Noise from Boiler But Only When Heating Water Cynlinder

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I have a two year old Vaillant ecoTEC Plus 615 system boiler which runs the heating and charges a Megaflow hot water cylinder.

I've noticed a rushing noise (like theres debris in the water) from it when its heating the cylinder. It kicks in when the flow temperature reaches approx 75c -80c and will then continue through to and during during pump overrun. When the flow diverts to rads after heating the hot water, theres what sounds like a lot of air whooshing through the rads for a few minutes then it is and remains nice and quite. Strangely, when I bleed the rads there is little if any air.

I can't say how long its been doing this because the boiler is in the airing cupboard and I don't usually go in the cupboard when the boiler is heating the hot water. I have been monitoring this for a few months now and it seems to be getting worse.

Things to note -

The pump speed is set to speed 1 for rads and overrun, and 2 for hot water.

The boiler is the highest point in the system and I have opened the AAV fitted to the pump.

Theres also an AAV fitted to the loop that feeds the hot water cylinder which is open.

Boiler is set to and holding a pressure of 1.5 bar.


Can anyone help me? Thanks.
 
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so canu tellme how this pump knows to go from 1 spedd to the other??
as i cant??
Oh, I didn't mention that boiler control is a VRC430 weather compensator, and the hw cylinder stat and DVs are wired through a VR65 control centre. Consequently the boiler knows if the demand is for heating or hot water. Within the boiler configuration menus, setting d.19 (pump speed) is set to 1 = heating speed 1, hot water speed 2.
 
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some one else may be able to correct me on this one but i don't think the 630 is fitted with the two speed pump!
 
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what size are your revovler circuit's and when the noise appears is the boiler sitting at s.53??
 
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some one else may be able to correct me on this one but i don't think the 630 is fitted with the two speed pump!
Ecotec Plus version of combi and system boilers have a two speed pump, Ecotec Pro versions have single speed. OV boilers have single speed.

The OP has a "Plus" version, so it has a two-speed pump.
 
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what size are your revovler circuit's and when the noise appears is the boiler sitting at s.53??

Forgive my ignorance, but what are revolver circuits and how would I determine their size?

With ref to the noise, the boiler is at s.24 when it starts and the noise continues through s.27. When i checked this yesterday, the noise started when the flow temperature reached 65c.

Cheers.
 
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Be aware that AAVs may have a loose cap but still be blocked!

Sometimes poking with a pin will cause them to unblock or unjam.

I am not yet totally convinced that the cause is air in the system but oviously I would be checking the AAV is really venting first.

Tony
 
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Be aware that AAVs may have a loose cap but still be blocked!

Sometimes poking with a pin will cause them to unblock or unjam.

I am not yet totally convinced that the cause is air in the system but oviously I would be checking the AAV is really venting first.

Tony

Tony,

I did test this yesterday but only the one fitted to the heating circuit which seems to be working fine which was expected as I replaced this a few months back as the previous one leaked like an incontinent pensioner.

I'm bit reluctant to test the one fitted to the side of the pump in the boiler as I don't want to spray water on the boilers PCB. However, as the boiler is higher than the AAV fitted to the heating loop, I think I will try this evening after covering everything with towels.....

Thanks for the tip.
 
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I'm bit reluctant to test the one fitted to the side of the pump in the boiler as I don't want to spray water on the boilers PCB. However, as the boiler is higher than the AAV fitted to the heating loop, I think I will try this evening after covering everything with towels.....

UPDATE

I couldn't test the AAV fitted to the pump as the cap does not fully unscrew.

However, I did tinker around a bit and I think it may be air or some sort of gas causing the problem. Here's what I did -

1. Start boiler with just DV for rads open - Initially what sounds like a lot of air whooshes around the system, then it goes very quite and stays quite.

2. Stop boiler, close DV to rads, start boiler and open DV for cylinder - Nice and quite until flow temp reaches 65c, then what sounds like air rushing around gradually gets worse as the flow temp increases.

3. Stop boiler, close DV to cylinder and allow to cool. Start boiler and open DV to cylinder - Initially what sounds like a lot of air whooshes around the system, then it goes very quite until flow temp reaches 65c, then what sounds like air rushing around gradually gets worse as the flow temp increases.

4. Leave boiler running and DV to cylinder open and open DV to rads - Initially what sounds like a lot of air whooshes around the rads, then both the boiler, rads and cylinder circuit go very quite even when the flow temp reaches 65-80c.

Any ideas?
 
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Problem solved!

For those who may be interested, I drained down the system, did a cold flush, refilled and treated with Fernox F1. Its been almost a week now and the system is running very quite.

Why did I choose this course of action?

Well, first, the two plumbers I contacted did not return my calls so I decided to continue to pursue myself...... And after thinking long and hard I recalled that the problem probably started not long after I rerouted the pipes to the bathroom rad. When I refilled the system I couldn't get Fernox (originally used in the system), so I used Sentinel X100 instead. Not sure if the noise was because the x100 is an inferior product or down to the fact I that spilt some of it and probably under dosed the system.

Thanks to all those who gave up their time to post suggestions and (sometimes silly) comments.
 

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