Looking for a 3D printable adapter to convert an old Drayton TRV4 bayonet-clip radiator valve to M30×1.5 thread so I can fit a SONOFF TRVZB smart radiator head.
Specs needed:
-
Input side: Drayton TRV4 bayonet collar (smooth bore, 3-4 clip slots) — photos attached
-
Output side: M30×1.5 female thread (standard for smart TRV heads)
-
Material: PETG, 100% infill preferred for durability on radiator heat
Why: The official SONOFF kit doesn’t include an adapter for older Drayton bayonet valves. I’ve got a 3D printer available to print the design.
If you’ve designed something similar or can help, please reply! Happy to credit you or donate if needed.
2 Likes
@cornelliusfox I have no idea of what these things look like so I did a little research on line. The best I can come up with is something like this. Sorry but I don’t know the size or number of splines. This is mostly guess work. I wasn’t able to access any photos using the link above.
I used M30x1.5 male threads and M30x1.0 female threads
1 Like
Hmm, major problem with this as the threaded collar needs to be a separate part since you can’t turn the adapter itself to tighten since it is sliding onto splines.
I really need to see some images of how these things fir together and which has male threads and which has female.
I found a photo of an adapter on line and it appears that the Drayton has 12 splines? Can you confirm this? I think I calculated about a 105 degree angle for the faces?
I’m also unsure as to how this actually relates to what you need.
1 Like
Once I get some real dimensions I have a couple of options for the collar. The first is to print in place the collar as a single unit. It should print pretty cleanly that way.
The other is to make the part a push on adapter and then add a clamping tab that would be tightened into place using a small bolt, or to use something like a stainless steel hose clamp to keep it in place.
Another possibility would be to add an additional threaded joiner with a smaller diameter thread. It would allow a collar to be placed onto the Drayton side and then the two printed parts could be screwed together and the Sonoff could be attached to its threaded end.
Here is a print in place version
Can’t add any new posts so I am just adding edits.
Looking closer at the Sonoff design it appears that the Sonoff connects using a female collar. This means that the adapter has to have a M31x1.5 male thread. I have redesigned the adapter with this in mind. The adapter collar screws onto the Drayton valve at the bottom.
I have gone ahead and created a ‘Thing’ hoping that I can get some feedback to ensure the part will actually function as it should.
1 Like
Are you sure you want to use 3D printed parts in a pressurized hot water heating system? Just don’t tell your home insurance agent, I guess.
Its not really in direct contact with the hot or pressurized part. It is basically a small pin that pushes on the actual valve. Kind of like a handle on a tap.
The system uses a small motor to drive the pin in and let it up. I believe the original ones were essentially a rotating cap the turned it on or off by pressing down on the valve pin. All the home automation ones use a small motor controlled by a tiny controller board and gets its signals through wifi, bluetooth or zigbee. Batteries in the unit provide the power for the motor and the PCB.
The adapter just allows the Sonoff threaded part to fit an older Drayton thread but the problem is the gear or lobed section inside that keeps the head from turning. No one has given me measurements for those lobes so I have just guessed and I am probably wrong.
Ok, looked at the manuals for these things and see that the mount is not handling pressure. It it still attaching to a radiator valve body, though, so there’s going to be some heat there from time to time. Maybe consider designing for machined metal as an option - a service like PCBway (no affiliation) could make a one off or a small set of them. Watching videos of the controllers, it looks like the internal plastic parts they have that are in close contact with the valve body are a glass-filled resin.
All that said, I would not mess with it myself. If something ever goes wrong with the plumbing, insurance will use any reason to deny coverage. A non-OEM or non-standards-rated part, even if it had nothing to do with the failure, is like catnip to insurance adjusters.
Fun side note: when my basement flooded, the insurance adjuster insisted that I prove for how many hours a night I slept in the house in order to consider the house to be “occupied”. Imagine if they found a DIY printed part on the plumbing!
Yup, they are happy to take your money but are not so nice when it comes time to meet their obligations. Any excuse not to pay and they are one of the biggest profit grossing industries around. Some places are no longer insurable these days due to the issues with climate change. When my daughter bought her house she almost didn’t get a mortgage because there was a fire (kilometres away) and the insurance refused to give a policy until it was out, even though it wasn’t close and was extremely unlikely that it would get anywhere close to where she was buying.
