Digital Thermostat and Stove Top Cover

[Trailblazer]

This weekend I finally got around to doing some mods to the trailer I have been wanting to do for some time now. I replaced the original thermostat with a Digital one that I modified to allow switching for Hi and Lo fan speeds. I also added a stove top cover to provide additional counter space that flips out of the way when you want to use the stove. Here are links to the pictures:

Digital Thermostat

Stove Top Cover

[JohnB]

Trailblazer

Nice job. I see you are handy with sheet metal. Nice work

The T stat is cool too. And I looked at the rest of your rig pic's. That's a nice camper. I'm assuming those pics where still on the dealers lot? The Sealand kid on the side of the door poster looks just like the one in my manual, only bigger.

Happy camping

John

[Steve Collins]

Originally Posted by Trailblazer

This weekend I finally got around to doing some mods to the trailer I have been wanting to do for some time now. I replaced the original thermostat with a Digital one that I modified to allow switching for Hi and Lo fan speeds.

Is the digital thermostat an RV model or is it a standard residential one that you've adapted for use in an RV?

My thermostat in the trailer is partly shot. The temperature slider is grossly out of adjustment, and the folks at the RV parts counter tell me there is no fixing things inside of the unit.

So, do I shell out the $55 they want for an exact replacement, or do I check out my local Home Depot?

Reading over on rv.net, some folks like the Lux or Hunter digital thermostats, and others think they're junk. Anybody got any feelings here? I understand you can get one of these at Wal-Mart for under $25, but that may be a statement in itself...

And someone over there (rv.net) says the digital thermostats don't use coach voltage, but rather a lower voltage from their own internal batteries. Anybody know more about that?

And about the hi/low fan switch: got a simple schematic you can share?

Thanks!

[Trailblazer]

Originally Posted by Steve Collins

Is the digital thermostat an RV model or is it a standard residential one that you've adapted for use in an RV?

My thermostat in the trailer is partly shot. The temperature slider is grossly out of adjustment, and the folks at the RV parts counter tell me there is no fixing things inside of the unit.

So, do I shell out the $55 they want for an exact replacement, or do I check out my local Home Depot?

Thanks!

This is a residential thermostat that I adapted to for use in the RV. I purchased mine in a local Canadian Tire Store here in Canada. Basically any digital thermostat will work in an RV, however you will need to add a SPST switch if you want to control the Hi/Lo fan speed. I followed the instructions of another individually who modifiled a Hunter Thermostat he purchased from Walmart in the US for about $20.00 The SPST switch took me less than 1 hour to mount and solder up in the body of the thermostat. It took about another 30 minutes to hook everything up and test in the trailer. Here are a couple of links I read before I attempted this myself:

Hunter 4299B Installation

Installation of Hunter Digital Thermostat

To answer some of your other questions, Yes the digital thermostat does run on 2 AA batteries instead of the coaches batteries. In my research it appears that most home systems run in 24 volt but our coaches are only 12volt. The thermostat I purchased and from my understanding of the Hunter unit, they are microvolt thermostats. This allows it to run on 2 AA batteries or 3 volts. Although I do know why but the power connection at the original thermostat is 7.5 volt. Since you will not be using the power from the coarch, you will need to tape off the 7.5 volt wire to ensure it does not short out to any other wires. Anyways, from what I understand the microvolt thermostats will run for more than 1 year on a pair of AA batteries. I wil keep a spare set of batteries in the trailer at all times just in case they die early. With this setup the problem is that if you do not have battery power then the thermostat will not operate. I have also kept the original thermostat in the trailer and if necessary I can re install it in about 15 minutes or less.

The wiring for the Hi/Lo switch is very simple. You run one wire from the SPST switch to the low speed fan connection on the thermostat. The high speed fan wire is then connect to the other terminal on the switch. When the switch is in the open position, no connection is made to the high speed wire and the fan runs at low speed. When you close the switch and contact is made with the high speed wire the fan speeds up. This was actually a pretty simple wiring job.

As far as which thermostat to buy, it really doesn't matter as long as it works on a microvolt system. I have friends who have done this mod with LUX, Hunter and Honeywell thermostat, and no one has had any problems with any of them and they all are very happy with the results. I used a Noma thermostat as it was the only one I could find that was not programmable. Personally I did not see the need of having a set back programmable thermostat in the trailer, but you could definitely use one if thought it would be a benefit. The entire trick to this mod is just transferring the wires correctly from one thermostat to another as not all thermostat use the same codes.

I hope this helps. Please let me know if you need anymore information.

[Trailblazer]

Originally Posted by JohnB

Nice job. I see you are handy with sheet metal. Nice work

I'm assuming those pics where still on the dealers lot?
Happy camping

John

I wish I could take credit for the metal work, but this one was bought from Camping World. I had originally planned to make it myself, but when I saw it at Camping World and with my limited amount of time at the moment I decided it would be quicker if I just purchased it.

Yes, the pictures of the trailer were taken on the dealers lot when we first purchased it last year.

[Steve Collins]

Trailblazer,

Thank you! I am going to do this just as soon as I get to a Wal-Mart or Home Depot and find the right digital thermostat. (It's a 30 minute drive to anything from where I live... )

I agree with you that there probably is no need for a programmable one as most of us don't occupy our rigs full time where there may be some real benefit from programmability. Most of the time, I just need to set a comfortable temperature and let the heater or AC do its job.

Perhaps some of the folks who sunbird it down south may find a programmable more to their needs.

Thanks again.

[Steve Collins]

UPDATE!

I picked up the Hunter 42995 at Wal-Mart this morning on our way out for a day trip in Ithaca, NY. It is still $19.97!!!!!

When we got home and settled in, I grabbed my tool box and replaced the crapped-out Duo-Therm with the Hunter in about 20 minutes. It works perfectly!

The only thing I didn't do was modify it for the High Fan switch yet.

The second set of instructions you listed were just right for my unit - all I had to do was change the wire colors to match mine. This is the URL for those instructions:

http://www.rverscorner.com/articles/hunterstat.htm

Thank you again!

[Honda03842]

I installed the same cover in my trailer and it is so much better than the standard cover and a snap to install. I bought mine at pplmotorhomes.com for $63.

Norm Milliard
1982 Sunline 15.5 SB

[precorguy]

ok, i am going to attempt this project --- i have read the various articles on this change over and am looking forward to it --- i think that i will be using a Honeywell Non-Programmable Digital Therm that i can pick up here in Canada for $39.00.

i have read the instructtions, seems to be the same as the others, here is the link:

http://yourhome.honeywell.com/Consum...al/Default.htm

this is a single stage Heating/Cooling for Gas heat and compressor Air -- non programmable, battery operated --- correct????

my only fuzzy bit in all of this ---- how is the switch installed for HI/LO fan ---- i don't quite follow?

it appears that:

---- orange -----> "G" terminal (low fan)

------ blue ------> switch (on/off type)------> "G" terminal as well (hi fan)

so when the switch is turned on (closed) the fan runs on HI

when the swtich is off (open) the fan runs on LOW

but both via the same "G" terminal in the new thermostat

IS THAT CORRECT??????

or have i completely screwed it up?

thanks

[Steve Collins]

Originally Posted by precorguy

this is a single stage Heating/Cooling for Gas heat and compressor Air -- non programmable, battery operated --- correct????

my only fuzzy bit in all of this ---- how is the switch installed for HI/LO fan ---- i don't quite follow?

it appears that:

---- orange -----> "G" terminal (low fan)

------ blue ------> switch (on/off type)------> "G" terminal as well (hi fan)

so when the switch is turned on (closed) the fan runs on HI

when the switch is off (open) the fan runs on LOW

but both via the same "G" terminal in the new thermostat

IS THAT CORRECT??????

or have i completely screwed it up?

thanks

You are on the right track.

First, you are correct about the type of thermostat; nothing fancy, non-programmable, single stage cooling & heating for gas heat.

When you do this, FIRST: Label and tape off the +12vdc wire. It is NOT used in this project. (This is a safety thing, plus you don't want to fry that brand new digital thermostat.)

You are also correct on the hi/lo fan switching for the A/C. They both end up on the G terminal, and the HI side is turned on and off via the switch in line on the blue wire.

The only reason I didn't hook up the HI is that I have a lot of other projects to finish this week before shoving off for the Adirondack M&G, and I want to think on how I am going to do the switch. Right now the blue wire is taped off, too. Everything else works fine, especially the heat which I am sure we'll need this weekend. There are no hookups where we're going to be, so the A/C is not really an issue anyway.

[Trailblazer]

Steve,

Glad to hear the installation went smooth and everything is working fine.

[thedeatons]

Hello all... I have been looking for a thread like this!!

I don't own a Sunline, but desperately want a programmable thermostat in our Jayco. We live in it, and it would help us save a lot of gas (winter) and electricity (summer).

I have some questions.

1) Is there a reason we cannot use the nice touchpad Honeywell programmables? That would be the ultimate for me, as I love gadgets. If not does anyone know of a good microvolt programmable with lots of features?

2) Why not just utilize the 7.5V line givent o us by the RV and step it down to 3V? This way we wouldn't need to worry about batteries...?

Any help would be great!

[Steve Collins]

Originally Posted by thedeatons

Hello all... I have been looking for a thread like this!!

I don't own a Sunline, but desperately want a programmable thermostat in our Jayco. We live in it, and it would help us save a lot of gas (winter) and electricity (summer).

I have some questions.

1) Is there a reason we cannot use the nice touchpad Honeywell programmables? That would be the ultimate for me, as I love gadgets. If not does anyone know of a good microvolt programmable with lots of features?

2) Why not just utilize the 7.5V line givent o us by the RV and step it down to 3V? This way we wouldn't need to worry about batteries...?

Any help would be great!

You can probably use any digital thermostat that you want. That's been chewed on several times over in another thread on RVNet.net. I guess it is mostly a matter of personal preference and individual need.

A lot of us agreed that for most RV purposes, the programming functionality would be overkill, and likely never used. Folks who full time in their RV's might have more use for a programmable unit in their rigs. Since we only tend to spend sleep time and maybe a few other hours of the day, depending on weather, etc. in the trailer, the programmability wasn't a big deal to us. And, we tend to stay in New York State campgrounds in the Adirondack Mountains which don't offer any electrical hookups. Thus, controlling the AC is not the priority to us that it may be to others.

Since you live in your trailer full time, the value of a programmable goes sky high.

One suggestion would be to verify before buying what voltage the programmable thermostat requires. Might be a tad frustrating to discover that it really does need 24v after you've bought it and modified it.

That is part of the appeal of the non-programmable units as they only need the 3 volts that is supplied by the batteries.

As for stepping down the 7.5 volts to 3 volts and not bothering with two AA batteries per year... I didn't feel it was worth it to build and install a special circuit to do this. For the price of a pair of AA's per year, it wasn't worth the time and effort.

Again, your situation might alter that equation. One thought is that if you modify the thermostat, you may void the warranty on the thermostat. Just a thought. But, if you have the tech skills to create the 3 volt step-down, it may be a fun project, too. If you really want to do that, use a battery until the warranty expires, and then have at it....

I think one of the issues for a lot of us was that we could replace the $60 Duotherm RV thermostat with a $20 digital one that works better and easier. And if the $20 one breaks in a couple of years, replacing it would be quite easy and low cost.

I haven't even gotten around to installing the high/low fan switch yet. The thing works so well that I just haven't made it a priority.

Good luck, and let us know how it turns out.

[MayDix2009]

I think you have done a good mods on your trailer... you have replaced the original thermostat with a Digital one that modified to allow switching for Hi and Lo fan speeds, that looks cool...




_________________
Programmable Thermostats

[henryj]

I'm in need of some help with the switchover to a digital thermostat.

The Noma thermostat that started off this thread apparently does not work. I've got one with the hole drilled and SPST switch installed and all it does is run the HI fan. Trailblazer confirmed that he also has not gotten this thermostat to work despite his original post.

In addition, Trailblazer installed the Hunter while at Buttonwood and it also did not work.

I'm going to be in the US over the weekend and am debating buying the Hunter, but don't want to throw more good money onto a lost cause.

I would really appreciate some response from people who have done this mod--successfully or unsuccessfully--especially JohnB and Steve Collins who I know have done it.

Also, some of the other electrically knowledgeable people in SOC, what's going on here?? Why does a thermostat fire virtually identical appliances in one camper and not another? Have there been some subtle changes to thermostat design--this is an old thread? Both Trailblazer and I have CSA trailers. I'm not aware that this would create a problem. The only electrical difference is the microwave/HWH lockout switch on the AC side. I can't imagine there are any differences on the DC side. I know the OEM feed is 7.5V, and the digital is 1.5V. Is that where the problem lies? And if so, why does it work in some trailers??

Thanks for reading and adding to this old thread, but I thought it was better than starting a new one.

Henry

[264SRinPA]

I installed a Hunter thermostat 2 years ago with no problems. Did you follow all the directions?

[Steve Collins]

DO NOT use the 7.5vdc line. Tape it off (per the instructions) and let the batteries in the thermostat do their job. (The 7.5vdc comes from the AC unit to drive the Duotherm thermostat. It is not needed for the Hunter conversion.)

Several of us have successfully done this mod. Please tell us what you have done, and include pics so that we can help troubleshoot it. Without knowing exactly what was done, it is not possible for us to figure out the problem. I am certain that there is something minor that can be easily corrected.

Here is a recap of the wiring converting from a standard Duotherm RV thermostat to a Hunter:

Duo-Therm Color Hunter
+7.5 vdc RED Not Used (Tape Off)
Cool YEL Y
Furnace WHT W
Hi Fan BLU Through a SPST to W
Fan BRN G
Ground GRN RC + jumper to RH
Hunter thermostat Heating System Selector set to "HG"
"F/C" selector switch to "F"

A couple of notes here. First, the wire colors may not be exactly the same. One guy had different colors so he pulled a bit of the cable out of the wall and found a splice. No big deal.

What matters is that you take whatever color wire is on each terminal of the Duotherm and move it to the proper terminal on the Hunter per this chart.

[Trailblazer]

First let me preface this post with saying I have done this mod successfully in approx 5 trailers of friends and had no issues with the exception of my trailer. As Henry has indicated, there seems to be something different with the Sunline Canadian CSA built trailers. Although I initially posted this thread, none of the three thermostats,(Noma, Honeywell, Rite time and the now the fourth a hunter), I have installed in my trailer have been able to run the AC. First off, do not use a Noma thermostat. For some reason they do not work on RV's and this has been confirmed by several other who have tired to install them on various forums. Now with regard to mine and Henry's problem I have spend a lot of time testing and tracing all the circuits related to the problem of the digital thermostats not working on the CSA built trailers. I can confirm the wiring colors are all the same as the US models and they match up correctly to the colored wires in the install directions. I can also operate each of the systems by directly connecting each item, Furnace, fan and compressor to the ground wire. I can also confirm that both the A/C unit and the furnace relays are switched by the ground wire.

While heading down to the M&G I purchased the exact Hunter Thermostat that others have used. Now after being unsuccessful at getting the the Hunter Thermostat to work at the M&G I decided to do a lot more testing and tracing of wires and here is what I have been able to determine. In order to determine what is going on I decided to connect the wires in stages and test to see what works and when does not. I first connect the yellow A/C wire to the Y terminal, the tan wire to the G terminal and the Green wire to the RC terminal and removed the jumper between the RC and RH terminals. When the thermostat is set to call for cooling the compressor will kick on but the fan motor does not run. When the jumper is connected between the RC and RH terminal the Compressor turns off and the fan motor runs. Even after waiting and letting the fan motor run for 5 minutes, even though he stat was calling for cooling the compressor never turned on. The minute I disconnect the jumper wire the fan motor stops and the compressor turns on. I also get the same results when I connect up the blue high fan speed wire to the G terminal. Now if I manually connect the yellow, the tan and the green wires together the compressor kicks on and the fan motor runs. Testing the thermostat, when it calls for cooling the RC terminal. the Y terminal and the G terminal are all connected together. Now what makes no sense to me as to why the connection of the jumper wire between the RC and RH terminal causes the Fan motor to run and the compressor to stop. Testing the thermostat tells me the only time the RH terminal is in use is when the thermostat calls for heat. Going back to the A/C side of the stat, just to prove whether or not the thermostat could handle the running the compressor and the fan motor, I did the following experiment. I connect the tan wire and the green wire to the G terminal and the yellow to the Y terminal. Now as suspected the minute I turn on the power to the trailer the fan motor started right up because I effectively hardwired the fan and the ground directly together. Next I set the Thermostat to call for cooling. The result was both the fan motor and the compressor ran. Now keep in mind this was only a test setup and the fan motor constantly ran.

Based on all my testing there is no reason that I can see as to why the stat should not be able to run the A/C. At one point I was thinking I had a high resistance ground wire but the if that was the case my last test should not have worked. In addition the analog thermostat also should not work.

In order to test the thermostat I have taken a Hunter thermostat that worked in a friends unit and installed it in my unit and the A/C compressor would not kick on. I took my thermostat and installed it in the friends trailer and it worked without any issue.

I can tell you I have traced and tested ever possible connection with a multimeter and I can see no reason why the digital thermostat connected as described should not work, but for some reason it doesn't. Unless someone has another suggestion, I think the last thing left to do is run all new thermostat wires between the Thermostat, the A/C unit and the furnace.

[JohnB]

Trailblazer

Check the current draw on the compressor signal wire (hotwired to run) both on yours first and then buddies (in line with the hunter) who's works on the Hunter.

There may be, "something" to do with the CSA that requires more current draw. Why I have no idea….but… If the Hunter is using a solid state output device (I'm sure it is) it may only pass so much current. It sounds like you are not reaching the threshold voltage/current to pull in the AC unit. If the solid state device is limiting the current/voltage it will not turn it on.

If the AC will run hot wired and not run on the hunter, well it is not passing enough current to run it and the fan at one time.

But the compressor running and then fan goes off. Well that does not make much sense, just yet. Unless the current draw is turning off the SCR if it is DC or triac if it is AC.

Also, please throw a carriage return in every once in a while... Those high tech’y really long paragraphs are hard to read with these old eyes...

PS We really need a wiring diagram posted here so we can follow the wording. And if anyone has an actual electrical schematic at the board level, I use to be able to pick out how most of that use to work. However I have not done TTL logic in a few years.... everything now is programmable.... But RV's are as basic as they get so my rusty old skills might still work.

PS2 as a last resort, a small solid state type relay from Radio Shack may fix the problem if the Hunter can't pass enough current. I'll have to look on line what they have left in the solid state world. Every year less and less. Use to be you could build almost anything from them. Not now.

PS3. Remember current is measured in series. You may know this, but if you forgot it itn will save changing the fuse in your meter…..

[henryj]

Thanks to all who are continuing to contribute to this thread and to Trailblazer for ongoing efforts at troubleshooting the Hunter. I don't see any point in pursuing the Noma any further and so will not post any photos or wiring diagrams. Since virtually all of us live in the US, or travel there frequently, getting the more familiar Hunter to work in our CSA Sunlines seems to be the best bet.

The theory of what Trailblazer and JohnB are talking about goes way over my head, but if they can sort out the problem, I am good at following directions and have no phobias about doing electrical wiring.

In the meantime, I guess I'll hold off on getting the Hunter and if the problem can be solved will pick one up on a future US trip.

Henry