Air flow from the vent when the zone is OFF

All,

I got Mitsubishi Electric ducted air con installed this week. 10 outlets, 4 zones.
Zone 1 – Bed 1 + Bed 3
Zone 2 – Bed 2 + Bed 4
Zone 3 – Living, Dining and Kitchen
Zone 4 – Media

Now at 19 degrees, if I've Zone 3 ON and all other Zones OFF, I still see slight air flow in some of the bed rooms. Is this normal? I asked the air con guy who installed it and he said there's sponge and little air escapes out through the other vents and it's normal.

Have you experienced this sort of behaviour? Should I be concerned?

Thanks for your time!

This is normal as zone dampers don't seal 100%. There are zone dampers that seal 100% but you may not be able to justify the cost of them.

Bels

Appreciate your reply, I feel better now

Another question on sensors. Please see link below.

http://www.mitsubishielectric.com.au/zone-controller.html

Heading,
Averaging sensor control
The Zone controller has five sensors in the system (Main RC, Sub RC, Optional Sensor 1, Optional Sensor 2 and outdoor unit sensor). Control of the unit is based on averaging of the sensors of the active zones.

Question:
In the Zone controller display, I can see all the zones uses the same sensor called Indoor Sensor and all of the above sensors (i.e., Main RC, Sub RC etc.) are OFF / not assigned to any of the four zones.

Should I turn ON the above sensors and assign to one zone each (or) the way I've it now is good? i.e., all 4 zones are assigned to one sensor called 'IC' Indoor unit sensor.

Please share your thoughts.

We have the exact same problem. Called the AC guys out that installed it and was told it's normal.

I find it hard to believe that they can't design a gate that completely shuts off.

Ideally the best control is sensors in the active zones provided that they're not directly affected by the supplied air (air from diffusers blowing directly on them). You don't want to be controlling from inactive zones as you could overshoot and over cool or heat other zones. If your IC sensor (most likely the one in your wall controller) is in close proximity to your return air intake and you'd only got the one return air intake, then the temperature there will dictate what conditions are going to be in your active zones.

If you enable the other sensors, do they display a normal reading? If so you'd need to identify which sensor is which to be able to assign to the correct zone.


hth

Read my reply above. I'm sure if you're willing to foot the expense then someone will be happy to change all your zoning barrel dampers to 100% sealed ones.

Seems silly that these aren't fitted as standard. Why would someone want a zone off and still have air flow? Should be either open or closed.

It's scales of economy. If no one else is installing 100% sealed barrel dampers then how are you meant to be competitive on price if you are using them as standard? Who would be covering the extra cost of them?

It's not air flow into the off zone, it's air leakage. Air like water will always take the path of least resistance and flow into the open zones. The static pressure in the duct will always cause air to leak past as it's the higher pressure air in the duct trying to equalize with the lower pressure behind the damper.

Thanks Bels,

You're absolutely right in saying the below. From what I can see in the controller, all zones are assigned to the same IC sensor in the wall controller. And you're right, there is only one return air grill which is close to above the wall controller.

If your IC sensor (most likely the one in your wall controller) is in close proximity to your return air intake and you'd only got the one return air intake, then the temperature there will dictate what conditions are going to be in your active zones.

I'm not sure where the other sensors are located? How do I check for normal reading? And how do I identify the right sensor for a given zone? Apologies, this is the first time I've a zoned air con.

Appreciate your time again.

Just an observation -

I noted that only two of the rooms have bad leaks the other rooms are pretty OK. I'm surprised the two rooms that are leaking badly are in different zones as well. One of the rooms (zone OFF) is like, 50% air flow as that of the room with zone ON. The other OFF room less than 20% air flow which I think is acceptable.

Now, as I hear from Bels and sluggo, it's normal so I've to train my mind to accept it

Do you have sensors installed on walls elsewhere in your house? The rule of thumb is 1500 - 1650mm high. If you haven't got any installed then potentially they may not have installed them.

By normal reading I mean looks like it is reading correctly (not 300 degrees or -263 degrees for example)

hth

No other wall installation just the controller. Should I ask them to install other sensors if they have missed it. They completed the install last week only. Not sure if it's common for them to install only one sensor but I would ask if you suggest.

I'll simply try assigning other sensors to zones and see what the temperature is..

It really comes down to how much it annoys you and if it will benefit your installation. They are marked as optional though hence why they were probably not installed. You might be paying for the other sensors to be installed if it wasn't in the original scope. How beneficial they are really comes down to how your house is laid out, how the zones are split up and location of registers in each zone. With a single main return air intake, all the return air needs to flow back to that point. If there's factors which could affect the accurate measurement of the incoming return air such as solar load, then you'd definitely see a benefit to sensing across multiple zones and averaging the readings for control.

hth

Thanks mate I think it makes sense to leave it as-is with one sensor.

Is main RC, main remote control sensor and sub RC sub remote control sensor? Meaning the sensors are in the remote control and senses based on wherever the remote control is?

They didn't give me any remote control. Just the wifi app so if what I'm guessing is right, then those 2 sensors are not applicable in the first place.

Also the other sensor is outdoor sensor. Why would someone assign it to any indoor zone in the first place? Trying to understand.

Thanks so much!

Every manufacturer uses different terminology. Main RC is generally the sensor in the wallpad controller, sub RC is generally the coil sensor but don't quote me on that.

Outside air sensors are generally for ambient lockout function or for economy control.

Hth

Hi Bels,

I did a temperature test as suggested, please see below observation.

Zone 1 sensor set to the following -
1.) IC (Indoor Unit) = 29 degree C
Note: IC sensor was the setting I had for all zones when the AC guys finished. Works well.

2.) Main RC = 30 degree C
When I set the zone 1 sensor to Main RC, I get the following error on the controller display after a few mins.
Error code - 5191
Error unit - IC
Address - 001

3.) Sub RC = 8 degree C (8 blinking)

4.) Optional Sensor 1 = 8 degree C (8 blinking)

5.) Optional Sensor 2 = 8 degree C (8 blinking)

With this, can we conclude whether additional sensors have been installed or not? It looks like the unit works based on only one sensor called 'IC' (Indoor Unit). Is it all good? or should I contact the air con company and ask about other sensors etc.

Appreciate your time & help again.

1. return air sensor

2. unsure of what this error is as it's not in my list of error codes. You may need to contact the installer if you need to find out what this is as I'm not sure of what your model of unit is.

3. likely not installed

4. Likely not installed

5. Likely not installed

Thanks Bels,

With this setup, is it all good (or) should I ask for more sensors? I would assume this is the standard installation by the air con guys but would definitely have a chat about the sensors and confirm.

And the model numbers below.

Model no: PEA-RP140GAA Indoor unit PUHZ-RP140VKA2 Outdoor unit

There's nothing wrong with the method of control of your system. The air supplied to the active zones still returns through the common return air intake and sensed by the indoor unit sensor. That said if you were after more exact control then you'd want sensors in each zone. Now with averaging sensors, if a sensor is in a zone with a high solar load, it would raise the averaged temperature sensed and bring on greater cooling or in the example of heating the opposite.

How do you feel your system is operating? Are the conditions comfortable in your house? Is there excessive or inadequate compressor on cycles? Do you feel there's room for improvement?

Sometimes people chasing absolutes end up dissatisfied or unhappy with an otherwise well functioning system. A mentor long ago knocked it into my thick head that air conditioning is an inexact science.

hth