HVAC HEATING LOAD CALCULATIONS

We have seen the basic concept of HVAC in our previous post "Heating ventilating and air conditioning (HVAC)" and we have also discussed the cooling load calculations by considering one example in my previous post "HVAC cooling load calculations".

Now it’s time to start our discussion over heating load calculations, let us understand how we should go for calculating the heating load for designing the correct HVAC system. 

Let us consider how we will calculate the cooling load calculation for HVAC system .Before starting the calculation of Cooling load , I will suggest to look previous post "Heating ventilating and air conditioning (HVAC)" for better understanding the concept of cooling load calculations. 

Heating Load Calculations

Calculation of heating load means heat losses through a various components of building as mentioned below in figure.

1. Walls
2. Roofs
3. Windows
4. Doors
5. Exposed floors
6. Basement walls
7. Basement floors
8. Duct loss
9. Infiltration
10. Ventilation

Now we will find equations to calculate the heat losses as mentioned below in table.

Sr. NO.	Heating Load sources	Calculating equation
1	Ceiling, Roofs, glass & walls	q= UA Δ t
2	Walls below grade	q= UA Δ t
3	Above grade floors
4	Infiltration & ventilation air
	Sensible	q s= 0.018 Q Δ t
	Latent	q t= 80.7 Q ΔW

Let us consider area of each room (Ft2)

                             

Description	Living room	Master bed room With attached bath room and closet	Bed room I	Bed room II	Kitchen	Total
West Wall	91	152				243
Partition	192	0				192
Roof	480	458	156	156	240	1490
West door	21	0				21
East wall		0	88	88	135	311
South wall		192	0	80		272
West glass	35	24				59
East glass					14	14
Shaded glass	13	13	13	13	11	63
Total area	834	839	257	337	389	389

Remarks- Let street b/w master bedroom and simple bed room is 5ft wide

We have counted bedroom master and bedroom I and II , kitchen individual so now calculation that we  have done earlier will be changed in excel file.

Let us consider about the guidelines in order to calculate the heating load

1. First we should select /chose weather conditions of outdoor design for example wind   speed, temperature and directions.
2. Selection of indoor-air temperature that should be maintained in each location
3. Temperature of attached garage & unheated-spaces might be calculated with the help of outdoor ambient temperature.
4. Selection of coefficients of heat transfer for inside walls, outside walls, glass, non basement floors, and ceilings.
5. Calculation of net applicable area of floors, walls, windows & ceilings
6. Calculation of heat losses due to transmission for roofs, walls, glass, ceiling
7. We can calculate heat losses with the help of equations of heat losses.
8.  Determination of heat losses from basement
9. Determination of associated energy with cold air across the window, outside doors, building construction materials
10. Total heating load will be the summation of energy associated with infiltration of cold air and transmission heat losses for roofs, walls, glass, and ceiling.

Heating Load Calculations

This blog is basically based on the process for calculating the Heating load calculations for HVAC system.

Image courtesy : Google

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