efficiency of 15 yr old peerless

[afrost]

i inspected a peerless boiler. #WB-125-WPC. it's about 15 years old.

owner is complaining of inefficiency in spite of regular service. the house remains unoccupied during the week but the heating costs are about the same as when it was occupied full time.

any ideas what to look for? is the furnace just old and inefficient?

thank you.

[David P. Valley]

Originally Posted by afrost

i inspected a peerless boiler. #WB-125-WPC. it's about 15 years old.

owner is complaining of inefficiency in spite of regular service. the house remains unoccupied during the week but the heating costs are about the same as when it was occupied full time.

any ideas what to look for? is the furnace just old and inefficient?

thank you.

First off, lets determine if this is a boiler as you originally stated or a furnace as you stated at the end of your post.

How do they know it's inefficient?

How many BTU's does this unit have and what's the square footage of the area it's conditioning?

One or two zones?

[afrost]

Originally Posted by dvalley

First off, lets determine if this is a boiler as you originally stated or a furnace as you stated at the end of your post.

How do they know it's inefficient?

How many BTU's does this unit have and what's the square footage of the area it's conditioning?

One or two zones?

dave, it is a boiler. wet baseboard radiation. 2 zones 1st floor, 3 zones basement. about 2500 sf.

inefficient because its costing $3000 (projected) this year to heat. heat set on 55 degrees upstairs, off downstairs monday thru friday. supplemental wood heat on weekends.

[William J. Decker]

If it is conventionally drafted, it is inefficient, when compared to the more modern cat 1, 3 and 4 boilers. Efficiency, technically, is the ratio of input BTUs to output BTUs. Then you have to figure in the building envelope insulation, drafts, windows, etc.

Efficiency can be determined in a variety of ways. Heating costs (which vary, depending of fuel type and costs) is not a meaningful measure of heating efficiency.

In other words, the situation is a lot more complex than assumed.

Call me, if you need verbiage.

Hope this helps;

[Brian A. MacNeish]

Originally Posted by afrost

dave, it is a boiler. wet baseboard radiation. 2 zones 1st floor, 3 zones basement. about 2500 sf.

inefficient because its costing $3000 (projected) this year to heat. heat set on 55 degrees upstairs, off downstairs monday thru friday. supplemental wood heat on weekends.

Got to start with an efficiency test! Compare fuel use from year to year in terms of btu's purchased not the total $$$ costs. Then analyze the house house for air leakage, insulation levels and any changes/additions/alterations made in the past year or two.

Ps: Just saw that Will covered some of these!! Started this post about 2 hours ago and just returned to finish it!

[Brian E. Kelly]

How much energy does it take to re heat a cold house every week? Might be better off setting it a low setting and leaving it.

[David P. Valley]

Originally Posted by afrost

dave, it is a boiler. wet baseboard radiation. 2 zones 1st floor, 3 zones basement. about 2500 sf.

inefficient because its costing $3000 (projected) this year to heat. heat set on 55 degrees upstairs, off downstairs monday thru friday. supplemental wood heat on weekends.

When it's freezing outside and the boiler thermostat is turned down, it doesn't necessarily mean that it's going to use less fuel. Let's say it's 40 degrees outside and the boiler thermostat is set at 55 degrees. This boiler will be kicking on every time there's a drop in temperature inside the home, which is every several minutes or so. The only time this boiler will not kick on and will be saving fuel, is when the thermostat senses that it's 55 degrees inside the home and this temperature stays at 55 degrees. But once the temperature drops again, the boiler will kick on. The only time I can see this boiler becoming efficient is when the outside temperature (which affects inside temperature) rises above the setting at the thermostat.

Another thing is a boiler is probably the single largest user of heating fuel (natural gas or fuel oil). Boiler systems are always inefficient users of fuel. At best, they may be 85% efficient and on average they are probably 60 to 75% efficient. This means that upwards of 40% of the energy in your heating fuel is wasted because it's going up the chimney.

If the owner is really concerned with saving money on fuel costs, simply recommend to have the boiler maintained and tested by a qualified Plumber. He can see what the problem may be.

I know an increase in stack temperature frequently signals soot or scale buildup inside the boiler. Have them make sure that an electronic combustion efficiency tester is used for the maintenance program. It analyzes flue gas and displays oxygen content, stack temperature and combustion efficiency. Comparison data from test to test will help pinpoint any maintenance requirements.

[Linas I. Dapkus]

Originally Posted by bkelly2

How much energy does it take to re heat a cold house every week? Might be better off setting it a low setting and leaving it.

Or move to Arizona.

[Brian A. MacNeish]

Originally Posted by bkelly2

How much energy does it take to re heat a cold house every week? Might be better off setting it a low setting and leaving it.

Heat flow out of a house by conduction is like current flow through a wire. And the equations are similar. I'll start with the electrical which everyone should be familiar with.

I (amps) = V (voltage) / R (resistance)........12 amps = 120 V /10 R


Current (electron) flow (I) is driven by the voltage.......The voltage may be looked at as the driving force or presssure that forces the electrons to move along the wire (Direct current). Double the voltage (V) and you double the current flow; halve the voltage and you halve the flow.

Current flow is reduced by the resistance (R). Double the R and halve the flow.

In a building, the heat flow, U, (current) is in btu's per hour per sq ft per degree temperature difference. The driving force (voltage) is temperature difference between outdoors and indoors (heat flows from higher to lower temps).....called Delta T (DT) in scientific terms. The higher the DT from inside to outside, the higher the heat flow. .

Heat flow U = TD / R If we double or halve the DT, we double or halve the heat flow. If we double the R, we halve the heat flow.

When we set the temperature back in a building, we reduce the temperature difference (DT) between inside-outside and thus the heat flow outwards is reduced due to a smaller driving force. Therefore heat is saved!! We have to be careful how far we set back due things like freezing of pipes and potential condensation from cooler air temps.

A little aside here: In testing materials for resistance to heat flow, they first find the heat flow through a material in btu's per hour per sq ft per degree temperature difference (btu's/hr/sq ft/deg). The R value we are familiar with is simply the reciprocal or inverse of the heat flow. If the heat flow was 0.1 btu's /hr/sq ft/deg, the R value would be 10. But the R we are familiar with does have units.....we just don't see them on insulation bags or charts:

note-dots are to keep units aligned.
R = hr-sq ft-deg .......the inverse of the flow .....btu
...........btu.................................... .......... hr-sq ft-deg


For the example, the outside temp is kept constant at 30 deg

Inside temp 70: DT = 40 deg;

U= 40 deg / 10 hr-sq ft-deg
.........................btu

Thus heat flow= 4 btu/hr/sq ft


setback to 60, DT now = 30:

U= 30 deg / 10 hr-sq ft-deg
..........................btu

Thus the heat flow= 3 btu/hr/sq ft

Therefore, the more we can safely set back, the more we will save.

Yes, when the t'stat calls for 70 degrees again, it will take longer to heat the house up than we see in a regular heating cycle........But when we first setback the temp, the walls and objects of the house will release stored heat (1,000's of btu's) to the air as its temperature drops. The heat source will not come on for quite a while until the air temp falls below the set back of 60 deg. So we have saved running time here.....this saved time should be equal to the time required to heat the house back up. This then is a balanced situation. Thus the savings during the setback period are real savings.

Fuel companies don't want us to set back and save. They use the "long running time" and "takes a lot more heat to warm back up" false arguments to make more $$$$. Isn't is "All about the money"?

[Brian A. MacNeish]

Originally Posted by dvalley

When it's freezing outside and the boiler thermostat is turned down, it doesn't necessarily mean that it's going to use less fuel. Let's say it's 40 degrees outside and the boiler thermostat is set at 55 degrees. This boiler will be kicking on every time there's a drop in temperature inside the home, which is every several minutes or so. The only time this boiler will not kick on and will be saving fuel, is when the thermostat senses that it's 55 degrees inside the home and this temperature stays at 55 degrees. But once the temperature drops again, the boiler will kick on.
Fuel companies love this reasoning

The only time I can see this boiler becoming efficient is when the outside temperature (which affects inside temperature) rises above the setting at the thermostat.
This boiler may very efficient (such as a modulating, condensing gas unit at 90%+) and produce heat fairly cheaply. When the outdoor temps rise above the set temp, heat loss esentially stops and there is no need for the system to run. It has nothing to do with the efficiency of the furnace/boiler.......A 45% efficient furnace/boiler will look very efficient if it does not have to run at all.

This field is something we need good courses in. We all may be giving advice to people that we believe to be true. I just happen to have been working in energy conservation either full or part time since 1977. For example, I did an inspection 60 miles from home yesterday AM, then my son (to be back in university in January) and I blew an attic with cellulose from 3-8 pm

[phinsperger]

Originally Posted by afrost

.... the house remains unoccupied during the week but the heating costs are about the same as when it was occupied full time.

I read the orginal question as to why there is a suspected decrease in the eff of the boiler - not how efficient or inefficient boilers are, or heat loss dynamics from the building envelope (which I assume is unchanged)

Because its a boiler and there is suspected decrease in efficiency, scalling would be high on my list of possible causes. Boilers and the their associated piping are very prone mineral build-up.

The next question to ask is over what time frame decrase in effiecent is noticed to have taken place. (ie, gradually over many years, or sharpely over a year or two)

[Brian A. MacNeish]

Originally Posted by phinsperger

I read the orginal question as to why there is a suspected decrease in the eff of the boiler - not how efficient or inefficient boilers are, or heat loss dynamics from the building envelope (which I assume is unchanged)

Because its a boiler and there is suspected decrease in efficiency, scalling would be high on my list of possible causes. Boilers and the their associated piping are very prone mineral build-up.
Got to start with an efficiency test!

The next question to ask is over what time frame decrase in effiecent is noticed to have taken place. (ie, gradually over many years, or sharpely over a year or two)
Compare fuel use from year to year in terms of btu's purchased not the total $$$ costs.

Paul:

As you can see, I essentially stated this earlier on the third or fourth post in the thread.

Then analyze the house house for air leakage, insulation levels and any changes/additions/alterations made in the past year or two.