Combi install do I need an external ABV?

[Ironman2024]

Hi all,

I have an ideal logic Combi max2 30kwh that was installed in my hose prior to buying it.

It feeds 11 radiators in total, they are all type 22 and replaced at time of boiler I think.

1600x500 X 2
1800 x 500
1200x500 x3
1000x500
700x500
500x500 x3

There is one bypass road which is a 500x500 and the rest have TRVs

The issue I’m having is radiators upstairs close to the boiler all hiss, no matter what is done. It’s less so with fully open trv.

I can live with that but what’s getting to me is, where upstairs meets downstairs in the wall there is pipes carrying the flow/return (Qualplex) and these have a tapping/ticking noise a lot of the time. I was wondering is this due to the boiler being oversized and when trvs close the pressure is too high. There’s no external ABV from what I can tell.

As a diagnostic measure I picked a larger radiator in the hallway 1600x500 and fully opened the trv and lockshield as a makeshift bypass but the issue stayed the same.

Has anyone an idea of what this could be?

Thanks all!

I’ve included a video of the sound within the wall below.

https://imgur.com/a/qXps9Nq

 

[Johntheo5]

Hi all,

I have an ideal logic Combi max2 30kwh that was installed in my hose prior to buying it.

It feeds 11 radiators in total, they are all type 22 and replaced at time of boiler I think.

1600x500 X 2
1800 x 500
1200x500 x3
1000x500
700x500
500x500 x3

There is one bypass road which is a 500x500 and the rest have TRVs

The issue I’m having is radiators upstairs close to the boiler all hiss, no matter what is done. It’s less so with fully open trv.

I can live with that but what’s getting to me is, where upstairs meets downstairs in the wall there is pipes carrying the flow/return (Qualplex) and these have a tapping/ticking noise a lot of the time. I was wondering is this due to the boiler being oversized and when trvs close the pressure is too high. There’s no external ABV from what I can tell.

As a diagnostic measure I picked a larger radiator in the hallway 1600x500 and fully opened the trv and lockshield as a makeshift bypass but the issue stayed the same.

Has anyone an idea of what this could be?

Thanks all!

I’ve included a video of the sound within the wall below.

https://imgur.com/a/qXps9Nq

Have you done the obvious and vented all the rads with boiler off?. there is also a automatic venting function, see below. I think the boiler has a 7M pump which is automatically controlled but you can set the minimum speed to 70% (it may have been set to 100%) which may help to reduce the hissing, see below.

 

[Madrab]

.... these have a tapping/ticking noise a lot of the time. I was wondering is this due to the boiler being oversized and when trvs close the pressure is too high.

No - if the pressure is the system is stable then it's nothing to do with the boiler being oversized and the pressure getting too high

If there is a rad with 2, always open, lockshield valves then that would be more than enough to act as a bypass ensuring min flow through the boiler on overrun, which is really the function of the ABV. The reason for ABV's these days is that a rad is no longer acceptable as a bypass.

The ticking will usually be down to expansion or contraction with the pipework heating up/cooling down and they creep against themselves or wood etc.

Hissing will be probably be down to the valves causing turbulence. When the system is cold and then turned on do the rads upstairs heat from the TRV end or the opposite side? When they hiss, from what side specifically, at the TRV end or the lockshield end?

 

[Ironman2024]

Thanks John!

I have tried venting all rads and all seem ok, no air. I’ve also given the auto venting function in the menu a shot on different occasions to no avail.

I viewed the pump speed stats and it does tend to sit at minimum which is around 1670rpm, not sure if it goes lower than that but that’s the lowest mine goes at the minute.

 

[Johntheo5]

Thanks John!

I have tried venting all rads and all seem ok, no air. I’ve also given the auto venting function in the menu a shot on different occasions to no avail.

I viewed the pump speed stats and it does tend to sit at minimum which is around 1670rpm, not sure if it goes lower than that but that’s the lowest mine goes at the minute.

Very unlikely so IMO that excessive pump head is causing the noisy operation, 1670rpm of a probable max of 2900rpm will only result in a ~ 2.5/3M pump head, if the minimum speed is 70% then the pump head will still only be a max of 3.4M which shouldn't cause problems, the flow/return dT might give some indication of the circflow,
Can't think of much else except something to do with the water quality or excessive inhibitor, does reducing the flow temp make any difference?.