriselevate]

Pump is bled (by using a flat screwdriver to release the silver plate on the side) and the pump is about 7 years old.

The 22mm pipes above and below it become very hot very quickly and the pump itself gets VERY hot. I just can't work this one out. I've drained the system loads of times before and it's ALWAYS come back on fine. This is why I suspect something strange is going on with the radiator I've removed you see.

Just can't work it out.

p.s. the pump does a lot of humming (buzzing) but I'm not sure I'm 100% convinced it's turning. I think it might be moving but when I change the setting from III to II or to I I can hear a slight change in noise but I'm note sure if it's turning. Is it work isolating the pump and removing it to take better look at it? Will it show me anything if I remove it or not?

Thanks

 

[gigz]

Take the big screw out of the pump and place a small screwdriver in the centre, you'll be able to tell if its spinning. Have you checked the cold fill isn't blocked/partially blocked ? Put a magnet where it joins the system.

 

[chriselevate]

Thanks for your help... really appreciate those idea/thoughts.

Take the silver screw completely off the side? Won't water go everywhere if it's not isolated and still running?
**edit** just done this and it's spinning. So this eliminates the pump? Or is it spinning slower than it should and therefore not enough to push the water round?

When you say the cold fill... What do you mean by that? And a magnet to do what?

 

[gigz]

The cold fill might be blocked and the magnet will stick to the magnetite (won't stick to copper if its clean)

 

[chriselevate]

Where is the cold fill?

If all radiators in the house are off and the one furthest away is fully open and it's getting SLIGHTLY warm (and I mean only just slightly warm) what would you say the problem is? Surely this won't be air as it means that the water is getting through (all be it very slowly and very cold by the time it gets there).

Thanks

 

[Agile]

Are you regularly bleeding the pump screw?

You may need to do it 20-40 times to let entrained air out.

May have already been stated but one way to get things moving is to close all but one rad and slowly move the open one along.

Tony

 

[chriselevate]

Thanks but tried all that and no luck so far

 

[gigz]

The cold fill, if you follow the outlet of the small header tank (usually 15 mm but could be a combined 22 mm) where this tees into the pipework below, it could go into an aerjec (google it). This sometimes blocks and will fill the system VERY slowly. Are you sure pump valves are fully open ? Bypass is set correctly ? I would close the bypass and all the rads bar one, get it hot and work round the rest, do downstairs first.