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Author Topic: Air-con proposal, Yikes help please!  (Read 328 times)

Ken Webster

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Air-con proposal, Yikes help please!
« on: February 10, 2019, 04:40:04 am »

Today at our church leaders meeting, the pastor announced that a member had offered to install air-con in the chapel at a very low rate.

Well, it's summer here and we have been having severe drought and record high temperatures.  There have been some humid days in the mix.  While we only do a morning service and therefore escape the worst of it, some members have obviously been having difficulty coping with the conditions during the service so it is understandable this proposal gains immediate support.

I don't have any information on the unit in question but I am pretty certain it will one of those bolt on split systems.  I have a Daikin which has become so noisy, I canít stand to watch movies while itís on.  I am extremely concerned that this could totally impair the efforts and commitment of the worship and sound teams to deliver a meaningful service.  However, I concede there is a need to cool the room to an acceptable level.

Can anyone offer some advice on types of air-con systems that would be appropriate please?
The chapel, built in the 80s could hold about 200 people at a squeeze and has a fairly high shallow pitched roof.  I am not sure of the exact dimensions at this time but I am not trying to assess air-con capacity, just appropriate system types.

Thanks,
Ken
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Tim Hite

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Re: Air-con proposal, Yikes help please!
« Reply #1 on: February 10, 2019, 01:36:01 pm »

Mitsubishi makes the best mini-split units, as far as I know. I have a couple in various places. They are so quiet you don't even know they are running. The energy efficiency is hard to beat. The LG units are also very good.

I'm in the desert in Southern California. I have a bunch of friends who have them in their bedrooms and absolutely love them. Ductless mini-splits have been known to save marriages in the summers out here.

When I was working in the Middle East for a large energy services company we had hundreds of these units and the HVAC guys swore they were the best things ever for ease of maintenance.

The cheaper brands are generally reported as noisier and having more issues. I have several friend with cheap models on their vacation trailer in Baja California. They are using units that cost $300-$400 US.

Assuming you can calculate the appropriate size on your own. Having some extra capacity has proven useful if you want absolute control over temperature. You can order pre-charged line-sets with your unit and that apparently makes the install performable by the homeowner.


Today at our church leaders meeting, the pastor announced that a member had offered to install air-con in the chapel at a very low rate.

Well, it's summer here and we have been having severe drought and record high temperatures.  There have been some humid days in the mix.  While we only do a morning service and therefore escape the worst of it, some members have obviously been having difficulty coping with the conditions during the service so it is understandable this proposal gains immediate support.

I don't have any information on the unit in question but I am pretty certain it will one of those bolt on split systems.  I have a Daikin which has become so noisy, I canít stand to watch movies while itís on.  I am extremely concerned that this could totally impair the efforts and commitment of the worship and sound teams to deliver a meaningful service.  However, I concede there is a need to cool the room to an acceptable level.

Can anyone offer some advice on types of air-con systems that would be appropriate please?
The chapel, built in the 80s could hold about 200 people at a squeeze and has a fairly high shallow pitched roof.  I am not sure of the exact dimensions at this time but I am not trying to assess air-con capacity, just appropriate system types.

Thanks,
Ken
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Taylor Phillips

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Re: Air-con proposal, Yikes help please!
« Reply #2 on: February 10, 2019, 02:30:48 pm »

Today at our church leaders meeting, the pastor announced that a member had offered to install air-con in the chapel at a very low rate.

Well, it's summer here and we have been having severe drought and record high temperatures.  There have been some humid days in the mix.  While we only do a morning service and therefore escape the worst of it, some members have obviously been having difficulty coping with the conditions during the service so it is understandable this proposal gains immediate support.

I don't have any information on the unit in question but I am pretty certain it will one of those bolt on split systems.  I have a Daikin which has become so noisy, I canít stand to watch movies while itís on.  I am extremely concerned that this could totally impair the efforts and commitment of the worship and sound teams to deliver a meaningful service.  However, I concede there is a need to cool the room to an acceptable level.

Can anyone offer some advice on types of air-con systems that would be appropriate please?
The chapel, built in the 80s could hold about 200 people at a squeeze and has a fairly high shallow pitched roof.  I am not sure of the exact dimensions at this time but I am not trying to assess air-con capacity, just appropriate system types.

Thanks,
Ken
200 seat chapel with a high ceiling is going to call for a good bit of cooling power from the AC.  Is the member a professional HVAC installer?  If he is, then whatever he gets you should be sufficient for the space.  If not, then the church needs to push for at least a professional calculation of the needed cooling capacity.

The mini-splits seem to be fairly popular when putting AC in older church buildings because there is no duct work.  The disadvantage is that you need multiple units to cool a large space evenly, so one of the main benefits that you get with them in a home, the ability to only cool rooms that you need cooled, is not there.  The advantage of a ducted system is that you can use can place the air handler in a place that minimizes noise, and the ducts can evenly distribute the air throughout the building.  If you have room under the floor or above the ceiling for the ducts, then that type of system might be the better solution, but if not, then the mini-splits would likely be better.  Also, if there is no room for an air handler inside for a ducted system, there are "package" units which house both the condenser and air handler in one unit outside of the building.  The cost of either type of system was pretty much equal the last time I looked into it. 
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Erik Jerde

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Re: Air-con proposal, Yikes help please!
« Reply #3 on: February 10, 2019, 04:45:39 pm »

Is there a spec sheet for the chosen system?  Those will usually list an operating noise level.
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Jeremy Young

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Re: Air-con proposal, Yikes help please!
« Reply #4 on: February 10, 2019, 10:57:53 pm »

Air conditioner load calculations require details of the building construction and dimensions (surface area of everything separating outdoors to indoors with defined r-values), as well as the orientation of any glazings (N/S/E/W) and distances from overhanging roofs above them, and how far the overhang extends, any window dressing or blinds used, etc.  The math is based on the Delta T (difference in temperature) between the outdoors and indoors on a "design day" which will be different for each town and the globe.  Commercial load calculations also include things like lighting loads, occupants, electronics, and dehumidification loads.  Advanced calculations also include knowing ventilation loads and what sort of surfaces are outside the windows (black asphalt versus green grass makes a difference).

The best air conditioner in the world, improperly applied, will be the worst investment you can make.  Brand and make does not matter if it's the wrong size or format for the space, period.  I'll say that again.  Don't spend money on something unless you know it's right for YOUR space and budget.

Start with a proper load calculation - in this case called a heat-gain calculations (Assuming you're in the USA, get someone who can do a site survey and provide a Manual-J or equivalent load calculation, if you're in Canada it would be CSA F280-12) in order to select the capacity and determine placement if going ductless.  High ceilings and ductless don't always work well together depending on the required throw, but sound levels will be published for outdoor and indoor units and there are plenty of quiet systems on the market (I've designed cooling systems for University recording studios, and met their NC10 criteria).

Either an A/C Contractor or your local wholesaler/supply house should be able to do the load calculations, usually for a fairly minimal fee (and sometimes that is waived if you buy the equipment).  Try calling your local HVAC wholesalers to get recommendations and get three quotes and ask for their work.  Take the cheapest one and throw it out.  A site visit might be avoided if you have detailed scaled floorpans available that reflect the current construction and use, digital is usually preferred these days since all the software is CAD based now so PDF or DWG files can be loaded directly and traced into a 3D model.

Cooling capacity is typically rated in tons (12,000 btu/hr per ton) and will be specified at various outdoor temperatures.  Efficiency will be rated in SEER, higher numbers are more efficient.  There are lots of good brands, each with multiple tiers of price point/features/efficiency.  Usually installers will be dealers of one or two major brands that they are experienced or even factory trained in, so you might get different quotes from different companies and that's quite normal.

In Canada where I am, most major manufacturers that involve any form of field-charging of the refrigerant (basically everything split, but precluding packaged rooftop units and similar) won't cover warranty if installed by someone without a valid refrigeration ticket. 

Might be different south of the boarder, but I've been in the HVAC industry 12 years at a wholesaler running the heating department, so I have a bit of expertise here, but our cooling season is about 2-4 weeks where I live so I'm not as experienced with A/C as people further south but we are in Heatpump country so I know the technology well. 

Charging the system with a nitrogen purge is an art, and any contamination of that circuit will take years off the life of the system.  An improper charge is like driving with a flat tire, efficiency and comfort will suffer.  When I hear "volunteer" and "air conditioning" I suspect you'll be replacing it in two years.... unless you get lucky.  YMMV, good luck!
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Ken Webster

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Re: Air-con proposal, Yikes help please!
« Reply #5 on: February 11, 2019, 07:39:31 am »

200 seat chapel with a high ceiling is going to call for a good bit of cooling power from the AC.  Is the member a professional HVAC installer?

He is a professional Air-con installer and business owner here in Australia.  I will talk to him at some point but want to be independently informed 1st.
« Last Edit: February 11, 2019, 07:54:14 am by Ken Webster »
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Ken Webster

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Re: Air-con proposal, Yikes help please!
« Reply #6 on: February 11, 2019, 07:40:17 am »

Is there a spec sheet for the chosen system?  Those will usually list an operating noise level.

Not that I know of.  I have written up a case for the need to consider the impacts on worship based on increased noise floor requiring increased sound levels.  We are pretty much at the limit of what I would consider efficacious to worship.  I think the pushing into 90 - 100 dBC to retain current S/N (including environmental noise floor) is going to destroy that.  I just want them to be really considered in their choices.  It seems like they just want to slap some cheap system in ASAP.
« Last Edit: February 11, 2019, 07:50:57 am by Ken Webster »
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Cailen Waddell

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Re: Air-con proposal, Yikes help please!
« Reply #7 on: February 11, 2019, 07:52:24 am »

He is a professional Air-con installer and business owner.  I will talk to him at some point but want to be independently informed 1st.

There is lots of good info here.  I will add that typically a theater or church, to avoid noise, is looking for high volume but low velocity air movement.  In non mini split packages that often means very large duct work with large registers and grills to avoid noise.  It also can mean variable speed fan motors and cooling capacity to provide only the cooling you need - thus further minimizing noise...


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Keith Broughton

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Re: Air-con proposal, Yikes help please!
« Reply #8 on: February 11, 2019, 11:34:44 am »

It seems like they just want to slap some cheap system in ASAP.
And that won't end well!
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Jeremy Young

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Re: Air-con proposal, Yikes help please!
« Reply #9 on: February 11, 2019, 01:36:06 pm »

That's good that the volunteer is properly trained, but when noise is a concern sizing properly will be the key to success.  We're on opposite sides of the world, so any tips I have about brands won't be very meaningful I'm sure.

Typically air conditioners move about 400 CFM per ton (but this will be equipment specific), so once you know the design load you can begin duct sizing.  Lower air velocities can be achieved with larger diameter duct which will reduce noise and pressure drop at the cost of space and price.  There are special grilles and diffusers available that are intended for lower velocities to still maintain the required throw while low noise.  Linear slot diffusers are commonly used for this around here because they terminate into an insulated plenum cabinet first and are very effective at low velocity throw.

If you can opt for something with two stages, or inverter driven (effectively hundreds of stages) then the equipment can deliver the cooling at smaller capacities and longer runtimes when under partial load.  This will help keep the equipment lasting longer (less starts and stops), more efficient (less energy being wasted in compressor starts) and is usually less distracting than something that repeatedly cycles as it can disappear into the background noise when it's a constant sound.  Longer runtimes also help dehumidification  performance which is a big part of being comfortable when it's hot.

Good luck!
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Brown Bear Sound
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