Houghton a/c youtube re: humidity issues

[John E Davies]

40 minutes ago, Geronimo John said:

My recollection is that the thermister changes resistance based upon temperature.  The mother board of the unit is set up to interpert resistance and map it to a temperature setting and unit response.  If we cut the wires to the thermister and extend them, that would change the overall resistance of the thermister and original wire resistance as seen by the mother board.  Would that cause other issues?

You can extend any thermostor/aka temp sensor a reasonable distance, just use HIGH quality connections (solder and heat shrink) and use an equal or heavier gauge (smaller number) wires. Then no worries - you won’t see any significant resistance increase. Especially for a sensor that has a range of 15,000 to 30000 ohms like the Zamp solar one!. Adding a few ohms to those figures is irrelevant.

NO, NOPE, NO WAY:

If you do anything in terms of splicing or repairing, always test the sensor before and then after the operation, in equal environmental conditions..

https://olivertraveltrailers.com/forums/topic/4205-how-to-check-your-zamp-battery-temperature-sensor-for-proper-operation/

John Davies

Spokane WA

[Geronimo John]

On 8/10/2023 at 10:24 AM, John E Davies said:

You can extend any thermostor/aka temp sensor a reasonable distance, just use HIGH quality connections (solder and heat shrink) and use an equal or heavier gauge (smaller number) wires. Then no worries - you won’t see any significant resistance increase. Especially for a sensor that has a range of 15,000 to 30000 ohms like the Zamp solar one!. Adding a few ohms to those figures is irrelevant.

John D.

Thank you for the above response.   Great to know that there is a path forward.

GJ

[Geronimo John]

On 8/6/2023 at 11:51 AM, GSMBear said:

Unfortunately, it's a little misleading about how to get wires from the exposed portion of the rooftop unit into the sealed portion that can be seen by looking up from the inside when the plenum is removed.  

GSM Bear:

The thermister wires pass from the control board and then down into the Return Air path "tube"  (inside the 14 X 14 roof penetration).  For a non-ducted system it can be seen from the cabin with removal of the inside air distribution panel. 

I suspect that splicing in a long section of wire (As presented by John Davies above) at the roof penetration level in the 14 x 14 penetration would leasily give you a path between your two hulls for mounting of the sensor inside the cabin.

GJ

[GSMBear]

On 8/11/2023 at 5:29 PM, Geronimo John said:

The thermister wires pass from the control board and then down into the Return Air path "tube"  (inside the 14 X 14 roof penetration).  For a non-ducted system it can be seen from the cabin with removal of the inside air distribution panel. 

Yes, but. . . 

I have seen the thermistor by looking up into the return air duct after removing the inside plenum.  There's a short section of wire that leads to an exit path on the STREET side of the unit.  And you would think this would exit into the rooftop section on the STREET side making a replacement a simple task.

However, my experience is this:  From on top of the roof, the lead wire from the control board enters the protected/sealed area under the Styrofoam on the CURB side of the unit.  From there, it appears to travel to the STREET side of the unit in a way that I think can only be accessed by unsealing the Styrofoam and removing it.  A task I'm not keen on doing.

When I attempted to feed a new thermistor into the access hole on the STREET side of the rooftop unit, it never appeared on the inside when looking up into the return air duct.  Where that lead wire went, I have no idea.  I'm guessing it got all bunched up on something.  (If someone else has done this, I wanna hear from you!)

In the attached pictures, marker #1 is the entry path to the sealed area on the CURB side while marker #2 is an entry path on the STREET side.

My findings might be wrong, and I hope they are.  But I gave up on the task because the unit is new and apart from the roughly 4 degree temperature change for cycling, I have it working well.

I'm definitely in agreement with John's remarks about soldering an equivalent gauge wire to the thermistor to extend it. The problem is, without the ability to easily feed the wire from the rooftop section to the interior section (the issue described above), there isn't enough slack wire to get it to an easily workable area with a soldering iron.  It's pretty tight quarters up in the return air duct.  My brother has some experience with this and I'm planning to wait for a return visit from him to explore it more.

[Geronimo John]

On 8/16/2023 at 5:34 AM, GSMBear said:

I'm definitely in agreement with John's remarks about soldering an equivalent gauge wire to the thermistor to extend it. The problem is, without the ability to easily feed the wire from the rooftop section to the interior section (the issue described above), there isn't enough slack wire to get it to an easily workable area with a soldering iron.  It's pretty tight quarters up in the return air duct

First my assumption is that we are using the former Dometic thermostat wires to control the gas heater and have done so using a new thermostat at the location of the old Domet stat.  That said:

Your assessment matches what I observed.  That path is not worth the effort.  HOWEVER:

I believe that the thermistor wires end up at the control board.  My suggestion is to disconnect or intercept them at the control board and then connect a new one (with a much longer lead) in its place and locate the new thermistor in a place that better represents the cabin temperature.

GJ

[GSMBear]

6 hours ago, Geronimo John said:

I believe that the thermistor wires end up at the control board.  My suggestion is to disconnect or intercept them at the control board and then connect a new one (with a much longer lead) in its place and locate the new thermistor in a place that better represents the cabin temperature.

Hi John -- yes, the thermistor wires end up on a 2-pin connector on the control board on the curb side of the rooftop unit.  The problem is getting a replacement thermistor wire from the outdoor/exposed area of the rooftop unit into the interior/sealed section that is accessible from inside the RV looking up into the unit after removing the ceiling plenum.

In the pictures from the post directly above, the thermistor wire goes from the control board and enters the sealed Styrofoam area at marker #1.  However -- and this is the part to really understand -- that thermistor wire does not appear anywhere from inside the RV looking up until it comes out of the area by marker #2.  How that wire gets through the sealed area from marker #1 to maker #2 (on the inside) is not clear to me.  I think I would have to unseal the Styrofoam section to see and follow that path and I'm not keen on doing that.

I already have a new thermistor and I tried feeding it through the entry point at marker #2 and it never showed up inside the RV.  Where it went, I don't know.  But I'm not convinced that's the path to use.  To make matters worse, there appears to be some cable ties (a reflection of a good quality build, IMO) that would prevent me from splicing wire from the outdoor rooftop side (where I have good access and can use a soldering iron easily) and gently pulling it though whatever path it takes.  So it's a bit of a pickle, to say the least.

[NCeagle]

I made the change to the Houghton with the relay to keep the fan from running when the compressor is off.  It has made a world of difference with the humidity and dew point overall.  As expected, the temperature difference between the temperature set on the Houghton and the actual cabin temperature increased significantly.  A solution I have found is to point a small fan up towards the Houghton so the thermistor gets better temp readings from the cabin when the compressor and internal fan are off.  In a nutshell it works fantastic - we keep a fan on our nightstand running anyhow so pointing it up a bit was no problem.

I'm interested in moving the thermistor as well as a long term solution, but it does seem risky to completely disassemble the Houghton and install a new thermistor that may or may not work as we expect.  I'm waiting for one of you brave souls to try this before I do!  🙂

 

[GSMBear]

1 hour ago, NCeagle said:

I'm interested in moving the thermistor as well as a long term solution, but it does seem risky to completely disassemble the Houghton and install a new thermistor that may or may not work as we expect.  I'm waiting for one of you brave souls to try this before I do!  🙂

I hear ya!  I won't be that brave soul. . . but my brother might!  He lives out of state but he loves the Great Smoky Mountains so it's not hard to convince him to visit, when he has time.  When he does visit, he stays in the Airstream that is tucked away nicely in its own "AirPort" not far from the house.  He's an electrical engineer and is always curious about solving problems like this.  He has seen where the thermistor is and knows that soldering new extension wires would be an over-the-head task.  But I think he's open to it.  Whether we can get all of the necessary hands up into the area to manage the task is yet to be seen.

[GSMBear]

On another note. . . 

In previous posts and also in a PDF "how-to" document I posted, I referenced about a 4 degree temperature swing with the wiring mod to cycle the interior fan with he compressor.

My updated experience is this temperature swing has been as much as 8 degrees!  I have temperature sensors in 3 different places inside my 23' RV (it's an Airstream, not an Oliver) and they all give different readings.  I'm not too surprised by that.  Only the one that is somewhat in a path of the air out of the air distribution box on the ceiling gives a reading close to the set-point on the Houghton.

I'm also experimenting with setting the fan to Auto only at night.  This is the setting that turns the fan off when the compressor is not running.  Then, during the day, I'll set the fan on medium which allows it to run all the time as designed by Houghton.

I started this approach yesterday and during the day, the interior RH reading was in the upper 50s.  I only have sensors to measure RH.  I left the fan on medium overnight and woke up to an interior RH reading of 78%.  I slept in the house so it wasn't my breathing that added any humidity.

I'll continue to monitor it today with the fan on medium and see if the interior RH drops.

BTW, I appreciate the engagement here on this topic.  I've posted remarks and questions about this on the AirForums and there hasn't been much engagement.  I also find myself looking more and more at those nifty Oliver Legacy Elite II's!  A lot less tongue weight for my F150 than my comparably sized 23' Airstream.  I like the twin bed offering, too.  A buddy of mine and I want to hitch up and point ourselves west and "go see America" when we retire -- if my parents' health permits.  The two fixed twins would be ideal.

But, man, I'd hate to give up my front panoramic windows that I love so much!  Conundrum. . . 

[SeaDawg]

7 hours ago, GSMBear said:

BTW, I appreciate the engagement here on this topic.  I've posted remarks and questions about this on the AirForums and there hasn't been much engagement.  I also find myself looking more and more at those nifty Oliver Legacy Elite II's!  A lot less tongue weight for my F150 than my comparably sized 23' Airstream.  I like the twin bed offering, too.  A buddy of mine and I want to hitch up and point ourselves west and "go see America" when we retire -- if my parents' health permits.  The two fixed twins would be ideal.

But, man, I'd hate to give up my front panoramic windows that I love so much!  Conundrum. . . 

We appreciate your thoughtful contributions.  There are (so far) just a few of us with Houghton units, but it's really an easy swap, and a very reasonable price, as an upgrade. The humidity issue, and the drain, have been the biggest downsides, for most. 

Feel free to visit the rally next year. I'm sure a lot if folks would love to see your modified Houghton in action, and you'd see a bunch of Olivers. 

If you were to decide to change it up, I think you'd miss your nifty  recliner upgrade more than the front pano window. In our experience,  the best views at parks and organized campgrounds are usually through the back window. With the aeodynamic Oliver sloped front/trollley roof, having the front occupied by bath and closet just makes sense.

 

[John E Davies]

1 hour ago, SeaDawg said:

If you were to decide to change it up, I think you'd miss your nifty  recliner upgrade more than the front pano window. 

No need to miss the recliner:

 

John Davies

Spokane WA

[GSMBear]

15 hours ago, SeaDawg said:

Feel free to visit the rally next year. I'm sure a lot if folks would love to see your modified Houghton in action, and you'd see a bunch of Olivers. 

It's very tempting!

And I agree about the best views being out the rear window.  I wish my floor plan had been reversed for this very reason.  Airstream no longer sells my model (23D but later called 23CB) and I suspect it is because of the narrow 48" fixed bed in the corner.  It's a bugger to make, for sure.  I lived in it by myself for a little over 2 years while having a house built and didn't go all Jack-Nicholson-The-Shining-Crazy during that time.  Adding a 2nd person for that length of time would no doubt have pushed me over the edge.

I can also say during that time I was able to confirm what I suspected:  the insulation is fantastically awful.  From some remarks in this thread, it appears Oliver does a much better job with this.  I imagine the Houghton would perform nicely on an Oliver.

So tell me. . . do the Olivers that came with factory Dometic ACs operate via a wall thermostat that also controls the gas furnace?  My Airstream did and the "brains" of that operation that allowed the furnace, AC/Heat Pump, and thermostat to all play nicely together was in the AC unit -- which is now out of the picture.

I'm going full low-tech on my gas furnace solution with an inexpensive 2-wire mechanical thermostat mounted in the same location as the original Dometic CCC2 (comfort control center?) thermostat.  I've yet to run that wiring but I don't expect it to be difficult given their respective locations.  Just waiting for a nice crisp autumn Saturday morning to do it.

I do, however, still have the phone cable that ran from the thermostat location to the 14" roof opening where the AC unit is.  That's the wire I have in mind to use and extend/relocate the thermistor for a better ambient reading if the wire gauge is the same or better.  Just need to get my brother here with his soldering iron to give it a go.  Of course, if/when that happens there will be a full write up to share!

[John E Davies]

Do NOT use a mechanical thermostat, they are horrible and you will hate it! Unreliable, big dead zone, hard to return to a setting you like. They use points like a 1950 Buick!!!, once the contacts get a little dirty, they arc and eventually quit. Buy this one and put a new battery in it annually.

Emerson 1E78-140 Non-Programmable Heat Only Thermostat for Single-Stage Systems

John Davies

Spokane WA

[GSMBear]

4 hours ago, John E Davies said:

Do NOT use a mechanical thermostat, they are horrible and you will hate it!

I hear ya!  I have my expectations set very low for the mechanical thermostat but it's already purchased with a custom 3D printed backer plate to cover the factory holes from the Dometic CCC2.  I will only need to use this when the temps get low enough that I need heat around the holding tanks.  Apart from that, I'll use the heat pump or an electric space heater.

[mossemi]

On 8/23/2023 at 7:03 AM, GSMBear said:

He has seen where the thermistor is and knows that soldering new extension wires would be an over-the-head task.  But I think he's open to it.  Whether we can get all of the necessary hands up into the area to manage the task is yet to be seen.

Have you thought about using a butt connector with heat shrink and solder using a heat gun instead of a soldering iron?  I also use the method below for connections where a stronger connection is needed such as pulling a wire that I have lengthened.

Mossey

 

[mossemi]

Another thought is to remove the MaxxFan for access to the space between the upper hulls.  It’s a much larger hole to work in.

Mossey 

[GSMBear]

On 8/30/2023 at 11:34 AM, mossemi said:

Have you thought about using a butt connector with heat shrink and solder using a heat gun instead of a soldering iron?

I wish I had taken a picture of the area where this work needs to be performed but I didn't.  It's really tight quarters.  And for that reason, I think the soldering iron will be necessary because the heat gun will spread heat in areas that might damage something nearby.  It's worth consideration, for sure, but I think it would be risky.

[mossemi]

On 9/1/2023 at 6:36 AM, GSMBear said:

I wish I had taken a picture of the area where this work needs to be performed but I didn't.  It's really tight quarters.  And for that reason, I think the soldering iron will be necessary because the heat gun will spread heat in areas that might damage something nearby.  It's worth consideration, for sure, but I think it would be risky.

This product is typically used to protect wood and other wall materials while soldering copper plumbing fittings, but I have used it in the Ollie to protect other wires.

Mossey

Edited September 2, 2023 by mossemi
Add photo

[GSMBear]

Now that some cooler weather is here I have spent some time in the RV with the Houghton/RecPro in heat-pump mode.  As a refresher, I added a relay as a modification to cycle the interior fan with the compressor on the low fan speed circuit.  This nicely solved the issue of pumping humid air back into the cabin when in AC mode and the compressor turned off.  But it introduced a problem (somewhat anticipated) with the unit having about an 8 degree differential for cycling on again when needed.

Also, with this modification, the fan would operate as intended by the manufacturer in Medium or High speed since only the Low fan speed was involved with the new relay.  In AC mode, this worked as expected.

Fast forward to now with the cooler weather and I'm finding the fan cycles with the compressor regardless of the speed selection when in heat-pump mode.  I'm not sure why this is the case.  I was thinking in heat mode I might like the fan to run continuously to help keep the set temperature and actual cabin temperature more aligned.  Fiddled with it some last night and nothing seemed to keep the fan running in heat mode.

I now have something new to keep me awake a night. . . 

[Geronimo John]

On 8/22/2023 at 11:11 PM, NCeagle said:

I'm interested in moving the thermistor as well as a long term solution, but it does seem risky to completely disassemble the Houghton and install a new thermistor that may or may not work as we expect.  I'm waiting for one of you brave souls to try this before I do!

Simple Path Idea:  Can we intercept the thermistor wire from the underside.  Extend the wire as JD has suggested.  Then route the wire through the OTT drain line back to the attic.  Cut the drain line and pull the wire and thermistor to the street side cabinet surface.  Drill a small hole to poke the thermistor end into the cabin just above the Smoke Detector.  There it would not be much of a visual issue. 

Your thoughts?

GJ

On 8/24/2023 at 3:19 AM, John E Davies said:

Buy this one and put a new battery in it annually.

Emerson 1E78-140 Non-Programmable Heat Only Thermostat for Single-Stage Systems

I second JD's suggestion this T-stat works exceptionally well to fire up the OE2 furnace. 

GJ

[NCeagle]

12 hours ago, Geronimo John said:

Can we interdept the thermister wire from the underside. 

I can't figure out an "easy" way to even get at that thermistor from the underside.  I can see it but it's protected in a "cage" that looks like it would require some disassembly to remove.

I like the routing path idea for a longer wired thermistor!  Maybe the original idea of replacing the current thermistor with another that has a long wire.  Would still have to figure out how to get through/under the Styrofoam insulation, but we could leave the original thermistor in place (disconnected at the control box) as a backup.  

[GSMBear]

Yes, the continuing saga of finding a way to add and relocate the temperature sensor to the Houghton/RecPro A3400 AC/Heat Pump.

Some backstory:  with engineering assistance from my brother, we added a relay to the interior fan so that it cycles with the compressor.  This made a substantial improvement in the interior humidity issue while in AC mode with the manufacturer’s design.  In fact, I’d say it eliminated the problem.

But this solution introduced a new problem:  Since cabin air isn’t constantly flowing over the temperature sensor mounted in the round return air chamber, there is an increased disparity in real cabin temperature versus the temperature observed by the sensor.  This prevents a steady and comfortable cabin temperature.

Relocating the temperature sensor to an external location away from direct air flow of the distribution box might solve this problem.  But finding a path from the rooftop control board location to the interior cabin space has been a problem.  And the existing sensor has no apparent slack in the wire as a means of extending it.  Nor do I want to cut it.

I removed the air distribution box today to examine the situation again and I think I might have found a path from the rooftop control board to the interior sealed area without breaching the seal — at least not much, anyway.

The attached pictures, in order, show the (1) current location of the temperature sensor, (2) enter/exit path of the wires from the rooftop section to the interior section.  I’m unable to get a wire pushed through this area to the visible area in the rooftop unit.  I can get a wire to go a short distance through this area but it hits something and just bunches up.  The situation is the same when approaching this from the rooftop side.

The new idea is to make use of this thing (3) — whatever it is.  I can poke my finger through the white covered hole in the middle.  Another inch or two above that is the interior side of the white Styrofoam insulation that seals the interior system from the exterior system.  I’m definitely opposed to removing this cover as it appears to be very well sealed by the manufacturer and I don’t want to disturb it.  But I’m not too opposed to poking a very small diameter hole in it with a hot coat hanger or something similar.  Any air gap around the new wire could be caulked and sealed.

Picture (4) is poorly focused but it shows the access point inside the red square while the arrow points to the white Styrofoam box that seals the system.  A small access hole melted into the foam straight up from the access point should lead right to the same corner in the rooftop section where the control board is.

From there, I’d disconnect the factory sensor and add the new sensor with plenty of cable length.  I’d then route the sensor through the attic space of my Airstream RV and out to the original location of the Dometic CCC2 thermostat that is no longer in the equation.  (I’m not sure how complicated this part gets with an Oliver.)

It might be a while before I actually tackle this.  I’m interested in hearing from all y’all about what it is I might be missing though!

(And, when I put the air distribution box back together, did I spot (5) the location of the temperature sensor in the version 1 model of this unit which would have placed it closer to the interior cabin air?)

[GSMBear]

Well, I just couldn’t stand it and had to give it a try.  The access method described above worked as expected.  The new thermistor, not so much.  I’m disappointed, for sure.

For testing, I just dangled the new thermistor directly down from the air distribution box which is centrally located in my RV.  The thermistor was about waist level.

In AC mode, it seemed to be a pretty good solution although I did not spend much time in this mode.  The compressor did come on as expected and seemed to turn off much closer to the set point when measured by an external inexpensive indoor/outdoor thermometer at countertop level.

In heat mode, the fan would never come on.  I could hear the compressor turn on as well as the fan in the rooftop unit, but the interior fan that blows the warm air never came on.  Heat was occurring in the coils because when I switched it from heat to fan-only mode, the fan did come on and the residual heat from the heat mode allowed for some warm air to come out.

This puzzles me and I can’t help but wonder if the prior fan modification is in the equation somehow.  That mod is described upstream in this thread.

Prior to the new thermistor, I did notice a change in the fan behavior between AC and Heat modes:  In AC mode, the fan cycles with the compressor only when the fan is in Auto mode.  It remains on all the time if the fan is switched to medium or high mode (can’t recall about low speed).  However, in Heat mode, the fan will cycle with the compressor no matter what speed the fan is set to, including auto.

After the new thermistor, the fan would not come on at all no matter what fan setting I used.

I returned the setup to what it was before I tinkered with it today and it’s back to running as expected in both AC and Heat modes.  HVAC and resistors are by no means my area of expertise.  I’d be interested to hear from those who know more on these subjects.

For the record, the replacement thermistor I bought is a 10K NTC thermistor.  That means absolutely nothing to me but there are gobs of these on Amazon with this specification and advertised as being suitable for mini-split systems which do both AC and heat.  So I figured I’d start there.  I can’t find any specs on the one Houghton uses.

[katanapilot]

Wonder if the thermistor located in the unit needs to sense the warm air being generated by the heat pump before it will turn on the fan?  I know when using the heat pump, the compressor runs for a bit before the fan turns on. 

By relocating the thermistor externally, you may have defeated the heat pumps ability to sense when warm air is being produced.

Just a WAG.

Edited October 22, 2023 by katanapilot
added text for clarification

[GSMBear]

Ah, methinks you're onto something!  Your remark about the heat pump not sensing that warmth is being produced made me look at the wiring diagram.  I'm now pretty sure that I mistakenly unplugged the interior coil sensor instead of the room sensor.  I know it was a yellow connector and the attached picture of the control board positions this one in the location of the interior coil sensor according to the schematic.  This adds up!  Without the interior coil sensor connected, the fan would continuously wait for the signal that the coils are warm enough to start blowing -- so the fan would never start!  OK, so stupid mistake on my part but there's hope left.  I will give it another try next weekend and report back.