Comparing modulating condensing boilers

By BOB “HOT ROD” ROHR

This month I will share some observations regarding modulating condensing (mod con) boiler features and installation comparisons. I’ve selected four brands that I have personally installed and operated. Two of the units are installed at my home and I have a heating season’s worth of experience with their operation. I have installed more than 30 mod cons, like the ones reviewed here, operating under a variety of conditions. Ten of the units have three heating seasons under their belts. About half of the units also supply domestic hot water (DHW) via indirect tanks or onboard heat exchangers.

When I compare boilers, I seriously consider the packaging and crating. This is an important feature. The closest supplier of ANY brand mod con in my area is 180 miles away. For the most part the final trip to my shop is via truck. If you have ever paid attention to the trucking companies cargo securing procedures, you will probably learn…there are none. At least my 10 years experience at this location indicates that to be true.

I have had freight arrive from all the large trucking companies, usually in an 18 wheeler with a 28- or 40-foot trailer. Occasionally I spot a cargo bar in the box of these trucks, but never in use. Therefore, the cargo (my boiler!) is free to shift, slide and tip over at whim. I have actually heard my indirect tanks rolling from side to side as the trucks lumber up my driveway.

I have high praise for the boiler companies that take the time to actually crate, in wood, the entire package. When they bolt the equipment to a fork lift-able pallet, they get a gold star. The Weil Ultra and Lochinvar Knight arrive in near bulletproof crates. I’ve yet to receive a freight damaged unit from either manufacturer.

Installation and operating instructions that have originated in this country (written in English with U.S. measurements) are a big thumbs up. Ideally, all manufacturers would have contractors proofread their manuals before printing them. I prefer the installation and owners operating manuals be two different pieces. Also, venting and water treatment sections or separate books for these topics are nice. A simple owner’s manual could be 10 pages or less if well written and formatted. That’s a manual that may get opened and read.

Another “atta boy” goes to the manufacturers that have all the manuals available online! Another gold star feature: mounting provisions and templates. The Viessmann Vitoden and the Laars Mascot mod cons provide very nice components and cardboard templates. Viessmann has a cool rough-in manifold assembly. It’s very well thought out and nicely built.

I love the multi-mount ability of the Weil McLain Ultra. It mounts easily — wall or floor — and has adjustable, leveling feet. I wish all mod cons offered this “either/or” mounting option. Weil is the only brand I have installed that offers top and bottom connections for supply and return, as well as gas line, connections. You can also use all four ports. Often I pipe the heating loads from the top and the indirect tank from the bottom connections; or vice versa if the heating is all below the boiler, as in a slab-only job.

The Prestige from Triangle Tube offers three bottom connections. A 4th would be nice to facilitate quick indirect piping. I’ve found you need to be very careful when screwing connections to the Prestige. The piping is soft copper from the brazing process. Be sure to back up that connection. I cut the threaded adapters off and solder pap adapters right to the copper. This creates a simple, clean, leak-proof connection. The swing out electrical panel on the Prestige allows wide-open access to the boiler components. Nice.

I like boiler brands that offer easy access for flue gas sampling. The Vitoden, Laars Mascot and Prestige offer specific windows just for this purpose. Thanks! It’s the little things that add up.

Access to the gas valve adjustments should not require a mirror, special tools or standing on one’s head.

Removing the burner to do a yearly heat exchanger clean out should be as painless as possible. The key to mod con longevity hinges on a good yearly maintenance and recalibration. Consumables like burner gaskets, etc. should be available and modestly priced. The manual should contain a concise procedure for doing a proper clean and check of the system.

I appreciate a sound approach for connecting the piping to the boiler. Viessmann and Laars include pre-built installation manifolds to speed this process. And it creates a clean, professional look. However, it does tie you in to their locations, somewhat.

Personally I feel ALL mod cons sold in the USA should have NPT or sweat connections. Odd, one-off BSP or other Euro connections should stay in the country of origin.

The same applies to non-typical fasteners. If special sized torx fasteners are used, the manufacturer should supply the correct tool with the unit (ala the tekmar screwdrivers) or offer a kit that has all the correct metric tools needed to adjust, disassemble and replace all the components. Better yet, give them away. I’d rather receive a nice tool kit than another ball cap, thank you.

Wiring accessibility is another feature that can make or break your day. The Lochinvar Knight is ahead of the pack with their large easily accessible terminal, which accepts multiple wire and both stranded or solid wire types. They include plenty of pre-punched knock outs, too. I love their easily removable front cover. No tools are needed and the nice snap fasteners hold up.

Good factory support is a must-have feature. Reps or dealers who change like the weather can leave you out in the rain. A mod con is a much more sophisticated appliance than a standing pilot cast iron boiler. You need easy access to someone, anyone, who has the correct answers to your start-up and repair questions. I fear for the www.buyers and do-it-yourselfers who have neither the tools or knowledge to install these high-tech devices.

Ongoing manufacturer training further represents the manufacturer’s commitment to the licensed certified installer.

I appreciate solid workmanship. So do you. We want to install mod cons that are well made, finely finished and, ok, handsome. Just as the appliance and forced air manufacturers have stepped up the look of their products, so should the boiler manufacturers. The trend is moving this way. Without question Viessmann wins the style prize, with high quality components and winning assembly workmanship. It is a nicely “engineered” brand and I am proud to put my signature on a Viessman installation.

I’m not inclined to pick a favorite. All these brands have pros and cons. Every contractor installer needs to consider the features, sizes, mountings, warranties, support and customer acceptance as he makes his or her decision. Life is a box of chocolates.

I hope to offer a series of columns on an array of mod cons. Stay tuned for “road test” results scattered amongst my monthly column line up. I’ll dig deeper into installation and service tips, tricks and opinions on these and other brands. May your load be light and your boilers condensing.

Bob “Hot Rod” Rohr is particularly interested in “hybrid” radiant systems — systems that utilize solar and wood energy in addition to, or in place of, fossil fuel. Also, systems that incorporate different methods of heat delivery. He owns and operates Show Me Radiant Heat and Solar, Inc. in southwest Missouri. Reach hot rod at hotrodradiant@aol.com or by calling 417/753.3998.