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0

Ok - when unmounting the thermostat, I noticed the manufacturer's name (Danfoss), and from that I was able to find the value type, which is Danfoss RAVL


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On the existing valve, you loosen or remove the screw. This will allow the fingers under the grey strap to expand, allowing you to just pull the thermostat off. To install your thermostat, move the metal ring down. It might actually be threaded, so turning it may be required. Push it on to the radiator, and move/turn the metal ring back in to place.


2

Simply turning off the breaker that feeds the furnace will turn off the thermostat power as well.


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Sounds like a dead thermostat. When it was working before, it hadn't died yet. Why it died is likely to remain a mystery. Things don't live forever (neither do people - dragons might, per one song.) Replace it.


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If the blower is continuously blowing, then one of the limit switches is open. It may not be the high limit, but it's certainly one of them. Without knowing more about the unit (model number, photo of the schematic, etc.), it's difficult to offer much more assistance.


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Based on the ladder diagram, it looks like the R terminal is only energized when all the limits (main limit and however many rollout limits there are) are closed. So if any of the limits open, the thermostat loses power (maybe). I can't say for sure; since I'm not familiar with that board, but if that's how the furnace disables itself during a problem. ...


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Yes. Old thermostats are passive devices - a bimetal strip with contact blades. The heater provides 24 volts AC via a transformer, used to switch the gas solenoid, fan relay, A/C relay etc. via the thermostat. Smart thermostats need power of their own. That's easy: there's a 24v transformer right there in your furnace, its terminals are called R (hot) and ...


1

Yes, that should be very straightforward. Simply wire the switch to interrupt the "W" wire, which is the one the thermostat uses to ask for heat. Its request will be unanswered obviously. Do this between the thermostat and what I presume is a big relay with a 24v coil that switches the 240v power on to the heaters. Turn the 240v off at the breakers ...


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Yes, it is possible and relatively easy since it is all low voltage and simple circuitry. If you have multiple heat zones, you need to be sure you have the termostat controlling the basement zone. If you have one heat zone for the whole house, just set up the thermostat in parallel with the other thermostat(s) in the house. Note, you might want to use a ...


1

First off -- option 1 will be...awkward. You are essentially connecting two transformers in not-quite-parallel here, and as a result, it may not work at all. I would recommend against it -- simply replace the thermostat in the summertime. As to a replacement transformer -- you can get a 240VAC to 24VAC control transformer as a standard part from an ...


-1

OK. I didn't read all the responses, but thought this would help. If your thermostat has a R and Rc, then there has to be a physical wire (jumper) connecting the R and Rc, along with the red wire going into the R slot. I didn't know this, as I inherited the thermostat from a friend. Heat turned on, AC did not. Once I read up, installed the jumper, ...


1

You should test the output of the thermocouple with a multi-meter to confirm that the replacement is working as expected. An 8-year old heater would have an "auto-reset" thermal cut-off switch built into the pilot assembly, to protect the burner compartment from overheating, these can go bad. Was that replaced when the thermocouple was replaced? For modern ...


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I assume the helper pump on the return line (the fifth pump on the other side of the boiler) runs if any of the zone pumps are running. If the living room zone pump has failed, the helper pump will force hot water through all four zones. To test this, temporarily disconnect power to the helper pump. Since the system is new, it seems more likely that the ...


1

The amount of heat going out of your house has to be made up by your heating system. When its cooler inside(winter) there is less temperature difference from inside to outside and therefore less pressure to move heat out. Therefore heat loss is lower. Looking at run times and saying savings are uncertain is disingenuous at best, except on a heat pump. ...


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Assuming the thermostats are working, you may be getting residual heat once the thermostat turns off. Do the pumps have speed controls? Many pumps have LOW, MEDIUM, and HIGH settings. A lower setting may avoid spikes in temperature. Also, many pumps have mixing valves near them that control the temperature of the water being sent to the radiators in that ...


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I don't understand this - how or why is the voltage falling so drastically under (0.25mA) load, preventing the transformer functioning? I don't understand why these lines are at 115VAC anyway. Generally when you see this sort of thing in an AC system it means that the line is floating. Lines running in close proximity have some stray capacitance ...


1

Beware Ghost voltages Typical UK central heating is wired like this (Honeywell Sundial S-Plan) It is not immediately obvious but essentially, the 240 live supply passes through a series of switches in this order: Mains supply (there is often a wall switch plate for heating). Provides power to ... Timer (AKA controller - ST9400A/C in diagram). Provides ...


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Since this is a mains (240VAC) system, a diode isn't going to do what you want. However, you can use a relay to turn the boiler on from the Nest without the boiler timer turning the pump on. Connect the relay coil from CH (Nest output) to N, the relay NO contact to HW, and the relay Common terminal to L. That way, the Nest's output turns on CH, which turns ...



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