matching indoor/outdoor units

[botching]

Hi,
Should the indoor unit of a split ac should always be the same capacity as the outdoor unit ? I've read somewhere that indoor unit can be as much as 130% of the outdoor unit.
Thanks in advance.

[multisync]

You are thinking of VRV for 130%

Most would void warranty if you mixed and some would not run. Hitachi does have tha function but the dip switches must be adjusted to suit.

[botching]

I'm actually thinking of a standard split ac units not using vrv. What will be the effects of over sizing the indoor unit by 10-15 % higher than the condensing unit. Will the compressor burn in the long run?

[nike123]

I'm actually thinking of a standard split ac units not using vrv. What will be the effects of over sizing the indoor unit by 10-15 % higher than the condensing unit. Will the compressor burn in the long run?

Why would you oversize indoor unit when they are sold in matched pairs?

[K.R.Iyer]

What will be the effects of over sizing the indoor unit by 10-15 % higher than the condensing unit. Will the compressor burn in the long run?

The Ac manufacturers match the Indoor and outdoor units to have the right system balancing, to deliver required cooling capacity without exceeding compressor safe operating parameters. Unless you have a manufacturer giving you options of different Indoor units, it may not be worth your time in the field. POssibility of compressor burning will depend on the suction gas temperature for motor cooling and the operating pressure ratio. If the units are incorrectly matched against the mfr. specs., you can expect it to nuisance trip when you need it the most i.e. peak summer.

[botching]

i'm actually in the process of selecting several combination of trane indoor/outdoor units (dx coils,5-20 tr) where the AHU (fresh air handling units) will be matched with trane voyager series condensing units. I'm getting 10.3 tons total capacity for one AHU while the corresponding condensing units capacity is 10 tr max. I think with little oversizing(indoor units), there won't be a big reduction in the performance of the units.

[BritCit_Juve]

The manufacturers make their matches to do a specific job without the evaporating and condensing pressures going outside of useable limits or the need for expensive controls.
If you take a large evaporator and match it with a smaller sized condensing unit the evaporating temperature will go up resulting in high sensible cooling.
if the system is a heatpump though the condensing temperature in heating will be too low due to the large coil in the ahu.
if you fit a smaller evaporator to a larger condensing unit the evaporating temperature will fall in cooling and the condensing temperature will rise in heating.
The manufacturers are limited by the compressor which usually is designed for -10°C to +10°C saturated suction and a 35° to 55°C condnsing temperature as well as a need for the coils to not get too hot or more important not get too cold and freeze.
A VRV/VRF has the capability due to its fancy controls and outdoor unit design to limit the outputs off the indoor units whilest maximise the outputs on the outdoor coils.
What you need to do is find a condensing unit that will provide the required duty with a saturated suction temp of around 2°C for comfort cooling or 7°C for high sensible cooling iat the design temperature BUT doesn't go above 10°C saturated suction temp at the MAXIMUM ambient likely to be seen.

Brit