Domestic installation Question

[Redfish]

Hi, I am having A/C installed in a three story house in France and have a question relating to individual temperature control in the ducted supply to the three bedrooms. The installer (in France) has recommended a Daikin 4 MXS80E heat pump to supply the 3 bedrooms (about 30 cubic meters each) and the lounge (about 75 cubic meters). The ducted supply to the bedrooms will come from a Daikin FBQ50C. Now, since I want each bedroom to have its own temperature control the installer has recommended he install electrically controlled valves in the ducts to the rooms and that excess air be vented to the loft (where the Daikin FBQ50C will be installed). Another installer recommended installing individual units for each bedroom (ATLANTIC Type ARYF9LALUI ), this was more expensive but with individual inlet and outlet vents in each room seems the optimum. My question is: Would the cheaper installation with one main unit and three valves and an excess-air vent to the loft be a good solution or should I opt for the dearer answer. I could, of course, go with wall units in the bedrooms which would be cheaper still.
Thanks for your professional expertise.

[frank]

Hi Redfish

The Daikin MXS80 has the capacity to connect a maximum of 4 x individual indoor units, so connecting 4, i.e. 1 for each room will be OK.

You say that the bedrooms will be served by a single ducted unit but you don't say what will serve the Lounge?

The idea of dumping excess heat/cooling into the loft void when the bedrooms are satisfied seems a really wierd set up and you will be paying for this lost energy. It would be much better if you had individual fan coils in each room. The more thermostats, duct valves, etc on 1 system = much more to control and go wrong!

One of the drawbacks of the Daikin MXS is that it can only heat or cool at any one time - that is, all of the indoor units will have to be in heating mode or cooling mode at the same time. You can't have one room heating and another room cooling. At this price level, you would be better having seperate split systems if this is one of your requirements.

You could of course go with the Daikin MXS outdoor unit and fit individual wall fan coils in each room as this would give you individual room temperature control for a reasonable investment. The Daikin fan coils are very quiet as well, which, if you are installing in bedrooms, is an important factor.

[Redfish]

Thanks for your reply, Frank. The unit supplying the lounge would be a Daikin wall unit FTXS42G.
Yes, it struck me as wastefull to void to the loft and I thought of asking that this excess be vented to the upstairs landing ( where the air inlet for the loft unit feeding the bedrooms will be). At least that would cool that part of the house and hopefully the air fed to the loft unit. It seems that should one bedroom demand cool air then the loft unit is obliged to produce enough for all three bedrooms and if they have no demand then it must vent the excess somewhere. I imagine that sensors in each bedroom will control the temperature but it seems a shame to take warm, hot even, air from the landing to cool it for the bedrooms which may already be fairly cool. That does not seem to be efficient to me but I am ready to be corrected.
In the end the best, most efficient and cheapest method would seem to be wall units. I was hoping to avoid them.
As regards the impossibility heating one area while cooling another I cannot imagine this being a difficulty in this small house where the problem is overheating in the summer. But I take your point.

[Slim R410a]

Thanks for your reply, Frank. The unit supplying the lounge would be a Daikin wall unit FTXS42G.
Yes, it struck me as wastefull to void to the loft and I thought of asking that this excess be vented to the upstairs landing ( where the air inlet for the loft unit feeding the bedrooms will be). At least that would cool that part of the house and hopefully the air fed to the loft unit. It seems that should one bedroom demand cool air then the loft unit is obliged to produce enough for all three bedrooms and if they have no demand then it must vent the excess somewhere. I imagine that sensors in each bedroom will control the temperature but it seems a shame to take warm, hot even, air from the landing to cool it for the bedrooms which may already be fairly cool. That does not seem to be efficient to me but I am ready to be corrected.
In the end the best, most efficient and cheapest method would seem to be wall units. I was hoping to avoid them.
As regards the impossibility heating one area while cooling another I cannot imagine this being a difficulty in this small house where the problem is overheating in the summer. But I take your point.


Surely if one bedroom demands cooling the other 2 bedrooms' dampers will close and all of the supply air will be forced down the one duct?
I'd steer away from the idea of the one ducted unit if your main concern is accurate temperature control in each bedroom. Like Frank said, at this sort of price you would be better paying that bit extra and going for either;

A) 1No. 3MXS outdoor with a wall mount in each bedroom. Lounge single split FTXS42/RXS42.
B) 1No. 3MXS outdoor with a ducted unit above each bedroom. Lounge single split.

Obviously the ducted indoors cost more+duct however remember the wall may require condensate pumps where the ducted most of time can be gravity fed to outside from the loft.
Personally I'd keep the lounge on a seperate system then at least if an outdoor had a fault you would still have either upstairs or downstairs cool.
If the cost becomes an issue then start looking at the same set up with cheaper brands i.e Toshiba, Panasonic, Mitsi Heavy etc.

[Redfish]

Thanks for your input, Slim. I think I will ask the installer to quote me for ducted units to each bedroom - this seems to be the most rational solution - cost aside.
This house is on three floors with the lounge on the second and the bedrooms on the third. On the ground floor there is a bedroom I use as an office and I have asked for a single split for that (RXS20G/FTXS20G). The plan was that the lounge and other bedrooms would have the 4MXS80E outside. I am a little concerned with lining the outside of the house with three units and presumably extra cost, but will ask for a quote on a seperate split unit for the lounge.