Query regarding power consumption on an air conditioner?

euser1984 · 03-09-2011 01:34PM #1

Hi,

Can you anybody tell me how much it would cost to cool a room and maintain at 21c with about 1.2kWh of heat being generated within the room.

This is what I'm looking at:
http://toshiba-klima.at/produkt/artikel.php?id=634&lang=2

Thanks a mill.

Dardania · 03-09-2011 05:53PM

rough calc:

According to its tech specs from here: http://toshiba-klima.at/produkt/artikel_tech.php?id=634&lang=2 the annual cooling energy consumption is 540kWh. Presumably that is at it's rated cooling capacity of 3.5kWt, so divide 540kWh by 2.91 to represent your cooling load: 185kWh

If you're on 24 hour billing, and assuming your electricity costs 17cent per kWh that'll cost €31.45 per year

seems extremely cheap to me. I wonder is the external unit in Siberia or something?!

Bruthal · 03-09-2011 08:23PM

But the power consumption is 540kwh a year when cooling. This would be the electrical consumption in cooling mode ( evaporator inside, condensor outside). So €92.

Its power consumption while actualy running is 1kw. So 1 x 24 x 365 = 8760 kwh in a year if continously running, so in the anual usage in the specs, its only running 6% of the time, so the condensor must indeed be out in siberia.

But the items generating the heat in the room (computers?), if they are properly extracted, the heat wont be getting generated into the room, and hardly any cooling would be needed anyway on average throughout the year.

euser1984 · 03-09-2011 08:35PM

robbie7730 wrote: »

But the power consumption is 540kwh a year when cooling. This would be the electrical consumption in cooling mode ( evaporator inside, condensor outside). So €92.

Its power consumption while actualy running is 1kw. So 1 x 24 x 365 = 8760 kwh in a year if continously running, so in the anual usage in the specs, its only running 6% of the time, so the condensor must indeed be out in siberia.

But the items generating the heat in the room (computers?), if they are properly extracted, the heat wont be getting generated into the room, and hardly any cooling would be needed anyway on average throughout the year.

How do you propose I can extract the heat Robbie? I mentioned it to the air-con guy and he seemed to think it messes with the airflow or something.

When it was sold I was told 1kW in should give 3 out. I assumed this meant if I put 2kW in I would get 6kW out at the time. If my computers are generating 5kW of heat does that mean I need 5kW to cool it?

Bruthal · 03-09-2011 08:40PM

The ratio of electrical kw in to cooling kw out would depend on the temperature in the shed compared to outside. To maintain a 21 degree temp in the shed should not be overly expensive anyway, but the running time of the AC unit will be higher when the temp outside is higher than inside.

In the winter it would be likely the split AC unit would go into heating mode to maintain 21 degrees as the shed temp will probably be below 21 anyway in cold weather, if it was setup to maintain 21 degrees constantly.

euser1984 · 03-09-2011 08:43PM

robbie7730 wrote: »

The ratio of electrical kw in to cooling kw out would depend on the temperature in the shed compared to outside. To maintain a 21 degree temp in the shed should not be overly expensive anyway. In the winter it would be likely the split AC unit would go into heating mode to maintain 21 degrees as the shed temp will peobably be below 21 anyway in cold weather.

Sorry not sure I understand what you're saying here.

I decided the shed was a bad idea and have it in a room in the house now!

- Trying to make it into a professional setup now. I think I was fooling around thinking I could do everything for a fraction of the price.

DublinDilbert · 03-09-2011 08:50PM

Why fight it with air con? Surely a good extration system would be able to take out the 1.2kw of heat. Surely it could be passed across a heat exchanger to warm incoming air that could be used else where in the building.

I'd guess the air con guy just wants to sell air con. Would seem like a waste of money IMO. Especially as your only trying to get rid of the heat from a 1 bar electric fire!

Bruthal · 03-09-2011 08:50PM

euser1984 wrote: »

Sorry not sure I understand what you're saying here.

I decided the shed was a bad idea and have it in a room in the house now! - Trying to make it into a professional setup now. I think I was fooling around thinking I could do everything for a fraction of the price.

They probably would of natuarally stayed cooler in the shed, the house will likely be better insulated, so the room may retain more heat.

Anyway, basically whay i said in the last post was, it will be doing more work in the summer to keep the room cooler, than in winter.

Im would of thought myself that extractor fans with ducting direct to the air output from the computers would of directed most of the heat out of the room.

Bruthal · 03-09-2011 08:52PM

DublinDilbert wrote: »

Why fight it with air con? Surely a good extration system would be able to take out the 1.2kw of heat. Surely it could be passed across a heat exchanger to warm incoming air that could be used else where in the building.

I'd guess the air con guy just wants to sell air con. Would seem like a waste of money IMO. Especially as your only trying to get rid of the heat from a 1 bar electric fire!

Spot on, more or less what i have just written at the same time.

euser1984 · 03-09-2011 08:58PM

Sorry I've made a mistake here. It's a total of 5kWh my computers are generating, not 1.2.

Bruthal · 03-09-2011 09:05PM

Yes but 5kw should not need to be removed by a split unit alone. A proper extraction setup should work, even if it was just the computer output cooling vent ducted through the wall. That would also be a very handy amount of heat to use in other rooms in the winter. Or a heat exchanger and you could heat water. A huge waste simply using a split AC unit to heat pump that heat out into the air outside.

euser1984 · 03-09-2011 09:09PM

robbie7730 wrote: »

Yes but 5kw should not need to be removed by a split unit alone. A proper extraction setup should work, even if it was just the computer output cooling vent ducted through the wall. That would also be a very handy amount of heat to use in other rooms in the winter. Or a heat exchanger and you could heat water. A huge waste simply using a split AC unit to heat pump that heat out into the air outside.

Everybody seemed to be saying air con was the way to go. All companies use this as well?

I do have a speed controlled vortice extractor fan capable of moving up to 2000m3/h.

I suggested this to a professional ducting technician/installer and he was worried about really cold air in the winter and very hot days during the summer. He spoke to an engineer that designs computer rooms about my custom ducting idea but the engineer said air con was the only way to go.

Bruthal · 03-09-2011 09:13PM

euser1984 wrote: »

Everybody seemed to be saying air con was the way to go. All companies use this as well?

I do have a speed controlled vortice extractor fan capable of moving up to 2000m3/h.

I suggested this to a professional ducting technician/installer and he was worried about really cold air in the winter and very hot days during the summer. He spoke to an engineer that designs computer rooms about my custom ducting idea but the engineer said air con was the only way to go.

You would of thought they would have the exact running costs for you then. Or reasonably close at least?

euser1984 · 03-09-2011 09:17PM

robbie7730 wrote: »

You would of thought they would have the exact running costs for you then. Or reasonably close at least?

I'm beginning to believe it's not about cost comparison - maybe wrong tool for the job.

I "am" still open minded on using an extractor fan to take the heat into the attic to be reused, my own view is that it would be difficult to maintain a stable temp level though. My fan has a manual speed controller I "could" set (given that it's capable of 67 air changes an hour for the size of the room). It would be switched on by a temperature sensor in the room when required if I was to go that route.

The air conditioner could then be used when required but that would be hard to manage.

robbie7730 wrote: »

Yes but 5kw should not need to be removed by a split unit alone. A proper extraction setup should work, even if it was just the computer output cooling vent ducted through the wall. That would also be a very handy amount of heat to use in other rooms in the winter. Or a heat exchanger and you could heat water. A huge waste simply using a split AC unit to heat pump that heat out into the air outside.

Regarding this post, I did really want to reuse some of the heat for other uses with the air conditioner still running, it is such a waste of heat. The air con guy said people have tried this in the past but it doesn't really work. It upsets the airflow apparently.

Bruthal · 03-09-2011 09:27PM

euser1984 wrote: »

I would have thought it's not about cost comparison - maybe just wrong tool for the job?

The reason i mentioned cost was, that was your question.

I am still open minded on using an extractor fan to take the heat into the attic to be reused, my own view is that it would be difficult to maintain a stable level. My fan has a manual speed controller I could set. It would be switched on by a temperature sensor in the room then.

The experts mentioned AC is the only way. Well in a commercial setup, AC involves a number of air changes per hour, which in simple terms is extraction. Cooling of the fresh intake of air is only part of it.

euser1984 · 03-09-2011 09:46PM

robbie7730 wrote: »

The reason i mentioned cost was, that was your question.

True, but my question was the cost to run the conditioner. Not to say I don't want to talk about cheaper methods though, even if that was not my original intention for this thread. You did mention a cost comparison should have been given by the engineer which would have been "unprofessional and possibly reputation damaging" given the assumed "professional information" I have now been given by my air con man. I'd be inclined to believe him seeing as all server rooms are designed with conditioning which must cost a fortune for businesses to run.

robbie7730 wrote: »

The experts mentioned AC is the only way. Well in a commercial setup, AC involves a number of air changes per hour, which in simple terms is extraction. Cooling of the fresh intake of air is only part of it.

I can't really comment specifically with understanding as I don't know much about commerical setups. All I can think of possible directions for me to go to understand this is "dual systems within the air con realm" research on google? I did get the impression from my air con man though that this is what he was referring to when he said and I quote "people have tried this in the past but it doesn't really work, it messes with the airflow".

While you are saying the air con in commercial setups does involve air changes, it is the one system? I'm open minded about my air con mans statement (at the same time my computers are losing me money whenever there switched off, it would have to be very cost effective to bring them down for testing ventilation systems), do you know of anybody that is doing this dual system successfully?

My idea "was" to do this dual system initally and I was still considering checking this out down the line (even after he mentioned airflow problems), it would be great to make it more cost efficient to run.

DublinDilbert · 03-09-2011 10:56PM

Yea lots of big companies use air con like this, but they typically like to waste lots of money anyway. They love installing new things that sound great at meetings, rather than we installed a fan to blow the warm air out. The waste in some companies is criminal.

Did you look up heat recovery systems?

Bruthal · 03-09-2011 11:29PM

euser1984 wrote: »

You did mention a cost comparison should have been given by the engineer which would have been "unprofessional and possibly reputation damaging" given the assumed "professional information" I have now been given by my air con man. I'd be inclined to believe him seeing as all server rooms are designed with conditioning which must cost a fortune for businesses to run.

Well i would of though the running cost would be a fairly impoirtant factor for a house installation of an AC unit, and it would be more unprofessional of them not to tell a client that asks this.

I didnt actually say the costs should have been given, i was assuming you would of asked the experts before asking on boards.

While you are saying the air con in commercial setups does involve air changes, it is the one system? I'm open minded about my air con mans statement (at the same time my computers are losing me money whenever there switched off, it would have to be very cost effective to bring them down for testing ventilation systems), do you know of anybody that is doing this dual system successfully?

A split AC unit just recirculates the same air around a room while filtering and cooling (or heating it). So it would be hugely wasteful to depend on it to transfer the entire heat produced by the computers to its condensor unit through refrigeration. Some ventilation will be needed in the room. If the air is extracted in a room, this would remove the majority of the heat from the room as long as the outside air is not warmer than inside, and that the extracted air is in fact repalced with air from outside, rather than air from the rest of the house. In winter especially, if the air outside is nice and cool, then extracting warm air heated by the computers and replacing it with cool air from outside is common sense. If the experts dispute that, then it seems common sense is gone.

My idea "was" to do this dual system initally and I was still considering checking this out down the line (even after he mentioned airflow problems),

The extraction rate would want to be causing nearly a vacuum in the room to upset the computers own fans that badly. As long as the air flow is in the same direction as the computers own cooling fans air flow, then i cant see how there is a problem with some extraction.

Bruthal · 03-09-2011 11:33PM

One of them air source heat pumps that heats water, with the evaporator in the computer room would help cool the room and heat the water too. They work great when the air going through the evaporator is warm or hot.

euser1984 · 03-09-2011 11:42PM

So do you think I could do it without the air conditioner at all? Can a heat pump do that?

Stoner · 03-09-2011 11:46PM

euser1984, for the record an AC cooled room the most stable environment from the options you have discussed in the various threads. There are all kinds of passive comms rooms out there but so many have failed and the AC stable environment is preferred option for many.
Passive rooms can have exposed concrete ceilings and walls to dissipate heat, or are cooled at night and used as a kind of heatsink during the day, so don't worry about your shed option it was never going to do be able to do all that, these rooms are generally carefully designed into buildings at an early stage.

However you need to check if its a heating and cooling unit, as Robbie says not only will some units cool to a level, if it drops below that level some will heat the air to maintain it at that temperature, your energy usage will depend on the delta temp that you need to make up in heating plus cooling.
The AC unit is the "install and don't worry about it" option, you could reuse the heat and be clever with how you do things but you'd have to fiddle with things IMO as the lads have said it's not a huge amount of energy to deal with anyway. I've often walked past our own coms room with the corridor cold and the coms room colder, I've been tempted to turn off the AC and open the door! but our coms room is fire sealed for H&S reasons so I don't.

also don't forget that you can maintain the humidity with the AC unit too, there is more to cooling a coms room than simply dumping heat, otherwise coms rooms would all be located on an external wall with vented doors. CRACs are popular these days, even companies with full building AC will still want independent standalone (and sometimes with back up N+1 etc) AC in their comms rooms, because they value the data and want things kept at set conditions 24/7 without change or having to keep watch on things.

It all depends on the value of the data and how much time you want to spend fluting around with fans and opening doors etc, but sure your shed idea might have worked, so long as it wasn't a coirrigated iron roof!!:eek:.

all the more reason for the cloud anyway.

Bruthal · 03-09-2011 11:48PM

A split AC unit is a form of heat pump, except the heat is just being pumped to the outside air. A heat pump to heat the water would only run for so long until the cylinder of water was heated up. But i just think a proper extraction setup would do the job for a couple of computers, and certainly will in the cooler months, and the water heating heat pump could take advantage of the heat produced.

euser1984 · 03-09-2011 11:57PM

Just if I can add this...and it's in relation to the idea that pulling cool air in via extraction when it's cold outside will cut lots of cost.

Is it not the case that the AC does not have to work as hard anyway when it's cold outside? I have maintained my room at 19c today and earlier on my condenser was blowing heat out if I put my hand up to the exhaust fan. However, if I check it now it's blowing cool air out - it's 12c outside btw at the moment.

Does this mean my air con is now using very little power? Perhaps less than a 200watt extractor fan?

Also I have the unit set to cooling only.

I know this still doesn't solve the higher external temps issue.

Bruthal · 04-09-2011 12:10AM

euser1984 wrote: »

Is it not the case that the AC does not have to work as hard anyway when it's cold outside?

Yes the colder it is outside, the easier it is for the heat pump to transfer heat out. The colder air being blown over the condensor tubes means a lower volume of air needs to be blown through, to release the heat from the condensed refrigerant. But this is also the time the AC cooling requirement is least needed amyway, as a colder ambient temperature in an installation that draws in the cooler air during air changes needs to do less cooling to the air, and in fact may heat it if its a stable temperature required.

Its the same for heating a room. If its hot outside, it would be very easy for the AC heat pump to heat the cooler room, but again, this is when the heat would be least needed.

euser1984 · 04-09-2011 12:44AM

robbie7730 wrote: »

A split AC unit is a form of heat pump, except the heat is just being pumped to the outside air. A heat pump to heat the water would only run for so long until the cylinder of water was heated up. But i just think a proper extraction setup would do the job for a couple of computers, and certainly will in the cooler months, and the water heating heat pump could take advantage of the heat produced.

With extraction and external intake would I need to worry about other things like humidity?

euser1984 · 12-09-2011 01:55AM

I'm going to read over this thread again when it comes time do really start deciding what I am going to do. After discussing this with a friend today he has suggested ducting the heat away from the computers and through coils with cool water in them and back into the room then some it's the same circulation or air system for the conditioner.

Anyone ever hear of doing something like this? It would also cut out humidity and filtering as the heat could be used for the radiators - maybe a small bit of power would still be required to bring the water up to a higher temp. However, it would also mean the conditioner would use less power.

Any idea if something like this could work?

Query regarding power consumption on an air conditioner?

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