Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation as HVAC&R or HVACR, or "ventilation" is dropped, as in HACR (as in the designation of HACR-rated circuit breakers).
HVAC is an important part of residential structures such as single family homes, apartment buildings, hotels, and senior living facilities; medium to large industrial and office buildings such as skyscrapers and hospitals; vehicles such as cars, trains, airplanes, ships and submarines; and in marine environments, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fresh air from outdoors.
Ventilating or ventilation (the "V" in HVAC) is the process of exchanging or replacing air in any space to provide high indoor air quality which involves temperature control, oxygen replenishment, and removal of moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and other gases. Ventilation removes unpleasant smells and excessive moisture, introduces outside air, keeps interior building air circulating, and prevents stagnation of the interior air. Methods for ventilating a building are divided into mechanical/forced and natural types.

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  1. N

    Unvented water heater

    Hi, I have an unvented water heater which for some reason every year causes me issues. At the end of 2023 I noticed that the pressure valve gauge was going up when the water tank was switched on. My local plumber came and re-pressured the expansion vessel as it was flat, afterwards we tested...
  2. P

    Dangerous Plaque Heater

    We have a situation on our allotment where we have a large propane tank (free standing) inside a portacabin (not chained) connected to a plaque heater (outdated flexible hose) which is laid on its back (on the carpet) to serve as a burner to boil water for tea and to heat the portacabin. What...
  3. T

    Emersion heater install

    I am fitting a 80 lt back up emersion, flat tank it's back up while I interview the existing gas boiler, mechanically not gas wise. I only have 14 mm pipes up stairs the run to shower is 2m for hot and cold pipes. There is no chance to fit a larger supply pipe. I am aware of press reduction...
  4. W

    Old radiant heater system bleed valves

    Hi, I'm in New Mexico US... I have a fifties boiler with floorboard radiant hydronic heating. The old valves are corroded and not working. I have found a bushing valve combo that has same threading but different profile. Please anyone knows of source for old valve types... Or, can the new...
  5. B

    Santon Unvented Direct PP120E - Help Please

    Hi everyone, I have a Santon Premier Plus PP120E (unvented direct immersion heater) fitted with two thermostats, which provides hot water to taps and shower. The central heating runs from a separate system. On the PP120E: Bottom thermostat is set it to 4 out of 5 (approx. 60C), and connected...
  6. S

    Dual immersion heater question

    I recently posted to request information about supply of a "dual Immersion heater". Two members kindly replied with helpful advice. I tried to respond with thanks but the system persistently refused to accept this; quoting: "Your content can not be submitted. This is likely because your content...
  7. S

    Dual immersion heater with sink/bath switch

    I have read of hot water cylinders being heated with a dual element immersion heater. The main principle being that a shorter element heats the top of the tank and then, subsequently, a longer element comes into play. With a bath/sink switch the longer element may be disabled. The topic of such...
  8. B

    electric shower vs. mains from dual cylinder submersion heater

    Hello, and thank you for reading. My partner and I have just purchased our first property that came with a dual cylinder electric water heater, and an electric shower in the bathroom. As it happens, the shower needs replacement, and we were thinking of removing the electric shower (Mira Sport)...
  9. B

    Part of Immersion Heater Element Fell into Tank

    Struggled with an element that was far too wide to come out of the aperture (how was it ever put in ?) I had to cut one loop. After some brute force the head broke off leaving the broken ends of the element protruding. I wiggled half of it out at which point the other half fell back into the...
  10. H

    Selling my new 30KW 5-start heater with 2 controllers

    Hey guys, I've just installed a reverse cycle ducted heating/cooling in my new built house and took out the heater. The heater hasn't been used nor even commissioned so it new. I thought of putting this post here - if allowed - to see if any of you would need to install a new one? It is in...
  11. D

    Tankless Water Heater in Closet

    'd like to replace this with a tankless water heater. We live in a condo and this currently power vents out to I believe the roof. We are on the 3rd floor of a 4 floor building. Can I replace this with a tankless water heater? Will there be enough combustible air around the unit? Can it...
  12. K

    Looking for answer to water heater sme

    At our wits end. Remodeled a farm house in 2020, installed the water heater and due to appliances being backordered couldn't move in until Nov. of that year. After a hot shower we noticed a terrible smell. We had the lines smoked, venting tested, used a camera on the lines, all from a local...
  13. M

    Water Heater Leaking from back of heater

    Hi we have an Ariston new europrisma 10 UR 3KW heater and it has started to leak from a hole that is covered with tape at the back of the heater. I have tried to find something that explains what this hole is but can't find anything. The heater has been in about 3-4 years and only started...
  14. DJseals

    Immersion heater replacement

    I want to replace my old immersion heater, it currently has a dual immersion with bath/sink switch, we only ever need the whole tank heated so can i replace with a single immersion? or if i am doing it a a DIYer is like for like easier.
  15. J

    Immersion heater noise

    I had a new water heater element fitted a few weeks ago that heats water at night on economy 7. Previous heater elements have been very quiet but I can hear the new one heating the tank at night. It sounds a bit like a boiling kettle. Is this normal? It’s driving me mad!
  16. D

    Unvented water heater advise

    Been to a site today and every sink has a 15l water heater underneath on each of the prv's discharge after the tundish their is only about 200mm of 22mm copper before it enters the sink waste below each sink been like this 10+ years their is no other pipework local to each and most of the...
  17. D

    Ariston Next Evo X SFT multipoint water heater. Temperature issues.

    Hi all:) This is my first post here. My Dad recently had an Ariston Next Evo X SFT 16L multipoint water heater installed to replace the previous one that was leaking. What concerns me is that it basically takes about one and a half minutes for the water to reach even a a basic useful...
  18. W

    Do I need to shutdown water heater if main is shut off?

    I noticed the other day, I had to repair a leaky valve that fed water to the refrigerator and washing machine. I noticed after I turned the main water off, that, after cutting the pipe... a bunch of hot steaming water came out. I didn't expect that to happen. Another Texas winter event is...
  19. J

    Electric water heater - recommendations?

    Hi all, My customer needs a new water heater/boiler - preferably electric. (Getting the gas pipe through to the desired location is a bit of a no-go. It's a tiny stone-walled, screed floored terraced cottage, with no easy route for the gas pipe. So we're looking at electric options). Two people...
  20. F

    Immersion heater coming on too early

    Hi all I’m not a plumber or a DIYer. I need help! My immersion heater has started coming on at about 10.15 pm. I dont know when this started happening but normally it comes on after midnight ( it runs on eco 7). The immersion is wired into a switch on the wall that lights up when the heater is...
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