Mini-split heat side update

robertglines1 · December 10, 2011, 11:42:47 AM

19 F this am cold bus turned 1ea 9000 & 1 ea 12000 soleus mini split on at 8am. checked at 10 am outside temp 24F inside bus 70F units cycled off. Ongoing test to see how low these units will preform. Inside unheated shop 45ft coach with 3 slides floor not insulated(plan to do so). I have no $ intrest in these units just reporting results. Power usage for the 9000 is 7amps and the 12000 is 9 amps of 120 volt power. Bob

rv_safetyman · December 10, 2011, 05:10:35 PM

Bob, thanks for doing the testing and reporting your results. I am lost as to the heating process of these units. It sounds like they are heat pumps. If that is the case, it will be very interesting to see what your results are at lower ambient temperatures.

By your measurements, you are using 16 amps at 120 volts or close to 2 kilowatts. Our cost of electricity in the Denver area is about $0.12 per KWhr. For your numbers that would be about 24 cents per hour for each running hour of the units. Doesn't sound like much, but it can really add up. I used an electric heater in the bus last winter that had a temperature setting. Problem is, it would only go down to 60*. It ran a bunch during the Dec.-Feb. time frame. I estimated that it ran at about 16 hours per day for the coldest days (bus not well insulated) At 12 cents per hour (1000 watt setting) that could amount to about $60 per month. I am now playing with a thermostat outlet that turns on at 35* and off at 45*. My manual electric heater is plugged into that outlet. I have my AquaHot operating on only once circuit (bay/bathroom) and only on electric (shut off diesel). I consider the AquaHot to be the backup if something with the electric heater malfunctions. Right now, I can check on it each day to monitor my latest attempt to minimize cost of heating.

Keeping these beasts above freezing in the winter can be costly.

Jim

robertglines1 · December 10, 2011, 05:23:43 PM

Suppose to go down to single didgets F and work. Heat pump inverter technology -410 refrigerant. once bus is @ 70.--- I can maintain with one 9000 unit. Will ck and see what lowest setting is tomorrow when I go up to work on bus. It sure is nice to go up turn on and in a short time shed coat. I find 65 About rite to work inside on projects. They make one with elect heat element back up.I don't plan to be in that situation

. The 12000 is on sale now for $699 includes shipping. Heat&air. Bob

Nick Badame Refrig/ACC · December 10, 2011, 05:24:19 PM

Hi Bobby,

Glad to hear they are proforming well..

One more test you may need to take. 3 day run with low 20's to see if they will be able to defrost themselves

and still keep the inside at 70.

This is one of the main issues with ductless HP's that come in as service calls.

Nick-

robertglines1 · December 10, 2011, 05:31:13 PM

Will have to wait awhile for that one but I do understand what you are getting at. Defrost cycle. Would this be effected by condensor placement? Weather here is to moderate after tomorrow. Would prob not effect my application much: as I said I don't plan on having coach very long in those conditions. I know one member using them in apartments in Alaska. Will include in test.. Bob

Nick Badame Refrig/ACC · December 10, 2011, 05:38:49 PM

Placement.

Well, if they are in a compartment, it may defrost quicker because of the small space.

This is why conventional home type heat pumps have up to 20kw of electric resistance heat

to supply warm air into the living area when the condencer is defrosting.

Even I have defrost issues with my 2 Dometic basement HP's in my coach when it's in the 20's.

I normally just use my Proheat through the colder months.

Nick-

luvrbus · December 10, 2011, 05:40:13 PM

These units are inside the bus right not out side in the weather the outlet temps are low on cold day on my heat pump what is outlet air temp that is a good output for less than a 2 ton unit

good luck

robertglines1 · December 10, 2011, 05:48:48 PM

I have one condensor mounted in the spare tire compartment---the second in the orignal condensor compartment. The third which I did not operate in this test in the old evaporator compartment. the air intake is from the bottom of the coach in the last two with exit thru the side. Will also add these discharge temp to observations. The third unit I have always viewed as a back up and has proven on both the ac and heat side 100F to 19F to be just that not needed but there if needed. Maybe if one did freeze up the back up could be kicked on. Good points from all. to add to observations!! Bob

pvcces · December 10, 2011, 10:48:38 PM

We have 13 of the 13 SEER units, about 8 HSPF, installed. One is installed in each apartment, and all of them work down into the teens. They are all sizes from 9000 to 18000 BTU.

Compared to hydronic heating, there is a lot more air movement. Defrosts take from 4 minutes to 8 or 10 minutes, depending whose specs you are reading.

We have been using these for three years and plan to install one in every apartment.

We had our first component failure; a 9000 compressor quit producing much pressure. We have sent the outdoor unit to the seller and he has said he will be replacing it. We have to pay the shipping both directions, as far as I know.

We planned on keeping one spare of each size so that a failed unit could be replaced quickly.

We have retained the oil fired hydronic heat in case of record cold. We have 10 of these units where we were able to shut down the oil fired equipment completely. Those have not been turned on this winter, yet. The remaining ones are on systems that don't have all their heat pumps, yet.

For what it's worth.

Tom Caffrey

luvrbus · December 11, 2011, 04:53:42 AM

How can the split units be compared in apartments to a bus application that is the question I have,Bob has made it clear he doesn't plan on using the units in extreme cold weather + 24 degrees in a shop is a lot different than -24 in Wy on a nice Jan day lol.
I been around buses with heat pumps in 30 degree weather pretty useless IMO but were house type units and the Rv type,good work Bob but I think I would have a 45,000 btu backup diesel or propane or stay in AZ or FL

The 2 Sanyo units in the shop that belong to a friend that decided not to use they have a electric emergency system backup do all the split unit have the backup

good luck

robertglines1 · December 11, 2011, 06:32:29 AM

More to come. Rite now my emergency back up (temp) would be electric heat + generator or plugged in or bus heat. Will not leave for Florida till mid February this year. Plenty of time left to complete test and work on bus. These are 16 seer units. Since I pay for electric for monthly rental at campground it is in my intrest to keep the unit as energy efficient as possible. My present coach uses almost 1/2 the amount of elect as our sticks and staples friends. I think this build will be even more efficient. Bob

luvrbus · December 11, 2011, 06:52:22 AM

I do understand how that system will work for you Bob it's clear you plan on being tied to a pole but with me the system would not work we do not like campgrounds and being tied to a pole, a mountain top in Idaho for 3 or 4 weeks or on the Payette river for a month is our gig but I like your thinking

good luck

robertglines1 · December 11, 2011, 07:13:09 AM

Clifford: I respect the guys that like the freedom from the pole. Just not us at this time. Might change some day! Will never say never! Will build to those specks then. For now the time we have is mostly to and from a rv campground with a occasional non hookup overnite without shore power-few days at most. Life is a adventure. There is room for battery banks and other mods ---Future unknown??? anything possible....Bob

sledhead · December 11, 2011, 09:28:34 AM

I just tried my 9000 split unit as a test in the house (same as bus unit ) 24 f . defrost came on for about 7 or 8 min. works fine warm air now nice. at what point dose it take more power to use and is the defrost a 15 amp heater ? thanks dave

pvcces · December 11, 2011, 10:30:24 PM

Cliff, I posted the apartment information for those that might be interested. Some of our apartments are bus sized. And none of our heat pumps use any supplemental heat, regardless of temperature. We have the hydronic heat if any is needed.

Our defrost setup uses the heating caused by running the compressor without running the fans. Right at the end of the defrost cycle there is a short blast of cold air, then the heating resumes.

When the temperature is low, and the output is down, the power consumption is reduced, not increased. Since the system is less efficient when it is cold, the heat output drops a little more than the power consumption does.

We were hoping to put one of these in our bus, but I haven't found out if they will operate OK on modified signwave power. We don't want to have to change inverters and metering gear to use the heat pump. We haven't had the time for the last two years.

If anyone has run a mini-split on MSW power, I would like to know about it.

When I get that part tested, I plan on posting the results.

Tom Caffrey