Is it possible to test a boiler efficiency?

larryjbjr

Is it possible to test a boiler's efficiency?

I have a 20 some odd-year-old burnham boiler in my basement. Someone came over last year and was checking it out. They drilled a hole in the exhaust and put a probe in there to test the efficiency and said that it was if performing as it is supposed to. ( what that means I don't know, they never explained)

Just curious if that really means anything or did I just get snookered?

EBEBRATT-Ed

What the technician did was check the combustion efficiency. If the boiler is running satisfactory you should have a combustion efficiency of 80% +. 84 or 85% would be the best that can be expected with a conventional non condensing boiler. If it's down in the 70s not so good.

Combustion efficiency shows "generally" how efficient the boiler is. There could be other factors involved that affect the total efficiency of the system. A couple of examples:

The combustion efficiency could be 80% but maybe the pipes are not insulated, so you loose heat even though the boiler is ok you burn more fuel

Or, the combustion efficiency could be 80% but the boiler may be oversized (more likely) or undersized (less likely) which causes the total efficiency to be not good.

What the tech did was correct, no reason to think you got snookered

Steamhead

Did the tech print out the test results? What were they?

HVACNUT

The fact that the tech had to make a test hole on a 20+ year old boiler is a bit scary. Testing (probably with a wet kit in the beginning) should have been performed annually from year 1.
And like @Steamhead said, where's the print out of the techs analysis? That's seems a little sketchy. Even of he was out of printer paper, he should have shown you the display.

larryjbjr

No print out.

It was a "tech" that came out last winter thru the Wisconsin energy assistance emergency furnace repair program. My boiler was making a loud noise. Turned out to be the draft inducer. But he checked the efficiency at my request. Said it was fine.

I think I may just hire someone to come out and inspect it for me.

I have tried searching for a contractor on this site, but it says no one within a hundred miles of me.

I live near Sheboygan Wisconsin. Anybody know a contractor out here you would recommend?

captainco

He may not be on this site but D & M Plb and Htg in Sheboygan has been Certified in combustion testing in the past. Based on the real rules of combustion the maximum efficiency of your boiler is about 71% which is comparable to most boilers today except the modulating ones. Unfortunately a combustion analyzer will say it is much higher but it doesn't include latent heat loss which is about 14%.

larryjbjr

> @captainco said:
> Based on the real rules of combustion the maximum efficiency of your boiler is about 71% which is comparable to most boilers today except the modulating ones. Unfortunately a combustion analyzer will say it is much higher but it doesn't include latent heat loss which is about 14%.

Would you mind elaborating on this a little bit?

captainco

I have been doing combustion testing for almost 40 years and have been teaching it for over 30 years.
I helped many contractors and engineers to tune-up their equipment. The combustion analyzers rarely showed any major improvement and in many cases just the opposite while people were saving hundreds, or thousands or ten of thousands of dollars. This made me research how efficiency is calculated. It is universal so if I disagree with it I am a bad guy.

Anyway, fuel consists of carbon and hydrogen. 90% is carbon and 10% is hydrogen. In the combustion process hydrogen or water becomes up to 18% of the available btus. With excess air this drops to about 14% latent heat.
O2 or excess air in the flue gas wastes heat but is necessary for safe combustion. Every percent of O2 in the flue gas is 1% additional loss. Normal lowest O2 is 6%. 6 + 14 = 20% loss

Flue temperature is the next measurement that is part of the efficiency calculation. Every 30 degrees the flue temperature is above room temperature is another 1% loss. Normal minimum flue temperature for your boiler making 180 degree water would be 350 degrees. 350 - 70 = 280 divided by 30 = 9.33%. 70.67% is the efficiency which is the best anyone can get except Mod-Cons.

After 39 years of testing and evaluating, these calculations are as close to reality as possible. But I am just the bad guy!!

larryjbjr

So if what you're saying is correct, then I would save a ton of money by switching to a modulating condensing boiler?

captainco

Absolutely!! They actually operate around 90%.

HVACNUT

Also keep in mind, the AFUE rating was implemented for warm air furnaces only. Since the introduction of mod cons, AFUE is accurate at design conditions due to low stand by heat loss. The yellow tag on your atmospheric boiler does not represent true efficiency.

Paul48

This can't be stressed enough.......The mod/con must be sized and installed by a skilled craftsman.

captainco

If one checks the IBR rating of a boiler, it is closer to a correct efficiency than any other. It is still a calculation versus a measurement.

Input = 100,000 output = 80,000 = 80% Efficiency
IBR = 68,000 output = 68% Efficiency

AFUE is the most inaccurate efficiency this industry has ever had!!

captainco

Right on Paul!!!

EBEBRATT-Ed

So you are are saying a mod-con will give you 90% with 180 degree water?? Not sure about that

captainco

You are correct Ed. The hotter the water in a Mod-Con the lower the efficiency. The 90% was using the lower temperatures.. At 180 degrees water it is closer to 85% to 87%. But a lot better than 65% to 70%.

Tim McElwain

Eliminate the heat losses in the house first, then look at installing a Mod/Con. I was on a job recently that had so many air changes that getting any kind of overall efficiency is slim to none. They had spent some big bucks to have a Mod/Con boiler installed by a friend.
I put them in touch with a contractor who came in and did some major improvements to eliminate heat loss.

A heat loss was done and we are looking at a boiler which is now oversized. You just can't win if you do not do a complete evaluation of buildings.

larryjbjr

> @Tim McElwain said:
> Eliminate the heat losses in the house first, then look at installing a Mod/Con. I was on a job recently that had so many air changes that getting any kind of overall efficiency is slim to none. They had spent some big bucks to have a Mod/Con boiler installed by a friend.
> I put them in touch with a contractor who came in and did some major improvements to eliminate heat loss.
>
> A heat loss was done and we are looking at a boiler which is now oversized. You just can't win if you do not do a complete evaluation of buildings.

Absolutely. I am planning in the next couple weeks to take all the siding off the house, blow insulation where it needs to be blown in, put up three-quarter inch foam board, and tape all the seams. Then hopefully next summer I can put new siding up.

I'm sure that by itself will cut back on a lot of my heat loss.

j a_2

I personally think there are way to many variables to be able to test it once and say this is what my analyzer says..and that's it....your unit will only reach its highest efficiency if it is attached to the boiler piping and house heating system correctly...As well as your heating system matches the heat loss to your house....Long of it there is no simple test, in my old opinion

Gordy

Very true @ja those variables you mention changes system efficiency a lot.

j a_2

Gordy said:

Very true @ja those variables you mention changes system efficiency a lot.

We know, but homeowners only want to hear efficiency, from the realtor selling them the home...then Mr. home inspector comes in and has not a clue what he's looking at in terms of heat..and anything associated with it....but takes there money anyway...Gordy you know the rest of the story,I am sure

ChrisJ

j a said:

Gordy said:

Very true @ja those variables you mention changes system efficiency a lot.

We know, but homeowners only want to hear efficiency, from the realtor selling them the home...then Mr. home inspector comes in and has not a clue what he's looking at in terms of heat..and anything associated with it....but takes there money anyway...Gordy you know the rest of the story,I am sure

What do you expect when that's all that has been drilled into their heads for the past 10+ years?

Homeowners only know what they are told.

What I've learned is, and of course this is only my personal opinion, but both AFUE and SEER are a crock of poo.

I feel EER is decent for air conditioning, but have no clue what to use for boilers and furnaces. I guess combustion efficiency is the best we've got, but even that varies.

Can we trust the DOE rating on a boiler vs it's input on a boiler?

Gordy

Total system efficiency is the only real world measure. The efficiency in Producing the cooling, or heating brush feeding the system is only part of the picture.

As the btu requirement goes up, and down the building envelope, and delivery infrastructure plays a huge role in the total system efficiency.

Tim McElwain

Bottom line the true test of efficiency is your fuel bill. It to can be deceiving especially with gas as you have other equipment so you have to be able to measure actual heating system usage.

ChrisJ

Tim McElwain said:

Bottom line the true test of efficiency is your fuel bill. It to can be deceiving especially with gas as you have other equipment so you have to be able to measure actual heating system usage.

True, except for the constant changing weather, changing loads in the house, sun loading etc. I've found it impossible to track small changes.

I wanted to rig up something to collect condensate for an hour to see exactly how my steam I produced, but it's too much work and I can't say if my measuring would be accurate enough.


I still feel the #1 thing when it comes to efficiency, is the one I've done nothing with (go ahead and say it @Gordy ). Insulation and drafts. You can have a super tight, well insulated (6" thick walls full etc) house with a 60% boiler and a drafty un-insulated house with a 90% boiler and the 60% owner is going to spend less money all year and probably be more comfortable.


Comparing to neighbors with similar buildings is very helpful though.

For me.........my best test of my own steam system was our next door neighbor with a typical 80% forced air furnace in an almost identical age house to mine, even built by the same family in the 1860s except with all much newer windows.

My gas bill was consistently less. Not much less, but always less. That was a good sign I had things working about as good as they could for this house in it's present condition.

Gordy

Btus/sf/hdd is best method. You can actually see how system efficiency goes up as heating load increases.

Gordy

ChrisJ said:

Tim McElwain said:

Bottom line the true test of efficiency is your fuel bill. It to can be deceiving especially with gas as you have other equipment so you have to be able to measure actual heating system usage.

True, except for the constant changing weather, changing loads in the house, sun loading etc. I've found it impossible to track small changes.

I wanted to rig up something to collect condensate for an hour to see exactly how my steam I produced, but it's too much work and I can't say if my measuring would be accurate enough.


I still feel the #1 thing when it comes to efficiency, is the one I've done nothing with (go ahead and say it @Gordy ). Insulation and drafts. You can have a super tight, well insulated (6" thick walls full etc) house with a 60% boiler and a drafty un-insulated house with a 90% boiler and the 60% owner is going to spend less money all year and probably be more comfortable.


Comparing to neighbors with similar buildings is very helpful though.

For me.........my best test of my own steam system was our next door neighbor with a typical 80% forced air furnace in an almost identical age house to mine, even built by the same family in the 1860s except with all much newer windows.

My gas bill was consistently less. Not much less, but always less. That was a good sign I had things working about as good as they could for this house in it's present condition.

Were setpoints identical, and usage habits? Set back etc.

ChrisJ

Gordy said:

ChrisJ said:

Tim McElwain said:

Bottom line the true test of efficiency is your fuel bill. It to can be deceiving especially with gas as you have other equipment so you have to be able to measure actual heating system usage.

True, except for the constant changing weather, changing loads in the house, sun loading etc. I've found it impossible to track small changes.

I wanted to rig up something to collect condensate for an hour to see exactly how my steam I produced, but it's too much work and I can't say if my measuring would be accurate enough.


I still feel the #1 thing when it comes to efficiency, is the one I've done nothing with (go ahead and say it @Gordy ). Insulation and drafts. You can have a super tight, well insulated (6" thick walls full etc) house with a 60% boiler and a drafty un-insulated house with a 90% boiler and the 60% owner is going to spend less money all year and probably be more comfortable.


Comparing to neighbors with similar buildings is very helpful though.

For me.........my best test of my own steam system was our next door neighbor with a typical 80% forced air furnace in an almost identical age house to mine, even built by the same family in the 1860s except with all much newer windows.

My gas bill was consistently less. Not much less, but always less. That was a good sign I had things working about as good as they could for this house in it's present condition.

We're setpoints identical, and usage habits? Set back etc.

Set points were the same. Usage habits? He heats his house with it. As far as HW usage, similar familes etc. They have an electric clothes drier and stove tho, mine is gas as is my one Weber grill.

Btus/sf/hdd doesn't necessarily work that good either because HDD are very often calculated at other locations, especially when dealing with the gas company.

I've found even using stations on Weather Underground close to me, they see different results.


Btus/sf/hdd is ok for a general idea, but I don't feel it's useful for small changes such as 1-3% in efficiency. There's no way to know for sure what changed.

larryjbjr

What is HDD?

ChrisJ

larryjbjr said:

What is HDD?

Heating Degree Days.
It's calculated off of your alleged local temperature, but often it's done from temperatures pretty far away and inaccurate.

Your gas company or electric company may even show them on your bills.

Gordy

Heating degree days

Gordy

Usage habits. People entering/exiting frequency, cooking, lighting, laundry,exhaust fans. Those are things that have great bearing on fuel consumption for heating, and cooling.

ChrisJ

Gordy said:

Usage habits. People entering/exiting frequency, cooking, lighting, laundry,exhaust fans. Those are things that have great bearing on fuel consumption for heating, and cooling.

Cloudy days vs sunny days.
Wind
wind direction
How many people are in the house.
Equipment running
electronics.

Gordy

System efficiency is a moving target. You will see very wild swings from mild to design days. Double digit % loss, or gain.

captainco

NCI had a satellite company in Iowa a few years ago that did energy audits. They checked the fuel usage on 100 homes that had been tightened, insulation, windows, ducts sealed etc. The heating system was ignored. Each and every home saw no savings whatsoever and in most cases their bills went up.
In one example, a home was weatherized to the hilt and a new modulating furnace installed. A neighbor had nothing done to his house but bought a single stage 90% furnace. When they compared the fuel bill for the next three years, the weatherized and improved home used over 30% more energy each year and this home was 200 sq.ft. smaller.
Fixing the home and not knowing how to operate the system correctly doesn't do much either.
Many utilities throughout the country have had rebate programs for years based on deemed (fictious, misrepresented, exagerated) savings. In most cases "deemed savings" equals "doomed savings".
Fortunately, Mod-Con boilers have been the most efficient piece of the box equipment I have ever seen. Still can be improved. Furnaces on the hand need a lot of work.

ChrisJ

captainco said:

NCI had a satellite company in Iowa a few years ago that did energy audits. They checked the fuel usage on 100 homes that had been tightened, insulation, windows, ducts sealed etc. The heating system was ignored. Each and every home saw no savings whatsoever and in most cases their bills went up.
In one example, a home was weatherized to the hilt and a new modulating furnace installed. A neighbor had nothing done to his house but bought a single stage 90% furnace. When they compared the fuel bill for the next three years, the weatherized and improved home used over 30% more energy each year and this home was 200 sq.ft. smaller.
Fixing the home and not knowing how to operate the system correctly doesn't do much either.
Many utilities throughout the country have had rebate programs for years based on deemed (fictious, misrepresented, exagerated) savings. In most cases "deemed savings" equals "doomed savings".
Fortunately, Mod-Con boilers have been the most efficient piece of the box equipment I have ever seen. Still can be improved. Furnaces on the hand need a lot of work.

How exactly is it possible to reduce heatloss, and have a heating bill go up?

Where did that extra energy go?

HVACNUT

> @ChrisJ said:
>
> How exactly is it possible to reduce heatloss, and have a heating bill go up?
>
> Where did that extra energy go?

>>yeah, that seems a little weird.
I don't mean to get political, but,
Fake News, Fake News!

captainco

That started baffling people back in the 80's with many government programs. Lots of assumed savings but nothing near what was promised if any. Of course most of these were low income houses that got the work for free from government and utility programs so no one really paid any attention.

Sealing ductwork that is already suffering from bad airflow only makes it worse. NCI field studies have shown that the average system efficiency of 95% furnaces in the field is 59%. That is lower than most old furnaces that required less airflow.

We have been doing training in California for the past 4 years with the Energy Department. California has had more energy programs than any other state. But not one of them prior to us showed any savings because it was all about the building and not the system. Although we have only dealt with the A/C system, it has made a major difference. Gas companies aren't that receptive because I don't think they really want to cut usage. Too much gas available and the price is low.

captainco

Not sure any industry has put out more Fake News than ours.

Gordy

captainco said:

NCI had a satellite company in Iowa a few years ago that did energy audits. They checked the fuel usage on 100 homes that had been tightened, insulation, windows, ducts sealed etc. The heating system was ignored. Each and every home saw no savings whatsoever and in most cases their bills went up.
In one example, a home was weatherized to the hilt and a new modulating furnace installed. A neighbor had nothing done to his house but bought a single stage 90% furnace. When they compared the fuel bill for the next three years, the weatherized and improved home used over 30% more energy each year and this home was 200 sq.ft. smaller.
Fixing the home and not knowing how to operate the system correctly doesn't do much either.
Many utilities throughout the country have had rebate programs for years based on deemed (fictious, misrepresented, exagerated) savings. In most cases "deemed savings" equals "doomed savings".
Fortunately, Mod-Con boilers have been the most efficient piece of the box equipment I have ever seen. Still can be improved. Furnaces on the hand need a lot of work.

I would have to question NCI's satellite company's energy auditing methods, and or motives. Because that is just a bunch of BS period.

HVACNUT

That article is VERY misleading. Combustion analysis calculates the "useable" parameters of the fuel, O2, CO2 and net flue temperature.

If you give me 4 quarters, then take back 25 cents, I've got 75 cents as a "whole" to work with, not a dollar. Adding your 25 cents into my equation doesn't work because I never really had it in the first place.