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Mod Con Efficiency

 
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Old 05-02-2019, 09:11 PM   #1
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Mod Con Efficiency


I've heard statements like this;

"When a condensing boiler is not in condensing mode efficiencies can be as low as 70%"

One specific condensing unit says 91% efficient and shows
Input 105 btu
Doe 97 btu
Net 84 btu
I see net ibr as around 88% with these numbers and all specs I see show similar.
How does one come up with efficiencies as low as 70% when IBR is in the upper 80's?
If efficiency was 70 ish % how could ibr be 84 kbtu?

Using 70% of the 105 kbtu input the IBR could be no more than 73.5 kbtu and therefore how could one size a boiler using these efficiency numbers?
I'm not getting this!
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Old 05-03-2019, 09:33 PM   #2
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Re: Mod Con Efficiency


Quote:
Originally Posted by Kirkhj View Post
I've heard statements like this;

"When a condensing boiler is not in condensing mode efficiencies can be as low as 70%"

Generally said by people that are not pro mod/con.

One specific condensing unit says 91% efficient and shows
Input 105 btu
Doe 97 btu
Net 84 btu
I see net ibr as around 88% with these numbers and all specs I see show similar.
How does one come up with efficiencies as low as 70% when IBR is in the upper 80's?
If efficiency was 70 ish % how could ibr be 84 kbtu?

Using 70% of the 105 kbtu input the IBR could be no more than 73.5 kbtu and therefore how could one size a boiler using these efficiency numbers?
I'm not getting this!
A condensing boiler operating at a water temp of 180F, will still be at least 80% efficient. Some designs higher yet.

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Old 05-04-2019, 07:53 AM   #3
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Re: Mod Con Efficiency


"Generally said by those not pro modcon"

Absolutely true!

"Been There" Thanks. Maybe you could answer a few more things for me. Allow me to explain. Hopefully you'll bear with my rambling I'm so infamous for on here.

This 1980 ish weil standing pilot 150 input 104 IBR according to the label, heats the 500 ish feet of pipe and cast rads in this old house extremely well but is very tired as it was poorly maintained.

In comparison to several neighbors, local contractors and past homes I have lived in, my gas bill is suprisingly low, but obviously could be better. Main thing is I want to make sure something KEEPS heating the house.

The past 3 winters I have educated myself with a lot of help from guys on this site and other avenues. Through my past experiences with sealing up old homes, and the new tweaking and adjusting I have learned to do with all of your help (first residential boiler I have had)the results are evident. This past winter was the coldest of the 3 here I've seen yet. For more than 3 weeks steady the temps stayed well below advertised design temps, and the average temps were worse, this boiler still had no problem at all keeping up AND the total gas usage is still lower than the first and second winters.

My heat loss calc ( which I have painstakingly done) says somewhere around 88 mbu. Judging by how this boiler cycles and heats the house, and by using IBR stated on this boiler, I have great faith that this number of 88 mbu is extremely close.

Assuming that my gross output IS still 120 k and assuming that this arbitrary IBR rating of 104 k IS actually what I'm seeing, that 88 k heat loss using the IBR as my gauge for new boiler sizing should be my number?

Design temp here is -21 F
My chosen design temp for heat loss -28F

Temp for 3 weeks here ( coldest it's been in many years) -35 to - 40 F.
Rarely came up to design temp and boiler still ran cycles. Even on the very coldest highest windchill day of the full winter the boiler never ran for more than an hour and a half and would shut down at limit of 170 or if therm was satisfied first would shut down for 20- 30 minutes.
On some of those cold days I would raise the temp to 75 and the thermostat would eventually be satisfied...

I am limited to contractors here.
There won't be much available in terms of service.
Full modcon would be nice but given my situation I'm not sure that's the smartest route to go.

Weil mclein is common here and all considered...

First option IF the pro agrees;

GV 90+4 is cast iron and condensing simplified.
105 in 97 doe 84 net (Hence the inquisition on efficiencies)

The same thing I like about it is the thing I don't. Internal circulators. Common taco 007's variable speed controlled by IBC.

Large 2" waterways.

Eliminates the chimney (adding indirect DHW as well)
Eliminates the use of indoor combustion air.
Efficiency at 91%
Eliminates need for thermic boiler protection and bypass.

Second option; IF the pro agrees( likely would be their choice. Remains to be seen)
Weil Cgi 5
119 in 100 Doe 87 net

Induced draft (seems to me that consensus here is get rid of that chimney!)
Must add thermic boiler protection (ESBE) and bypass, which I would deem to be more reliable and more energy efficient vs built in circulators.

What will change either way:

Adding primary secondary.
Adding indirect
Changing from 1 zone presently circulated by 15-58 on return side to 2 zones circulated by variable speed, (on secondary supply sides I believe would be correct.)

There are 6 supply and 6 return lines on a "header" which can be split into 2 sets of 3, each set of 3 could be circulated by 1 delta t variable pump. Since 1 pump works fairly well with all 6 at now, thought is that 2 sets of 3 will allow a bit more control. One end of the house is a little slower to respond and a little cooler. ( 3 supply and returns)
Pro advice will be the final determining factor here of course.

If I had one of you guys out here modcon WOULD go in.

I'm pretty sure I've found a pro. Highly experienced boiler installer with long term business out here. Takes the time to challenge me, listen and advise but leary on modcon so...

Last edited by Kirkhj; 05-04-2019 at 08:17 AM.
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Old 05-05-2019, 04:10 AM   #4
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Re: Mod Con Efficiency


Main draw back of a mod/con is the lack of either contractors that understand them, or distributors that stock parts for them. So your right to be a tad leery of one of your contractor doesn't normally install them.


DOE rating adds in all heat that enters the house from the boiler, including the heat from the boilers jacket and the piping in the basement. IBR only considers the heat from the water flowing through the boiler in its heat rating.


Primary secondary is the way to go with the boiler piping. Along with direct venting, as that will actually lower your homes heat loss a bit.


The CGI series is a long standing staple of Weil McLains, truely tried and tested.



Personally, I prefer the Weil McLain Ultra series over the GV.


Makes sure all heat zones get their 4 GPM water flow rate.


https://www.supplyhouse.com/Weil-Mcl...xoCjqEQAvD_BwE
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Old 05-05-2019, 09:37 AM   #5
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Re: Mod Con Efficiency


There are so many reasons to get a mod con, but yet so many in my specific situation as to why not. Still pondering. That's why I'm here!

That big ol masonry chimney, most on here seem to agree, should be closed up, newer lining or not.
From what I've learned on here and read elsewhere, I agree as well. Might make a good air intake? Is that feasible?

Please understand my concerns...

My experience with industrial modulating units is also one of the reasons I am leary. It seemed like the only units that ever posed a problem, and seemed to happen often, were(4-19 million btu.) two MUA and two heating units. All were m-trac controlled and less than 2 years old at that time (electrical work and troubleshooting is a strength I possess btw.) It was almost always related to the modulation in one way or another. All of the other units in that facility such as 2 stage conventional, radiant tubes and even mid eff residential funaces in specific areas that did NOT modulate had very few issues and were very easy for me to troubleshoot...

I am NOT a pro but was in charge of maintenence at a 65,000 Sq. ft. Welding, sandblasting, coatings shop built in 2005 because I could figure out and fix things and keep that shop running.
The m-trac modulating units I could not, for the most part, figure out. Even the pros I had to call out on several occasions had difficulties. They are complex. So...

If the pros out there were having problems with modulating gas systems, and the pros out here are afraid of the modulating residential units because they do not understand them and they are smart enough to NOT want to install them because they do not understand them, then that is very good reason to make me leary of them!
Do you agree?
Like I said if I had one of you guys out here modcon WOULD go in.

GV does not modulate. Likely not an accurate comparison, but this is where I'm at!

The gv seems pretty simple among other things, but is a weighty beast at 350 lbs. Narrow steep basement stairs, but I really like the cast iron/ss hx idea with this 115 year old black iron pipes/ column rads 80 ish gallon system...

For cast aluminum that ultra sure has chunk, but it is cast aluminum. Should that worry me because it does!
Over 200 lbs surprises me. Floor standing, awesome controls and general consensus seems to be that this is one amazing unit.
Come install one for me please. Lol

I managed to get someone from the city here who wanted to install an ECO, admitted he never has, (thats the approach I like!) and really was Gung ho about it. As he dug deeper he started seeing several issues I am and was aware of, and he changed the quote 3 times. I think he started realizing modcon here was not a simple task. I have since realized how I myself can overcome some of these issues, such as how and where to place intake and exhaust, and how and where to pump condensate. (brick house, stone foundation, windows everywhere, cast iron drainage pipes, lack of floor drains ,etc)
He also said he simply would not install a GV here and I can't remember why.

There is a company I have not approached yet 1.5 hours away. They specialize in making modular boiler boards and market the fact that heat loss etc MUST be done. They insist hydronic heating is a SYSTEM, not just a unit and that is IMO the only correct approach! All they do is boiler stuff. That I like.

They also sell only Trinity (HTI?) and pricing seems really good on the units themselves (yes they actually advertise the price to the public!) But I really don't think brand has much of anything to do with this. I truly do believe from everything I've read the last few years, that 98+% of mod con or ANY boiler fails has to do with contractor. It's rare and almost impossible to find a boiler review of a system in a heating contractors own home that is problematic and trust me, I've read hundreds. Lol

A review of my infamous rambling again
:0)
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Old 05-05-2019, 12:59 PM   #6
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Re: Mod Con Efficiency


It's also important for me to consider...
Annual service costs.
Ultra vs eco vs gv vs cgi

Repair costs.
Full mod con can be/IS expensive to repair...

The standing pilot I now own costs almost nothing yearly. Cleaned and repaired by me. A thermocouple cost me 20$. New expansion tank 30$ new tridicator 30$ Inspected by a pro under 75$. But it's old and has to go.

Seems that if I simply changed out this 150 input to a 119 input cgi and it produces the same output, I effectively would gain a 20% ish fuel saving? What is a realistic number?

This old standing pilot natural draft doesn't even have a flue damper on it!

Let's assume I change this out for that cgi and assume a 20% saving. That's 400ish$ a year and that includes our big full gas kitchen stove. Ill be eliminating that electric hwt which will lower my electric bill far more than the increase i will see on the gas bill.
For an extra 1000$ up front the gv saves what another 50$ a year?
If all this is true seems like the roi on a cgi could be my best bet?


There again comes in the simplicity and questions that I need to ask my pro.
How much is each one going to cost me yearly and how much will I really save?

You know how much an ultra service costs to service and maintain in comparison to say a cgi. I have no idea and I can't do it myself because that'll kill the warranty...
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Old 05-05-2019, 08:44 PM   #7
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Re: Mod Con Efficiency


If your boiler is Natural Gas fired, you can count meter revolutions per (30 seconds?) a period of time while the boiler is firing to check to see if you are over or under inputting the unit, its is part of checking regulator and jets setting/sizing during installation..
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Old 05-06-2019, 04:40 AM   #8
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Re: Mod Con Efficiency


Fourth Gen great idea.
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Old 05-06-2019, 05:58 PM   #9
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Re: Mod Con Efficiency


Fourth Gen I almost left work early so I could run this test. Lol

So input is rated at 150 and The test shows around 144 in. I ran a full 2 minutes with a stopwatch. The meter was replaced in November.

I believe the altitude here is 856' above sea level so all considered it sounds like this boiler is drawing about what it should?

So now does this mean my IBR, rated at 104, would be very close. The math shows an IBR of around 100 now with that corrected input.

Sound right?

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