I have recently moved to a very hot climate whereby air conditioning is indispensable.
My bedroom has a thermostat that makes a loud clicking noise whenever it switches. I expect there is some electromagnet slamming a contact into place or something. It is loud enough to bring me back from the edge of falling asleep.
I have complained to the building’s maintenance team and they have said this is normal. I have asked if I can pay to get it replaced with a different model, they said sure.
The model they have offered is a Honeywell T6861H2WG-R. Can I expect this to be less noisy? Do all thermostats work with the same slamming electromagnetic switch?
Older thermostats use a mercury switch, and you can get a bit of a spark when they turn on or off. Also, are you sure it’s the thermostat that’s making the noise and not the appliance it’s connected to? My furnace makes quite a noise when it’s turned on, and it might feel like it’s the thermostat doing it.
That’s essentially the definition of a relay and almost certainly what you’re hearing. Even the small ones that fit inside more modern t-stats still (usually) make an audible click. It allows the t-stat to control a higher amperage load, while not having to require the (rest of the) on board components to also be able to handle that same load, which would require them to be larger.
Similarly, the click/clank/thunk you hear coming from your air handler (typically your forced air furnace, even for AC) are relays used to turn on and off other components. Both so lower amp controls can turn on/off higher amp parts of the system, but it’s also a very convenient way for a 24vdc power supply to control a 120vac load.
Maybe, maybe not. It’s still possible to buy cheap analog thermostats (like this one) that are built around a bimetallic coil for temperature measurement. Whereas these used to use a mercury switch for opening/closing the contacts that called for heating/cooling, they now use a little magnetic switch instead: when the bimetallic coil moves the magnet close enough to its contact, the magnet pulls it the rest of the way with a thunk and holds it tight, making a good, firm electrical connection. When the temperature comes up or down to where it’s supposed to be, the coil pulls harder and harder on the magnet until it finally lets go of the contact and opens the connection (though typically there’s no thunk this time).
If you have a fully digital thermostat and you’re hearing a click when it calls for heating/cooling, then yeah, that’s a mechanical relay doing it’s thing, because the manufacturer was too cheap to use silent, solid-state relays.
There typically is a click, but the loudness may be different between different thermostats. I recently replaced the thermostats in my house with Honeywell ones, but the clicks were so loud that I returned them. The thermostat was in the hallway but I could hear it in the bedroom. The previous thermostats had a soft click, but the Honeywell ones were sharp and loud and also bothered my sleep. I didn’t have your model of Honeywell, but it was similar. I ended up getting a different thermostat which has a softer click. I guess the relay in the Honeywell is louder than others.
I just went over to an electrical forum and saw this response to a similar question:
When you screw the t-stat to the wall, put o-rings between the wall and the t-stat. Then the little click is not amplified by the wall. I cut little squares of thin foam for stuff like this.
Which is eminently practical and borders on genius.
I had actually tried something similar with my Honeywell thermostats and it didn’t really make a difference. Even not attached to the wall it was still just as loud. Maybe it depends on the position of the relay inside the unit as to which direction the sound goes. Maybe the hard plastic backing reflects the click outward. It would be easy enough to try, but I wouldn’t expect a great reduction in the loudness.
Unsightly isn’t the issue. The issue would be that you may insulate it from the rest of the room. If it’s on an inside wall in a central part of the house, it may just mean it’ll take longer (like, a lot longer) to react because of how long it takes for the area inside the box to be the same as the area outside the box. If it’s on an outside wall (which it shouldn’t be anyway) it may end up reacting more to the outside temp than the house temp.
In any case, yeah, don’t cover your t-stat unless you allow for a lot of ambient air to move past it. And at the point that enough air can move past it so it can correctly read the temperature of the house, you’re probably not going to be blocking that much sound.
I was running late. My apologies for passing bad info. I had coffee in my hand, food on the stove, a contractor running late, and an appointment I was rushing out to.
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I was thinking exactly what Joey_P said about airflow. I just didn’t get it out.
There are no end of locking thermostat covers available:
They’re just vented on the L&R sides and the top and bottom. You could do something similar with a foam cover by Xacto knifing slots in the perimeter.
Even the plastic type in the picture could dampen the sound enough to make you happy. The price to find out isn’t very high.
The other question is whether the existing t’stat is compatible with a remote temperature sensor*. You could foam box the t’stat in (w/Velcro or similar), and remote mount a temp sensor (which should operate silently) so that the operation of the system isn’t affected.
The main value of an SSR over a tailored switching transistor design is that you can drop an SSR into a circuit intended for an electromechanical relay.
I got this thermostat to replace my loud Honeywells. It still has a click, but it’s very soft. I don’t notice it unless I’m right next to it.
One trick you can do with your Honeywells to avoid the click at bedtime is to have a program which drops the temp and kicks on just before bedtime. It will click on while you’re getting ready for bed, but then it will run for a while to get to that lower temp. Hopefully you’ll be fully asleep by the next time it has to turn on.
