Digital thermostat

[John in Santa Cruz]

meter in A(mps) mode...

 

[JohnK-ESC]

My meter does have a time limited amp measuring capability so I might give that a try.

 

[John in Santa Cruz]

a general note re amps mode on most digital multimeters... they have an internal fast blow fuse, usually 10A... if you leave it in "A" mode and connect it across a voltage source, that fuse will generally blow instantly. this will disable the "A" mode but everything else on the meter should continue to work just fine. on these Flukes, there's a special 'fluke' fuse that I can get locally at a lighting store that also runs an electrical contractor supply from the back room. I asked the counter guy for a 10A blah blah fuse, and got a blank stare until I mentioned it was for my Fluke meter, OH, you want a FLUKE fuse, right here (rustle rustle, pulls out a little box of them).

 

[JohnK-ESC]

My meter has an unfused 10 amp function position for 15 seconds as well as a mA position limited to a maximum of 200 mA. To be safe I first measured using the 10 amp function which read 0.14 amps. Then I switched to the mA position which read 132 mA. I'm now comfortable knowing that the 14 awg blue wiring in my system is for mA signal current values at least at the thermostat which for that purpose is overkill. Thank you for talking me through this John.

 

[marant]

Not sure about the Honeywell, but FYI this less expensive Lux Pro PSD010B definitely works for furnace-only control as a replacement for the 2-wire Dometic furnace-only thermostat (proven in my 2021 5.0 with no factory AC, also installed by several other members here)

Tip - as seen in the attached, both of my thermostat wires are blue; not sure if it makes any difference but tape/mark the one going to Lux terminal W1 before you pull it from the original thermostat to keep 'em straight just in case

https://www.amazon.com/dp/B002SR9PH...trial&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw&th=1

Centex
Finally getting around to replacing the Dometic thermostat in our 2022 21C. Looking at the Lux Pro PSD010B you recommend, but it specifies systems with no fan. Will it still work with our heaters, which do have a fan, though fan cannnot be operated separately?

 

[Centex]

Centex
Finally getting around to replacing the Dometic thermostat in our 2022 21C. Looking at the Lux Pro PSD010B you recommend, but it specifies systems with no fan. Will it still work with our heaters, which do have a fan, though fan cannnot be operated separately?

All I can offer is that mine as described in previous posts is still working just fine, the furnace fan operates 'automatically' just as it did with the OE thermostat (fan turns on with heat and turns off a short time after heating stops when it hits desired temp).

 

[Kingfisher]

it specifies systems with no fan

These thermostats are meant for household systems, so the “no fan” part means that this is not appropriate for household systems that have a forced air circulating fan along with forced air heat.

One thing to note is the location of the studs behind the thermostat when mounting the new thermostat. This is from our 2024 21C. You have at most 1-1/2” above the existing wire hole if you want to screw the new thermostat into a stud.

 

[Ron in BC]

Always appreciate it when framing and hidden space photos are posted.

Ron

 

[marant]

All I can offer is that mine as described in previous posts is still working just fine, the furnace fan operates 'automatically' just as it did with the OE thermostat (fan turns on with heat and turns off a short time after heating stops when it hits desired temp).

I already had a Honeywell thermostat that had the same warning, so I installed it. The only problem was that the Honeywell instructions did not say which of the 6 or 8 pins to attach our wires. Contacted them and was told to use the W and R posts. Does not matter which wire goes where. Works fine. probably the same for most Honeywell thermostats.

 

[John in Santa Cruz]

My classic Honeywell, its Rc and W, I forget the difference between Rc and R but R is unused for a simple heater control like this. Oh Rc and R are jumpered together if you're not using both

 

[CnK]

MVA, which size wire are you using at the thermostat? I replaced our Dometic thermostat with a AAA powered Honeywell set to furnace control only. The blue wires throughout our furnace wiring which used to terminate at the air conditioner but now terminate at the thermostat are 14 awg stranded copper. This is heavier than I would have expected for signal wire, certainly for .7 amp draw. The thermostat terminals are actually too small for 14 awg wire.

John

This just happened to me, while replacing the Dometic furnace-only thermostat with a Honeywell digital. JohnK, did you nut those 14AWG strands to a 16 wire to connect? It seems like the ETI wiring is larger than necessary and that stepping down to a 16 for this won't hurt anything.
But it sure feels like an electrical to do it.
(I have the same question in to ETI but wanted to ask here as well. I will post their answer back.)

 

[JohnK-ESC]

No I did not nut those 14 AWG strands to the 16 AWG wire to connect. I simply pulled out as many strands from the 14 AWG wire as the position on the thermostat could accommodate and plugged them in. Probably another electrical

.
John

 

[CnK]

Looks like it’s not a nono (in this case) to change wire size

My question to ETI

I am trying to replace the Dometic thermostat with a Honeywell digital version, and the new thermostat uses a stab in wiring block that has holes that are too small for your wiring.​

​

It look like you are using blue 14 AWG for this.​

​

Is it safe to use a wire nut (I’d use a clip Wago) to “step down” from the 14 to a 16 to attach the new thermostat?​

And their answer

I have confirmed with engineering that you can do the step down If you need anything else please let me know​

 

[oldwave]

The heat only thermostat wires are just a simple circuit that energizes the furnace control board and starts the sequence of fan, sail switch, and burner ignition. I did keep my wires sorted when I replaced mine, though given it’s just a simple circuit it might not need to be. If you’re replacing one with ac, then the cooling control might be a bit more polarity sensitive. Also most of the simple heat only state they are for 24 volt systems, but with a battery option that’s moot point.