Thermostate on AC/Heat

1000islander

1000islander

Member
Jul 9, 2007
115
1000 Islands
Boat Info
420 Sundancer
Engines
Cummins
We have just started our season here in the north east. We are using our heat at night and it is very hard to regulate the temperature in our 420. I think the sensor needs to be relocated to the cabin area, it currently is in front of the condenser coil. Early in the season the area where the units are located are very cold due to the 40 degree water the boat sits in. Has anyone had a similar problem regulating the temperature?
 
Gotta be honest with you 1000Islander I'm not sure what sensor you are referring to but I doubt that it is related to your problem. Thermostats have a "Anticipation" circuit built into them to assist in regulating the temperature in the room, or cabin in your case. If your cabin temperature is all over the wall my bet is that this feature is not working properly.
I'm sure that you will get a bunch other ideas here in a minute but for now I would be looking at the thermostat.

Cheers,

Jim
 
The thermostats are not the same as in your home. They have a temp sensor that is located in front of the condenser coil on the units. I don't think they operate like a home thermostat. When you hold the snsor in you fingers the temp on the thermostat rises. I think this is what is used to determine the "room" temp, even though it is mounted in a obscure location, down on the floor, not in the room where you live.
 
I had the same problem and moved the sensor further away from the unit and closer to the air intake vent that returns the air and it did much better.It seemed to sense the real air temp instead of the heat that was coming off the unit itself.
 
I just did an internet search and found they make different lengths for the sensor cable. They recommend that the sensor be located in the return air "area" but as close to the room being heated/cooled. I may order a longer sensor cable and move it to the return air grill in the salon instead of the closed area of the AC unit. My AC unit is located in an enclosed area that does not have alot of "conditioned" air flow. It is mounted on the bottom of the boat where (this time of year) is quite cold, making the unit run even though the room is comfortable. We have to set the temp to 58 in order for the salon to be 68ish. I think moving the sensor is a good idea.
 
1000islander said:
The thermostats are not the same as in your home. They have a temp sensor that is located in front of the condenser coil on the units.
Click to expand...

Correct, except it's the evaporator coil. This problem is widespread. Two remedies; make sure the fan is set to run continuously during the heat/cool mode. This will keep "room" air circulating past the sensor at all times providing a more accurate reading, and secondly, make sure the metal part of the sensor is not making contact with the metal portion of the clamp that is holding it to the evaporator coil frame. Use a plastic wire tie to secure the sensor and provide a thermal break so the cold evaporator frame does not influence the sensor.
 
Read your installation manual and learn how to get into the set up software. The sensor is to be located by the condensor coil near a return vent. Set a candy thermometer in the cabin where you want the temperature to match the stat on the wall. Adjust the "offset" until you get the same temp on the candy thermometer as the wall stat. It will take some trial and error but you can get pretty close.
 
I moved the sensor one year and changed the fan to cycle on and off. That seemed to make more sense to me in that it works like your home system.. Nada... Temperature swings, inconsistent fan cycling... just didn't work right. My opinion is that the system works 'best' the way the manufacturer and builder set-it up in the first place. SBW1 amd JG300 are right on their respective points. Just wish it was a bit quieter...
 
Gerryb, One suggestion to deal with the constant fan noise: Try adjusting the slow speed setting on the fan. On a previous boat I set the low fan speed very slow, which gave the unit the wafting air it needed but was quiet enough to let us sleep at night.
 
I set my fan to intermittant and moved the sensor 18" to just outside the air intake for the unit, just under the edge of the mattress in the forward berth. I also have the fan set to run slow with small temp changes, and speed up if more change is required.

I also set the fan's max speed down to about 75% of the original value. The manual tells you to do this. Lower the max speed until you can hear it decrease, then go up a notch or two. This runs it at the most efficient level to minimize electrical consumption.

I'm very happy with the results. I hate wasting energy. Running the fan 24/7 is annoying and wastes electricity and fan life.
 
I used a regular thermostat to recalibrate the thermostat in the SMX unit. I did it a couple times and seems to be working alright now. I put regular thermostat in the middle of the salon away from any airflow and let it stay there for a couple hours. I then took the reading to recalibrate the unit. Maybe this is an option?
 
In order for the sensor to work properly the fan needs to be set to on ........ No debate to had there. U can relocate the sensor closer to the return. DO NOT take it out of the return and place in the cabin. IT must be in the return air flow . Changing fan speed for noise issues great ideas.... Cleaning ur filter monthly is a must if ur a/c - heat is used often. Alot good helpful ideas. nicely done guys .

Rob
 
Hampton said:
I set my fan to intermittant and moved the sensor 18" to just outside the air intake for the unit, just under the edge of the mattress in the forward berth. I also have the fan set to run slow with small temp changes, and speed up if more change is required.

I also set the fan's max speed down to about 75% of the original value. The manual tells you to do this. Lower the max speed until you can hear it decrease, then go up a notch or two. This runs it at the most efficient level to minimize electrical consumption.

I'm very happy with the results. I hate wasting energy. Running the fan 24/7 is annoying and wastes electricity and fan life.
Click to expand...

Hampton, thanks for your help on the A/C fault code on the other link. I am curious as to how do you set the fan speed?

Gotfish
 
Not really on point with the topic of this thread, but I have stopped using the aluminum mesh filter and replaced it with a micro filter cut to size from a larger piece sold at any hardware store. The filters are made for wall/window AC units and I get 4 pieces from one $11 filter. Much better than the goofy aluminum ones that don't filter the dust/pollen nearly as well and have to be cleaned every month.
 
I've found out the same on my 44DB. On other boats, I always set the fan to Intermittent. On this one, in the Summer, if I set it to intermittent, the temperature is showing 65 degrees when it is actually about 78 in the salon. The units don't work worth a darn like that. If I set it to continuous it works fine. But, I hate to run it all the time. Especially since I leave the units set to 85 when I'm not on board. During the Spring and Fall I can use the dehumidify cycle but not in the Summer.

Jet Lag
 
Gotfish said:
Hampton, thanks for your help on the A/C fault code on the other link. I am curious as to how do you set the fan speed?

Gotfish
Click to expand...

I missed this the first time through. You have to get the manual out and set the system to the program mode, then enter the code for fan speed, then start lowering it until you hear a difference in the motor speed, then go up a coule of clicks, and then save.

With the fan in intermittant, you have to move the temp sensor away from the cold, damp A/C unit. It's very simple. Look in the compartment with a flashlight and find the std temp sensor zip-tied to the unit. Cut the zip tie and extend the wire out and away from the unit. Tape it into a position where it senses room temp without interference from hot/cold surfaces. Try it out. If you don't like it, move it a little.

I have moved ours from the previous location (above). It is now about 8" inches lower with the end protruding up near a slit in the wooden panel where the return air flows. It works very well there. I taped it to the back of the wooden panel (out of sight). If you look closely in bright light, you can see the tip sticking up in the opening.
 
Jet,
U can change the seting in humidity mode so the unit runs longer and more often. Might be ur answer then leaving the unit on.

( if u need help Ill look up the codes for yea )

Rob
 
Thanks, I'll dig into the manual soon. We are battened down for Eduard now. I took all the Strataglass off today and tied her down well. We saw 25 minutes of 40 to 50 mph right off the stern yesterday from a squall associated with the low pressure but it's calm today and we're waiting on the blow. IF I CAN'T find the particular program function that I need for the longer run on the dehumidify mode, I'll check back. Thanks a ton, JetLag.
 
Ull have two choices to think about ... Frequency how many times u want it to come on in the day ... then how long u want it to run during those on times.


Rob
 
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