Hot feed and boiler noises

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Hi all,

New to this site.

I have an open vented pumped system, the boiler and HW cylinder were installed october 2009. Although only moved to this house last year.
I have recently drained down my system and replaced a radiator as the old one had seen better days.

I have refilled and bled the system, no more air seems to be in the system.
However when I turn the heating on either by the programmer or when the stat calls for heat I get gurgling noises from the boiler, like water is being poured down the pipes to the boiler. But only for the first 5 or 10 seconds then it stops. When you turn the boiler off you hear another noise which sounds like a bubble of air going back up the pipe from the boiler.

I thought it may still be air, so I have had the system on and bled several times and occasionally get a very small amount of air out of the bathroom rad upstairs.
The noise is still there. I checked the expansion tank in the loft and this has water in it. I did notice that when the boiler is switched off the pump stops but about a cup full of water gets pushed up the vent pipe and in to the F & E tank.

I have changed the arrangement of the pipes because of this and T'ed the feed in to the vent about 6 inches above the 'H' section.

Now when the pump is turned off I get hot water coming in to the F&E tank from the feed pipe, but it doesn't pump over through the vent or overflow to outside. I get about a cup of water come in, and the feed pipe gets red hot all the way up to the tank from the 'H' section, about 3 foot.

Then when the pump starts up again I still get the trickling noise in to the boiler, and it draws water down the feed as the feed goes cold again. I have been around the accessible pipes with a magnet and the only part where it slightly sticks to is where the return from the rads and hot water cylinder T in to the return to the boiler. Could there be a restriction here causing my issues?

I'm guessing hot water shouldn't come in to the F&E tank from the feed like this. I am also worried that the F&E tank cannot take hot water and will split.
I have put some X800 in to see if that will give it a good clean out. But still seems the same. ​

The boiler makes these noises everytime it is switched on and off.

I don't know what else to try. Appolgies for the long post.
Any ideas appreciated.
Cheers
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[Anders0n]

What boiler have you got? Is there not a vent on it?

 

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Thanks for the reply.
It is a Potterton Promax 15 SL.

The only vent I have is located near the hot water cylinder, and one on top of the magnaclean which is after the pump. This is all located in the cupboard upstairs, boiler down stairs in Kitchen. I have vented these and no air only water comes out.

 

[Anders0n]

It sounds to me like there is air trapped in the pipe work above the boiler. Usually over time it just finds its way to the top of a radiator or gets out though the vent pipe.

Is there a drain off point above your boiler? If there is I'd get the open into a bucket.

 

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No drain off point above the boiler. There is a drain off on the heat exchanger though according to the manual. Wouldn't it have worked its way out since July when the system was first drained down to fit the rad? This is why i am beginning to think it isn't air. Although I have drained it down recently to add the cleaner, but not full drain down.
What puzzles me is everything works. I get hot rads and hot water. Could a partial blockage in the return to the boiler make hot water flow up the feed pipe in to the tank? would trapped air do this?

 

[Halesowen1]

Give us some more detail about the pipe layout in the A/C. Where the pump is, where the Diverter(s) is, where feed from F/E is and where vent is, also measure roughly the distances between these.

 

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Give us some more detail about the pipe layout in the A/C. Where the pump is, where the Diverter(s) is, where feed from F/E is and where vent is, also measure roughly the distances between these.

Thanks for the reply.

Here goes, excuse the drawing, I never was very good. The distance from the H section to the bottom of the tank is approx 800mm, with the vent about another 500mm above this. I will measure again tonight, but from memory this is correct. The distance between the feed and vent is 100mm. Since the picture below was taken I have T'ed the feed in to the vent approx 120mm above the 'H' section (the evnt has stayed in the same place on the left) as previously I was getting pump over when the pump was switched off, now I get hot water travelling up the 15mm feed in to the F&E tank when pump switches off. Any ideas greatfully recieved, I've completely run out of ideas. Oh I have also straightened the magnaclean up so it now sits vertical.

 

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Ok, just checked the measurements. From the 'H' section to the ceiling is 800mm plus ceiling joists, so I guess its about 900mm to the base of the tank. There is around 100mm of water in the tank, with the vent 420mm above the water level. The feed and vent are 85mm apart.
No water comes out of the vent. But water comes up the feed filling the tank with hot water when the pump stops. When the pump starts again the feed goes cold, so it is drawing in water from the tank when it starts up.
If I block off the feed with my finger in the F&E tank, then switch the pump off water gets forced up the vent and in to the tank, so neither of these seem to be blocked.

Hope someone here can help, as I really haven't got a clue now.

 

[jase158]

Did you bleed pump and magnaclean when you filled system back up?

 

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Did you bleed pump and magnaclean when you filled system back up?

Thanks for the reply.
I bled all downstairs rads first, then upstairs, then HW cylinder, magnaclean and pump.
When I done the pump only a dribble of water came out.

 

[jase158]

Are your pipes coming from above boiler? if so could you put non return valve on flow, so that water doesnt come back after system is switched off?

could just be air in system, maybe drain down again and see if you can get it out,

try turning pump down or up

maybe an automatic air valve to get rid of air in system.

And finnaly I would suggest moving the H section a bit lower, this may be why you are getting such hot water in tank as it is so close to tank and heat is transfering up pipe.

Others opinions please as I don't have extensive experience with these things.

 

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Are your pipes coming from above boiler? if so could you put non return valve on flow, so that water doesnt come back after system is switched off?

could just be air in system, maybe drain down again and see if you can get it out,

try turning pump down or up

maybe an automatic air valve to get rid of air in system.

And finnaly I would suggest moving the H section a bit lower, this may be why you are getting such hot water in tank as it is so close to tank and heat is transfering up pipe.

Others opinions please as I don't have extensive experience with these things.

Thanks for the reply, the hot water in the tank is getting pushed up the pipe from the 'H' section, you can feel the heat with your hand when the pump is switched off. The pipes do come out of the top of the boiler, but I do not get any noises from the flow side of the boiler but the return. I have an auto air vent at the moment but no air comes out.

My current theory is there is a partial blockage in the return (I get the magnet attracting to a T where it goes under the floor from the HW cylinder, this is where the rad returns also join), so when the pump turns off circulation still occurs for a few seconds as the pump stops, because there is no restriction in the flow side of the system but there is in the return the water has to go somewhere and so goes up the feed to the tank.

Does this sound feasible to you guys? Or am I completely off the mark?

 

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Do you guys think converting to a combined vent and feed would cure the problem as air could not enter the system?

 

[Halesowen1]

You have already converted it to a combined vent and feed you said, and no it wont make any difference as it would still climb up there as it was going up the vent before so you joined in the feed and it still goes up. I am at odds about the water sound but i would imagine the rising hot water problem is due to the way its been piped up.
I would be wanting to pipe this Y plan up again, get everything teed in lower down, get the pump lower down too.

 

[Halesowen1]

Converting to a sealed system would solve both problems I reckon, remove F/E tank, and fit expansion vessel, but still wants pipe work altering i reckon, as the pump is too high and could run dry.

 

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You have already converted it to a combined vent and feed you said, and no it wont make any difference as it would still climb up there as it was going up the vent before so you joined in the feed and it still goes up. I am at odds about the water sound but i would imagine the rising hot water problem is due to the way its been piped up.
I would be wanting to pipe this Y plan up again, get everything teed in lower down, get the pump lower down too.

By combined vent and feed I ment one single 22mm pipe from the tank and no vent. I don't think there is enough room to move everything lower down. According to the boiler instal manual, the heights are all within spec.
Do you think everything could be done DIY? either the sealed system route or moving everything lower?

 

[Halesowen1]

I would not recommend DIY, but it depends on the person I suppose.
The pump can be moved lower as can the vent and feed. Also good idea to fit a airjec while doing this.

 

[fuzzy]

i dont like pumps pumping down they always create problems

id fit a airjeck, not that i think they are great but your design should have one anyway

 

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Do any of you think there could be a partial blockage in the return pipe to the boiler could cause this? As I have checked an area, with a magnet, where the return from the rads and return from the HW cylinder connect to the main return back to the boiler and the magnet gets attracted to this. This section is about 900mm from the pump. Could this be restricting the flow through the pipes and the water ends up going up the feed?

 

[fuzzy]

unlikely imo, poor set up is causing the issues for me

 

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unlikely imo, poor set up is causing the issues for me

Thanks Fuzzy, Rules that one out at least.
I guess its going to be get someone in to pipe it up properly, move everything lower!

The only other place I have not checked is if the 'H' section is partially blocked, as on pump speed 3 it pumps over and goes up the feed.