Buderus GB142 vs. Monitor MZ40C

Brad White_38

I have a Monitor MZ25C granted not the 40. Works fine but is on-off, does not modulate and can cycle like crazy IMHO. Given a choice between the two, I would take modulating in a heartbeat.

Monitor makes a fine product but they have, in my opinion, sat on their laurels about having a condensing boiler with a long-time track record and never really improved it from there. They are only now getting to the point of making a modulating boiler (sure to be a good thing) but also maintain that efficiency boost from modulation is over-rated. I could not disagree more.

Chad W. Campbell

Buderus GB142 vs. Monitor MZ40C

My home is currently equipped with a 100 year old Sunray boiler working on a gravity fed system over two floors with old cast iron radiators but I plan on adding a new radiator to the third floor as my home is a duplex and currently there’s no heat going to the third floor. I sought out advice from several contactors in the area, Seattle, and up to this point I’ve thought a Buderus GB142 would be the answer. However, I’ve had a couple of heating contractors suggest the Monitor MZ40C as an alternative because of their longer track record for condensing boilers. I also plan to use the boiler to heat the hot water (there’s currently two hotwater heaters, one for each unit) and also a 4 person hot tub. Thoughts on which model would be a better investment?

Mad Dog_2

The GB has a running track record of 10 years

in Europe...and the monitor? Mad Dog

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Joe@buderus_2

GB History

The current design of the GB142 has been used in Europe for the last 15 years. The previous model was in use for 5 years. The GB142 has a twenty year history. It has been available in the United States for one year. Thanks

Chad W. Campbell

Buderus GB142 vs. Monitor MZ40C or another suggestion

Thank you for the information below. Anyone want to suggest another condensing boiler besides the two previously mentioned that would work with my circumstances below?

Chad W. Campbell

Buderus GB142 vs. Monitor MZ40C or another suggestion

Thank you for the information below. Anyone want to suggest another condensing boiler besides the two previously mentioned that would work with my circumstances below?

Uni R

Other suggestions?

Viessmann Vitodens, W-M Ultra, Lochinvar Knight or the Triangle-Tube Prestige are all well regarded MoCo boilers.

Jerry_15

The Prestige is a killer. Good controls, easy to program, set up for dhw, check it out.

Constantin

I'd contact Paul Pollets

He's in your region, an excellent installer, and a really nice guy too. I've seen a number of his Viessmann Vitodens installs that could only be described as works of art. Good luck!

Alan(CaliforniaRadiant)Forbes

Only problem

with a Vitodens is that they won't operate above 167° unless you jump the "external heat demand" contacts which will be used for DHW.

I myself am not sold on the idea of a condensing boiler for a radiator system. You're spending a lot more money for what may be a small increase in efficiency. I don't think it will condense that much given the high return water temperatures.

I won't rule it out, though since we have installed this configuration a few times, mostly because of space considerations where there's no room for a normal atmospheric boiler.

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Brad White_9

Depends....

Not talking Grown-Up Diapers here

The BNL study pretty much established that hours of heating weather in the northeast at least, were sufficient to promote condensing with reset. (Reset temperatures coincident to supply and return water temperatures were below dewpoint.) And that was for baseboard sized for 180 F EWT.

With proper selection (oversizing) of radiators to make use of low water temperatures, anything is possible, especially with reset.

With cast iron radiators: Especially if sized originally for an uninsulated house and by the Mills Rule when applied to an updated envelope can run at significantly low temperatures, 110, 120 or so supply water in many cases.

Not the same as radiant slab, but still, not bad..

Respectfully Submitted,

Brad

Chad W. Campbell

Condensing Boilers and radiant heat.

Makes sense to me. I’m sure that my house fit’s into this description, as it is 100 years old with wood siding. The radiators typically don’t get that hot, and the settings I have currently on the Sunray boiler are 160 degrees on the high end, and 135 on the low end.
Also, when the temp outside is 40 degrees or warmer, from what I’ve been told I’ll be able to realize the 93-97% efficiency, and when the temp drops below say 35 degrees F. then my efficiency would match that of a cast iron boiler. So in other words, most of the time I’d be in the higher efficiency percentages as it doesn’t get that cold in Seattle most of the time. Sorry I’m not speaking in the professional jargon, but I’m just the homeowner not a heating professional.

Brad White_9

Plain English Spoken Here, Chad! The less jargon the better

Not sure about Sunray boilers, but the temperatures you cite are warmer than will promote condensing. To achieve anything above 92% you are looking at condensing and to do that you need return water in the range of 127 degrees or less in general.

My default condensing design temperatures by the way are 140 degree supply and 100 to 120 degrees return on the coldest day. Point of reference only.

Mike T., Swampeast MO

167° Limit

Alan:

I suppose you've encountered the 167° limit problem with cast iron radiators? Gravity conversion systems yet?

Of the systems I've personally measured (my town & St. Louis) and ones I've verified (all over from data supplied by homeowners who write to me), I've yet to find an original system that cannot be supplied with 167° supply temp--usually MUCH less--think 140° or lower. It's later modifications where different types of emitters and/or those sized for 180° average supply have been added (or a significant number of radiators removed) that causes the problems I've seen.

Could this be a problem peculiar to your climate?

Mike T., Swampeast MO

Sounds like you're well-suited to a condensing/modulating boiler.

Not sure about your weather, but if you get a cold snap, try (after at least 24 hours without ANY setback):

1) Significantly lowering your boiler high limit (say to 140°) and low limit (say to 115°).

2) Raising the thermostat WELL ABOVE the temp you want to keep.

Do this overnight. Check room temp in the morning. If above your normal daytime setpoint then the supply temp is still too high and you'll have LOTS to gain from condensation. If below your normal setpoint, raise the high limit a bit and repeat.

DO NOT RETAIN SUCH LOW SETTINGS FOR ANY LENGTHY PERIOD OF TIME as condensation becomes a possibility. (Fortunately gravity conversions seem nearly immune to this--particuarly with an oversized, cast iron boiler--but do be aware that it can occur.) Condensation in a non-condensing boiler (or the flue) is BAD!

The Buderus GB has a wonderful control system when used with the RC-10 vector-driven thermostat. BUT, finding the ideal location for the RC-10 can be a PITA and any existing imbalance in heat among rooms is likely to be magnified. Thermostatic Radiator Valves (TRVs) are a WONDERFUL addition to ANY gravity conversion system. You get room-by-room "zoning" without wires. Both the Buderus GB and the Viessmann Vitodens will utterly thrive driving a TRVd system as they are optimized for such. Depending on how much your radiators and current boiler are oversized, you can expect energy savings from "very significant" to "phenomenal".

Alan(CaliforniaRadiant)Forbes

Go for it

In that case, I'd recommend the Buderus GB132: modulating, condensing and very stable. And made in Germany, my fatherland.

"Deutschland, Deutschland, uber alles..."

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