did i over-do it?

[souroull]

i have a 38sq meter space and i installed 2 MHI 35zjx units (3.5 cooling 4.3 heating each)

the space has a high ceiling (3m) with 3 windows (all externally shaded with shutters)and a front door. Half the space has outdoor facing walls and the other half indoor.

its the middle of the "winter" and the units go into idle mode very often. i thought inverters just throttled down, but when they reach desired temp i guess they do shut off like traditional on/off units... right? Granted i dont live in the UK, but Cyprus, where the temp right now is around 15deg but still... both units operate almost constantly on low mode and often go into hibernation (flaps up and just recycle air)

I didnt own the units during our fierce summer weather (30deg avg, often upto 40) but i wonder whether i made the right choice or not..

thanks!

[install monkey]

its always better to have extra capacity,and by having 2 units you have a back up incase 1 fails

[Tayters]

Rule of thumb for heating are anywhere between 60 and 110W/ m2. This gives you 2.3 - 4.2kW depending on what figure you use. While it may not be totally accurate it's a fair indication of what you need.

In cooling anywhere up to 150W/m2. This gives you 5.7kW so your sizing there might not be too bad if that's the kind of summer temperatures you're expecting.



If your winter is 15*C then you've definitely overdone it but then you've got to size for the summer so it seems fair to me.
If the units have eached setpoint then the inverters wind down. Eventually they will stop if there is no demand as you have found.

I seem to recall having to set some dipswitches on an MHI system as units were oversized as current room was going to be knocked through and made a lot bigger. The dips set capacity of the unit.
Set them down but as you might have guessed everyone still moaned about being to cold. Hey ho.

Cheers,
Andy.

[Magoo]

I think you have under estimated the summer load with +40'c ambient add the loss of performance with high amdient.

[souroull]

Thanks for the replies guys.

I visited a few aircon places before i made up my mind and they all said around 22-24kbtu for the main room and 12-16 for the bedroom (18sq meters). I took that to an MHI only place and the engineer there agreed, and even said that a 3.5 would be marginal for the bedroom... so i was like.. eh why the hell not. In heating mode, that one goes off as often as the main room ones do!

I ended up with the specific units since they were the most energy efficient (2nd to the Toshiba's but those were +30% in price). What i really hope now is that at partial load they go up in efficiency, at least nearer to their 2.5kw siblings which have phenomenal consumption. (anyone got a chart? i managed to find an input vs output chart for the toshibas but not the MHI's)

Time will tell i guess, 30deg summer is only a couple of months away!. I only have 1 unit running for heating the big room right now and it doesnt even break a sweat, but then again the temp differential is only 10 degrees or so.

[back2space]

Run the fan speeds in LOW so there is less cycling and it will keep a more even temperature.

My units are oversized when set on high fan speed and cycle on and off all the time but when I run in low speed they cycle less often.