Heat Pump and Furnace Operation

[FullTimeAlpine]

Hi. First time poster here. I searched the threads but couldn't find exactly what I'm looking for.

2022 Alpine 3220RL
3 rooftop units - front: AC, mid: main AC, rear: heat pump

I bought the trailer used and the original owner was not technical at all, so he didn't understand the trailer.

I noticed that right before my furnace kicks on, the rear rooftop unit comes on. I asked Keystone about it, and the lady told my I probably have a heat pump. This was a surprise to me.

I gather from another thread here, that this is just a fan that helps distribute the air through the overhead ducting. That's too bad because I was hoping it was an AC turning on to help with humidity. Wouldn't that be nice...

I wanted to try heating just using the heat pump because it's so much quieter and electricity is cheaper, so in iN-Command I set the heat source on the Living Room AC to Electric. When it turns on, the fan (I presume) comes on and runs for several minutes, and then the breaker trips.

I'm running on a 30A supply and my voltage is near 120, nothing else of note is running.

Do I need a 50A supply to run the heat pump? Or is there something wrong with the unit?

[LHaven]

Very few rigs are wired to deliver all 50A to any component inside -- usually one leg runs one A/C and the other leg runs the other, with other components distributed between the legs. Your heat pump MAY be wired for 50A, but I would be surprised, especially given the fact that it tries to run at all (because it would need 240V). The model number of the heat pump will tell you right off. I'm thinking that the heat pump is just faulty.

My last rig (1998-2018) had a combo A/C-heat pump and was only a 30A rig. We used the heat pump pretty near exclusively and loved it, didn't use much propane at all in 20 years.

[JRTJH]

Originally Posted by FullTimeAlpine

...

I'm running on a 30A supply and my voltage is near 120, nothing else of note is running.

Do I need a 50A supply to run the heat pump? Or is there something wrong with the unit?

I'm "reading between the lines" on this response, and the "guessing" may not be accurate, but this is what I think is happening based on your comment above:

You say you're running on a 30 amp supply and the voltage is "NEAR 120"...

I'd also guess that you have a residential refrigerator (?) and that the converter/charger is also operating, along with the furnace fan (12VDC supplied by the converter) ???

If so, and the voltage is "near 120" then you may be overloading your 30 amp circuit and suffering from a voltage drop as well.

I'd recommend taking a critical look at the voltage source where the trailer is plugged in, measure the voltage there, look for other things that may be using that same line/plug circuit. You may not have the full 30 amps available and you may have a voltage drop being caused by the distance from the plug to the trailer power center/circuit breakers....

I'd guess your "heat pump/rooftop air conditioner" is on its own 20 amp breaker, then the residential refrigerator is likely on its own 15 or 20 amp breaker and the converter/charger is also on its own 15 amp breaker. If you're blowing the source 30 amp breaker, you're probably overloading that circuit, even though it "seems like not much is turned on"....

Now, another comment you made that "might also be a cause" is when you said that the heat pump is the REAR unit and you commented, "When I turn on the front unit to heat..." If (a guess) the front unit is actually an air conditioner (not a heat pump) and you turn it on "HEAT", then it may have a "resistor type heater (usually 15 amps) added in the return air chamber inside the unit".... If so, when you're running the rear heat pump (15 amps), the refrigerator, the converter and then turn on the front air conditioner with its resistor heat strip, you're going to be drawing significantly more than 30 amps. Even if you're only drawing "right at but not more than 30 amps" you may be having a voltage drop that will cause the amperage draw to increase which would load the system above 30 amps... So, pull the inside cover from the front air conditioner and see if there's a "heat strip accessory" installed. If so, that's likely to be your "overload that pops the breaker"....

A last comment, if you have the rear unit fan set to HI or LO, it will always run with the furnace fan. It's designed and wired that way to augment warm air distribution. If you do not want the overhead unit fan to run with the furnace fan, set the fan switch to AUTO and it will not operate with the furnace fan.....

If some of the above "guesses on my part" are not correct, please post the detailed conditions and voltage measurements you have and we can dig a bit deeper into the causes and solutions.... GOOD LUCK

[chuckster57]

Originally Posted by LHaven

Very few rigs are wired to deliver all 50A to any component inside -- usually one leg runs one A/C and the other leg runs the other, with other components distributed between the legs. Your heat pump MAY be wired for 50A, but I would be surprised, especially given the fact that it tries to run at all (because it would need 240V). The model number of the heat pump will tell you right off. I'm thinking that the heat pump is just faulty.

My last rig (1998-2018) had a combo A/C-heat pump and was only a 30A rig. We used the heat pump pretty near exclusively and loved it, didn't use much propane at all in 20 years.

Roof top AC units with a heat pump option have a “reversing valve” that basically makes the refrigerant go “backwards”. They don’t do well below about 40 degrees. And operate on 120VAC

[LHaven]

Originally Posted by chuckster57

Roof top AC units with a heat pump option have a “reversing valve” that basically makes the refrigerant go “backwards”. They don’t do well below about 40 degrees.

Absolutely true. But (back then, when I was living in New England) why would I take a vacation somewhere freezing when I could just stay home?

[flybouy]

Originally Posted by LHaven

Absolutely true. But (back then, when I was living in New England) why would I take a vacation somewhere freezing when I could just stay home?

How many guesses do we get?

[FullTimeAlpine]

Originally Posted by JRTJH

You say you're running on a 30 amp supply and the voltage is "NEAR 120"...

To be clear here, I live in a campground and my voltage is pretty good, but it does drop off quickly as I use more stuff. I'm only a couple feet from the pedestal so the distance for the power to travel is the length of the stock cord.

I have a plug in voltage monitor that I checked against my Fluke and it shows about 3V lower than the Fluke. So by pretty good, I mean when I'm not using anything major, I see it go up to 117V. I do understand the concept of chargers running invisibly and how that affects my available amperage.

I do not have a residential fridge, just a large Norcold.

Originally Posted by JRTJH

I'd guess your "heat pump/rooftop air conditioner" is on its own 20 amp breaker, then the residential refrigerator is likely on its own 15 or 20 amp breaker and the converter/charger is also on its own 15 amp breaker. If you're blowing the source 30 amp breaker, you're probably overloading that circuit, even though it "seems like not much is turned on"....

I should have specified, the breaker that trips is in my interior breaker box. And judging by the label, yes it's dedicated to the heat pump. I have 3 poorly labeled 15A breakers: AC, second AC, third AC. The one that trips is the "AC" breaker.

Originally Posted by JRTJH

Now, another comment you made that "might also be a cause" is when you said that the heat pump is the REAR unit and you commented, "When I turn on the front unit to heat..."

I never mentioned "front". I'm strictly talking about the rear unit.

Originally Posted by JRTJH

So, pull the inside cover from the front air conditioner and see if there's a "heat strip accessory" installed. If so, that's likely to be your "overload that pops the breaker"....

I may end up pulling it to take a look at what I've got.

Originally Posted by JRTJH

A last comment, if you have the rear unit fan set to HI or LO, it will always run with the furnace fan. It's designed and wired that way to augment warm air distribution. If you do not want the overhead unit fan to run with the furnace fan, set the fan switch to AUTO and it will not operate with the furnace fan.....

This is not quite how mine works, but close. With mine, if the fan is set to HI or LOW, it runs constantly. If it's set to OFF, it only runs when the heat source is set to ELECTRIC. AUTO makes it run with the furnace.

[El Paso]

Can you turn off the breaker to the fridge and other appliances and just try and run the heat pump?

You are measuring voltage but its the current draw that is shutting you down and you would need an ammeter to measure that accurately.

I'm looking at trading my 2022 Passport 282QB for an Alpine 3912, and was researching the heat pump when I came across your post.

Interested to see how you enjoy it and how you enjoy full timing in the Alpine, lots of others reported the heat pump worked well on 50A service but it was the sound level I was curious about.

[FullTimeAlpine]

That's a thought. Might give it a try tomorrow.

I talked about my living experience in the Alpine here: https://www.keystoneforums.com/forum...ad.php?t=56021

[JRTJH]

Originally Posted by FullTimeAlpine

That's a thought. Might give it a try tomorrow.

...

As an example, 1800 watts at 123 VAC is 14.63 amps and that same 1800 watts at 115 VAC is 15.65 amps. At the "extreme", 1800 watts at 107 VAC (the typical cutoff on most EMS systems) is 16.82 amps.

So, if you have a 15 amp circuit breaker and a 1800 watt load on it, it may work well (not interrupt power) at a voltage higher than 120 VAC and trip that same circuit breaker when the voltage drops below 115 VAC.

From what you've posted, I'd first confirm that all connections at the heat pump and at the circuit breaker panel are tight and show no evidence of heat (melted or charred insulation) and no corrosion or discoloration of the copper wire. These "rolling earthquake shelters" that we call travel trailers often vibrate screw connectors enough to loosen the electrical connections, increase the heat buildup which further increases the resistance and when coupled with a "low voltage condition" (even if the voltage is in the acceptable range) may be just enough to trip a breaker that looks like it's not even close to the amperage load.....