Condensing Boilers

CMadatMe

Surprised how quite manufacturers of condensing boilers have been the last couple of weeks. Anyone surprised at the AFUE ratings being posted up on the AHRI Directory? Some very interesting results. I'm kind of baffled at the differences in AFUE between those that have retested when they uses the same heat exchangers on their models. Very surprised to see one manufacture drop almost a full 5% after retest.



Those that install, how do you think the AFUE effect is going to hamper sales to consumers? How do you now show the dreaded ROI?

Zman

What's next

Chris,

I am not sure what they are thinking with the ratings. A huge deal is being made about these inaccuracies in the test. The irony is that they are still ignoring the 2 biggest factors. Return water temp and boiler sizing are still the biggest factors in overall system efficiency.

We have a local code which requires 90%+ boilers. The code does not require a heat loss calc or or a low temp design. It would be completely legal to install a 96% efficient boiler that is 10x over sized and set the water temp to 190. You would not be allowed to install a properly sized and controlled 84% efficient unit. We all know which would run more efficiently.

As for the roi estimates. I don't think it is accurate to use the manufactures rating for either appliance. The 75-80% rating on appliance you are replacing is not really accurate any more than the 96% rating on one you are installing.

Siegenthaler's "Modern Hydronic Heating"  has some good estimates on the effects of cycle length on efficiency.Flue and jacket losses are also a major factor.

I have found that a 20-30% savings is virtually guaranteed. When replacing real "basket case" older systems 50% is not uncommon. I think the explanation for this is that the new mod/con is running at a net of 85-90% and that the existing system was really running a net somewhere in the 60% range.

Thanks for posting this one, this one has been on my mind lately.

Carl

CMadatMe

Consumers

Only understand one thing, that yellow label on the side of the boiler. I agree on the return water temp but the dew point isn't a constant. It changes and so does the required water temp to condense. Condensate is the best measurement as to efficiency in my mind. The more condensate I can pull the more btu/hr I save.



As for heat losses. It should be a requirement from municiplaties at the time a permit is pulled. At inspection that piece of equipment should be no more then 10-15% btu/hr over that required to overcome the heat loss. This is just my opinion..

Jean-David Beyer

no more then 10-15% btu/hr over that required

"At inspection that piece of equipment should be no more then 10-15%

btu/hr over that required to overcome the heat loss."



That would be great, but how can you do that when mod-con boilers seem to come at about 2:1 differences and the lowest ratings I saw when I got mine was 80,000 BTU/hour and modulated down to 16,000 BTU/hour? On a 0F day, I need only 30,000 BTU/hour, and design day is only 14F. I do not think I could get one that small even today.



Makes me think about using a hot water heater instead. (I am not serious about that.)

CMadatMe

Sure They Do

Here is the ACV (Triangle) Prestige that isn't here but over there. This is just one example of many across the pond.



http://www.acv.com/dwl_gateaway.php?f=MTMxN19kb3dubG9hZC5wZGY=&n=UHJlc3RpZ2VfMTgtMzJfbWtJSUlfYnJvY2h1cmUucGRm



The technology is there to do it here. Maybe it is also time for us to really begin at looking how systems are being installed in new construction homes and force the isse. Again, just my thoughts and opinion..

SWEI

18 kW

is 61k BTU/hr -- think PST60.  Interesting that they offer a smaller Excellence over there - wish we had that option available to us here.



There is definitely a market for a good 30-40k mod/con here.  I'm starting to spec Thermolec TMB's here due to lack of appropriately sized gas-fired alternatives.

CMadatMe

The Minimum

Is 3KW and in this version you can set Min and Max load in percentage. Can't do that with the version here.. Page EN37...I can make this a 11,000-30,000 btu/hr boiler in the field.



http://www.acv.com/dwl_gateaway.php?f=MTI5MV9kb3dubG9hZC5wZGY=&n=TlRfNjY0WTQyMDBfSF9QcmVzdGlnZV9Na0lJSV9FTi5wZGY=

SWEI

minimum rate

I asked TT about this last month, after noticing that the Lochinvar WHN055 fires at an 11k minimum rate.  They feel their single replacement parts kit across the range is more important than the lower firing rate.  I'd rather have the lower firing option, personally.  Might have to go get trained on the WHN...

CMadatMe

What would they Have to Change?

Its the same HX, Burner and Control. It's a software change..

SWEI

blower change

I believe was the issue.

Jean-David Beyer

Sure They Do

Well, the small one is 61,000 BTU/hour and that is double what I need when the outdoor temperature is 0F. And here the design day is 14F. That is only a little smaller than my 80,000 BTU/hour unit.

The minimum is about 10,000 BTU/hour which is better than my 16,000 BTU/hour, but that is still lots more than I need when only the upstairs zone is calling or heat.

Paul48

Over There

Across the pond....their lifestyles tend to be different than here in the states. Their living accomodations tend to be smaller, and focused  more on function than luxury. That's not to say there aren't luxurious accomodations there, but even in those, you'll notice subtle differences. We are still stuck in the Cadillac Escalade mentality. Or should I say, we've fallen back into it.They, like us, got burned once and changed their ways forever. We allowed ourselves to be be burned twice.....as the old saying goes....shame on us.

CMadatMe

Comfort

All I want is comfort and a boiler that can be installed that produces it while providing efficiency. If Triangle would make this subtle change here they would have something the competition does not.



The market will change product offerings just as it has in the past. Just need someone to step up to the plate. With this AFUE change the time may have come.

Paul48

Intelligent

How much more would it take to make an intelligent mod/con. The best mod/cons have stupid controls. Some are easier than others, or have more options, but all are only slightly better than MS/DOS. You have outdoor sensors and indoors sensors....why can't you just input the heat loss of the structure, and have it learn what it needs to do?

SWEI

less unintelligent

The newer controls are quite a bit better than what we had to work with before, but there is still plenty room for improvement.  I suspect something can be done via the modbus interface, but it would require quite a bit of work to make it work across multiple manufacturers.

Gordan

I wonder whether WM is going to change the name of their WM97+

Their brochure states in the same breath that they have 5:1 turndown and that their min/max inputs are (23-70) for the WM97+ 70 and (37-110) for the WM97+ 110. Must be that new math.



And there's that picture of the family where the "woman" couldn't biologically be the kids' mother, more like their slightly older sister. Must be the new model. Green, yes, but saves green? Probably not. Kudos to WM for getting with the times, though.