I guess I posted too much info and everyone gets bored before reaching the questions.

Can anyone verify I'm understanding how the system works? When one unit gets heat, they all do, whether they need it or not? The only zoning is how fast the fan blows?

 

Most ductless units can only perform one comfort function at a time, heat or cool.
You usually set one zone/head unit as the priority and that is the function it will do. Once that zone is satisfied, then the other zones can, should there be a need, function as needed.
Each call for heat or cool must be completed prior to changing over. Theoretically, you could have one zone never shut off and any other zone would not be able to heat or cool.

Usually the other zones do not have refrigerant flowing to them if they are not calling for the same function the in use zone is.

Higher end units may have the ability to do both at the same time.

 

Not looking to have one cool while the other heats. It was made clear to me that's not possible with this system. I just don't want it pushing out heat when it's not needed. (As I mentioned, I don't really know all the technical terms. I said "refrigerant" since that's what the techs call it, but in this case it's heating, not cooling. I don't know if it's called something else at that point or not.)

All 3 units are in heat mode. The house has 3 floors, upstairs, main and family room. Heat flows upstairs by convection quite well.

When the family room (lowest) unit calls for heat, all three units get heat. Since the fan on all 3 units runs on low continuously, all three put out some heat when there's heat in the system.

Typically the downstairs unit will bump the fan up, so it's putting out more. The upstairs unit doesn't really need heat at all during the day. It gets all it needs flowing up from downstairs. (I live in Seattle, aside from days like today, it's typically not that cold around here) If I leave it on, that room is too warm. At night, I sometimes need that one for additional heat.

So, my question is whether all 3 units should be getting heat when one calls for it. They are in my case, but I'm curious if that's how it's supposed to work? This may be a Carrier specific question I'm guessing.

 

I would think that you could, at the very least, turn a zone completely off, if not 2 zones.

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I would think that you could, at the very least, turn a zone completely off, if not 2 zones.

Yes, and that's exactly what I do. However, considering the cost of this system, it's a far less elegant solution than what I expected. I just figured I'd set the temp for each room, and that was it. I was aware I'd need to switch from heat to a/c and they did warn me that while one unit works fine on the "auto" setting where it switches as need, multiple heads don't work well that way and it's not recommended. That's fine, we don't need a/c often and when we do, it's not cold enough to need heat on the same day. But I did expect to be able to pick a mode, set temps, and then basically forget about it.

 

If you post the model numbers of the complete system, someone will come by soon enough and answer these questions.

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If you post the model numbers of the complete system

Heat pump is Carrier 38MGRQ36D-3
Wall Units 40MAQB09B-3

 

Jacobk, will know.

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What is the model number of the outside unit, and the three head units?

 

3 units in the house and being used. There’s a 4th unit in the garage area, which I plan to convert to a craft / hobby space. Currently it’s off.

 

Was that not the info you were looking for?

You're correct it's a 3 ton 4 head unit. I'm using all 4 heads, though only 3 of the of the units are turned on most of the time. I've run the 4th a couple times to verify operation and that's it. The 4th one will be used once I get the space properly insulated and set up. However, I had them all installed since I knew it was easier and probably cheaper to just do them all at once.

 

Looks like Lion's Lair lost interest. Anyone else care to take a shot at this?

Heat pump is Carrier 38MGRQ36D-3 36000 BTU unit
Wall Units 4 each 40MAQB09B-3 9000 BTU high wall units.

Let's start with the basic question. 3 units are running, one is intentionally off. When one of the 3 units calls for heat, all 3 units get heat, no matter what temp they're set to, or what the ambient temp in that area is. The fan speeds may be different on them, but when one pushes heat, they all do.

Is that the normal operation for this system?

 

Looks like Lion's Lair lost interest. Anyone else care to take a shot at this?

Heat pump is Carrier 38MGRQ36D-3 36000 BTU unit
Wall Units 4 each 40MAQB09B-3 9000 BTU high wall units.

Let's start with the basic question. 3 units are running, one is intentionally off. When one of the 3 units calls for heat, all 3 units get heat, no matter what temp they're set to, or what the ambient temp in that area is. The fan speeds may be different on them, but when one pushes heat, they all do.

Is the that normal operation for this system?

Sorry. Really busy, for this time of year. I didn't get a definite answer. Boss isn't a pro with mini split systems either. But he did make a wag at it.. yes the units that aren't turned off, would still have "some degree" of refrigerant flow, but didn't think it was supposed to actually circulate the air.
Was hoping jacobk would pop in.

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The tech rep for your local Carrier dealer will need to be involved. Nowhere in the available literature, that I can see, does it make a definitive statement either way on the expansion valve position.

Another MFR, know their commerical product at least, does not fully close the expansion valve for compressor protection. With this in mind they have a setting to ramp the fan down to barely on.

So you need to determine;
1) if the expansion valve FULLY closes when there is no call?
2) can the fan be turned off or down if not heating?

 

So you need to determine;
1) if the expansion valve FULLY closes when there is no call?
2) can the fan be turned off or down if not heating?

It appears the valve does not close fully, based on the fact I get heat from all of them when one calls for heat.

The fan runs at a very low speed when not heating, a gentle movement, just enough to circulate the air a bit. It's nearly silent and hardly any force.
When a unit calls for heat, that unit will ramp up its fan. The others do not increase speed, they just stay at very low.

There's also a "silent" mode. I tried that but it made no difference. I think what that does is hold the fan in low at all times, even if the unit is heating, so there is very little noise. However, since the units not heating already stay on low fan, it doesn't change anything in this case.

The only way to turn the fan off is to turn the unit off. In fact, it appears that "off" only does two things. It stops the unit from calling for heat, and turns off the fan and closes the vent door. Based on feeling the line for my garage unit, there is still some heat going to a unit even when it is off.

 

If this was a computer program, I would propose the following edit to the code.

When any unit calls for heat:
On the unit(s) making the call for heat: Turn UP the fan.
On any unit(s) at or above temp: Turn OFF the fan and close the vent door until the end of the heat cycle. When the heat cycle is over, turn the fan back on.

Simple enough, right? Carrier, please do a firmware update.

 

That's not a Carrier product its someone else's with a Carrier Logo on it.
As far as I know Mitsubishi, Fujitsu and Daikin don't have these issues!

 

Hindsite is always 20/20. Maybe you should have had 2 independent systems for the top 2 floors.
You say they always blow. Why? Is there not a setting for the blowers upstairs to be in auto mode, like a regular system? I wouldn't want them to blow all the time.

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You say they always blow. Why? Is there not a setting for the blowers upstairs to be in auto mode, like a regular system? I wouldn't want them to blow all the time.

Most ductless have the temp sensor in the head unit.
For that reason the fan usually never fully shuts off.
Some may have a setting to lower the fan speed beyond its normal low speed or have an option to fully shut it off. These would be settings to enable, not default. The other thing is some of the info is only known if it has been encountered/looked into. It is not in the standard info available to the installer/tech.

 

The answer to your question is here..
https://r.tapatalk.com/shareLink?ur...443/vbb/showthread.php?t=2204622&share_tid=2204622&share_fid=35652&share_type=t

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Yep, I think that's the case.

So, my next question is "What is the difference when the unit is powered off?" Does that simply mean no fan and no calls for heat?

If that's the case, why not have a unit that is on stop the fan when it's hotter than intended and there's heat in the system?

 

So, I have found a partial solution for this. The units are large enough that unless it's really cold and windy, the fans run on low.

I turned the fan on the lowest unit to "mid", rather than low, meaning when it calls for heat, it's pushing more are. I left the living room one on auto and turned the bedroom (upper floor) to whisper mode, lowest of the four speeds.

This has resulted in more heat being pushed into the space, and the units don't put out heat for quite as long in that mode.

Basically, by controlling fan speed, I was able to balance things a bit better. Still not as automatic as I'd like but it's better.

 

Updating this, though no real changes. The end result was that I only run the two downstairs units most times, with the lower one with the fan on medium rather than auto. The heat flows upstairs well enough that the upstairs only needs heat when it's below freezing or very cold and windy.

I do really like the uniform heat, no more 10 degree temps swings, but it's not quite as automatic as I was hoping.

In related news, I had multiple issues of the system losing refrigerant in the first year of service. The first time it last less than 24 hours. Subsequent times were better, but it would still only last a month or two. It got to the point I could tell by the sound of the refrigerant flow when it was getting low. Does it sound like a toilet flushing when it goes into defrost (another clue you have a problem, frequent defrosts)? If it does, then it's getting low.

The system has 4 heads and one of the runs is moderately long. After about 4 or 5 times of coming out, tightening things up, re-charging etc, all on warranty, they'd had enough. They sent a crew out and spent a day soldering all the connections and getting rid of the compression fittings. Then a second day to purge, recharge and test the system, again on warranty. I will give them credit for standing behind their work, they lost money on this one. (I'm pretty sure that by this point, I'm not exactly their favorite customer, but none of it is my fault). That did the trick, and it's been holding well since. Been probably close to a year now, so I think they found the issue.

 

Soldering lines?

 

Soldering, brazing, whatever the proper method is, I'm not a tech.

They cut out the compression fittings, slid a larger section of copper pipe over the two smaller ones to form a mechanical bond and soldered (or whatever) them together. It looked like soldering copper pipes together for water lines at a glance, I didn't ask for details. (Just fix the damn thing, LOL!)

 

The compression fittings hopefully are Flair Fittings. Used on and approved for ALL mini split.
Brazing or soldering requires lot more steps!

 

And is frowned upon by most mfrs because proper steps are rarely taken.

 

I know that at least the Carrier multizone Mini-Splits valves in the outdoor units do not close 100% when a zone is not calling for heat. Since the fan runs continuously to monitor return air temp and if other zones are operating in heat the zone that is not calling will have some heat moving through the line set. When you have a small zone it is possible for it to exceed its target temp since the blower runs continuously to monitor that zones Return air temp, ambient temp. There is an option/Feature you can enable for the blower to only come on intermittently in heating mode to prevent that zone from exceeding its target temp. It will turn the fan on every certain amount of minutes to monitor room temp. I can not remember the exact interval the fan operates and is common when you have a very small zone. I have to look up how to enable this feature. I had a 40MAQB/38MGRQ 4 zone system that had a small bedroom that constantly exceeded its target. when that zone was satisfied and other zones were operating you could feel heated air blowing out at a very low speed.

Carrier mini-splits are manufactured by Midea, as the 3 top USA major manufacturers don't design and manufacturer their own ductless mini-split equipment. Trane rebrands Mitsubishi, which are my favorite brand of mini-splits, and Lennox i believe rebrands Gree. I know Gree is the largest manufacturer of ductless mini-splits in the world currently. I'm not much a fan of Fujitsu/Sanyo mini-splits. It's just personal preference. I don't work on many Fujitsu and/or Sanyo Mini-splits so that is probably the reason for my preference in Brands. Fujitsu also seems to have the most fault codes I've ever come across

Mitsubishi seems to have the best tech support I've come across on the equipment I have worked on. Mitsubishi is great Especially when trying to determine when you have an inverter or compressor issue that's more difficult to troubleshoot especially when the compressor winding resistance and resistance to ground it normal. Mitsubishi had to elevate me to their second-tier support to determine if the compressor had failed and not an issue with the inverter/PC Board/IPM?reactor.

Cheers

(i hope what i wrote makes sense. I just banged out my reply very quickly so pardon and grammer/spelling issues.)