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Heating, ventilation and air conditioning (HVAC) is the technology of indoor and vehicular environmental comfort. 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 ventilating is dropped as in HACR (such as 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, onboard vessels, 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.
Ventilation includes both the exchange of air to the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality in buildings. Methods for ventilating a building may be divided into mechanical/forced and natural types.

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  1. M

    Hot radiators remain when heating goes off - maybe from hot water storage cylinder ?

    Hot water coming out of the hot water storage cylinder into upstairs radiators after heating/HW turns off and running out of hot water in the mornings. I have a Glow Worm 24HX Condensing boiler on the ground floor with a pump in the same cupboard, a hot water storage cylinder in the airing...
  2. T

    25 years experience gas heating engineer looking for new role London area

    Hi I'm a 57 year old mature gas heating engineer 25 years experience looking for a good solid position in London. Have all ACS quals, unvented and analyser. Previously held OFTEC, part P and LPG. Also have F-gas and BS4872 welding. Ex-forces so have insane work ethic. If anyone has anything...
  3. L

    Heating vs hot water...can this happen?!

    Hi there, we have bought a new house and been in for 8 months. We have a Hollywell heating system with 2 thermostats, one for the downstairs and one for the upstairs, in the master bedroom. The back of the house was connected up wrongly, so the back house downstairs came on with the upstairs...
  4. S

    Getting a Remote Control RFWRT thermostat talking to a Worcester Boiler 28i

    Getting a Remote Control RFWRT thermostat talking to a Worcester Boiler 28i, changed the batteries, no heating, hot water working ?
  5. Christopher buzzard

    Uponor underfloor heating valve.

    Can some please identify the valve on this underfloor manifold ( with the black wire coming out of the top). Have an issue where the system is turning off every 10-20 minutes and staying off for a while then coming back on again. The room can’t get up to temperature because of this. Power was...
  6. D

    Boiler and Heating isssues

    Good Morning, I was wondering if anyone can help. About 4 months ago I have had a new Worcester Greenstar fitted in my home with new radiators apart from one 2 ina 4 bedroom house. The old system was a water tank. Since we have had it installed we have noticed around a month after...
  7. C

    Heating / hot water glitch ?

    Good day . The heating and hot water on my vaillant boiler work fine independently . If my heating is on and a hot water tap is opened or shower used - the heating [ if on ] refuses to come back on and if left will stay off . If I hit the reset button the boiler will fire and the heating comes...
  8. C

    Heating won't come back on after using hot water tap / shower

    Good evening . I have a Vaillant boiler that although the heating and hot water work perfectly independently the heating if in use will not come back on after using a hot tap or shower . If I press the reset button the heating will come back on but will not do so on it's own accord . Any advice...
  9. S

    Why is my radiator making clicking noises when the heating is on?

    I hope someone can help. I have had an issue with the radiator in my room for months. Every time the heating is switched on, the radiator makes an awful clicking noise. It's so irritating that I can't sleep. I've tried bleeding the radiator several times and this hasn't solved the issue. What do...
  10. S

    Boiler fires up when heating off

    Hello. Wouldn’t if someone could help. I have a boiler Downstairs in utility with a separate hot water cylinder upstairs in en-suite. hot water is turned off at the controller, central heating is on at controller but thermostat is below room temperature. boiler is still firing up and running...
  11. jontyking

    Polypipe underfloor heating not working

    Complete amateur here. I had a Polypipe underfloor heating system put into a new extension 3yrs ago but the plumber who fit it is now no longer available - he's just had a career change, he didn't go out of business. It's just a single zone system connected to my main central heating system but...
  12. P

    One Radiator not heating

    HI. I have one radiator in the house of 8 not heating. I have removed twice and flush through replacing the TRV value also. After refitting both times the radiator gets hot but after two days it stops getting warm. I;ve checked and theres no air and the pipework is all copper with no changes to...
  13. CorgiDirect

    Anton make the job of a heating engineer easier

    Innovative Market Leading Products. Anton make the job of a heating engineer easier. Top Quality, Professional Products all available from CORGI direct View: VIEW HERE
  14. Roger of Weston

    Boiler connection 22mm

    I have a 40CDi combi boiler in a 1920s house. The heating does not get hot just warm. I have 22mm from the boiler to under the floor but then connects to original half inch/15mm copper lagged with hessian. I believe I am losing heat as some of the runs are quite long. A local plumber said I need...
  15. R

    Improving pressure in direct heating installation

    My flat suffers from poor mains pressure and we have a direct heat setup with combi boiler. The boiler is rated up to 3Bar, so I was thinking of installing a cold water tank to feed a twin pump supply cold and into the boiler for hot (both 15mm). My questions are Is this a feasible setup Can I...
  16. D

    Banging pipes and trouble heating water

    Hi everyone, really hoping someone can help me as I’m a complete novice. I moved into a house over a year ago. The house has an open fire, and oil heating. however if we have the fire lit or oil heating on it has never heated the water. Every day we would need to switch on the electrical...
  17. plumb_know

    Valliant Eco tec combi HE - heating issue

    Hi everyone, I have an issue with Valliant eco tec combi, tenant complaining heating is coming on sometimes when programable wired room stats (danfoss) are up to temperature. Typically when i attend it is always working fine so intermittent fault. I replaced both room stats for first measure...
  18. S

    URGENT no hot water of heating

    I have no hot water or heating, my boiler has no error symbols, my cylinder has gone cold, pump seems to be working well it’s making the same usual noise/vibrations, pipe under th boiler are hot but none near the cylinder is! Can anyone help
  19. kenjiru

    Underfloor heating not working correctly

    I've bought an old house and converted it from radiator heating to underfloor heating. I've reused the old gas boiler Vaillant ecoCOMPACT VSC 206/4-5 90 that had an multiMATIC 700 module already installed. Heating work fine for the first floor, but it does not work correctly for the upper...
  20. siricosm

    How to reduce corrosion in vented heating systems

    Some vented heating systems seem to sludge up, and yet other remain remain remarkably clean after many years service. Why? Corrosion is caused by oxygen. Eliminating leaks and inhibitor helps, but the F&E tank is open to the air, so oxygen can freely get in there. Is it possible to design a...