Non-Condensing Modulating boiler

Brad White_9

The non-condensing part I get but how do you figure modulating? All I have seen is on-off in the residential range anyway. Commercial boilers like the Burnham V11 series have Low-High-Low in the smaller sizes then modulating above certain sizes. But not in house boilers. What am I missing?

DZaker

Do they make em'?

I want to replace my good running, but fuel wasting 50 yr. old NRC boiler (that was converted from oil to gas 25 yr. ago) in my well insulated 1600 sq.ft. ranch. I have read many divided opinions on THE WALL about mod/com vs. C.I. I have been convinced to go with a new C.I. boiler. In an attempt to achieve more efficiency, do any manufacturers make an atmospherically aspirated MODulating boiler in the 60-80,000 BTU output range?

Thanks in advance

Mike T., Swampeast MO

Ain't gonna happen without solid fuel. Trade in your 50 year-old boiler for an 80 year-old boiler and use coal if you want atmospheric and modulating.

Tony_23

non-con/modulator

Laars Endurance.

NOT CI. NOT atmospheric. 2:1 turndown.

If you want CI, you won't get modulating. Why bother ?

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DZaker

like the concept

I like the concept of modulation for efficiency, kinda like outdoor reset...only better. Modulate burner to heat loss demand, for maybe only cost of control/modulating valve?

Tony_23

Not that simple



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Mike T., Swampeast MO

Unless you're burning solid fuel and even then it's FAR from "that simple" to either regulate or achieve efficiency anywhere near that of a mod-con.

Tony_23

You can lead a horse to water...

but you can't make him sip

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Joannie_11

Atmospheric Modulating

The thing you run into with atmospheric modulating is that you do not have the ability to control the air part of the air-fuel mixture. Therefore, when the gas is modulated down, the combustion becomes less efficient. The input may be less, and the amount of fuel being used may be lower, but how efficiently that fuel is used goes down. Tough to fight physics on that one (yes, even on the atmospheric modulating and step-fired units that my company sells).

Tony mentioned the Laars Endurance. That is a non-condensing sealed combustion modulating unit. The air and gas are both controlled. Efficiency stays at about 87% thoughout the firing range. Nice middle-road between full condensing and atmospheric, and has the benefit of modulation for lower input when full input is not needed.

I hope this information helps you.

Joannie

Laars Heating Systems

Brad White_9

Given a choice

between condensing with on-off control and modulating but without condensing temperatures, I would take modulation in a second.

Condensing efficiencies are measurable in percentages akin to AFUE (for what that is worth!) in that you will go from the low to mid 80%'s to the low to mid 90%'s. As a percentage of the range you gain 10 to 15 percent which is all well and good. Sure, I will take that.

But with modulation, even in the 85% range (if there is such a beast in these small boilers as there are in larger commercial offerings):

My combustion efficiencies can be tracked, my low-fire efficiencies increase, my cycle losses are greatly reduced, equipment wear and tear is minimized and above all my fuel input more closely matches my load, even if not being burned to saturation.

On the system side I can decouple and deplete the HWS to practically room temperature return water and get excellent system efficiencies.

With a condensing on-off boiler as I now have, my efficiencies were no better than my Burnham 204 with a Centra 4-way mixing valve and OD reset.

Small wonder "Mod" is first in Mod-Con. Naturally I will take both as offered.

As Joannie said, though, in atmospheric fired equipment it is not entirely practical; you have to control both variables of air and gas in parallel.

My $0.02

Brad

Boilerpro_5

They've been made for years

but not in cast iron, that I'm aware of. Raypack has been using simple modulating gas valves with about an 8 to 1 or so downturn. I suspect that the very short (heightwise) heat exchangers in conventional copper tube boilers will allow some reduction in air flow in addition to reduced gas flow. Triangle tube is upgrading thier Delta units to modulating non condensing and you get hot water too. I'd install a Raypack in a heartbeat..Very well proven units.

Boilerpro



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D107

Peerless Pinnacle (Gas Fired) Also Mod-only

Tony_23

Pinnacle

Is condensing. It's a Munchkin in disguise.

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D107

Are you sure? --brochure never says 'condensing'

I know the new oil version is condensing...

Tony_23

Every one

I've seen is condensing. Can't imagine having two w/ the same name and different characteristics.

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D107

how they measure up against others?

I'm looking at a mod con install here. Their turndown ratio on the 80 is 4 to 1 which isn't bad. --not as good as Knight, Munchkin or WM Ultra...but does the combustion air vary with the modulation?

Thanks,

David

Perry_2

What if...

Even a 2 stage boiler would provide many efficiencies, as most of the year in many parts the boiler would only need to fire at the low rate.

It would not be the smallest boiler (by modern standards); but there is no reason you could not have an atmospherically vented boiler that had two burner assemblies. Then something like an outdoor temp switch would determine if the boiler only fired on one burner or both of them (or one of them continously and the other intermittently).

Perry

Mark Hunt

David


the Pinnacle is purchased by Peerless From HTP. It is a Munchkin with a green wrapper.

Perhaps you are looking at older Munchkin literature when referring to the turn down ratios, but Munchkin/Pinnacle are one in the same.

Mark H

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Brad White_9

Raypak

Makes one as does Laars I believe. There are days before ModCons that I would have given my wisdom teeth for one. Even now I sometimes see a benefit to a 30 MBH input boiler on 40-something degree days.

The staging is based on an internal aquastat. When the load changes (heat absorbed to the space) the temperature drops and the second stage of the burner comes on. Great with OD reset too for a little more complexity. Beats on-off any day; two boilers in one if you ask me.

But still, you can do even better today albeit at a price.

Joannie_11

Two-stage

Just a clarification, though.

On our atmospheric units (and Raypak's, I believe), this is not done with two "banks" of burners. There is one valve, and that valve is run on both full fire and "half" fire, based on what the temperature is calling for it to do.

Our MiniTherm JVS100, 125, 160 and 225 are two-stage units and atmospheric.

It can help to prevent short-cycling, as well.

A lot of people still want atmospheric, 80-83% efficient units, and we still sell a good number of these "older technology" types.

Joannie

Laars Heating Systems

S Ebels

Available from nearly every manufacturer

It's called a modulating/condensing boiler being run at non condensing temperatures, This is what you're dealing with anyhow isn't it?

S Ebels

Brad

That was said somewhat tongue in cheek.

It is true to a certain extent though. On the Vitodens for example, you just set the shift and curve high enough to get into non condensing territory and the burner will still modulate based on demand. It'll short cycle with fairly undesirable frequency until the load gets above the minimum firing rate but it will modulate once there.

I still have to wonder what particular type of system would be better served by a non condensing/modulating boiler than by a condenser. I guess in hydronics, if you build it that way, that's the way it is.:)

Brad White_121

Thanks, Steve

Did not see your smiley face and I am as guilty of that as anybody!

I have a "condensing only" boiler and it is like the difference between "promising happily ever after" and "getting lucky on the first date". Both are good, one is a much better investment :P