Combi Boilers: Three Facts of Life

Hydronic heating is nothing new. In fact, it’s been around since the mid-1800s; only the technological details have changed. Where once you would have had a massive central boiler that served an entire building, or perhaps a connection to a municipal district heating service, nowadays we see small self-contained systems. The advantages of this are greater control, efficiency, and redundancy, in that the failure of one boiler won’t take heat from the entire building.

Accordingly, combi boilers are becoming more and more commonplace, especially in apartment condominium complexes. They’re called combi boilers because they employ a single heat exchanger in a double-duty combination, heating both the domestic hot water supply and the fluid circulated through floors, ceilings or radiators in a hydronic heating system.

Consider the oil in your car: if you never change the oil, the car will continue to run for quite some time, but you’ll create a condition inside the engine that will drastically shorten its operational life, leading to premature and expensive repairs.

If you’ve acquired a property that employs one or more of these boilers, you owe it to yourself to know the three things they require to operate safely and to avoid costly failures: proper ventilation, good water quality, and annual visits for monitoring and inspection.

 

Proper Combustion Airflow

As with all things that burn gas, venting is literally a matter of life and death! Every gas appliance needs to breathe properly. Not only is it vital to have expert installation and strict adherence to building codes, but over time incidental damage or obstruction can interfere with intake and exhaust vents. The best way to determine this is visual inspection coupled with combustion testing.

Just one example of do-it-yourself-ism gone wrong: many such boilers have dual venting schemes (one for concentric venting, and one for separate intake and exhaust). Any time a gas appliance is not getting adequate intake air, it should shut itself down; this is a good thing! However, if one were to remove the plug on the alternate intake, the appliance might resume. This is not a safe operating condition, as it merely defeats a vital safety feature and runs the risk of elevating carbon monoxide levels in your home.

 

Water Quality

With the combi boiler, water quality is a twofold concern. We’re not just talking about the domestic supply, but also the water/glycol mix used for heating the home.

For domestic supply, soft water is a requirement. As we’ve mentioned previously, Calgary’s water supply is exceptionally clean, safe, and high in mineral content. The hardness of the water here makes the inclusion of a water softener a necessity with your combi boiler. You’ll find this stated in your equipment manual, but sadly too many condominium developers have ignored this. If your boiler fails in the first five years due to an excessively hard domestic water supply, you’ll find it’s not covered by the warranty. This is potentially a ten thousand dollar trap for second-hand condominium owners, so buyer beware!

For the hydronic heating, a chemically stable, oxygen depleted mixture with correct pH balance is essential for the prevention of mineral buildup and to prevent corrosion of internal parts. Sure, the heating system could successfully operate with simple tap water, but that would also contain unacceptable levels of chlorine, about 8% dissolved air (including oxygen to corrode internal parts) not to mention mineral content. Over time, as the fluid recirculates, this would lead to the system becoming fouled with calcium deposits and the byproducts of it own internal corrosion. It’s not a pretty picture, and it’s not cheap to fix. This is why we use an inhibited glycol mixture to keep all these factors under control, and this mixture requires regular monitoring.

 

Regular Service

All too often owners of these systems regard them as a simple widget that’s either heating water or not; as long as they have hot water, everything must be OK, right? This “what, me worry?” approach will cost you big time. Just running it until it won’t run anymore is a sure fire method to shorten the life of your expensive equipment.

Like maintaining your car, regular inspection and scheduled maintenance can make the difference between your combi boiler lasting five years versus fifteen to twenty. In the life of a boiler, component failures will occur, but vigilance in the form of annual service means affordable fixes will be far more likely than expensive disasters!

 

Call for a Free Consultation

We have extensive experience installing and maintaining combi boilers. Common brands include Baxi, Navien, Rinnai, Laars and IBC, but they all require the same tender loving care! Call and talk to one of our hydronic heating experts if you have questions about your combi boiler.

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