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Thread: Design principles for a comfortable HVAC system

  1. #1
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    Design principles for a comfortable HVAC system

    Hi!

    I had a long discussion with my friend, and I created a long list of dos and don'ts but since I consider myself a greenhorn in the HVAC matter I would like you to take a look and tell me - is it a good approach?


    1) H - Heating - We consider the installation individually for each room. Precise floor heating or a convection heater on a partition wall.

    - A heated floor (not to be confused with underfloor heating!!) requires adequate thermal insulation, the recommended minimum is 20 cm of insulation from the ground.

    -In case of poorer insulation, it is better to avoid stone floors in favor of "warmer" panels or parquet and install the convection heater on the partition wall.

    Automation for cables, mats, or radiators is so precise that there is no danger of oversizing, so you can install heating from 50 to 100W/m2. In bathrooms, it is recommended to use 160 and more W/m2, controlled by a time-programmable thermostat. In bathrooms, high-powered heaters with downward-flowing hot air are sensational. They can raise the temperature in a few seconds for the duration of the bath.

    2) V - ventilation. Mechanical ventilation with heat recovery is selected according to the number of people. Regular household members times 30m3/h. The central unit is selected 3 times larger than the calculated flow.

    In the case of a bigger cubature of the house and the same number of people, the stream may be a bit smaller. A bigger house means more leaks and a bigger share of diffusion in the limitation of H2O and CO2 growth.

    We place the vents in the rooms. We direct the largest flow to the bedrooms, there will be often closed doors. The location of the diffuser on the ceiling is of no importance as far as ventilation is concerned, it is only aesthetic.

    The air should be exhausted through the bathrooms and kitchen. Since there is usually no door between the supply in the living room and the exhaust in the kitchen, the exhaust should be MINIMUM !!! 2 times smaller than in the bathroom or toilet.

    If you oversize the air handling unit, it must be regulated from 10%.

    Since adding channels above the optimum will not increase the ventilation flow, I give the maximum distributors for the air handling units with different outputs

    -fi 125 not more than 6x75

    -fi 160 not more than 8x75

    -fi 200/300m3/h 10x75

    -fi 200/400m3/h 12x75

    Larger air handling units do not make sense in houses. In such cases, it is better to do zone ventilation on several units.

    3) AC - Air condition A reversible heat pump is responsible for the air quality, except for ventilation. It maintains a comfortable air temperature all year round and comfortable humidity in summer (during the heating period this role is fulfilled by ventilation).

    The power of the reversible heat pump is calculated by multiplying m2 x 40W. Since the devices have their own series of types, it is often necessary to choose a slightly larger or smaller RPC. In the case of old uninsulated houses, it is possible to choose devices up to 50W/m2, in the case of new houses up to 30W/m2.

    A split wall unit will do the job if you don't close the doors in the rooms. For houses, the ducted version works best. Very good results are given by the Multi system (one outdoor unit and several indoor units) in the configuration of a duct for bedrooms, split for the living room, or two ducts.

    The manifold is selected in the same way as for ventilation, the surface area of the RPC outlet divided by the number of inlet points and rounded up, e.g. 600cm2 outlet for 4 points - is a duct fi 160, for 5 points it may be 125mm.

    Ducts should be insulated, reinforced, and antibacterial. In the room, the termination point is a nozzle or a flat anemostat.

    RPC is 100% recirculation, so as with the supply, take care to minimize the return flow attenuation. It is also good to avoid air vents in kitchens and bathrooms. There the warm air will come in through the exhaust ventilation.

    Notes on operation - ventilation and heat pump should not be turned off even if you are away from home for more than a weekend.

  2. #2
    Join Date
    May 2009
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    Quote Originally Posted by Jamesss View Post
    Hi!

    I had a long discussion with my friend, and I created a long list of dos and don'ts but since I consider myself a greenhorn in the HVAC matter I would like you to take a look and tell me - is it a good approach?


    1) H - Heating - We consider the installation individually for each room. Precise floor heating or a convection heater on a partition wall.

    - A heated floor (not to be confused with underfloor heating!!) requires adequate thermal insulation, the recommended minimum is 20 cm of insulation from the ground.

    -In case of poorer insulation, it is better to avoid stone floors in favor of "warmer" panels or parquet and install the convection heater on the partition wall.

    Automation for cables, mats, or radiators is so precise that there is no danger of oversizing, so you can install heating from 50 to 100W/m2. In bathrooms, it is recommended to use 160 and more W/m2, controlled by a time-programmable thermostat. In bathrooms, high-powered heaters with downward-flowing hot air are sensational. They can raise the temperature in a few seconds for the duration of the bath.

    2) V - ventilation. Mechanical ventilation with heat recovery is selected according to the number of people. Regular household members times 30m3/h. The central unit is selected 3 times larger than the calculated flow.

    In the case of a bigger cubature of the house and the same number of people, the stream may be a bit smaller. A bigger house means more leaks and a bigger share of diffusion in the limitation of H2O and CO2 growth.

    We place the vents in the rooms. We direct the largest flow to the bedrooms, there will be often closed doors. The location of the diffuser on the ceiling is of no importance as far as ventilation is concerned, it is only aesthetic.

    The air should be exhausted through the bathrooms and kitchen. Since there is usually no door between the supply in the living room and the exhaust in the kitchen, the exhaust should be MINIMUM !!! 2 times smaller than in the bathroom or toilet.

    If you oversize the air handling unit, it must be regulated from 10%.

    Since adding channels above the optimum will not increase the ventilation flow, I give the maximum distributors for the air handling units with different outputs

    -fi 125 not more than 6x75

    -fi 160 not more than 8x75

    -fi 200/300m3/h 10x75

    -fi 200/400m3/h 12x75

    Larger air handling units do not make sense in houses. In such cases, it is better to do zone ventilation on several units.

    3) AC - Air condition A reversible heat pump is responsible for the air quality, except for ventilation. It maintains a comfortable air temperature all year round and comfortable humidity in summer (during the heating period this role is fulfilled by ventilation).

    The power of the reversible heat pump is calculated by multiplying m2 x 40W. Since the devices have their own series of types, it is often necessary to choose a slightly larger or smaller RPC. In the case of old uninsulated houses, it is possible to choose devices up to 50W/m2, in the case of new houses up to 30W/m2.

    A split wall unit will do the job if you don't close the doors in the rooms. For houses, the ducted version works best. Very good results are given by the Multi system (one outdoor unit and several indoor units) in the configuration of a duct for bedrooms, split for the living room, or two ducts.

    The manifold is selected in the same way as for ventilation, the surface area of the RPC outlet divided by the number of inlet points and rounded up, e.g. 600cm2 outlet for 4 points - is a duct fi 160, for 5 points it may be 125mm.

    Ducts should be insulated, reinforced, and antibacterial. In the room, the termination point is a nozzle or a flat anemostat.

    RPC is 100% recirculation, so as with the supply, take care to minimize the return flow attenuation. It is also good to avoid air vents in kitchens and bathrooms. There the warm air will come in through the exhaust ventilation.

    Notes on operation - ventilation and heat pump should not be turned off even if you are away from home for more than a weekend.


    I see nobody has taken the time to answer your post.... So here goes.

    It's great that you're interested in the trade. Welcome.

    Do you have a good approach here? Sorry. No.

    Unfortunately, it's a bit more complicated.

    Advice....... Look for a good school with a good HVAC program, then get yourself enrolled.
    Often times, your local Jr College has a HVAC program that might start you off. Be careful of the "for profit" schools.

    The process you are asking about is generally the following.......

    An owner wants a new building.
    Someone performs a load calculation, then does equipment selection.
    The building is constructed. The building is commissioned.
    The owner occupies the building.

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