confused about boiler types

IZZY

I could not tell you what my local installers are putting in - I don't know. I'm a straight line plumber for 13 years, so I don't have the experience with heating systems...but this is for my house (incidentally, I own and have read every Dan Holohan book, but reading and doing are 2 different things). The reason I like the Energy Kinetics System 2000 is because it is fully convertible between oil and gas, you just swap out the burner.
Anyway, I know these boilers have high efficiencies, but are they going to cost me less to run, or will I be just as well off with a cast iron boiler with an outdoor reset control?
Also, how are the modulating and ModCon boilers vented? Can I go into my chimney? It seems that the exhaust gases are very cool from these units, so I probably won't get any draft up the chimney, right?

IZZY

confused about boiler types

I need to replace my boiler. I have hot water boiler with sunrad cast iron radiators. I've been seeing a lot of advertising about condensing, modulating, and low mass boilers. What's the difference. Can I use any of them. It seems like they only reach the high advertised efficiencies when they are used for low temperature applications, like radiant, which I don't have. A friend has me sort of hooked on the Energy Kinetics System 2000, but again, same thing - can I use it with a higher temp system and still gain from their efficiency? Thanks.
Izzy

Steve L.

You can use a lower water temp with cast iron baseboard. You need a way to control the temp of the water in the baseboard (be it a modulating, condensing, injection etc..) based on outside temperature. So on a 40 degree day you might run 130 degree water and on a 0 degree day you might need 180 degree water. (based on haeting curve)

jim_57

Boiler types

Because System 2000 is not a condensing type boiler it does not rely on cool returns to achieve its high system efficiency. With a high mass distribution system, such as CI rads, it is recommended to use a primary/secondary setup. This assures even heating in all the rads and also as outside temps change the run time for each call changes proportionately, thus in effect modulating the supply loop temp.

Brad White_9

Types of Boilers

Here is a general list of types of boilers as I see them:

Modulating Condensing ("ModCon"): Highest efficiency, operating below the flue gas dewpoint and constructed accordingly. Modulating fire promotes close control of input to heat load required.

Condensing: As above but without modulation.

Low-Mass (AKA "Copper-Tube"): As implied, low material mass, these require constant and predictable water flow. The low water content would flash into steam should flow be interupted. Combustion tends to be atmospheric and single-stage (on-off) or two-stage (low-high). Requires primary-secondary to assure constant flow on the boiler side.

Cast Iron: Usually sectional, these are the workhorses supporting the oldest hot water and steam systems. Not forgiving of thermal shock or condensing (with limited exceptions), these may be atmospheric or sealed combustion, the former Gas-only, the latter gas or oil with forced draft combustion.

Fire-Tube: Getting into commercial-industrial here, the combustion products travel in tubes within a shell containing water (or water-steam). Often low to medium pressure for it is easier to make a water tube to a high pressure than a large shell.

Water-Tube: Another variation of commercial-industrial, these are also low water content in nature, generally. Used for higher pressures, these are what you find in high temperature hot water and high pressure steam plants, power generating plants and the occassional process/laundry.

IZZY

Thanks, more questions later.

Kevin O. Pulver

Well said Brad,

But aren't the ModCon a low mass also and subject to the same flow scrutiny/PriSec? Kevin

IZZY

Okay. I got the boiler types down. So, now what would be the most practical type for my needs. I have 431 square feet of sunrad cast iron radiation right now (got that number by adding up all the sections and then going to Dan's EDR book). (I also need to know what temp should they be run at, because I don't know really what btu output they are until I know what temp they are running at.)
Should I use a conventional cast iron boiler, or can I use one of the newer types. I really want to go modern, but am nervous.

Brad White_118

Thanks, Kevin

No, not all ModCons require P/S. Some do (Munchkin being one) but the Vitodens and others do not necessarily. I say "necessarily" because of course you always can and may want to, such as when your system flow exceeds boiler flow (and all other good reasons). The "Mod" (modulation) in a ModCon is what separates the need for constant primary flow from a low-mass copper fin boiler. The firing rate drops in parallel with a drop in flow as an illustration.

Brad White_118

Izzy

What is your home heat loss? All things start there.


I will take your 431 SF as the correct EDR measurement; it will emit, at 170 degree average water temperature (180 F in, 160 F out), a total of 64,650 BTUH. If your heat loss is about that, you will need 180 degree supply water but only on the coldest day... rare in terms of total hours. Plenty of room for setback.

If your heat loss is less than that, all the better. If your heat loss is around 38,000, you can get away with a 140 degree average water temperature. Again, that is on the coldest day. In theory, you can use water at practically ten degrees above room temperature when it is 60 degrees out. Your internal gains may offset that. Plenty of reset room even if you need 180 degrees supply water on the coldest day. Just means a steeper curve that is all.

By all means go modern with a ModCon. If you are still nervous, Diazepam works well

IZZY

Thanks for the info, so now I know I've got options. Any prefferences from anybody. I know there is no end to the controls I could put into the system, but I don't need to engineer the next wonder of the universe - I've only got about two more weeks to make this happen before my wife evicts me. Pure advertising has lured me to the Weil McLain Ultra and the Dunkirk Quantum 95M, and I've still got my eyes on the Energy Kinetics System 2000, and another friend told me he has a Lars unit that works well in his house. Too many choices...help.

Brad White_128

Of the manufacturer's

you noted, which does your local installer best support?

The first two would have my vote but that is based on less familiarity with the latter names. I have specified the Ultra several times with success (such as one season would tell and more in the pipeline so to speak, for this coming season).

EDIT: Modulation beats condensing alone, IMHO. With condensing and modulation you have the best of everything. As Jim said below, it give up heat only to the degree it is needed. No "bang-bang" (on-off) control. Very smooth as is true of most mod-cons.

Jim Farrell

Boiler ???

Take a look at Weil-McLain ULTRA Gas Boiler...
www.weil-mclain.com

90+ Efficency depending on water temperature...
Best bang for you buck...I believe...Full Mod/Condensing Boiler...Only turns on btu needed at the time of a call for heat...Instead of boiler turning on at full rate...

Food for thought...