Wiring to indoor mini split.

[Telstar_2112]

Anyone know why they call for 14 AWG wire to power the indoor units of a mini split system? Namplate info on the indoor unit list a max current draw of 0.21 amps (at 220v)?

Seems like a much smaller wire would be fine but of course I will have it installed to spec. Its just that I have 4 indoor units going to one outdoor unit and am having the wires snaked through some tight areas trying to minimize any re-sheetrocking or patching and by the time you add in 4 of these control wires it gets pretty big.

Thanks.

[cadillackid]

if you look at the way the indoor wiring goes from the outdoor unit to the indoor units you will likely find that it is a near direct connection from the supply mains to each indoor unit.. and if not the only fusing on the indoor wiring is a high voltage fuse on the outdoor PCB at the input...

ther wiring from outdoor to indoor is typically required to handle a short circuit and blow out the mains or the large fuse on the outdoor PCB...

it is also typically S.O. cable which 14 gauge is a very common size and easy for the manufacturer to source (and the installer)...

typically your indoor unit on a multisplit will still have 220 going to it from the outdoor... and the red signal wire is usually 18-30 volt Opto-isolated LIN-bus type signal...

what kind of multi split is this?
-Christopher

[Telstar_2112]

It is one of the commonly considered "cheap" Grunaire units, which I have to say looks great. Very nice fit and finish on everything. I hope it functions and lasts as well as it looks.

The inside units are definitely 220V, I put that question mark by mistake. It is too bad they didn't just add the necessary fuses at the outdoor unit and allow the use of far smaller wire.

[cadillackid]

which Quad-zone Grunaire is it? ( I work on those and know quite a bit about Grunaire)... is it the HXB series?

the Grunaires all ship with the same wiring harnesses standard... they used to ship with li9nesets too but changed that as everyone's requirements are different...

I had some issues in the beginnings with my grunaire units but grunaire and my distributor (ac-wholesalers) have been Very attentive and pro-active at making sure everything is good..

MAKE SURE YOU TORQUE YOUR FLAIRS!! with a torque-spanner..DONT just snug them and be happy...

improper torque on the flairs and these units WILL LEAK..!

-Christopher

[Telstar_2112]

Yes it is a GMU028HXB-4 with 9+9+12+12 indoor units bought from the same supplier you mentioned, AC Wholesalers. I do have a regular precision ratchet style click torgue wrench I planned to use with some of those "crows feet" open end adapters. (I can account for the extra inch if necessary).

I bought all the linesets pre-made with the flares when I bought the units but did not buy the interconnecting wire. I need runs 50', 50', 25', 15'.

With the flares being so critical, if I have an extra 3- 4' or so of lineset should I just coil it in a hidden location or is it worth cutting and re-flaring? Also, I have seen some conflicting information on using a little refrigerant oil on the flare or on the back of the flare, did you find a particular method that works best on these units? To me it seems as if adding oil to the back of the flare would greatly change the torque values and may lead to overtightening.

Your help is much appreciated. Thanks!
Steve.

[cadillackid]

I put just a small amount of oil on my fingers and ran my finger over both flare surfaces and over the rear of the flare but not on the threads of the fittings... definately take into account the extra inch on the crow foot and make sure your torque wrench is straight on from the crow foot.....

also you are going to need some extra refrigerant if you are running those line lengths.. I am running the HX singles and not the HXB multis so I dont have the exact charge amounts... herein was where there was a discrepency...

CHigo the manufacturer (china) of these units states that units are pre-charged for 15 feet of line... AC-wholesalers states units are fully charged for 25 feet.....

I did some playing around and took the middle.. added refrigerant as if each unit was charged for 20 ft of line and that was where i got my best results.. the HXB-series might be different...

and im sure you know you need to deep vacuum the system, check for leaks before releasing the King-valves... it is REAL important for 410A DO NOT skimp and omit this step..

and finally the system you got has indoor units that add up to 42,000 BTU and your outdoor unit maxxes out at 34,000 BTU.. so be aware that will be a limitation when all the zones are calling hard..
-Christopher

[Telstar_2112]

Thanks, That is good information. I am using an experianced a/c pro once I get everything mounted and run but I wanted to know everything myself to make sure it is done right and in case he is not overly familiar with a multi ductless system. Since this is a 4 unit machine AC wholesalers said it is charged for a total of 100 feet.

We do plan on doing the deep vacuum and we will watch it for leaks. Do you do any pressure test for leaks as well, or just pull the vacuum, close it off, and watch it for 15-20 minutes or so?

The units are a bit oversized for the rooms so I should be fine with the BTUs.

Thanks,
Steve.

[cadillackid]

I did a Deep vacuum on mine.. pull down to 500 microns not just look at the vacuum scale on a gauge..

also if the tech is not used to ductless splits he will need to have the fitting adapter for it as the service fittings are not standard HVAC... any supplier these days sells them....

again the charge issue.. when I got mine ACW told me it was chartged for 25 ft (single unit) and yet chigo the china manufacturer said 15 feet....

I picked 20 feet as my median amount and they work fine with 5 feet extra charge.. this is a newer unit it may be different..

if the charge is low you will not notice it except on heating mode.. they will cool fine...

the tech MUST WEIGH in additional charge.. this is an inverter he cannot charge with gauges and expect to get it right.... if you can find the Chigo number on the outdoor unit I can see if a Service manual is available for it.. I do believe I have the extra charge formulas around here somewhere as you will be over 100 feet with your setup...

whereabouts are you what is your climate?

-Christopher

[Telstar_2112]

They told me to weigh in .7 oz. per extra foot.

[Telstar_2112]

I'm in New York, on long island.

[cadillackid]

if the liquid line of your indoor unit is 1/4" you add .3 oz per foot.. if the liquid line is 3/8 you add .7 oz per foot....

when you have a combination you will have to add and subtract for each run and come up with a total amount you need to add.
-Christopher

[Telstar_2112]

Wow, Thanks for the info. It seems like there is some varying recomendations out there.

It does seem to conflict with the information posted on a sticker inside the unit. This is inside the main panel on the outdoor unit. First time trying to post a picture using a web link so hope it works. Edit: Link did nto work since I need to post more than 15 posts to be allowed to add a link.

According to the sticker, if I am reading it right, I would need to add a total of 2.06oz. (I have 140 total feet of ¼” liquid line which is 42.67meters., According to the sticker, Additional refrigerant (g)= 22x(42.67m-40m)=58.74g. 58.74g=2.06 oz.

Using A/C Wholesalers recommendation I would add 28oz. This is a huge difference.

The liquid lines are all ¼”.

I believe the sticker is wrong or I am reading it wrong as 2.06 oz seems like way too little. I emailed ti to A/c wholesalers so we will see what they say.


Thanks,
Steve.

[Telstar_2112]

I mounted the first 2 units yesterday, snaking the pipes, drain and wire up inside a wall I didn't want to open was tough, but went ok. I think I did screw up the torque on one unit as the manual lists the torque in a chart by "Hex nut diameter" when I think they meant tubing diameter. But I was trying to finish up and I guess rushing a little so just looked at the chart, measure the diameter of the hex and started tightening. When I went to do the 1/4 line I realized that the torque was way too much and then realized that the manual was wrong. Typical chinese translation issues although it is my fault as I should have realized it.

So, if I torqued those two flares way too much would you suggest just leaving them until I get the vacuum test done, or cutting and re-flaring them now. (and is is important to use the rolling style clutch flare tool or will a standard one work?)

The 1/4" line is probably close to double the torque, maybe around 38-40 Nm when the spec is 15-20Nm.

Thanks.
Steve

[cadillackid]

I would go ahead and just re-torque and then do the vac test and see... the issue will come when the system goes to heat as parts expand at different rates and you could risk cracking the nut..

ytou definately need the correct flare tool if you are going to flare.. or if your connections are outside of the building you can cut the flares off and braze the linesets together with a nitrogen purge..

or try HVAC super pro.. ive done some testing with HVAC super pro and so far so good but I dont have any long term testing to see if its going to hold under heat pump conditions...

obviously in a multi-split system a leak is costly as you have to lose quite a bit of the charge before you notice performance issues esp in cooling mode...

as for the charge discrepencies what a pain.. Ill have to pop the cover off of one of my outdoor units and see if the formula differs from the book... ..

the label inside is going to be straight from the manufacturer in china (chigo) and so is the book...

last summer when I dealt with this.. AC wholesalers, Buyunit and a couple other Grunaire dealers all said the Grunaire units were specially made and charged for 25 ft of line per indoor unit..

my contact at Chigo told me that none of the units for any brand in that series left the factory with more than charge for 15 ft of line per indoor unit.....

AmcorAire (defunct now) sold the exact same unit and told me it was charged for 15 ft of line.. and when asked the charge amount.. the charge listed on the outside plate was exactly the same as the grunaire... so thats when I played around a little and ended up taking the middle of the road approach with them and assumed them craged at 20 ft and added accordingly..

2 of my units are identical and side by side I ran one with weight on label and the other assuming it was precharged for 15 feet (I have 25 ft).. it was clear the one ran in heat mode like it was a bit low hot gas line temp was much higher than I liked... added enough for 5 more feet (assuming now it would be at 20 ft charge) and it ran identical to the one that was charged for 25 feet...

so take it or leave it but the issue is no one seems to have a real handle on the charge...

-Christopher

[Telstar_2112]

ACW got back to me saying just to use what it says on the sticker but with no explanation as to why the huge difference. I do not think they really looked into it.

Grunaire also finally emailed me back and said to use what is on the sticker and that the unit is charged for 100'

The unit sticker implies it is charged to 40m which is 131' clearly different from their own email. So it seems as if no one knows. I do not know how they can sell this unit and know nothing about this. This is an important critical bit of information.

So I need to put in somwhere between 2 oz and 28oz!

Also, most of the flares on the pre-flared pipes were terrible, one even pratically had a fold in it, and needed to be re-done.

These inverter driven ductless systems are pretty nice and I can see them taking off here in America but they need to get their acts together.

Steve.

[cadillackid]

telstar.. correct... if you note my posts on this board I found exactly the same thing with the units... note its not the flares on the units, its the flares on the LINESET that are terrible.. originally ACW shipped units complete with linesets as grunaire packaged them that way... i got pretty good linesets at that time....

later on they started packaging and selling separately.. and those linesets were not as good a quality.. they are boxed differently so presumably they are made by a different company...

the issue is that getting information from Chigo in china is the tough part... CHigo claims they NEVER alter their charge on the assembly line for ANYONE.. so what is in the Book is what they say to use...

and I have done as you may have seen quite a bit of testing with this.. yse they will RUN out of the box with the factory charge but i dound in heating on colder days they struggled.. and adding some refrigerant helped and did not affect cooling...

I added an amount in between what the book said to add... the refrigerantr charge on the label in pounds was somewhat correct... it varied a little when I weighed the charge out into a bottle...// prseumably some of the variance being that refrigerant in my machine or hoses etc may not may not register on the scale when taking out a charge...

There have also been MANY software updates to the grunaire units as well... the HXB multi series has the later program loads in them which will help things out a bit.. but you truly will not know if the charge is 100% dead on until you have all zones calling in heat mode on a cooler day...

if it is low you will find even when forced to medium fan speed there will be HUGE amount of sub-cooling across the indoor coil... (difference in temperature from the inlet (large line) to the outlet (small line)..

Overcharging will affect the units ability to heat and cool.. although will be noticed in cooling cycle first...

-Christopher

[airconlad]

Anyone know why they call for 14 AWG wire to power the indoor units of a mini split system? Namplate info on the indoor unit list a max current draw of 0.21 amps (at 220v)?

Seems like a much smaller wire would be fine but of course I will have it installed to spec. Its just that I have 4 indoor units going to one outdoor unit and am having the wires snaked through some tight areas trying to minimize any re-sheetrocking or patching and by the time you add in 4 of these control wires it gets pretty big.

Thanks.

Hi in answer to your question

If any internal unit (now using thinner cable than the cable used to supply power to the condensor) developed a short circuit, this thin cable could / would melt and catch fire before the circuit breaker / fuse feeding system trips off / blows, this is dispite the internal unit only using a max of 0.21 amps, its a saftey thing.

Rated on the side of caution it could happen.

Some guy could stick a nail though the thinner 22awg cable shorting it out, the rest of the system is using thick 14awg rated at 20 amps protected by a 16 amp braker (a guess) the thiner 22awg wire is rated at a 2 amps (also a guess) what do you think will happen first ?

The thinner wire is lightly to get pretty warm in a short amount of time as it will see at least 16 amps (about 14 amps more than its safe rating) if not more for the few milliseconds it takes the breaker to actually trip out, result melted wires or maybe a burnt down building in worse case.

The same thikness cable is generally used thoughout the system as a potential short could happen 14awg can handel say 20 amps and braker rated at 16, breaker will trip BEFORE wire even has time to get warm in short curcuit situation.

I have no idea what current rating for 14 or 22 awg cable is nor the braker your using, I am using this as an example please don't linch me over the current ratings of cable / brakers.

Hope this helps anyone who has a question like this understand why the same thikness cable is used thoughout a system.


Airconlad

[Telstar_2112]

Thanks to both.

As far as what the book says about adding refrigerant, well, the manuals that came with the units do not say a word about adding refrigerant! Maybe ther is another, more descriptive, installation manual?

Are we sure there is no way to use the gauges to tell proper charge? Will putting all 4 of the indoor units into a "test mode" run the compressor flat out possibly allowing this?

The wire issue answer makes sense and I did use the 14 ga. It just seemed as if there could have been some 1 amp fast blow fuses in the outside unit to allow finer wire. Not a big deal though.

Sure wish someone at ACW or Grunaire would get me a straight answer. Since I am trimming some of the linesets, if it really was pre-charged to 40m, which is what the sticker implies, I would be pretty much at that exact length!
Thanks,
Steve.

[pilgrim]

I too just installed Grunaire unit, the new "Delux" 25k unit. I spoke with goductless.com aka acwholesale.com and the tech told me that they are charged for 15-25 feet. He said an indeterminate test amount of 410a is put in the unit for testing and that you may have to add or take out depending on what they put in and what line set you have. I had right at 15 foot line set. The tech who tested and set up my unit seemed to think according to his calculations that the amount of 410a was correct. I do like the unit, I however am not impressed with the lack of tech/information support of this company.

[kevperro]

I just bought one of the GSI121HX units..... 12,000 BTU from AC Wholesalers.

I ordered the 15ft line set and I'm a complete newb when it comes to heat pumps. I assume I'll need to go out and pick up the torq wrenches to get the right torq on the flare and I'm hiring someone to do the initial leak-test and charge. From what I gather.... I won't need to add 410A unless something is wrong.

One other thing I'm doing is installing the outdoor unit in my crawlspace. I have a encapsulated crawl with drainage and a sump pump. I wanted some extra dehumidification so the outdoor unit should draw some water vapor out of the air. My ambient temp below the house also stays within a 48-57 deg. range year round so I figured it would be like getting the benefit of a GSHP in an inexpensive air source unit. The crawlspace temps are dominated by the ground temp and I have active ventilation that occurs only when outdoor temps are high and vapor pressure low.

Any input on how I should direct the contractor for testing and topping off 410A would be welcome. Also a source for the torq wrenches online would be welcome to.