Conservatory AC

[freezy]

Hi all,

I've been asked to fit AC in a conservatory which is south east facing, measures 4.2m x 4.3m, has blinds fitted and has an opening in the wall where it joins the house to a kitchen.

I propose to fit a high wall mount in one corner on the hose wall and use the vertical louvres to direct air into the room.

Will the kitchen make any difference to the load as the whole area gets hot but I feel that the sun through the glass affects the kitchen and it wont matter?

What size unit do you think? Someone suggested 6 Kw but after reading the heat load thread I'm not sure. I once went to a unit in a south facing conservatory that had broken down and the candles in the room had wilted due to the heat.

Would appreciate any advice.

[Andy W]

A 6 kw will work just fine, I usually recommend some kind of window blind to reduce the heat load further. I presume you have got a polycarbonate roof and not glass, if it is glass take your original heat load, multiply by your phone number divide by your dogs age and you should be some where near.

[chemi-cool]

I agree with Andy,
Looks OK,

One thing though, the blinds you have mentioned are on the inside, which means that the glass will get hot when in direct sun rays.
It is my advice to use some kind of shade, outside the windows to eliminate the radiation all together.

Chemi

[freezy]

Thanks guys, I now need to find a decent wall mount, maybe Daikin. Anyone know a good supplier/ contact.

[Abe]

Daikin Direct

Tel 0121 377 8686

Dont even think of cheapos..........
Unless u want probs...........

[botrous]

Everything has it's own price , the peace of mind has one and it's high . . . i prefer to buy my peace of mind not to sell it when buying cheapos ....................

[frank]

and the candles in the room had wilted due to the heat.

now doesn't that conjure up a picture

Daikin Direct

Tel 0121 377 8686

A good link Abe

[dogma]

I'm going with a 4kw

[eggs]

I'm going with a 4kw

well i hope it's a 4kw cheapo, because your getting called back anyway

cheers

eggs

[dogma]

well i hope it's a 4kw cheapo, because your getting called back anyway

cheers

eggs

Yes thats only 200Watts/m2. my mistake

now I'm comming back with a massive number. wtf.
With full glass walls x 3 and no blinds I'm getting 18kw.
What am I doing wrong. I'm using Xwatts/m2 + Xwatts for the glass. I must be wrong. Well I've got something to ask my tafe teacher now .

[eggs]

what i find with conservatories is this.

if you size it correctly, in a south facing conservatory, the evaporator will be bigger that the room and you will need 3 phase power.

all you can do, is explain to the customer, that whatever you fit will be better that nothing.

i usually go for 400w/m2 and use an inverter driven system. This does the job ok. BUT...... if the a/c is switched on at 1pm and the temp is already 55degc in there, we are struggleing.

cheers

eggs

[freezy]

I fitted the Daikin inverter unit in the summer. It worked a treat and the temp came down quite rapidly even though it was one of the hottest days of the year, customer was very happy, I used to work for a company who fitted 2 - 3 kW splits on the cheap and they struggled on hot days but the price was good, its all about what the customer wants to pay.

[R1976]

Hi

I am also looking at a conservatory for a friend and don't want any embarassment.

North facing and 5.5 x 3.2m and unit needs to be floor mounted ideally on the short wall.

my concerns are these.....

Will the airflow be okay across 5.5m?

How many watts/square meter?

Will the heat function work well sized on the cooling load?

We're going with Mitsi Electric and I find conservatory heat gains unpredictable. There are blinds on the windows but not the roof which is plastic and pitched.

Regards

[glenn1340]

I`ve got a conservatory job comming up too, about the same size. I`ve worked out a 5.5kw should do but i`m going for a 6.5kw just to make sure.

[R1976]

Hi Glenn,

Is yours South or North facing?

I fitted a 6kW in a South facing conservatory once and it worked like magic on the hottest day of the year and I switched it on about 2 O' clock and the temp came straight down.

This is North facing and I don't want to over size it.

[nike123]

Hi

I am also looking at a conservatory for a friend and don't want any embarassment.

North facing and 5.5 x 3.2m and unit needs to be floor mounted ideally on the short wall.

my concerns are these.....

Will the airflow be okay across 5.5m?

How many watts/square meter?

Will the heat function work well sized on the cooling load?

We're going with Mitsi Electric and I find conservatory heat gains unpredictable. There are blinds on the windows but not the roof which is plastic and pitched.

Regards

If you want correct size, then you should do heat load and cooling load calculation according to materials used, air circulation, climate conditions and amount of heat generated inside.

[glenn1340]

Hi Glenn,

Is yours South or North facing?

I fitted a 6kW in a South facing conservatory once and it worked like magic on the hottest day of the year and I switched it on about 2 O' clock and the temp came straight down.

This is North facing and I don't want to over size it.

South facing and with perspex tinted roof. The unit will be a floor mounted one. Probably better to err on the size of caution and oversize it by one, they can always turn the fan speed down to minnimum. On the other hand they`ll be straight on the phone first hot day and they`re sweating their wotsits off with the air con on max.

Glenn

[frank]

I`ve got a conservatory job comming up too, about the same size. I`ve worked out a 5.5kw should do but i`m going for a 6.5kw just to make sure.

If you have done the calculations and it's 5.5kW, I don't understand why you need to install a 6.5kW unit?

Can you post your calcs?

[frank]

I fitted a 6kW in a South facing conservatory once and it worked like magic on the hottest day of the year and I switched it on about 2 O' clock and the temp came straight down.

It sounds like the system was oversized.

[glenn1340]

If you have done the calculations and it's 5.5kW, I don't understand why you need to install a 6.5kW unit?

Can you post your calcs?

Sorry Frank, didn`t see the last bit about my calculations. A bit late at night now so I`ll try and post them tomorrow.

[R1976]

It sounds like the system was oversized.

frank,

Why do you say it was over sized?

I have found that all split ac systems bring the temp down to 21/22 degrees in about half an hour. Being an inverter unit, this is not really an issue anyway. I think 5 - 6 kW is good for a south facing conservatory of 20-30 square meters.

Regards

[frank]

frank,

Why do you say it was over sized?

I have found that all split ac systems bring the temp down to 21/22 degrees in about half an hour. Being an inverter unit, this is not really an issue anyway. I think 5 - 6 kW is good for a south facing conservatory of 20-30 square meters.

Regards

Imagine that your unit was not an inverter.

You switch it on in a high internal temp and it brings it down to set point in 30 mins then switches off.

The temp then rises a couple of degrees and it switches back on.

now it only has a couple of degrees to handle, it will take a matter of minutes. So it is on and off continuously. Not good for the compressor. System is over sized.

With an oversized inverter system, the unit will back off as it approaches set point, and therefore spends the majority of its time at low hertz, part load. Not good for energy efficiency, oil return due to low gas velocities, and air flow velocities (the indoor fan backs off as well. )

When an inverter system spends most of its time in low hertz, part load, it's a sign that it is oversized.

Guessing what size system to use instead of doing the heat gain calculations is not the right way to do it.

[back2space]

When an inverter system spends most of its time in low hertz, part load, it's a sign that it is oversized.

.

Frank sorry for the dumb question but can you explain what the problem is with the inverter running at low hertz all the time. I thought the point of the inverter was to avoid the on off cycles. If a unit can float along at low hertz all day and not do any off cycles thats good isnt it?

WHat about inverter units that run at low hertz and then cycle off because the room temp continues to drop?

[beagle]

Conservatory jobs are a pain in the balls, size correctly and there's a good chance you'll be undercut by a local split basher chucking in something with half the duty required and at a stupidly low price. Best to walk away unless the end user gives the impression that they have the willingness and the financial means to get the job done properly, I maybe unlucky but in my experience they generally don't.

[glenn1340]

In view of the various answers to questions I`m going to revist my calculations. Seems like 6.5kw is oversized for my job

So much knowledge on this site, its a pity air compressor guys don`t help each other as much

[Prince Vaillant]

I have a simple calculation program here

[nike123]

I have a simple calculation program here

That is totaly usless for conservatory load calculations.

[frank]

Frank sorry for the dumb question but can you explain what the problem is with the inverter running at low hertz all the time. I thought the point of the inverter was to avoid the on off cycles. If a unit can float along at low hertz all day and not do any off cycles thats good isnt it?

If you consider that it is all right for an inverter driven condensing unit to just 'float along all day at low hertz' would you consider that a 14kW inverter driven system would be suitable for any size load up to 14 kW?

After all, it could easily deal with the heat gain and then just back off without stopping?

Inverter driven or not, a system should be selected as close as possible to the load it is designed to deal with. If it is too big then it will consume extra energy and may fail prematurely through excessive wear. Too small and it won't be able to deal with the load at peak periods.

Inverter drives haven't been designed to compensate for over sizing.

[frank]

I notice that the unit of measurement in that calculator (Metric) gives an Imperial answer

[back2space]

If you consider that it is all right for an inverter driven condensing unit to just 'float along all day at low hertz' would you consider that a 14kW inverter driven system would be suitable for any size load up to 14 kW?

After all, it could easily deal with the heat gain and then just back off without stopping?

Inverter driven or not, a system should be selected as close as possible to the load it is designed to deal with. If it is too big then it will consume extra energy and may fail prematurely through excessive wear. Too small and it won't be able to deal with the load at peak periods.

Inverter drives haven't been designed to compensate for over sizing.

I am still not understanding why its not ok to oversize inverters? My system was oversized purposely so that when its very hot or very cold or that we have house parties the extra 1.5kw capacity is there should it need it. The system at low capacity will just ramp right down sometimes cycling off.

I know that theres a limit at how far it can ramp down and the lowest capacity it could provide but in theory if you are putting in a 5.5kw unit when only 3.5kw is needed then it should be fine as it should be able to ramp down to about 1.5kw should it need to.

However if you are putting in a 14kw unit when only 6kw are needed the unit might only be able to ramp down to about 6kw meaning lots of cycling off and on due to being majorly oversized.

When my system was sold to me they sold the inverter as a benefit at being able to oversize a little due to it being able to adjust itself to the capacity needed.

My understanding of this was that even if a unit is sized correctly eg cooling load is 3.5kw at the hottest point in the day then there will be times such as cooler days or less occupents in the room or cloudy day where the unit will ramp right down and happily remain there. So the cooling capacity required would drop to about 1.5kw perhaps meaning the correctly sized unit would then be "oversized" but being an inverter its "designed" to be able to adjust to the load required and remain there if needed.

I certainly do not think it is detrimental to a units reliability if the inverter system is oversized a 1-2kw as it will be able to adjust.

Obviously with a fixed speed system it cannnot adjust so it will burn full power and stop and start all the time due to outputting full capacity even when not needed.

If oversized massively say 6kw the unit is not going to be able to ramp down low enough.

The approach I would take is theres a limit to how much you can oversize inverters. But where do you draw that limit.

Or is this not the case?

Is this not the case?

[back2space]

If you consider that it is all right for an inverter driven condensing unit to just 'float along all day at low hertz' would you consider that a 14kW inverter driven system would be suitable for any size load up to 14 kW?

Inverter drives haven't been designed to compensate for over sizing.

As I say you still need to size on worst case conditions in the space to be cooled and on normal load conditions and meet in the middle. Each situation is different. Times of days where sunlight might not enter the building.

You wouldnt go putting in a 14kw unit if only 5kw normal load is required but perhaps you might put a 7kw in as then it allows for extra capacity should it need it. Excessive hot days etc where a bang on perfect sized unit may struggle.

I thought thats exactly what inverters were designed to do. A unit is oversized when full capacity of the unit is not required, once it has reached its set point it becomes oversized, it then ramps down and lowers its capacity? Isnt that what it was designed to do?