Gas Boiler

Below is illustration of a typical high efficiency boiler system.

  • Expansion tank is to provide extra room for water expansion when water temperature increases.

  • Circulation pump is to push water through water pipe.

  • Two venting pipe is to provide sealed combustion. It takes fresh air in and push fume out


The most important things to be considered:

1. Modulating burner

  • The heat we need is not constant. We need more heat in cold days and less heat in mild days. 

  • Modulating burner can produce heat incrementally to best match weather condition

  • We size the heating capacity of boiler based on the coldest weather condition. In mild days, non-modulating burner wll have short on-off cycle which decreases efficiency and shortens life span of boiler.


2. Efficiency

  • The higher, the better.

  • Choose 90% up. It's called condensing boiler or high efficiency boiler which can be vented by PVC pipe.

  • High efficiency boiler provides sealed combustion. It's cleaner and safer


3.  The material of burner

  • Typically there are 3 type of material for burner: Stainless Steel, Cast Aluminum, Cast Iron

  •  Stainless Steel Burner and Cast Aluminum Burner are common in high efficiency boiler . They are light weight and endure acid from condensing

  • Cast Iron Burner is mostly for mid-efficiency boiler 


Factors related installation:

1. Venting

  • High efficiency boiler will be vented by two PVC pipe through side wall. One pipe is for fresh air intake and another pipe is for exhaust.

  • Vent terminal on outside wall has to be 3 feet away from gas meter and 12" away from any opening


2. Draining of condensation water

  • High efficiency boiler will make condensation water while in use.

  • Condensation water comes out from bottom of boiler. It can run to floor drain easily. Or if there is no floor drain around, a condensation pumpshould be installed.

  • Condensation water can't be pumped to outside of house directly.


The further factors to be considered:

1. Insulation

  • Regardless how efficient the boiler system is, the house insulation still plays big role in terms of energy consumption

  • If you can't upgrade the insulation of whole house, the best bang for the buck is to upgrade insulation in attic.