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Hot Water

April 21, 2015

indirect-hot-water

The other day, my son asked about swapping out his current hot water system to an electric hot water tank.

He currently has what is called an indirect hot water heater that uses a zone off his oil fired boiler to make hot water. (See diagram)

There were a number of reasons why he considered doing this.

First, he has electric solar panels on the roof of his house which have lowered his electric costs significantly, so he thought an electric hot water tank might save money.

Second, in the winter, he had issues with his existing system providing enough hot water when he needed it for his morning shower.

Lastly, in the summer, he felt it was not efficient for the boiler to come on and heat up boiler water so it could produce hot domestic water.

electrical-hot-waterHe thought that maybe a stand-alone electric hot water tank (see diagram left) could cost less, provide consistent hot water, and be more efficient.

He asked me what I thought.

Before I tell you what I told him, I want to point out that  there is no simple answer. There are many variables in determining the ‘best’ way to produce hot water.  Variables, like what kinds of fuel are available, what type of budget one has for the initial cost of the equipment, monthly usage cost, and annual maintenance cost.  Also, where he lives enters into fuel costs and availability of expertise in the various solutions.  Other variables are family size and  hot water usage or demands.

Finally, technology and efficiency standards are constantly changing so the answer depends on when he wants to make this change.

To compare heating options, I first need to define a term called BTU’s (British Thermal Unit).  A BTU is a measurement of energy and is defined as the amount of energy to raise one pound of water 1 degree Fahrenheit.  Or for those who are visual, one BTU is equal to burning one kitchen match.

I will limit this analysis to the most common fuel types.  If we look at just cost per BTU, natural gas is the first choice, followed by fuel oil and then propane and electric.

However, fuel costs are seasonal and they vary significantly over time and within the US.fuel-oil-costs

The chart on the above shows that  fuel oil costs for the past two years varied from $2.75 per gallon to over $4.00 per gallon.

 

If we look at propane prices over the past two years (below), we see a big spike to $4.00 per gallon in the winter of 2013-2014 and a leveling of costs in the winter of 2014 – 2015 to around $2.30 per gallon.Propane-costs

 

Natural gas is measured in cubic feet.  Prices fluctuate with demand, so it goes up in the winter time (see below)Natural Gas costCurrently, natural gas prices are very low.  In the last year, prices varied from a low of $9.49 to a high of $17.39 per thousand cubic feet.

Electric costs are measured in kilowatt per hour or kWh.  The costs vary seasonally and throughout the US (see below).  electric cost

The US average is 9.94 cents per kWh.  However, if you live in New England, where my son lives, the cost can vary from 15.94 cents to 20.45 cents, a significant difference.

To compare fuel costs to heat water, we need to determine the BTU’s in a unit of fuel.  Then we also need to take into account two efficiency factors. One is the efficiency of taking the energy in a unit of fuel to BTU’s. And the other is the efficiency to heat water with those BTU’s to the desired hot water temperature.

Below is a chart of the BTU’s in each fuel type and efficiency in converting it to BTU’s. This chart calculates the cost for a million BTU’s using the low and high prices throughout the heating season and various parts of the US.

Unit cost Cost per million BTU’s
BTU’s Units Low  High  Eff. low high
Natural Gas 1,028,000 mcf $9.490 $17.390 82% $11.26 $20.63
Oil #2 138,000 gal $2.900 $3.550 82% $25.63 $31.37
Propane 91,800 gal $2.400 $4.000 82% $31.88 $53.14
Electrical 3,412 Kw $0.098 $0.245 100% $28.84 $71.81

But we still have not made hot water. We only have cost per BTU. Let’s now apply the second efficiency factor to those BTU’s to make water. To get this efficiency, we need to know the input water temperature, the output temperature, the heat loss of the tank, the efficiency of the burners or elements, and heat transfer efficiency.

This can get complex.  However manufactures of hot water systems do provide this data for their equipment. To find it, read the specifications for the system or look for it on a tag that is normally attached.

For my analysis, I’ll simplify it and use the following percentages: fuel oil and gas efficiency hot water tanks are in the 60 – 65% efficiency range; electric hot water tanks are in the 90 – 95% range.

To compare costs for hot water, it really does not matter what we assume for usage, as long as we apply the same usage to the various fuel types. The data is valid for comparison purposes.   I will use 70 gallons of hot water per day for a family of four, input water temperature of 60 degrees, output temperature of 120 degrees which requires 16.3 million BTU’s per year.   The chart below shows the range of low and high annual cost.

Cost  1 million BTUs. Annual cost
BTU’s Units System Efficency low high low high
Natural Gas 1,028,000 mcf 0.62 $18.16 $33.27 $296 $542
Oil #2 138,000 gal 0.62 $41.33 $50.60 $674 $825
Propane 91,800 gal 0.62 $51.42 $85.71 $838 $1,397
Electrical 3,412 Kw 0.92 $31.35 $78.05 $511 $1,272

The bottom line is that for tank type heaters, natural gas is best.  Fuel oil is second best and propane and electric the most costly.

So, what did I tell my son?  Since, he already has a indirect system using his fuel oil fired boiler, the additional cost of getting hot water in the heating season is very small.  So, I told him that replacing his fuel oil indirect hot water tank with a classic electrical hot tank will not be a good idea. His solar power electrical panels may produce electricity cheap, but a hot water tank would exceed the capacity of his panels, causing him to extra kilowatts from his local electric company.

However I should also point out that there are newer technologies on the market.  Tankless hot water, or on demand, systems have been on the market for some time and electric hybrid heat pump hot water tanks are now available.   There are also solar heaters and drain-water heat recover systems.  These systems may offer cost benefits over today’s classic solutions.

There is no simple answer to what is the best way to get hot water.  Below you can find pointers to various websites that I used to answer my son’s question.  You can use them to get an ideal on how to determine the best answer for your own situation.

What is a BTU: www.businessdictionary.com/ and wikipedia.org

How much water average homes uses: http://www.oeic.us

Average electrical cost – www.eia.gov

Selecting a new hot water heater: energy.gov

To calculate cost of fuel to generate BTU’s: http://nepacrossroads.com/fuel-comparison-calculator.php

Average hot water usage and cost per year:  ugi.com

 

 

This blog was written by Fred Wilbur. Fred was an employee of Keith Specialty Store from 2005 – 2015 and today enjoys sharing information to help people have a better life.

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Why Use Proper Case?

September 15, 2014

Today’s world of text messaging, Face Book posts, Twitter tweets, and smart phones applications have many people using only lower case letters in their communications. This blog entry is to point out a problem that may convince you to use appropriate upper case when you fill in an order form.

Consider the example:  “apt l06”.

Is this Apartment “106” as in one hundred and six, or is it “L06” and in “ell zero six”?

Depending on the font used to translate your entry, the number one is hard to distinguish from the lower case letter “L”.

So, if you live in apartment number one hundred and six , and if you write your address as Apt 106, I can assume since you capitalize the letter “A” in “Apt”, that the “1” in “106” is, in fact, the number one.

But if you lived in apartment number “L06” and you wrote: “apt l06”, what assumption can I make from the “l” in “l06”? Don’t say I should just cut and past the characters into the address line, for that just pushes the problem to the person delivering the package.  If you wrote:  “Apt L06”, I would have no question nor have to make any assumptions.

What prompted me to write about this case issue? I got an order to send something to a military base and they had an address line of “mfc llc”.  Initially I thought it was some military acronym and wrote the address as “MFC  11C”. But my co-worker pointed out that the “11c” was actually the LLC and the ‘mfc’ was the company name.

A day later, I was setting up an application on my smart phone to allow me to deposit checks into my bank account using the phone’s camera.  The instructions said that my user ID was the characters: “l006 followed by the characters I entered for my ID.  I had a number of failed attempts to log in until I realized that maybe the first character may be the letter ‘L’, not the number “one”. When I tried the ID with the letter “L” it worked. To even hone in the point, the first letter had to be the upper case “L”.  G0 f1gure!

Oil Burner Electrodes

September 20, 2013

Here is an answer to an often asked question.  Oil Burner Electrodes can vary from furnace to furnace and are not always obvious with the furnace burner and serial number as burners are sometimes exchanged by service professionals from the original.   Therefore the electrodes might have been changed and need to be matched with that burner.     Sometimes burners change within model numbers too.    We have found the best way to find which oil burner electrodes you need to purchase is to match the electrodes by shape and size. We do not have a simple way to identify them from your oil burner model number.

Other than shape, there are three measurements you need ;  The diameter of the porcelain, the length of the porcelain, and the distance from the end of the porcelain to the end of the tip (measure straight – not along the bends). See diagram on picture attached/below:
Inline image 2
We carry a wide number of popular electrodes but we do not carry all of them. We can special order some that we do not stock.  We have listed our supplier’s catalog pages on our website that you can use to match up against yours.  Look at the two pages :http://goo.gl/S21dbk and http://goo.gl/Wx13i5 If your browser shows these pages too small, often if you click on  it, your browser will enlarge the picture. You can also hold down the CTRL key and press the + sign to zoom in (holding the CTRL key and pressing the – sign zooms out.)
If you find a electrode on either of these pages that match yours, send us the ‘Cat. No.’ and we will get you a price and availability. Ignore the prices on these pages, they are not accurate.
If you cannot find a electrodes that match yours on our website page or on one of the two supplier’s catalog pages, then we most likely cannot get it.
Hope this helps,
Please review your shopping experience – review our store.Keith Specialty Store
keithspecialty.com 
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724-397-8838 (outside the US)
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