central heating pump cavitation when hot wilo Gold R550 pump,

[kimbo]

You have to find the root cause of the problem a new pump would not sort it out. In the installation of the pumps paprwork it does say it can be pumping downwards but as diamondgas says it is better pumping up as it tends to naturally get rid of the air trapped. Also the height of the pump from the header tank should be a minimum of 1/3rd of its head and the feed and vent needs sorting as previously mentioned.

 

[M7R]

get a gsr

GSR??

Do you have a separate feed and vent pipe or is it a combined feed and vent pipe? Is that the loft space directly above the boiler? how much head of water is there from the flow pipe in the loft to the water level in the f&e tank? Lot of questions i know but it sounds like you are drawing in air, as mentioned, Which will stop circulation in its tracks and then the boiler will overheat! A bit more understanding of the lay out above the boiler would be of benefit 🙂

A downward pointing pump is not the best by the way! They'll always struggle to clear air!!

I have no idea why they have put the pump facing down, for me it seems daft as air will always rise in water... so it will just get stuck in the pump fighting against the slow of water.

here are pics of the pipe work in the loft, if you need any more pics let me know as I have tried to get the best pics I can.

it appears there is some kind of automatic bleed valve I guess standing up, however this appears to be on the return pipe and not the feed pipe.

there are 2 pipes Tee'd off the hot pipe, one goes up and one goes down, they are Tee'd off next to each other, the one that goes down goes to the bottom of the header tank, and the one that goes up goes to the top of the header tank (i think thats how I remember it, I should have tanke a pad and pen and drawn the lay out with notes if I am honest... ill go back up later)

 

[diamondgas]

See if I have fathomed these out correctly Hopefully you can make out the labelling I've wrote.🙂

If there's a separate feed and vent, which sounds like thats what you're describing, it could be possible to fit an air separator on the heating flow and combine the feed and vent pipes to overcome any possibility of your issue being 'air'. Take this as just a suggestion though as without first hand knowledge I wouldn't commit to it being a cure! Combining the feed and vent will certainly alleviate the possibility of air being drawn in or 'surging' occurring 🙂

 

[M7R]

yep that looks to be right, with the return having some kind of filler / bleed fitted? (the tops screwed on tight, I moved it with some pliers but it started to weep a drop so I chickedned out and did it back up)

 

[diamondgas]

yep that looks to be right, with the return having some kind of filler / bleed fitted? (the tops screwed on tight, I moved it with some pliers but it started to weep a drop so I chickedned out and did it back up)

If the pipes are as I'v perceived then the vent and feed are decently placed and the vent should dicipate any air before getting close to the pump! However as said before, a combined f&v would eliminate any 'drawing in' issues!

IF your cold feed is blocked then you could have air drawn down the vent! I'll emphasise IF!

Seeing the layout in the loft though I'd be back down stairs wondering WTF!!!! lol

 

[M7R]

The feed is working as when I added the fernox to the system I bailed out header then opened a bleed valve to dran some more out and the level was dropping,

The service guy is coming monday so he says he will see what's happening and how to fix it, earlier this eve the pump was running silent at 60degs!

 

[diamondgas]

How about the downstairs rads? lol

We're still compramised with circulation if the rooms you want heated are cold yeh?

 

[M7R]

down stairs rads get hot, take a bit longer (a while longer in a few cases) but they do atleast get hot and dont seem to collect air.

the only one that doesnt work quite right is the big hall one like I said on my OP, as the inlet red hot and the tops hot but the outlets cold, even after a few hours as is an area around the outlet at the bottom. the valve is wide open though ( 2 new valves fitted last year when we swapped the rad) and I know its open as a couple of weeks ago I closed the inlet and opened the bleed to try and see if the rad would allow the warm water in backwards... not really even though I did drain about 1.5L from the rad in the end)

 

[jhon lennon]

you need a new pump the one that's in is worn that's why the hotter it gets the nosier it becomes the cool hall rad is due to balancing and to do it right is not the dark arts just time consuming good luck let us know how you get on

 

[Billy Bob Bob]

M7R is your house a bungerlow?

 

[M7R]

as i have said further up I have just changed the pump for brand spanking new smart pump, and I was still having the same problem.. it seems to be quieter for longer now but was still making a noise, I will keep an eye on it and see if it gets better or worse.

and no not a bunga, a 1950s semi house.

I have tried to balance the rads, but it seemed to make no odds, however that was with a noisey pump which wont be 100% efficent, so once the pump is sorted I will give it another go.

 

[diamondgas]

What happens when the hot water is satisfied? Does the heating get any hotter, the rad that's poor does that get hotter on heating only?

I noticed you have ballancing valve on the hot water return, is that fully open or has it been turned back? Is there a bypass, it looks like there's a pipe taken off before the diverter, is that the bypass? If so is that fully open, closed off or even automatic?

You're describing a definite circulation/ballance issue. Have you/can you check the problem radiator for a restriction internaly?

Just a few more things to try for you :lol:

 

[M7R]

What happens when the hot water is satisfied? Does the heating get any hotter, the rad that's poor does that get hotter on heating only?:lol:

it doesn't seem to make any odds, and never really sure when the hot waters satisfied if I am honest...however if I run just heating only the hall rad still seems to hot one end cold on the outlet and near it..but I will keep an eye on it and see what happens when running CH only.

I have just been and had a play though, both HW and CH were on, clicked to turn HW off and it made no change to the noise (pump was pretty much silent bar the odd tiny gurgle even at 50+ deg) set it to HW only and then it made a gurgle and I could hear what sounded like air rising, then the pump went noisey, and about 30 seconds later the boiler clicked out) then set the controls back to both HW and CH, but it was still a bit noisey.. so now got it on just CH and seeing if it quietens down again.

I noticed you have ballancing valve on the hot water return, is that fully open or has it been turned back?

just checked it was wide open, I am guessing it should be closed a bit to help send more heat round the CH system? closed it a little now but when it got too shut it was making running water noises a bit.

Is there a bypass, it looks like there's a pipe taken off before the diverter, is that the bypass? If so is that fully open, closed off or even automatic?

where abouts am I looking? and I will go and check?

You're describing a definite circulation/ballance issue. Have you/can you check the problem radiator for a restriction internaly?

nope not checked it, however its just a year old, and if I close the inlet I can bleed the rad via the outlet easily enough.

 

[diamondgas]

just checked it was wide open, I am guessing it should be closed a bit to help send more heat round the CH system? closed it a little now but when it got too shut it was making running water noises a bit.

Try cracking to 1/4 open as a start point. You've got to guarantee enough flow on h/w only through the boiler otherwise it'll trip on o/heat.

where abouts am I looking? and I will go and check?

There seemed to be a 15mm pipe teed off after the pump and before the diverter valve, it carries on down from the pump and seems to go under the floorboards. 🙂

What you'll fiind when both hot water and heating are calling is that the priority flow will travel through the hot water circuit unless you restrict the flow via the ballancing valve!.. Idealy you are looking for 11 deg C diff between the F&R pipes at the cylinder from cold! To small a difference tends to indicate the flow is fast, especially if the cylinder of water is cold!

 

[Nostrum]

A good way to test if your drawing air, get a 22mm speed fit cap end. Let system cool completely, vent all the rads, the vent in the loft (the one which weeped water so you ran away) stick the 22mm cap on the vent pipe which goes over the F&E tank in the loft. Pump speed on 2 and let it run for an hour.

This is a TEMPORARY test only, if it stops the problem you have an issue with your vent configuration so call a professional in. The system will work like a combined cold feed and vent but only using the 15mm cold feed so it is not satisfactory to leave it like this for any lengthy period of time.

You could stand up there with a jar full of water but this is a bit easier to do.

It sounds like you have multiple problems with the install, balancing and air ingress

Sam

 

[M7R]

A good way to test if your drawing air, get a 22mm speed fit cap end. Let system cool completely, vent all the rads, the vent in the loft (the one which weeped water so you ran away) stick the 22mm cap on the vent pipe which goes over the F&E tank in the loft. Pump speed on 2 and let it run for an hour.

This is a TEMPORARY test only, if it stops the problem you have an issue with your vent configuration so call a professional in. The system will work like a combined cold feed and vent but only using the 15mm cold feed so it is not satisfactory to leave it like this for any lengthy period of time.

You could stand up there with a jar full of water but this is a bit easier to do.

It sounds like you have multiple problems with the install, balancing and air ingress

Sam

Okay I will have a look at this, I will let the vent in the loft bleed just encase there is air in there.

I am guessing to let it run for a hour with the boiler on and at normal temp (about 55 -60 deg or so).

The lad that came and serviced the boiler yesterday (it got a clean bill of health so I know thats good all he had to do with give it a quick hoover out but that was it) he suggested another fix would be converting the system to pressurised. he said it shouldn't cost that much as we would need a new water cylinder, and the pipe work in the loft changinging a little, plus a cold feed adding inot the system (which is easy as there is a cold feed going into the loft for the tanks running right next to the boiler).

is there any down side to going pressurised? and will till most likely fix my probs? as getting rid of the header tank in the loft would be a bonus as we plan on doing a loft conversion in a couple of years time.

 

[diamondgas]

Pressurising comes with potential problems increasing the chance of water leaks. A typical pressurised system is set to 1bar. That's the equivalent of raising your header tank to 10m high. Added to that the pressure is allowed to get to 3bar before safety devices cut in then you're system is going to be introduced to a great deal more pressure than it is at the moment use to! There are other potential problems too but the major one is will your system stand the increased pressure. Personally combining the feed and vent does just as good a job as 'sealing' it IMHO 🙂

 

[M7R]

I think most of the pipe work is new, but then again I will try the combined vent and feed and see what happens (also thats cheaper).

(I was playing with trying to balance the hot water tank last night, and setting the thermostat on the tank to the right temp) and at one point there was a massive glug of air rising from within the tank and seemed to go up into the loft!

 

[diamondgas]

I think most of the pipe work is new, but then again I will try the combined vent and feed and see what happens (also thats cheaper).

(I was playing with trying to balance the hot water tank last night, and setting the thermostat on the tank to the right temp) and at one point there was a massive glug of air rising from within the tank and seemed to go up into the loft!

Once the f&v are one the pump can not 'suck' anything but water down the pipe which will eliminate the chance that air is being drawn in from above! The pipe needs to be 22mm minimum but check the mi's to make sure you can do this for your make of boiler. Being a modern one though I doubt it'd be an issue!