Just installed a Grunaire GMU243HX ductless heat pump with two air handlers. I had to cut the lines for a neater installation. The system started up and ran for about 10 seconds then shut itself down. Initial start up pressure on the low side was 100 psi. Not knowing what the line pressure should be I assumed that the system was overcharged due to shortening of the freon lines. I bled some charge off of the system but it kept shutting down and restarting every 3 minutes. The indoor unit displays an error code of FC. I have checked the line voltage and it is a little high at 243 volts. The installation says max 220 but usually there is a 10% variance acceptable on line voltage. Obviously, there is a safety shutoff feature that is shutting the system down or the compressor would not kick on. Any help would be appreciated as Grunaire's assistance is still forthcoming.
The ONLY CORRECT way to charge a mini or Multi split unit is to WEIGH in the charge.. these units operate with electronic Expansion valves and there is no high side port on purpose..
Grunaire units are precharged for 25 ft of line on each indoor unit... measure your lineset size and subtract 0.7 oz of refrigerant for each foot of 1/4" liquid line less than 25 feet you have on each indoor unit.. the result is your new charge amount...
the base charge can be found on the outdoor unit Label..
an FC error code can occur for many reasons... a bad PFC board.. (this is the board with the MOSFETS thaty actually drives the compressor)..
over charge can be an issue as well due to high standing pressure resulting in the drive not able to overcome the backpressure to start the compressor...
high line voltage will issue error codes as well... 243 seems high but still normal... make sure each of your legs is equal...
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Re: compressor shutting down
FC IS FREON CHARGE, WHAT YOU ARE GETTING IS A HIGH PRESURE CUT OFF FAILURE. THE LABEL PRESURE IS TEST PRESURE. THE RUN PRESURE ON LOW SIDE IN AC MODE IS ABOUT 65 AT 75 T0 80 DEGREES INSIDE AND ABOUT 200-300 HIGH SIDE AT 75 -85 OUTSIDE TEMP. IN HEAT THE LARGE COPPER LINE BECOMES HIGH SIDE HOT WHEN YOU FEEL IT. IF YOUR FREON IS LOW WILL WILL ALSO GET SHUTDOWN. YOU WILL NEED SET OF FREON GAGES AND CONTACT ME BACK
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Ductless split air conditioning units are the very best thing for some situations. Of course they can be installed in the place of most any central air conditioning unit. They also are a very good alternative to window air conditioning units. I will explore the use of these units more closely and look at how they can be used effectively. One of the many problems encountered by the professional is when they are asked to install central air conditioning in an older home that was never designed with air conditioning as even a possibility. The walls may be very thick stone. Often they have very little or no insulation. The floor structures may be rough cut lumber. The joists spacing may be random. Walls and ceilings are plaster and lathe. Basically everything is stacked against any type of ducted central air conditioning. Many log style homes also are not very easy to get any kind of ducted central air conditioning installed. The open ceilings and the bare log wall design does not allow for any kind of ducting. I'm sure there are other situations. These are the ones that I have come across most frequently. If you have a home or building that falls into one of these categories you may want to investigate installing a ductless air conditioner. This type of air conditioner can be installed in almost any home or building. The small indoor unit can be attached to the wall with a few screws. Most of the units only require that a three inch hole be bored through the outside wall. In new installations the units can be placed on inside walls with some fore thought and planning. For installation in older homes or homes that are already built you will want to plan the units to be on the outside walls. The outdoor condenser units can be placed up to one hundred feet away from the indoor units. One outdoor unit can be used for many indoor units. Up to four indoor units can be attached to the same outdoor condenser. Some very advanced electronics will control the operation of the condenser and compressor to supply the refrigerant to the indoor air handler units that are running at the time. With variable speed technology the compressor and the condenser fan will only run as fast as needed. This technology has become very efficient in the last few years. You do not have to give up any efficiency with these ductless split units. Another advantage to these mini split air conditioners is that they can be controlled to run only in the rooms that you actually need air conditioning in. If you are not going to be in a room you can shut down the unit. The units also have timers that can be set to turn the air conditioning on or off at preset times. If you are not going to be home all day the air conditioning can be setback or turned off. The timer will turn on the air conditioning so that you return to a cool house. Central air conditioning is very hard to zone effectively. Also with large central air conditioning systems the outdoor compressor will be running at full capacity even though only a few rooms amy be calling for cooling. There are some central air conditioning systems that are do some staging and variable speed technology. These are not as efficient or as effective as the ductless split technology. Ductless split heatpumps are another great idea to look at. For a few dollars more you can also very easily have heat from your air conditioning mini split. Then especially in the mild spring and fall weather you can have some very efficient heat with out starting up that big monster of a furnace or boiler in the basement. In southern climates the heatpump version of the ductless split system may provide enough heat year around. Ductless split air conditioning is definitely something that can solve many problems for some homeowners. Add to that the many advantages of these units and you will find that they are worth every penny that you will invest into them. As with any project like this make sure that you screen your contractor. These units are not for do it yourself people. There are many things that need to be done correctly for these units to work properly and efficiently. A refrigeration license is also required to install these air conditioners. By doing a little research and hiring the right person you will enjoy many years of trouble free service from your new ductless mini split system.
adding a tvx will not help. the sound you here is the pressure equalizing and that has got to happen for the compressor to start again the next time. A tvx will give you a higher efficiency because it can adjust to changing temperature conditions. Only way i know to quiet the noise is to try to insulate the lines better.
Some heat pumps have high and low pressure swiches installed to keep compressor from running when unsafe conditions occur that can damage the compressor. If the outside fan is not turing on, the unit is cycling on high pressure, if you see ice forming on the big refrigerant line coming from the air handler, then the compressor is shutting down on low pressure. Low pressure can be cause by lack of air flow through air handler or from a low refrigerant charge.
appliance repair or unplug it and ask grunaire for technical support before getting too serious with a BTU unit of 18000 somedisplays have energy efficient sleep modes built in and should awake when loss of power or carbon monoxide sensing. use the manufacturing labels to find a .com of technical support or leave that to the repair man.
very likely a defective compressor. while there are other things that could cause the tripping, 90% of time it will be the compressor. generally, it will not be cost effective to repair the system if it is.
Is this a split or packaged sysyem? In a heat pump condensing unit or package unit the indoor fan motor may be delayed due to a timer or program. Otherwise you may have a weak capacitor or a bad motor. The air handler is generally a 230 v unit due to the heat strip operation, have you checked line voltage from the main breaker
Hi, It sounds to me that this split system you have is a heat-pump and not a gas fire air handler. The noise that you are hearing must be the freon in the copper lines equalizing in the system upon shut down of the compressor. All systems must and will go through this sequence. It shouldn't be that loud though. The copper lines should have armor flex on at least the larger suction line for insulation and to keep it from condensating everywhere in the summer in the cooling mode.If you find it is bare with nothing on it, you can buy this insulated tubing at Home Depot or O.S.Hardware. Its black in color and is split down the entire 10' section with glue covered seams on it. This should cut down the noise. Depending on the unit size Tonnage wise, the suction line may be 3/4" or 5/8" in diameter.Just ask for there water line insulation and like I said it comes in 10' sections and is very cheap, 20cents a foot or so. Please keep me posted if this does not take care of the problem. It may be coming from the lines where they enter the air handler. I will wait for you're reply. Sincerely, Shastalaker7
If you are low on refrigerant, and if you have a low pressure switch, it will not allow the compressor to come on in heat or cool, until you put a jumper across the low pressure switch or add enough refrigerant to get the pressure up to close the switch. You can only add refrigerant to a system if the bottle pressure is higher than the unit pressure without the compressor running.
Normally a technician will hook his gages up if suspects the unit is low on charge or he will push the contacts closed on the contactor and feel the suction line to see if it's cold.