Atwood heat pump cycles on and off

[cavie]

Originally Posted by BeachFolks

Thanks for the reply, but I was speaking more of the A/C fan vs the Heat Pump. Our temp was at 65+ and the fan just kept running with the A/C in auto?

Just for clarification. There is only 1 fan and only 1 compressor.

[Duckogram]

I am on my maiden voyage and the OAT was 41* just before sun up. We had the thermostat set to heat and the fan on Auto. Even though “Furnace” was not selected, the furnace kicked on to heat the coach. Now it’s about 60* and the heat pump is going in and out of “sampling” mode. It draws less than 1 amp when it does that but it is a bit annoying. The good news is that we were warm and comfey all night. Soooo, I will research this sampling mode and post my findings. Meanwile, it works well and this may just be a peccadillo.

[Fisher72]

Heat pumps should work right before freezing temps . We must be lucky are unit works great .

[chroniekon]

This 'sampling' mode is the crux of the whole cycling issue. This heat pump uses information from an internal sensor along with information from the thermostat on the wall. It cycles the fan on in short bursts to flow air over the internal sensor.

[Fisher72]

Correct me if I am wrong all the heat pump is . Is a heat strip ?

[chroniekon]

It's actually a heat pump with a compressor. At least the one the OP has.

[Scrapper]

Originally Posted by Fisher72

Correct me if I am wrong all the heat pump is . Is a heat strip ?

If you have a setting on the thermostat that says Heat Pump, then the heat pump is your A/C with a reversing valve installed. If your thermostat has a "Heat" setting will be a 1500 watt heat strip. The thermostat will most always have a setting for "Furnace".

[Fisher72]

Then why does are heat pump work at such low outside temps ? It should only work down to 40 degrees or so . It keeps pumping really good heat into the low 30s
In theory It should not work that low is

[Fisher72]

Forgot to mention my dometic thermostat
Says heat pump on the display when using
Heat pump

[Scrapper]

Originally Posted by Fisher72

Then why does are heat pump work at such low outside temps ? It should only work down to 40 degrees or so . It keeps pumping really good heat into the low 30s
In theory It should not work that low is

My experience has been if the sun is shining on the unit they will produce some heat, but not as efficiently. The same unit when in A/C mode will not cool as well when sun is shining directly on it.

[cavie]

Originally Posted by Fisher72

Correct me if I am wrong all the heat pump is . Is a heat strip ?

OK consider yourself corrected. It called Heat Pump vs Straight cool. A heat pump system is a straight cool air conditioner system that uses the AC compressor to produce heat inside your unit. 1 compresser 1 fan motor. In AC mode the gases produce heat on the outside of your unit and cold gases on the inside of your unit. The fan blows the cold air in. When you put it heat mode there is a reversing valve that turns the gases around. Now the fan will blow hot air into your unit and cold air outside. In a residential unit, there is an aux back up heat strip. It is anywhere from 5 to 15 KW depending on the size of the AC system . MOST RV units do not use a heat strip as a backup. Your compressor is running in AC and HEAT mode. Remember I said 1 compressor and 1 fan drawing somewhere in the neighborhood of 13 to 15 amps. There is no room to add a heat strip on a 20 amp breaker. When the outside air gets below 35/40 degrees F the heap pump stops blowing heat inside and needs help. In an RV the help comes from the Furnace. That's the short of it.

[cavie]

Originally Posted by Scrapper

If you have a setting on the thermostat that says Heat Pump, then the heat pump is your A/C with a reversing valve installed. If your thermostat has a "Heat" setting will be a 1500 watt heat strip. The thermostat will most always have a setting for "Furnace".

With a heat pump system, the AC compressor is running. 1300 to 1500 watts you can not add a 1500 watt hear strip on 20 amp breaker.

[cavie]

Originally Posted by chroniekon

It's actually a heat pump with a compressor. At least the one the OP has.

The compressor is the heat pump. It has a reversing valve for the gas flow. Compressor runs in both heat and cool.

[cavie]

Originally Posted by Fisher72

Then why does are heat pump work at such low outside temps ? It should only work down to 40 degrees or so . It keeps pumping really good heat into the low 30s
In theory It should not work that low is

In theory, it should work down to 32 degrees. Anything below 40 is acceptable. My wifi t-stat at home tells me when the AUX strip comes on. it uses 35 degrees.

[westerm52]

We just bought a new 2401W MBS and also found the Atwood AC/Heat Pump short cycling. I looked over the install diagrams and info and could not find anything wrong with my install except the air baffle between the supply and return air was not very secure. I called Forest River and they had no clue except that they just recently changed to Atwood so I called Atwood as well. They would not let me talk to a tech but the answer was that 99% of the problems are install related. The return air sensor located on the indoor coil in the return air quickly changes temperature forcing the unit to short cycle.
My guess is that the air coming out of the vents gets pulled right back to the return and cycles it off. There is an ohm test I can do on the sensor but have not had time yet to do. I really believe the space in our unit is small enough that the temp cannot redistribute throughout the coach before it shuts down. Ill let everyone know what the results of the sensor test is when i get a chance.

[Scrapper]

Quote:
Originally Posted by Scrapper
If you have a setting on the thermostat that says Heat Pump, then the heat pump is your A/C with a reversing valve installed. If your thermostat has a "Heat" setting then there will be a 1500 watt heat strip. The thermostat will most always have a setting for "Furnace".

Quote from cavie:
With a heat pump system, the AC compressor is running. 1300 to 1500 watts you can not add a 1500 watt hear strip on 20 amp breaker.
__________________

You must have misread my post.

Some units have a "Heat Pump" setting on the thermostat, these units are Heat Pumps. The settings will be on the thermostat will be AC, Fan, Heat Pump, Furnace and Off.

Some units have a "Heat" setting on the thermostat, these units have a heat strip installed inside behind the filter. The settings will be on the thermostat will be AC, Fan, Heat, Furnace and Off.

Other units will have neither a heat pump or heat strip. The settings will be on the thermostat will be AC, Fan, Furnace and Off.

All 3 types of units have a "Furnace" setting on the thermostat which turns on the propane furnace.

[cavie]

Originally Posted by Scrapper

Quote:
Originally Posted by Scrapper
If you have a setting on the thermostat that says Heat Pump, then the heat pump is your A/C with a reversing valve installed. If your thermostat has a "Heat" setting then there will be a 1500 watt heat strip. The thermostat will most always have a setting for "Furnace".

Quote from cavie:
With a heat pump system, the AC compressor is running. 1300 to 1500 watts you can not add a 1500 watt hear strip on 20 amp breaker.
__________________

You must have misread my post.

Some units have a "Heat Pump" setting on the thermostat, these units are Heat Pumps. The settings will be on the thermostat will be AC, Fan, Heat Pump, Furnace and Off.

Some units have a "Heat" setting on the thermostat, these units have a heat strip installed inside behind the filter. The settings will be on the thermostat will be AC, Fan, Heat, Furnace and Off.

Other units will have neither a heat pump or heat strip. The settings will be on the thermostat will be AC, Fan, Furnace and Off.

All 3 types of units have a "Furnace" setting on the thermostat which turns on the propane furnace.

Sorry, I read it to say" the heat pump will run with the heat strip.

[Duckogram]

Guys, an awful lot of “discussion” that has zilch to do with the OP’s (and my) issue. So here is a recap of the topic along with some facts:

We have the Atwood Air Command AC-1511(w or b).
It is a 15,000 BTU rated heat pump.
It has no heat strip.
It is a ducted unit.
It has a 3 speed fan with an automatic function.
It has an integrated furnace function. This function enables the controller to engage the LP furnace when outside air temperatures drop below approx. 45 degrees.
It has a Dry function.

The issue. When in heat mode (thats heatpump function)
and the selected temperature is achieved, the unit stops however, approx. one minute later the fan comes on low and runs for approx. eight seconds. This process repeats continuously unless 1. The heat pump kicks back on, or 2. The furnace is activated.

Now I have an additional issue to plug into the topic. When in AC mode and the selected temp is achieved, the compressor kicks off however the fan remains running on low. This new issue leads me believe, after having read the service manual, that there may be a sensor/controller board related issue and probably not a thermostat issue.
I have contacted the dealer and have an appointment for diagnosis of the problem on Wednesday. More to come...

Meanwhile, here is a pic of the thermostat to answer some questions.

[s1njin]

Originally Posted by Duckogram

The issue. When in heat mode (thats heatpump function)
and the selected temperature is achieved, the unit stops however, approx. one minute later the fan comes on low and runs for approx. eight seconds. This process repeats continuously unless 1. The heat pump kicks back on, or 2. The furnace is activated.

Now I have an additional issue to plug into the topic. When in AC mode and the selected temp is achieved, the compressor kicks off however the fan remains running on low. This new issue leads me believe, after having read the service manual, that there may be a sensor/controller board related issue and probably not a thermostat issue.
I have contacted the dealer and have an appointment for diagnosis of the problem on Wednesday. More to come...

Meanwhile, here is a pic of the thermostat to answer some questions.

I could have sworn I read both scenarios you have is normal. The sampling of air is for the system to get a accurate reading of the air temperature in the coach as opposed to a stationary t-stat reading. And the AC fan continuing on low was also to encourage all the AC capacity of the unit to be used as there is still cold air to be had shortly after the compressor turns off. And in AC mode that low speed fan running all the time encourages good dispersal of that cool air and good air mixing.

I can't for the life of me found where I read it though.

[s1njin]

Atwood Air Command w/ Heat Pump - iRV2 Forums

They were discussing some of this hear. Apparently the unit turning on for a few seconds every minute or two is for it to evaluate the ambient temperature of the coach.