modulating v. nonmodulating gas boilers

Doug_3

The modulating btu feature of some of these wall hungs looks pretty neat. Most that modulate do so by varying gas flow and intake air flow to create a range of btu output, rather than confining the boiler to one pre-set on-or-off btu capacity. This feature seems especially attractive when combined with outdoor temp monitoring. On the other hand, many fine high efficiency boilers operate just fine without modulation, again, especially when combined with outdoor temp monitoring. Is modulation the wave of the future? If one is buying a 90+ boiler, is it a must?

Doug_3

didn't mean to leave out floor mounted boilers......

.....which feature modulation. Guess what I'm wondering is if you operate the boiler with advanced controls, is modulation overkill?

hr

The beauty is

these types of boilers or heat sources will adjust to varying loads. This can be very desireable on a multi zoned system. Low mass, low water content boilers are very prone to short cycling when attached to multi, micro zoned systems.

Suppose you have a job with a 80,000 BTU/hr total load. Suppose, as most radiant systems, this is split into 4 or 5 zones. With a modulating burner the boiler could adjust it's output to exactly meet the load of any or all zones.

The Munchkin, for example will mod from 22,000-80,000 output.

Ideally this boiler may fire in the fall and never shut down! It could concievably just ramp up and down all heating season long

Efficiency at it's finest, very little on/ off cycle wear on a boiler the rarely shuts down. Steady state is always the best way to run a fired device.

Throw it into condensing mode, where you extract more BTUs from the "waters of combustion," and now you are really styling.

I guess the short answer would be yes, these are the wave of the future, in my opinion anyways

hot rod

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Steve Ebels

Think of it this way

When a 90% eff non-mod boiler fires at, say, 100,000 btu's you are still blowing 10,000 btu's outside that you have paid for.

Now, most of the heating season your load is maybe 1/2 that 100K or less. Let's say for the sake of arguement that your avg. load is 50K. So your modulating boiler ramps down to meet that demand. At that point you are only wasting 10% of 50K instead of 100K btu's. A savings of 5000 btu's per hour of operation. That can add up to a fairly substantial number over a years time.

Troy_3

Modulating burner

I think it is the only way to go. In reality every boiler is overfired most of the time forcing it to short cycle and never reach it's afue rated efficiency. That's reality. It's like buying a car and never driving past the next block except on christmas. You won't get that gpm rating on the window when you bought the car. And the exhaust system will die early. That is no different in a boiler. Too many short cycles too much wet time in the flue spells trouble. Our loads are too varied for a set input burner. That's why automobiles have accelerators, boilers should too. IMHO!

Unknown

Modulating Boilers

Definitely the system of the future. The simple truth is that we waste a lot of BTU all season long because we fire at one rate no matter what the demand. If we can modulate input to meet demand the over all efficiency goes up. Add to that indoor/outdoor control and in some cases multiple boilers which I really like as a feature. Glenn Stanton has an interesting article in the News this week (Oct 14) about that.

The future I believe for heating systems is all air for combustion from outdoors, sealed combustion chamber, hot surface ignition with intelligence to control temperature and voltage,wall hung or small package mounted on a stand for easy access. Easy servicability for the technician and installers. In line with this also the ability to have low return water temperatures without damage to equipment.

Steve Ebels

I've been waiting for a manufacturer

To try this with scorched air. If they combined this with a variable speed drive on the blower they might actually come halfway close to the comfort level of a hydronic system. So far all I've seen is 2-stage burners.