Heat pump performance

Mongobird · 05-31-2022, 12:15 AM

I have a 2004 Itasca Meridian 34h with a basement heat pump. The prior owner said that he recently replaced both motors in the heat pump.

In general the unit provides cooling and provides heat, but I have some question as to it's overall performance and I'm hoping that owners was similar equipment might chime in.

On a recent day with 90° fahrenheit temperatures, and in the Sun, that is with no shade, with a fan setting on high I could only cool to 87° f. The unit was blowing cold air, and I did not have a good thermometer reading on it, an estimate the temperature to be about 50° f at the ceiling outlets. In an automobile I would normally be looking for 42° f.

The current draw was a nominal 17 A.

Normally I would expect that a heat pump or air conditioner could get things to a lower temperature, but I don't have a lot of RV experience and this is a relatively new to me vehicle.

What kind of cooling performance do others get with similar or identical equipment?

Thank you.

Mongobird · 05-31-2022, 12:24 AM

I should also add that I have verified that the coils appear to be clean, and the filter is fresh.

be happy · 05-31-2022, 04:31 AM

Were you or are you plugged into 50amp? This makes a big difference. I know I am going to miss state here so hopefully if I am wrong someone will correct.
At 30 amp you will only run one compressor at 50 you will beable to run both compressors. That makes a big difference (if I am correct)

Also even thought you have a clean removable filter, take a fine brush and vacuum to the coil just below the filter. I thought mine was clean, that was before I had to remove the unit for maintance. I found out how dirty that coil was.

The front windshield is like a big sun magnifying glass. You may want to upgrade to a more sun reflective type shade. I also have made a vent cover for the vent in the living area. Lots of cold air gets out through that area.

Good Luck safe travels

Mongobird · 05-31-2022, 05:23 AM

I was on both 50amp and also a 7500W genset.

I did vac the coils off in the winter and the heat pump has not been used since then.

In fairness the front windows were facing south, but I did have the shade halfway drawn.

My question could be stated differently. At 90° f what is a typical exhaust temperature in the ceiling vents?

be happy · 06-01-2022, 03:42 AM

I turned mine AC on yesterday for the first time this year. At home on 30amp instead of 50. The temp outside was 85+ the temp coming out of a vent was 67. I may have gotten colder, I just did not stay and wait any longer.

BobC · 06-01-2022, 08:42 AM

The temperature coming out of the vents isn't absolute but is relative to the ambient temperature going into the return. According to Airxcel, the current manufacturer:

The supply air temperature will vary somewhat proportionally with the temperature of the air being pulled through the return air grille(s) of the air conditioner. Additionally, the outdoor air temperature, humidity, air volume and even proper air conditioning maintenance all have an effect on the air conditioner supply air temperature.
An ideal cooling system should give you an output temperature range of 16-22 degrees lower than the temperature taken in at the filter. Humidity is a significant determining factor in this temperature difference.
You can test the temperature difference by taking a reading at your filter and the first register where air is leaving the system. Please use the same thermometer at each location.

Although the above doesn't specifically mention the basement air, I've read elsewhere that a poster was told by the manufacturer that a 20 degree differential is optimal for the basement air. For home air conditioners, I've read that the acceptable range to be between 14º F and 24º F, with 18º F to 20º F being ideal.

I have an inexpensive laser thermometer from Harbor Freight that I use for this and many other applications, both on the RV and at home.

The toughest job for an RV air conditioner is overcoming the initial heat load. We run ours off the generator while driving so, when we arrive at our destination, we don't have to wait for it to cool off our MH.

Morich · 06-01-2022, 09:11 AM

It will be difficult to compare the RV and auto air as the ducting is so much different. In a car it comes off the cooling coils and almost immediately inside, where in the RV, it may have to run through ducts that are 20+ feet long and may be running along the roof where the sun is really baking things! Situation where the AC is sending good cold air but by the time it gets to the front it has been cooked so much it isn't!

A good check of things is good but getting a good firm answer may be difficult as RV vary so much.

BobC · 06-01-2022, 09:35 AM

Quote:

Originally Posted by Morich

It will be difficult to compare the RV and auto air as the ducting is so much different. In a car it comes off the cooling coils and almost immediately inside, where in the RV, it may have to run through ducts that are 20+ feet long and may be running along the roof where the sun is really baking things! Situation where the AC is sending good cold air but by the time it gets to the front it has been cooked so much it isn't!

A good check of things is good but getting a good firm answer may be difficult as RV vary so much.

Morich makes a good point. To get a good idea of what your unit's actual temperature differential is, measure at your return and at the output vent closest to your return.

Mongobird · 06-02-2022, 07:01 AM

Thanks, guys.

The temp differential appears to be about 20°. When I get back home I will take more measurements.

In the meantime I have discovered that the second compressor does not always start, so I may have a capacitor problem there. At a campsite on grid power it appeared to eventually get started although I was not watching it closely. On the generator, which is 7500 w, it slowed or stalled the generator on start if I had the water heater on. Without the water heater it would still not start the second compressor. When I tested it a week or so ago at 80 degrees there was no problem. So I will do some more poking and your data points are all helpful.

BobC · 06-02-2022, 07:21 AM

There's no substitute for step-by-step troubleshooting. It can be tedious and it's tempting to jump to a conclusion or take a shotgun approach but it's the best way to sort things out. Here's the service manual. The troubleshooting section starts on page 13.

AFChap · 06-05-2022, 04:31 PM

"Motors" means blower motors I would guess? One inside, one outside. BUT ..
pulling 17a means only the first compressor is running, no question about it. With both running you will be pulling apx 24a. Best guess would be that you either have a bad start/run capacitor on the 2nd compressor, or a bad compressor.

Ramblin Dan · 06-05-2022, 06:03 PM

Check the ducts in the rear running up to the ceiling. Mine opened up letting a lot of air escape.

Rgrpm · 06-06-2022, 05:02 AM

I have a 2004 Winnebago Journey, 34H, Just replaced both fan motors and the return fan with 1/2” larger fan, had to cut the cage to install new fan. The unit kicks butt. 17 amp draw sounds like one compressor, 24 amp both on mine. I had ceramic film put on ALL windows, and Windshield. Worth every penny, What a difference. The factory windows are colored, NOT sun Tinted. AC and film made a Huge difference for us.I LOVE the basement air!

Cooperhawk · 06-06-2022, 08:16 AM

The real trick is to have the temps where you want them during the night and then to eliminate solar heating as much as you can. We pull down sun shades and close the curtain in front of the windshield. We also always try not to park with the sun shining in the windshield.

We had ours rebuilt a few years back and it works pretty well now.

Sailnjay · 06-18-2022, 06:58 PM

Similar question. On a recent trip to GA the temp outside was in the upper 90's. My AC kept the inside below 80. Is it safe to assume that all is working correctly and that's about all I can expect from the old basement unit? Thanks in advance for any comments.

Mongobird · 06-19-2022, 07:22 AM

Quote:

Originally Posted by Sailnjay

Similar question. On a recent trip to GA the temp outside was in the upper 90's. My AC kept the inside below 80. Is it safe to assume that all is working correctly and that's about all I can expect from the old basement unit? Thanks in advance for any comments.

In the research I did, I had several techs tell me that working well, there should be an approximately 20F drop in temperature. So that sounds about right in the scenario you mentioned.

Mongobird · 06-19-2022, 07:30 AM

My current progress on the original posting is that I believe I have starting capacitor issues on both compressor 1 and 2. If the compressor(s) start, I get good cooling performance. If both start, which can eventually happen, or happens more often when temperatures are cooler, then I get 20F of cooling, which is nominally the expected performance.

New starting capacitors are on order, and then I will install and try out.

It is notable that I had some confusion on access to the HP. I've seen pictures of a door open to the HP, but could not see any hinges. Well the hinges are there, just covered by trim. Thanks to another forum member who sent me a photo. Also notable that in three calls to Winnebago factory support, none of the techs could verify that the electrical parts of the HP were accessible without dropping the HP.

I will report back when the next step gets accomplished.

DancinCampers · 06-19-2022, 12:04 PM

All of your caps, except for the indoor blower motor I believe, should be available under the outside access panel to the pc board. I would give the techs a break, they haven't installed basement units in at least 10 years.