Talk:HVAC

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[edit] To-Do Lists for HVAC Article

[edit] Main To-Do List

If you have a suggestion of how someone with expert knowledge of HVAC systems could improve this article, put it here. This section is not the place for questions or comments, please put them in one of the other sections on this page, or make your own section. When an item on this list is completed, please move it to the "Completed To-Do Items List," if you think people could benefit from seeing it on the talk page, or just delete it completely.

[edit] 1. Broken Links in "Major Terms" Section

There where several terms in the "Major Terms" section that where not defined in the HVAC article, and that I could not find an article for elsewhere.

List of terms:

  1. once-through
  2. low-flow
  3. primary-secondary

I cannot create these articles because I do not what these terms mean.

Please either create articles for these terms, or define them within the HVAC article itself, and remove the links I created (instead of using links, just make the terms bold: once-through instead of once-through).

When you have completed this task, please remove this from the To-Do list.
Unit ventilator is another term we should define.
Atlant 19:34, 6 November 2006 (UTC)

Thank-you!

--VegKilla 18:49, 6 November 2006 (UTC)

[edit] All air and Air water

These terms are used a couple of times in the article but there is no explanation of what they mean and the differences between them. Could sombody please put this in.

thanks

[edit] Completed To-Do Items List

Move items here from the "Main To-Do List" when they are complete (or just delete them). Feel free to delete items from this list if it is no longer helpful to know that they have been completed.

[edit] Questions

Simple question:

[edit] Why does the air dry out in a heated house in the winter?

A dehumidifier is often run in cold climates in winter to reduce the humidity in the house. This is done to keep water from condensing on the interior of the windows, which would happen if you had warm, moist air on the inside, and a very cold window pain. Hope that helps. Mr Minchin 14:48, 14 June 2006 (UTC)

I think you mean a humidifier here. Most homes are too dry already in the wintertime, so running a dehumidifier would exacerbate the problem (which would cause higher heating bills, damaged woodwork, and excess static electricity in the home). Usually, the only people who use a wintertime dehumidifier are those who have an indoor pool, spa, leaky basement, or some other source of steam/water. Jeremy RBC 16:47, 30 August 2006 (UTC)
It is fairly simple. When it is cold outside, that air is typically quite dry, for example, at freezing, Relative Humidity could be as low as 10-15% or less. This is the only source of fresh air for your house during the heating season (or any season for that matter!). As dry outdoor air enters your house, it mixes with the 'indoor air' and reduces the overall relative humidity. A further reason your house will dry out is that your heating source will also 'dry' the air. Combine these factors, over a long winter, and you can appreciate how the air dries out. To maintain a constant temperature / humidity in a typically home would require a year round cooling source, a heating source, a humidification method and a de-humidification method. TIP: If you have a rare warm humid day during the winter you might want to consider opening enough doors and windows to bring in any available outdoor air humidity - this can replace moisture long gone in the structure and materials in your home. I suggest: ASHRAE, the self-directed professional organization, at ASHRAE.ORG as an excellent resource. —The preceding unsigned comment was added by 74.112.72.218 (talk • contribs) .

uh-oh. It goes like this: many houses are leaky although "you" can't feel the leaks. Place your hand over an electrical outlet during a winter wind storm and you'll notice the outsid eair coming through the walls. These houses have often felt to be "Dry" in winter. Many new houses are much more airtight but still not airtight. Kitchen and bathroom vents, windows, doors, all let air in. These houses are often felt to be too humid in winter. In both cases, humidity can build up in the attic -- since water vapor is lighter than air. - Plus, many people want to reduce Relative Humidity to belwo the optimal growing conditions for Dust Mites. (ie. below 60% at 72F, 20C). Dehumidifying in winter is common. People used to humidify in winter more than they do now.

[edit] If the moisture is being removed from the air, how does it happen and where is the water going?

If you're talking about a dehumidifier, it goes into what amounts to a bucket in the bottom of the machine. This has to be emptied from time to time. I imagine "plumbed in" ones where the water goes straight down the drain are available, and presumably this is the case with air-conditioning.

No, I don't mean with a dehumidifier. I mean that the house gets drier in the winter time merely by being heated.
this is a complex subject that I have been trying to understand over the past few months, so this may not the best answer, but better than none, I hope. Winter outside air is colder, this colder air has (an average) lesser amount of water vapor in it, over time heating an inside space that has leaks (doos/windows etc) will gradually reduce the average moisture inside the house, I'll write more soon, got to eat now, Teeteetee 18:52, 31 January 2006 (UTC)
To build on that thought, furnaces often use outdoor air for combustion and remove indoor air along with exhaust, creating a cycle where moist air is continuously replaced with dry. Add to that the fact that most homes don't have sealed ductwork and that heated air rises (often finding places to escape in the attic and ceiling), and you end up with a home that is drier than most deserts! Jeremy RBC 16:47, 30 August 2006 (UTC)

Cold air being warmed up will always feel dry when warm. Its RH is low. Its drying capacity is high. Even if no humidity is removed by any de-humidifier, it will feel dry and it will be rrelatively speaking fairly dry comapred to what one is used to.

[edit] Is it the case (as it seems to me) that steam radiators make for a drier house?

Can't see why steam radiators as opposed to water ones would make any difference. Radiators might be drier than air if the air being blown round were damp.

[edit] Relative Humidity

Air expands when heated, thereby increasing its ability to retain moisture. When it is cool outside, the warm air will tend to flow out of the house through structural leaks or an open door/window, carrying with it the humidity that was accumulated. BustlinSlug 23:33, 13 October 2005 (UTC)

Expanding on what BustlinSlug said, houses are not airtight and are constantly exchanging air with the outside. The cold outside air is carrying relatively little water vapor (as most of the vapor has condensed out or frozen out), so when that relatively dry air leaks/exchanges into the house and is heated, it is still carrying the same very small amount of water vapor, but is now (say) 60-70 degrees F hotter, so in terms of Relative humidity, it is now really, really dry.
Expanding on points made by others, you're then limited in how much you can humidify the air because wherever the humidified inside air reaches a cold surface (below the dew point of the humidified inside air), water vapor condenses out to form moisture. This can happen at windows, air leak points, and, much more insidiously, inside the thermal insulation inside your walls, possibly wetting your insulation (and thereby reducing its effectiveness) or even rotting the outer sheathing of your house.
Atlant 15:44, 14 June 2006 (UTC)
OK. I figured it out part of it. The relative humidity changes as cold air is heated. Warmer air can hold more water, so the relative humidity drops. So that leads to the next question. Why do we use relative humidity. Is it because our bodies feel relative humidity not specific humidity
http://www.talk-hvac.com/forums
CORRECT
Refer to a psychrometric chart:
The relative humidity of a sample of air falls as its temperature increases. The air then "feels" drier because it has the capacity to absorb more moisture. The water originally in the sample of air doesn't go away.
It is called "relative" humidity because it refers to the percentage of total water capacity of the air at that temperature. i.e. 30% R.H. air can absorb a lot more water while 100% R.H. Air is saturated.
The reason cold glass condenses drops of water is that the air that comes in contact with it is chilled to a lower temperature. When it reaches a temperature at which the air is 100% R.H., drops form.
Absolute humidity is a valid measurement. It is simply weight of water per weight of air. It's useful information when you're calculating how much liquid will be removed in a dehumidification process.
I think the above link needs to be updated; it currently goes to a GoDaddy parking page. Is it supposed to be http://www.hvac-talk.com/vbb/ instead? Jeremy RBC 16:47, 30 August 2006 (UTC)

[edit] More Questions

[edit] What HVAC software is that?

Could anyone enlighten me as to which software belongs this screenshot? The one in the caption...

Sorry if it's off topic, I'm just curious. --Clapaucius* 22:50, 26 August 2005 (UTC)

I was in an HVAC Course at N.A.I.T and we used a program like that it was called SIMUTECH it simulates things that could go wrong and what will go wrong if certain things happen to your system. It is a good training program.

[edit] Another simple question

Is it possible to keep a very large room (L100m x W60m x H4m) comfortable for humans without removing water vapor from the air, when the very large room is in a country that has a temperate climate such as the UK or Northern Europe ? Teeteetee 19:58, 31 January 2006 (UTC)

Well in the country you will get probably more moist air and you would probably have a higher humidity. So a Room L100m x W60m x H4m you should be able to keep comfortable very easy. You would just need a humidifyer for the winter time and a De-Humidifyer for the summer. you would also need probable in batween 20-30 diffusers for your system in this room but you can defenatly keep it comfertable

Umm... surely "a De-Humidifyer for the summer" is removing water ?? Teeteetee 04:12, 3 July 2006 (UTC)
Short Answer: No. You always need to exhaust what people breath out. That means the vapour is going out of the room. Sure, you could design a system to recover exhaust water vapour and return it to the supply air to the room, or add Humidification. —The preceding unsigned comment was added by 74.112.72.218 (talk • contribs) .

it is such a big room, the use is going to be for a bunch of people, from time to time, This is no residential application. Need a full-blown system, to handle air, to manage air, including heat and humidity/

[edit] Incorrect equation in Natural Ventilation section

The equation in the Natural Ventilation section was incorrect and I have now corrected it. It is disappointing, to say the least, that such a major error had occurred. We must learn to check and double-check equations before publishing them. - mbeychok 01:57, 13 April 2006 (UTC)

[edit] Removal of the image at beginning of this article

I have removed the image because it had absolutely no relevance to the subject matter in this article and, to the best of my knowledge, it isn't even referred to in the article. How does something like this happen and why had it not been picked up by some administrator by now??- mbeychok 05:52, 13 April 2006 (UTC)

The admins are too busy giving Wiki timeouts to middle-school kids who add erudite social commentary to articles. Seriously, this sort of thing is strictly up to us, the editors. If you see something that needs work, be bold and fix it!
Atlant 16:23, 29 June 2006 (UTC)

[edit] Removal of thermostat images

I am removing the two photo images of a Honeywell thermostat because they have very little connection to the context of this article. I think that they could perhaps be better used in Thermostat article. - mbeychok 16:05, 29 June 2006 (UTC)

I wondered the same thing. But you might have wanted to keep one image (the closed thermostat) because that round Honeywell thermostat is pretty much iconic of domestic HVAC, at least here in America.
Atlant 16:24, 29 June 2006 (UTC)
Atlant, if you can remember building a crystal radio set (on your user page), then you must be almost as old as I am. I still believe that the two photos served no useful purpose in HVAC, especially when there is an existing Thermostat article that might better use them. By the way, I live in California and our thermostat is rectangular .. so much for icons. :) - mbeychok 17:08, 29 June 2006 (UTC)
Atlant, if you can remember building a crystal radio set (on your user page), then you must be almost as old as I am.
Gee, thanks for reminding me! ;-) Does this fall under the proscriptions of WP:NPA? :-)
Obviously, I don't feel strongly about this thermostate image question or I would have edited one or the other back in. But in the interest of jazzing-up the page, we ought to come up with some image to put on the page. An air-handler, furnace, or photo of a big rooftop chiller would be an obvious choice.
Atlant 18:05, 29 June 2006 (UTC)

[edit] Re edits by User:Sandstein on August 10, 2006

First of all, I wholeheartedly agree with you that HVAC has too much "how to" information

As for the photo image you added, would you mind if I altered it with two small labels: one label reading "Central vent duct" and one label reading "Typical outlet", both with arrows pointing to the respective items? Please let me know. - mbeychok 05:27, 11 August 2006 (UTC)

I have no objection, and the photo licence allows such alteration. Although wouldn't it be easier just to describe this in the caption rather than to have to edit and re-upload the image? Sandstein 05:35, 11 August 2006 (UTC)
I really think labeling is simpler and requires much less verbiage ... so I will go ahead with it. Thanks for your cooperation. - mbeychok 06:41, 11 August 2006 (UTC)
Nice picture -- Thanks! I've now "stolen" it over to the recently-created Duct (HVAC) article where it fits very nicely.
Atlant 12:37, 11 August 2006 (UTC)

[edit] Recommend Exchange Section

Most new houses and buildings are very air tight, and the installation and use of air exchange systems for improving ventiliation while maintaining thermal efficiency has been on the rise since the mid-80s. Mugaliens

Yes, please be bold and add some references, noting that Wiki already has articles on heat recovery ventilation, superinsulation, and zero energy buildings.
Atlant 12:48, 14 August 2006 (UTC)

[edit] Transwiki

This is in reply to the following request on my talk page:

On August 10th, you posted "how-to" tags in two sections of they HVAC article, suggesting that the might qualify for moving to Wiki Books. I would like to implement that but I don't know how to do so. How about explaining how that is done (in step-by-step detail) on the Talk:HVAC page? - mbeychok 23:39, 12 October 2006 (UTC)

I'm not a Wikibooks user myself, so I can't provide a more detailed guide than what follows:

I hope this helps. Sandstein 05:12, 13 October 2006 (UTC)

As proposed by Sandstein on August 10th, I have transferred the two sections on residential ventilation to Wikibooks and included a prominent link to the pertinent Wikibook section. Accordingly, I also deleted the two {{how to}} links added by Sandstein. - mbeychok 02:43, 14 October 2006 (UTC)

[edit] Comfort

I think there should be a section added to the article on comfort. It comes up a couple of times in the ventilation section, but HVAC does not exist solely to keep people from freezing to death or dying of heat exhaustion. Comfort is a significant goal of all HVAC systems, and pretty much every non-budget system that is sold in the U.S. is bought as much for the comfort benefits as it is for the efficiency gains. Take a look at any equipment manufacturer's website; other than on the lowest-end systems, the features they discuss are always focused on comfort aspects, and often to a greater extent than health benefits. Not that wikipedia should focus on comfort because it is part of the marketing discussion, but this reflects what consumers are interested in.

Also, there's a big technical difference between entry-level systems and the higher-efficiency, comfort-driven systems. The latter systems are the ones that push technology development (R410a refrigerant, multiple- and variable-speed operation, advanced filtering/ventilation/IAQ, zoning, processor-driven thermostats, fuel cell, geothermal, etc). In fact, now that I look over it, it seems like the article could stand some overall reorganization. I know that this is a work-in-progress, and a large section was just moved over to wikibooks, but we should discuss this.

There is quite a bit of crossover between the different areas of HVAC (some examples: centralized heaters/coolers share the same air mover; ventilation works in tandem with the heater/cooler air filtration system; heat pumps suppliment heaters/coolers; efficiency rules are different between systems, but environmental impact is related to all). Perhaps it would be clearer if we broke this up into a history section, a energy use & ecological impact section, an air quality section, a new technology section, information about government and independent trade groups (ASHRAE, ACCA, ARI, RSES, HRAI, GAMA, NATE, EERE), and brief sections that cover (a list, perhaps?) of specific heating/cooling/ventilation technologies. Oh, and another thing...in trades, HVAC is increasingly looked at as HVAC/R, to include refrigeration in the discussion. After all, refrigeration is about air movement and climate control, so there is (again) overlap with the other HVAC disciplines.

I would just be bold and get crackin on this, but I don't want anyone to think I'm vandalizing, so let's discuss.

Jeremy RBC 14:38, 20 October 2006 (UTC)

Jeremy, I agree with your proposed revisions and expansion with a few qualifications. One, please avoid adding any 'how to' material for homeowners or other building owners. Two, I disagree with changing the article title and content from HVAC to HVAC/R because Wikipedia already has a good many articles on refrigeration and I don't believe we need any more.
I see from your user page that you are quite new to Wikipedia. Whenever you revise/expand an article extensively, it is best to have first created a personal sandbox page, copy and paste the existing article's Edit page to your sandbox, and do all your work on it until you are satisfied with it ... which may take a number of hours or even days. Then go the existing article, delete the all of the Edit page, and copy and paste your revised page from your sandbox into the article's Edit page. Regards, - mbeychok 16:45, 20 October 2006 (UTC)

[edit] Chilled water reversed return pipe line

please explain what is the main purpose and advantages of reversed return pipe in chilled water systems.and also please the chilled water expansion tank and how to design the tank.thanking you —The preceding unsigned comment was added by 217.17.254.129 (talk • contribs) .

With all due respect, if you are asking this question on Wikipedia, you are probably not qualified to design this system. But, for your future reference, a Reverse Return Piping System is designed so that the distance that water has to flow is equal in each and every engine (ie. Chiller or Boiler) in a Plant. That is my definition. You can draw your own conclusions on advantages. Expansion Tanks are sized according to the System pressures and volumes. You order them from the Manufacturer according to your specification. Please put your pencil down and step away from the drafting table. —The preceding unsigned comment was added by 74.112.72.218 (talk • contribs) .

[edit] Cleanup underway

FYI -- I'm sorting, etc. the article to make it flow better. Also will be moving the detailed ventilation stuff to the ventilation and natural ventilation pages. FactsAndFigures 15:05, 28 October 2006 (UTC) (An ASHRAE guy)

Cleanup continuing. More photos would be nice additions 129.237.114.171 20:48, 7 November 2006 (UTC)

[edit] Don't Add 'Spam' Links

I know it is tempting, but don't add 'spam' links to Web sites. FactsAndFigures 12:31, 18 January 2007 (UTC)

[edit] Delete External Links Section?

Looks like there are repeated problems with commercial links being added. Deleting the entire external links section (without embedding links elsewhere in the article) unfortunately would likely be the most effective method of reducing the added spam. What do you think? FactsAndFigures 12:31, 18 January 2007 (UTC)

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