Noisy Radiators

[rugbyscottie]

Did you previously have a bypass radiator with no TRV fitted to it, and if so do you still have no TRV on it or did you fit an HR92 to what used to be a bypass radiator ?

Do you have an automatic bypass valve installed on the pipe work near the boiler ?

Has the system been drained down or de-pressurised at all when the HR92's were fitted, or did you simply replace the TRV heads without touching any plumbing ?

Can't really think of any reason why replacing one kind of TRV with another (and presumably keeping the valve base itself) would make any difference to radiator gurgle. It's going to be something else in the system.

Hi,

I wasn't sure what an automatic bypass value was until I googled it! To be honest I don't know if one of these is fitted or not.

With regard to swapping the TRV's all that has changed is I removed manual TRV's heads and replaced them with HP92's heads there has been no changes to any plumbing or pipe work.

[Mavis]

Hi,

I wasn't sure what an automatic bypass value was until I googled it! To be honest I don't know if one of these is fitted or not.

Can I ask the same question please which may be pertinent for people getting the system installed. My Evohome was fitted by a reputable Central Heating Engineer but he had no experience of Evohome. I hasten to say that I have no problems with my Evo and am/was happy with the installation (and have gained a trusted tradesman)

Would I be right to presume that a bypass valve is something that a qualified heating person would check for/install regardless of inexperience of Evohome?

[HenGus]

Can I ask the same question please which may be pertinent for people getting the system installed. My Evohome was fitted by a reputable Central Heating Engineer but he had no experience of Evohome. I hasten to say that I have no problems with my Evo and am/was happy with the installation (and have gained a trusted tradesman)

Would I be right to presume that a bypass valve is something that a qualified heating person would check for/install regardless of inexperience of Evohome?

My answer to that would be 'Yes' - particularly, if the CH system used the time-honoured bypass configuration of leaving one or more radiators without a TRV. As it happens, my system does not have an automatic bypass valve but the pump does have a gated bypass pipe (that is, a pipe with an adjustable stop ****). I wasn't sure that much thought went into how this was set (clearly, it has to be partially open by any bypass to occur) once all my TRVs had HR02 heads fitted, but after 18 months of use I haven't had any issues.

Edit:

I found this piece of technical advice on a professional plumbers' forum:

its a bit of a fine balancing act it just need to give a flow path for the water so try it from fully closed crack it back about a half turn and see how it performs

if the downstairs radiators don't heat up, then close it half a turn.

[DBMandrake]

A bypass formed by a partially opened gate valve is old fashioned and doesn't meet current building regulations as far as I know.

It's also inefficient because there is always some flow through the partially open valve even when many radiators are calling for heat. Conversely when only one (or no) radiators are open, there is not enough flow through the valve causing the differential pressure to get too high. As the text you quote says "its a fine balancing act".

An automatic bypass valve is a spring loaded relief valve which remains completely closed until the differential pressure reaches the pre-set pressure, then it starts to open against the spring to regulate the pressure. So if you set it to 0.3 bars it would stay completely closed below 0.3 and then open progressively to regulate the differential pressure to 0.3 degrees as radiators close. Even with all radiators closed the pressure would not increase above the pre-set pressure.

So when you have many radiators open the pressure will be below the ABV pre-set pressure so it remains completely closed - efficiency is improved as there is no constant recirculation of hot water directly back to the boiler.

As radiators close a point will be reached where the valve starts to open, from that point on the pressure will not increase any further - this avoids the problem some systems have where only one open radiator can be quite noisy because the differential pressure is so high.

There is definitely an advantage to have an ABV retro-fitted, and if you want to add an HR92 to a radiator that was previously relied on as the "bypass" radiator, it's mandatory.

On our system the hallway radiator was originally the bypass radiator with no TRV valve fitted, and no ABV fitted to the system. (and not even a partially open gate valve) In this situation adding a TRV like an HR92 to the hallway radiator would not be possible as the Evohome system does under some conditions for short periods of time run the boiler with all radiator valves closed. Without an ABV this would cause a lockout on the boiler or possibly even cause the system to spring a leak due to very high differential pressure.

As to whether all engineers would install an ABV regardless of Evohome experience - I wouldn't be so sure. When we had initial work done on our heating system I specifically asked for an ABV to be installed because I knew I intended to install Evohome myself eventually. Because the hallway radiator at the time was a bypass radiator he insisted that I didn't need an ABV so it took some convincing on my part that I did really want one installed...

[HenGus]

Three well regarded heating firms looked closely at my system and all three told me - with out being prompted - that an automatic bypass valve wasn't mandatory or necessary for my CH system. I have an unvented system with an old conventional boiler (14 years old). I was told that there is no significant boiler over run. If I pay a company £1500 to install Evohome then I expect them to provide me with best advice. Eighteen months on, it is only Evohome that has given me any problems.

[top brake]

Adjust the setting on the ABV should cure this system noise issue. May also need to adjust the setting on the circulation pump. Can you get me some images of the ABV and pump please.

[emmeesse68]

To add something to discuss about, one of my rads suddenly begun making an incredibly loud noise that was more like an old Harley Davidson motorbike than a gentle hiss or a gurgle.

I noticed that it was enough to remove the hr92 head and turn the black dial a bit in either direction to make it stop.

I think this is the feared "valve hammering" effect, that depends on some mistake my plumber made more than 15 years ago when he installed my rads and old manual trvs... he mistakenly pulled the ingoing pipe in a recessed corner and the return pipe in a more accessible place, thus decided to install the trv on the return side to make it accessible.

15 years later, I replaced my old manual trv whith a brand new hr92, everything was looking fine, after a few months the surprise... that loud sound woke me up in the middle of the night, when the radiator got partially close... Now the issue reappears once in a while, I just pop the hr92 off and turn the dial, then put the hr92 back on, it cycles itself and sometimes the noise comes up again (I repeat until it stops, just once I had to repeat several times).

Apart of having the valves swapped (I'd wait to do this in summer, with the heating off), are there any orher suggestions?

Thanks!

[top brake]

Fit a TRV body that can accept installation at either end of the radiator. Honeywell Valencia for example

[emmeesse68]

Fit a TRV body that can accept installation at either end of the radiator. Honeywell Valencia for example

Good idea, thanks top brake... I didn't even know such trvs existed!

Still something to be done in the summer...