Rads kettling following a Drayton Wiser Install

MikeC1964

Novice Member
Joined
Mar 21, 2022
Messages
9
Reaction score
1
Points
1
Age
59
Location
Derby
Hello. I hope someone may have some advice for me. Pleas bear with me, it’s my first time and there’s no short way to relate this…

I had a new Baxi 800 combi installed at the end of last year and I was running a Gen 2 Nest with it. I wanted to have more granular control so I opted for Drayton Wiser.

My heating engineer installed the hub for me and on my request connected via the Opentherm module in the hub the Opentherm connections in the boiler (as far as I am aware).He was a little reluctant as he had no real knowledge of either Opentherm or Wiser, but in the Wiser app it does suggest that the Opentherm connection is being used.

Anyhoo, I went for a cautious approach as I have 15 rads I want to control eventually, but I didn’t want to commit to buying Wiser TRVs for all the rads without first having a play with their basic combi kit which consists of the hub, a room stat and two smart TRVs. I initially only installed the room stat as a direct replacement for the Nest and all was fine. I then played with the two smart TRVs to check that I wouldn’t have any connection issues (I live in a Victorian property and the hub is in the attic conversion along with the boiler). Everything fine there, although looking back in order not to disrupt the heating too much for the rest of the household I primarily tested that the TRVs could switch off rads whilst the rest of the house was being heated according to the room stat, rather than them calling for heat. Perhaps my mistake.

I then took the plunge and purchased an additional 12 TRVs and started rolling them out over the weekend and setting up the schedules. All seemed fine until my wife remarked that the rad in the hall and the heated towel rail in the bathroom were rather noisy. And she was right. They are kettling (if that’s the right term). Neither of these had TRVs to begin with as you would expect (the Nest was in the hall), but now I have rolled out most of the Smart TRVs I can report that some, but not all, of the smart TRV controlled rads also kettle.

I spoke to Drayton Wiser and they couldn’t really offer any solution. They checked the logs and noted that the ‘requested’ output temperature was around the 55 degree mark, but as to why the rads are kettling is best to be discussed with my heating engineer. I don’t know what the output temp was set to before the new hub was installed (I believe Opentherm now controls this and not the boiler?).

I will of course discuss with my engineer, but as he was not that confident with Opentherm as mentioned above, I thought I would turn the the internet community and see whether there are any suggestions here. I have bled all of the radiators, just to be sure. Most were fine.

Thanks,

Mike
 
By kettling do you mean you have a vibration or chatter at the TRVs? If yes, then you may have directional TRVs fitted the wrong way round. Some TRV valve bodies are universal, so can be fitted with water running in any direction through the valve, but others have to have flow in one direction, otherwise you get the valve plunger rattling against the valve seat as the water flows in the wrong direction through the valve body. So her your plumber ti check the data sheet/instructions for any valve bodies he’s supplied and fitted.
 
Hi Neil. Thanks for the reply.

By ‘kettling’ I mean the sound that a kettle makes when you switch it on. That ‘woooshing’ sound when the water is getting heated up. The sound isn’t coming from the TRVs but from within the radiator itself. The TRVs I have fitted (myself) are the Drayton Wiser smart TRVs. There’s no information in the use guide that suggests they can be fitted around the wrong way. Most of them are using a Danfoss adapter, although some are the metal ring screw fit style (again apologies if I’m using the wrong terminology). As mentioned this isn’t happening in all rads, so I’m at a bit of a loss.

Mike
 
Forgot to mention that I have been checking the output temp on the boiler and it seems to be around the 65 mark. I think that’s not untypical - could be wrong - but not what Drayton were telling me. May be timing of course. As a I understand it Opentherm is supposed to make your boiler run at a lower temperature for longer - so the 55 degrees Drayton are saying would make sense, but I haven’t seen that yet. Bear in mind the boiler is in the attic so Im not running up the stairs all that often!

We’ve also noticed that the rads are MUCH hotter then a they ever seemed to be before DW was installed.
 
Personally I’ve never heard a radiator kettle. I’ve heard them hiss quite loudly, usually on newer and or cleaner systems when the circulation is really good.

I take it you didn’t need to drain any water to fit these trvs as you mentioned an adapter? So no chance it’s air?

A heating system should be configured with at least one radiator without a trv to allow for circulation and to prevent the boiler overheating.

Would this “kettling” occur when you’ve got the majority of the radiators switched off and only 1or 2 on?

Could you open or close the lock shield end to try and counter this noise?
 
As with the previous post, if it’s a whooshing noise then firstly check for air and make sure the system is well bled, then look at the pump speed - maybe it’s high now that the system is operating without all rads fully open all the time.

Regarding boiler temperature, Opentherm sends a percentage demand to the boiler (or sometimes a boiler setpoint), based on the highest zone demand in the system. I don’t know what algorithm Drayton use, but I suspect it will ask for a high setpoint when rooms are a degrees or two below setpoint, and start to dial back the seams as the temperature falls within around a degree of setpoint. There may not be any maximum boiler setpoint setting in the Wiser control protocol (it’s not mandatory for Opentherm controls to set a maximum setpoint), so you may find that your boiler control thermostat still controls the maximum temperature, or it might be like Viessman where they disable the boiler stat as they expect the controls to set the maximum setpoint.

What all this means is that Opentherm is more a standard comms protocol rather than an absolute method of boiler control, so what you get depends on the controls implementation and the boiler implementation, and in many cases you’ll find it impossible to get any sensible info from any of the manufacturers! So don’t be surprised that your plumber is resistant - it’s a lottery to implement when the various manufacturers using the protocol will not tell you how it’s actually implemented, or help support systems that use it. When you try and get info to troubleshoot you’ll most often be told it’s nothing to do with the technical suport you are speaking too and all the fault of the other party, and that’s about as far as you get. Even when you use a boiler manufacturers own Opentherm controls you get little help in how it actually works or is meant to perform.

Welcome to the world of vested interests of manufacturers wanting to keep everything in-house rather than being an active participant in open systems and protocols,helping make installations perform much, much better than they currently do!
 
Personally I’ve never heard a radiator kettle. I’ve heard them hiss quite loudly, usually on newer and or cleaner systems when the circulation is really good.

I take it you didn’t need to drain any water to fit these trvs as you mentioned an adapter? So no chance it’s air?

A heating system should be configured with at least one radiator without a trv to allow for circulation and to prevent the boiler overheating.

Would this “kettling” occur when you’ve got the majority of the radiators switched off and only 1or 2 on?

Could you open or close the lock shield end to try and counter this noise?

Well, one person’s kettle may be another person’s hiss! It just sounds like a kettle getting up to speed to me.

No, no water was drained when installing the thermostats - the valve bodies are not changed just the thermostat on top. The install and integration into the system is very easy - well I managed it anyway! Connectivity and scheduling has all worked fine.

The number of rads or off doesn’t make any difference.

Neil, I think you are correct, I am piggy in the middle here. I’m sure the Drayton Tech was telling me this morning that it wasn’t the Wiser that determined the output temp, but it was Opentherm! As far as I was aware (I work in IT so I have a little bit of technical knowledge, just not in this sphere) as you have confirmed as well that Opentherm is a communications protocol rather which can tell the boiler what the output temp should be, but doesn’t determine what that value should be. This HAS to be the Wiser end.

I can’t put my finger on it but something is not functioning as it should here. My Heating Engineer won’t be much help as he advised me against this in the first place - he had heard there were connection issues with Wiser, but ironically that side of things has been fine. But you never know. I think it is time for more phone calls tomorrow.

I really don’t want to have to revert to my old NEST system as I really felt this could give me finer control over a the amount of gas I was using and I’m £600 into Wiser at the moment, but I can see that as a distinct possibility.
 
As with the previous post, if it’s a whooshing noise then firstly check for air and make sure the system is well bled, then look at the pump speed - maybe it’s high now that the system is operating without all rads fully open all the time.

Newsflash!

I have bled all of the radiators, BUT you may have a point regarding pump speed. I started researching pump speed and Baxi boilers and I found a thread on another forum asking how to alter the pump speed on his Baxi as the poster in question had installed smart TRVs and:

“I can hear the water circulating inside some of the radiators; I though this might be due to the pump speed..
I have noticed that if I turn on all the Tado valves together the water noise is acceptable, but as soon as I leave only one open, the noise is very loud”

So it appears my kettling could actually just be water circulating.

There is a “boost all” option in the Wiser app that I have just used to open up all of the TRVs…..and the noise all but disappeared.

This tallies with the weekend when we only noticed the issue when I was part way through installing the smart TRVs, so I must have reached some critical mass point at which the problem triggered.

Unfortunately there was no resolution posted, but at least this is something I can put to my heating engineer. I’m not sure there will be anything that can be done.

If this is about pump speed is it possible to explain what is happening here and why you suggested pump speed in the first place? The curious thing is that this does not affect all rads. Interestingly though, ignoring the heated towel rail, two of the affected rads are older single panel rads, although I do have another single panel rad that is NOT affected. None of the newer double panels seem to be affected from what I have found so far.
 
In new systems it’s more common to have variable speed pumps that will adapt their flow rate based on system resistance in an attempt to match the heating load (in terms of how many radiators are open at that time). Older pumps may only have three fixed speeds you can switch between, so if the pump is on speed 3 then you can try turning it down to a lower speed and se of it makes any difference. Ideally the pump is chosen to match the system design requirements, but often it’s just picked based on rules of thumb rather than proper deisgn measurements/calculations. It might also be the case that you have a system without any auto bypass which aims to open when reinsurance increases, and aims to maintain a minimum flow rate through the boiler too.

Regarding radiator noise, some times it’s purely a fluke that the flow rate and restrictions through a particular radiator hot a sweet slot in terms of harmonics that make it sound much louder than elsewhere in the system. Making a small adjustment to the lock shield valve on the opposite side to the TRV may change the flow characteristics enough to make this much less intrusive, but sometimes there may be nothing you can actively do other than live with the noise or change the radiator.
 
Hmmm. Well this is a brand new Baxi 800 so I’m not sure where this leaves me in terms of pumps (I’m assuming the pump,is part of the boiler and not separate to it). But it’s interesting information so I will discuss with my engineer…..when I can get hold of him! 😂 I’ll leave any adjusting of lock shield valves until then just in case I make anything worse.

Bear in mind that the two loudest culprits don’t actually have TRVs on them anyway - and may have to continue to be that way as I understand that in all systems you are advised to have at least one without a TRV in case the boiler needs to dump heat in an emergency - as well as the fact that in traditional systems this would be the rad nearest the single thermostat. I’m not sure ultimately whether the heated towel rail in the bathroom (the only other rad without a TRV here) is sufficient to perform that purpose so I could ultimately put a TRV on the hall radiator.

The fact that I have another single panel that does not seem to suffer from this issue offers some hope that this may be resolved, but I need to turn to the professionals now, so I will report back at some point.
 
There is a dedicated thread to gas central heating problems. It’s run by a heating engineer. Maybe post your questions in there see if he can help. Here’s a link.

 
There is a dedicated thread to gas central heating problems. It’s run by a heating engineer. Maybe post your questions in there see if he can help. Here’s a link.

Thank you. I note Neil is quite active in that forum, so it may or may not be worth me posting there.

For what it is with, I caught up with my engineer on the phone and he seemed to be concurring with what has been said above in a s much as what I’m hearing is water being forced through these two rads as there is a much smaller volume by a pump operating at the same speed as it would do if all rads were open. These smart systems turn the normal convention on its head whereby usually when the heating is on most rads are open to flow will a small number perhaps being closed off by their TRVs whereas with a smart system the point is that you often want to do the opposite.

He didn’t really offer any solutions. I mentioned trying to adjust the lock shield, but he pointed out that could have an adverse affect on the balance of the rest of the system.

The main consequence of this other than the noise is that the hall and bathroom are now excessively hot. The max temp I have any room set to is 20 degrees, but these two rooms are typically running at 23/24 when some other room is calling for heat, so I can’t be doing with this. I could of course have a TRV valve added to the hall rad and put a smart TRV on it as well, but don’t you always have to have one rad without a TRV for overrun? And that would still leave the towel rail in the bathroom.

Unfortunately I think I’m going to have to back this system out and hit eBay.
 
Last edited:

The latest video from AVForums

Is 4K Blu-ray Worth It?
Subscribe to our YouTube channel
Back
Top Bottom