Dometic Thermostat accuracy?

[JimM68]

Our Monaco has the 5 button Dometic thermostat, controlling 2 atwood furnaces and 2 dometic penguin a/c's with heat pumps.
It has remote temperature sensors, 1 near the passenger seat, and 1 on the sidewall near the back of the bedroom.

the systems have worked perfectly, except the digital thermostat settings have never been close to "Real" particularly with the furnaces.

Our "comfortable" night furnace setting is 53 degrees!
First thing in the morning, I'll bump em up to maybe 58-61...
The actual temp in the coach at night is cool but not chilly, and it is warm during the day set to 60.

The front/rear zone behavior is identical. (Thinking this would rule out a sensor or sensor location problem)

The a/c's / heat pumps are similar, but not as bad, it is the propane furnaces that are "way off"

Is there any kind of adjustment / setting so these things more accurately reflect "Reality"?

[Kayteg1]

Almost every thermostat has adjustment for cut in/out difference.
But that adjustment is behind the options available for users and is design for technicians only.
If you set thermostat for 1 degree difference in drastic weather, you will be facing the system coming in/out every minute or 2, what gets annoying.

[donfrump]

Kayteg1 wrote:
You are dealing with several symptoms and to really understand it might take some research.
1. the temperature sensor (thermostat) is usually located on interior wall.
Meaning in 110F outdoor heat- the wall with sensor might be 68, but exterior wall can be 80F or even >100F.
In 0F outside cold the same 68F internal wall will be paired with external wall at 30-50F while temperatures between the walls will wary.
2. the thermostat switch has cut-in and cut-out temperatures.
For AC you set cut out at 68, but cut in will be about 72F,
The same setting in heating mode will cut-in at 65F

the ones we are talking about here have "remote sensors" they do not register the temperature at the thermostat ( at least the ones I have used don't)
the one iam most familiar with does not cut in at temp A and out at temp B If I set AC for 72 it holds at 72 only warms to about 1 degree above setting and cuts back in
I cant set the AC for a low of 70 and high of 75 (eg)

[Kayteg1]

You are dealing with several symptoms and to really understand it might take some research.
1. the temperature sensor (thermostat) is usually located on interior wall.
Meaning in 110F outdoor heat- the wall with sensor might be 68, but exterior wall can be 80F or even >100F.
In 0F outside cold the same 68F internal wall will be paired with external wall at 30-50F while temperatures between the walls will wary.
2. the thermostat switch has cut-in and cut-out temperatures.
For AC you set cut out at 68, but cut in will be about 72F,
The same setting in heating mode will cut-in at 65F

[JimM68]

ok. we just live with it then.
thanks Doug.

[dougrainer]

JimM68 wrote:
ok, some of you guys are way confusing me...
Perhaps talking about several different systems?

I have a Dometic digital system with a 5 button controller that connects to the front AC with a 4 wire phone cable (the front AC then connects to the rear one with another 4 wire phone cable). This is a digital connection that has nothing in common with any thermostat used in a S&B house...

My "problem" (if you can call it one, cause the system works fine) is that in AC or heat pump mode, "Comfortable" is a normal 68ish setting on the thermostat.
If "furnace" mode, "comfortable" is about 55.

Vastly different.

I am wondering why the "number" is so different in different modes, and if anything can be done to make the number "kinda the same"

One would think that a setting of 68 on the thermostat would result in roughly the same temperature in the coach regardless of the AC / heat pump / propane furnace mode?

And again, this behavior is identical in both zones. Physically different hardware.

I'd really just like to see the same inside temp with the furnaces on as with the heat pumps on, with the same number set on the thermostat?

Your thought process is correct. It SHOULD be the same regardless of Furnace or Roof. But, due to designs of Rv's, the LP furnace systems blow out extremely hot air at the floor level and then that air dissipates before the wall sensor has a chance for an accurate reading. This is why HP's became so popular 16 years ago when they were originally offered. The Heat from an HP is a more gentle heat and comes out of the roof vents. As long as the outside temp is above 35 to 40 degrees, the HP will heat your RV more accurately. If you do NOT have a HP(AC only) then you live with the problem or go to someone that has the knowledge and experience to fix the sensor problem. Even in regular RV's that have a furnace and a mechanical tstat, the hotter furnace air is a problem as the air is so hot at the floor level. Doug

[JimM68]

ok, some of you guys are way confusing me...
Perhaps talking about several different systems?

I have a Dometic digital system with a 5 button controller that connects to the front AC with a 4 wire phone cable (the front AC then connects to the rear one with another 4 wire phone cable). This is a digital connection that has nothing in common with any thermostat used in a S&B house...

My "problem" (if you can call it one, cause the system works fine) is that in AC or heat pump mode, "Comfortable" is a normal 68ish setting on the thermostat.
If "furnace" mode, "comfortable" is about 55.

Vastly different.

I am wondering why the "number" is so different in different modes, and if anything can be done to make the number "kinda the same"

One would think that a setting of 68 on the thermostat would result in roughly the same temperature in the coach regardless of the AC / heat pump / propane furnace mode?

And again, this behavior is identical in both zones. Physically different hardware.

I'd really just like to see the same inside temp with the furnaces on as with the heat pumps on, with the same number set on the thermostat?

[donfrump]

Kayteg1 wrote:

donfrump wrote:

Kayteg1 wrote:
Thermometers do have big error margins by the principals and you always have to calibrate thermostat to your liking.
Than placement is important also.
Is the thermostat in spot with good air flow?
Is it in the place affected by heat from furnace, or cook-top, or cold draft from a window.?

you are referring to the remote sensors placements ? correct

not the thermostat body ?

I was talking about thermometers and thermometers build-into thermostats.
My home is in San Francisco area, I am checking temperature and thermostat settings in it right now from my laptop in Las Vegas.
Isn't technology wonderful?

got it. because we were discussing Motorhomes and the MH thermometer reads out on the stat via remote sensor is why I asked

[Kayteg1]

donfrump wrote:

Kayteg1 wrote:
Thermometers do have big error margins by the principals and you always have to calibrate thermostat to your liking.
Than placement is important also.
Is the thermostat in spot with good air flow?
Is it in the place affected by heat from furnace, or cook-top, or cold draft from a window.?

you are referring to the remote sensors placements ? correct

not the thermostat body ?

I was talking about thermometers and thermometers build-into thermostats.
My home is in San Francisco area, I am checking temperature and thermostat settings in it right now from my laptop in Las Vegas.
Isn't technology wonderful?

[donfrump]

dougrainer wrote:
With Dometic CCC tstats, you CANNOT replace with another brand Tstat. ONLY if you run new wiring from each Zone to the roof AC units and then replace the roof AC unit control box with a NON-digital Dometic control box. You would install a Analog Dometic control box in each unit. After 20 years of the Dometic CCC system, I NEVER get complaints from customers about inaccuracy unless the OEM has not installed the system correctly. THAT happens a lot. Once the customer has a specific complaint and they want to pay for the repair, I can fix the problem. But to state, they are junk, just shows you really do not know what you are talking about. Doug

I totally agree and as u have indicated and I also the inaccurate selection of where they put the remote sensors has a direct relationship as to what "feels" like a correct temperature

[dougrainer]

With Dometic CCC tstats, you CANNOT replace with another brand Tstat. ONLY if you run new wiring from each Zone to the roof AC units and then replace the roof AC unit control box with a NON-digital Dometic control box. You would install a Analog Dometic control box in each unit. After 20 years of the Dometic CCC system, I NEVER get complaints from customers about inaccuracy unless the OEM has not installed the system correctly. THAT happens a lot. Once the customer has a specific complaint and they want to pay for the repair, I can fix the problem. But to state, they are junk, just shows you really do not know what you are talking about. Doug

[donfrump]

Kayteg1 wrote:
Thermometers do have big error margins by the principals and you always have to calibrate thermostat to your liking.
Than placement is important also.
Is the thermostat in spot with good air flow?
Is it in the place affected by heat from furnace, or cook-top, or cold draft from a window.?

you are referring to the remote sensors placements ? correct

not the thermostat body ?

[Kayteg1]

Thermometers do have big error margins by the principals and you always have to calibrate thermostat to your liking.
Than placement is important also.
Is the thermostat in spot with good air flow?
Is it in the place affected by heat from furnace, or cook-top, or cold draft from a window.?

[donfrump]

Effy wrote:

donfrump wrote:

sdianel wrote:
from modmyrv.com: The standard analog thermostat found in most RVs doesn’t control the A/C and furnace with much accuracy. The “set” temperature is not always the temperature the thermostat cycles, which results in as much as a +/- 5°F temperature change before the A/C or furnace cycles on or off. This is known as the hysteresis of the thermostat. For example, if you have the furnace set at 72°F, this could mean the temperature would fall to 67°F before cycling on and rise to 77°F before cycling off! These temperature swings aren’t very comfortable so what to do? The digital thermostat mod of course. Analog thermostats have what’s called a mechanical heat anticipator, which essentially tells the thermostat when to cycle. Some anticipators are more accurate than others but for the most part are not very good at controlling temperatures accurately. The digital thermostat is much better at temperature control since it controls its hysteresis using electronics to within +/- 1°F degree of accuracy.

This mod is commonly performed using the Hunter brand residential thermostat. It’s cheap and very straightforward to install. Other residential thermostats can be used but this one seems to be the most popular. Just be sure the thermostat you select is battery powered.
We have not done this modification, we just got used to the fact that there are variances in the temperature and set the thermostat accordingly.

not sure what your point is but the OP already has a digital 5 program thermostat with remote sensors

The point is that the dometic or coleman mach stats that come with the units are junk. The only way to get a reliable one is to install your own.

But you missed my point also.their post talks about analogue stats ?? the OP has a digital that's why iam not sure why they brought up the article on the analogue stat. ???
mine is a Rv Comfort.ZC(coleman) digital with remote sensors and very accurate
one sensor in the middle of the ceiling in the front living/kitchen area and one in the middle of the bedroom area

[Effy]

donfrump wrote:

sdianel wrote:
from modmyrv.com: The standard analog thermostat found in most RVs doesn’t control the A/C and furnace with much accuracy. The “set” temperature is not always the temperature the thermostat cycles, which results in as much as a +/- 5°F temperature change before the A/C or furnace cycles on or off. This is known as the hysteresis of the thermostat. For example, if you have the furnace set at 72°F, this could mean the temperature would fall to 67°F before cycling on and rise to 77°F before cycling off! These temperature swings aren’t very comfortable so what to do? The digital thermostat mod of course. Analog thermostats have what’s called a mechanical heat anticipator, which essentially tells the thermostat when to cycle. Some anticipators are more accurate than others but for the most part are not very good at controlling temperatures accurately. The digital thermostat is much better at temperature control since it controls its hysteresis using electronics to within +/- 1°F degree of accuracy.

This mod is commonly performed using the Hunter brand residential thermostat. It’s cheap and very straightforward to install. Other residential thermostats can be used but this one seems to be the most popular. Just be sure the thermostat you select is battery powered.
We have not done this modification, we just got used to the fact that there are variances in the temperature and set the thermostat accordingly.

not sure what your point is but the OP already has a digital 5 program thermostat with remote sensors

The point is that the dometic or coleman mach stats that come with the units are junk. The only way to get a reliable one is to install your own.