Hey, would you mind sharing your radiator fan setup?
I’ve been meaning to strap a few 140mm Noctua PWM fans to the bottom of the K3 rad in my living room, with a PWM controller driving them.
If you can wait a couple of days, I’m just finishing up on a PCB I plan on posting here as well.
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Excellent! I’ll await your post; will it be in this thread?
I’m looking to use an off the shelf PWM controller with a thermistor probe adhered to the flow pipe of the radiator, with fan mounts/shrouds made from foam board and attached to the rad via magnets.
That’s exactly what I did, with this 12v controller. Does the job nicely.
PS: I split this out into a new thread as the previous one was getting too long.
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Another solution is to use a smart plug, and turn on the fans via WiFi when the heating is on.
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This also works nicely, especially combined with a simple manual PWM controller dial. My current goal is to have something smart as I want to use fan speed as an additional temperature control mechanism since a couple of my rooms drift apart at different temperatures - likely because the radiator coefficients are slightly different. This way I can keep all TRVs fully open and still have some individual temperature control. Having temperature sensors and also space for CO2 sensors in there is another bonus.
This is what I aim on building:
It has an M5stack Atom Lite as a pluggable controller and runs off 12V. There’s connectors for four fans, that can be independently controlled in blocks of 2 using PWM. The PWM signal uses an additional 5V line buffer to be able to cascade many fans on one connector. In case the fan does not support to be turned off with zero PWM duty, there’s a MOSFET to switch them off. In principle, the MOSFET supports fast switching so that normal 3-wire fans could also be driven using PWM on the power line. Also there are two sockets to connect DS18B20 temperature sensors. The Atom Lite has a Grove connector that allows to connect all sorts of modules like CO2 sensors.
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Amazing!
Will you be offering this to others?
I will fully open source this and also invite anyone who wants to contribute - also for designs of mechanical assemblies to hold the fans etc. What’s still needed is a housing. I’ll be ordering the first prototype PCBs this week.
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Not sure how much I can contribute, but I would love to buy a ready-made populated PCB unit if that’s possible.
I will look into ordering populated PCBs after the prototype stage - I’m sure there’s a solution we can find.
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Some more details on my setup. I have build a wooden frame to hold the fans, which is positioned on two L-Brackets in the wall. This completely decouples any direct noise between fans and radiator. However, I like @ectoplasmosis idea of using foam board and will try this for my other radiators.
Furthermore, I have ordered the first PCB prototypes and expect to be able to assemble and test them later this week.
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Very neat!
I’m now leaning towards using silicone fan mounting rods with neodymium magnets attached to the ends; the magnets will attach directly to the rad and suspend the fans decoupled via the silicone.
Can you share what exactly you have in mind there?
From experience I can tell you that good fans (e.g. Shadow Wings 2) are pretty much inaudible even without decoupling - you actually mostly hear the air flow. Still, proper decoupling gives that little extra bit of silence. The cheaper ones like Arctic can be louder. Most my fans run at around 500 RPM max and are completely silent.
What kind of power consumption are we looking at here?
How does one work out what the “correct” number of fans would be for a given radiator? “More is better”, probably, but when do we hit diminishing returns?
Electronics are significantly < 1W, the fans I use draw a maximum of 0.12 A at full speed. I’m using them at maybe half speed, so let’s assume 0.75 W per fan. Let’s say 5 x 140 mm fans per meter of Type 33 radiator, so that’s < 5 W per radiator for me.
I’m running my purely radiator-based (type 33 and 22) heating using a flow temperature of 30°C at 0°C outdoor temperature - the gains in COP definitely offset the maybe 40 W in added power draw for my house during the heating season.
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What would you estimate to be the gain in output by running the fans attached to a given radiator?
Very simple: using mounts similar to these, with each fan hole on one end of the silicone rod, and a small neodymium magnet disc (with hole) on the other, with a suitable length of silicone rod between them, allowing the fan to be suspended without swaying: https://noctua.at/en/products/accessories/na-sav3
My Type 33 radiator is in a bay window behind a sofa, so output is compromised by lack of radiant heating. Aesthetics is almost irrelevant, as none of the fan assembly will be seen.
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I did a couple of measurements last year looking at the temperature decay of the radiator when it’s full of hot water and the TRV closed. With fan, I’m seeing around 80-100% higher power output.
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The simplest solution is to tie the fans together using cable ties through the mounting holes and just glue foam pads and neodymium magnets on the fan cases, properly aligned so they hold on the radiator. This way you have decoupling via the foam pads. The Shadow Wings 2 have rubber mounting rods anyways, and I just glued some magnets directly on them (marked in red):
