Got multiple condensing boilers? Watch out. Here’s what the manufacturers WON’T tell you.
When I bought my first car, I was 16. It was a 1970 Morris Marina 1100 and I fell in love with it. That car would get me to and from school and work. Maybe even help me get dates. A really great investment with lots of promises made to me by the dealer.
One of these promises was remarkable gas mileage. Thirty-six miles to the gallon, it said on the manufacturer's sticker. Worth every penny. Dad told me to have the car checked out by a mechanic to see how it REALLY performed off the lot. Much like many of the things Dad told me, I didn’t listen. I was too excited. I had what I needed, and I was on my way. Six months later I was kicking myself for paying a premium for high efficiency without testing under real operating conditions.
The sticker didn’t point out that gas mileage plummets when five people are in the car vs. one. No one mentioned exactly how much performance suffers when towing items such as a boat. When a new job required me to add heavy traffic into my daily routine, I sure as hell wasn't getting 36 miles to the gallon!
Today I've decided that buying cars is a lot like buying condensing boilers. You’re promised all these bells and whistles by the manufacturer, but as soon as you need to add multiple boilers, they may no longer be certified for “high efficiency,” and that premium you paid was a joke. Will the manufacturer ever tell you that? [That’s a big, fat ‘No.’]
Before investing in a high-efficiency condensing boiler, put the manufacturer’s efficiency rating to the test – not just for one or two boilers, but under realistic conditions where multiple boilers are venting to a common chimney. Exactly what efficiency can you expect then? It's certainly worth testing.
ANSI 21.13: Putting the Squeeze on Category IV Boilers
The CSA Group has testing and installation guidelines in place for Category IV condensing boilers (ANSI Z21.13). You probably know this already. But I bet you didn’t know that the manufacturers can dictate how those boilers are tested, whether as a single boiler or in multiples (up to the max. number suggested).
When you build the boiler, you need to get it certified. Ideally you want at least 95% to get LEED Certification and qualify for incentives. Anyone could technically claim 99% efficiency, but says who – the manufacturer? Certified for WHAT – single or multiple boilers (and how many)? No one will ever tell you voluntarily that your 99% efficiency may become 88% when the rubber hits the road, so to speak.
Here’s my best advice…
Make sure a third party test agency has tested and certified your boiler for a multiple-boiler application up front. Verify that it will actually meet testing and installation standards both now and later.
It’s no secret that adding boilers has a negative impact on efficiency. Eventually everyone will hit a wall. In our experience, this may happen when you go above two condensing boilers. A mechanical draft system is the answer and will often be recommended by the third-party test agency.
Of course no boiler manufacturer will admit that their product doesn’t live up to the single-boiler efficiency under multiple boiler conditions, nor will they say you’ll need a mechanical draft system to get you there. Because right now they may be able to get away with it. THEY dictate for what operation conditions the boilers are certified, and they may not want to extend the testing to a number of multiple-boiler scenarios because it’s expensive! I can hear Dad now… “The onus is on YOU to ask for verification.”
The CSA will not issue a blank check on multiple boiler efficiency without testing. So you should ALWAYS test the suggested maximum number of Category IV boilers you expect to have in a single system. The test lab will test at that threshold so that you won’t have to downgrade the boiler.
The cost of NOT testing
Failure to test could mean failure to pass efficiency standards, and there’s no way you’ll be able to justify the premium cost of a high-efficiency boiler to the building owner.
Getting certified is simple for a single boiler system. When you get six boilers running common chimneys, all of a sudden your efficiency drops severely... Oops, sorry; now you no longer qualify. You lose certification and have paid for something you did not get.
How mechanical draft systems help
ENERVEX serves all boiler categories, but over the last five to 10 years, we’ve installed more and more mechanical draft systems for Category IV boilers. There are mechanical codes in place for these and rules you must follow when it comes to the venting itself. There’s also a test to the boiler standard. If the manufacturer never did testing on multiple boiler systems, maybe that’s an indication that it can’t live up to their efficiency during the test?
If you want to run in multiples, and remain certified, you MUST have a mechanical draft system. A mechanical draft system will protect your investment in high-efficiency boilers while mitigating the risk of current and future standard violations.
ENERVEX knows the standards, the codes, and what it takes to get certified. We can design a mechanical draft solution to ensure that you don’t drive off with a “lemon.” If really put to the test, your system should always perform the way the manufacturer promised. No matter how many boilers you will need in real operating conditions. We use a very well-known test laboratory that stands behind what they are doing.
So just like buying a car, venting multiple Category IV boilers requires doing your homework. Call the manufacturer out. Ask them point blank, “is your boiler still certified for xx% efficiency at six boilers?” They’ll either have to lie or tell the truth. If it’s not certified, don’t put it in. You may have to pick a different boiler manufacturer.
Need help determining the best mechanical draft system for your condensing boiler application? Contact us. Or learn more about mechanical draft systems.