Hot Water Heater Vs Oil Fired Hot Water


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Old 01-29-11, 11:20 AM
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Hot Water Heater Vs Oil Fired Hot Water

The above is on my home improvement list. I am considering adding a electric hot water heater or holding tank and disconnecting the piping and any controls on my oil burner with the help of my neighbor who is a heating specialist. "I'll be the helper". I am not happy with my present heating supply for hot water.
Natural gas is not available in my area.
The first order of business is the location of the new heater or holding tank which will be in the laundry room and will need approximately 40 feet of tubing from there to supply the original line located at the oil burner.
Also it has occured to me that the cold water supply from a laundry room takoff will now be the new pressure side for delivering hot water back through the hot water line to the original source. Then this will feed the rest of the house and all that is needed is to make some changes at the oil burner. If this can be done then I won't need 40 feet of supply tubing.
At this point in my planning, I am not sure which installation would be most economical to operate on a yearly basis.
Should I go with a electric water heater or a holding tank. We are a family of three adults and two children and I think a 60 gallon of either will suffice.
I also heard about the new type of water heaters which have a heat pump attached. But I do not think they been on the market long enough to render an opinion. But a plumber friend already told me that they are good for new construction and not recommended for old.
Then there are whole house instant water heaters to think about.
Which path should I take? Your opinions please.
 
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Old 01-29-11, 03:52 PM
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I'm having a little trouble understanding what you wrote so let me paraphrase it and you can correct any mistakes I make.

It sounds as if you have a boiler for your space heating needs and the domestic hot water is being supplied by a "tankless coil" inside the boiler. Is this correct? If so then you are now probably well aware that this is a terrible way to make hot water, only slightly better than a kettle on a wood-burning kitchen range.

While some people have installed a "holding tank" (along with the requisite pump and controls) on a tankless coil doing so only gives you a greater volume of hot water and does nothing for the inefficient tankless coil method of actually heating the water. The better way, which still utilizes the boiler, is to install an "indirect" water heater. The indirect heater will have a heat exchanger within its tank that has boiler water pumped to it to heat an amount of water also contained in the tank. The indirect water heater can then allow the boiler to go cold between calls for either heat or hot water, something the tankless cannot do.

Indirect water heaters are fairly pricey when all is said and one the cost may be close to $2000. but the indirect heaters usually last for several decades so the cost per year of life is actually fairly low. There is also a possibility that when your boiler is converted to a "cold start" that it may begin leaking when it cools off. This leaking is, unfortunately, not uncommon with cast iron sectional boilers that have spent their entire life being kept hot for domestic hot water.

Another option would be to install an oil-fired stand-alone water heater. This would have the advantage of a lower cost than an indirect (in most cases) but it adds another combustion appliance that will need to be serviced yearly. The oil-fired water heater will likely have a lower overall efficiency of your boiler, unless your boiler is really old. I don't know what the average lifespan of oil-fired water heaters is but I suspect that generally they are shorter lived than an indirect.
 
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Old 01-29-11, 07:46 PM
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"It sounds as if you have a boiler for your space heating needs and the domestic hot water is being supplied by a "tankless coil" inside the boiler. Is this correct? If so then you are now probably well aware that this is a terrible way to make hot water, only slightly better than a kettle on a wood-burning kitchen range."

Thanks Furd, Yes that is correct.
I'll be showing your reply to my heating specialist. You did not mention anything about an electric water heater. Am I to assume that an indirect water heater does not have an heating element and relys on heated water from the boiler to enter its heat exchanger? When I think about efficiancy, I am thinking at the same time about the temperature drop at the heat exchanger and length of time for the indirect water heater to recover to desired temperature.
Don't forget that I believe we need at least a 60 gallon tank for showers and laundry.
 
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Old 01-29-11, 08:15 PM
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Tank-type electric water heaters are the slowest to recover from a significant draw of hot water. I always remember a brochure for an instantaneous water heater I picked up from the state fair some fifty years ago where they stated that a gas fired water heater was about four times faster than the same size electric and an oil fired heater was nine times faster than the electric.

Electric water heaters are the most efficient at about 95 to 98 percent efficiency. This is, unfortunately, countered by the fact that in most cases electricity is the most expensive "fuel" you can use for heating domestic water. Even in my area where we have (relatively) inexpensive electricity that comes primarily from hydroelectric power stations AND have ridiculously high natural gas rates it is cheaper to use gas than electricity for water heating. I'll also go on record as stating that unless you have an inadequate electrical service that a new installation of an electric water heater will be cheaper than any other.

If you think that electric is right for you, based on all the information then I strongly suggest that you install an 80 gallon model. Contrary to what many people might tell you the heater is NOT constantly heating a large amount of water but only heats the incoming cold water when you actually use hot water. In my previous home I was able to take a shower comfortably with the stored hot water in my 80 gallon electric on the third full day of a power outage.

You are correct that an indirect water heater has no electric elements and relies on the hot water produced by the heating boiler. I don't know about your particular boiler but most residential boilers of the last decade or so are very efficient, much more so than a stand-alone fuel burning water heater and that efficiency translates to the water heating function with an indirect. The primary downside to the indirect is that it is completely dependent on the boiler for operation, lose the boiler and you also lose hot water. Generally an indirect is connected to the boiler controls through a "priority" control that will shunt the entire output to the water heater (shutting off heat to the house) until the water heater has recovered from a significant draw down. Independent heaters are insulated to about the same standards (or a bit better) as electric water heaters so their "standby losses" are quite low, generally no more than one degree Fahrenheit per hour. Even from a total draw down (complete use of stored hot water) I think that most properly matched (to the boiler's output) indirect heaters will recover in about 15 to 20 minutes whereas an electric will take at least an hour and often closer to two hours for complete recovery.
 
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Old 01-29-11, 08:31 PM
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Thanks again,
This is very good information.
 
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Old 01-30-11, 04:25 AM
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Furd,
I believe that there is one other option left. What can you tell me about LPG. When I was searching for a house, I came across one that had completly converted to it. So even if I installed a 40 gallon LPG water heater, what size storage tank would I need? And does the installation of a above ground LPG storage tank affect home insurance rates that could possibly wipe out any savings. What are your thoughts?
I also forgot to mention in my other post that my boiler provides very hot water for only about 1 minute or less and then the water turns warm enough to allow me to place my hands under it. I do not know the age of the boiler at this time, but I believe I have literature provided to me when I purchased my home that tells me when the boiler was installed.
 
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Old 02-01-11, 10:33 AM
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Liquid Petroleum Gas is a by-product of refining crude oil and as such its price will follow the price of crude. In other words, LPG (mostly propane) is EXPENSIVE and it has another drawback in that it is heavier than air and if your appliance (water heater) is in a basement then a dangerous amount of gas could accumulate from a leak with disastrous results. I think if I were in your position I would stay with oil or go with an electric stand-alone water heater..

You would likely need several hundred gallons of stored LPG to keep from having the truck visit you weekly, your local propane dealer would be able to give you better information and would also know more than I concerning any insurance increases and local regulations.

The coil in your boiler is probably "limed up" or coated internally with a calcium build up from hard water. Sometimes the coil can be cleaned but most often it is simply replaced. Replacement can also be problematic as it often happens that the bolts (or studs) into the boiler break off when trying to remove them.
 
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Old 02-02-11, 02:49 AM
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Thanks,
I checked a list of permits and saw that one was pulled for boiler, mechanical and electrical in 1989. So I suspect the boiler was replaced then. I will check with the municipal authority for any additional information.
So far, it appears that I still need an Indirect water heater and cleaning of the coil or replacement. One would think that cleaning of the coil should be part of the maintenance contract as the mechanic was here in November to do yearly maintence and he did not clean the coil. I'll re-check the oil burner contract. Now I need to find the expected life of the boiler to make a decision to replace it.
 
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Old 02-19-11, 02:46 PM
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If electricity is cheap in your area, instant water heater may be the best option. I can't image your family members taking showers all day long, so there is no apparent reason to keep a tank of hot water 24/7 on and keep paying electric bill for it. Just choose a whole house tankless water heater with flow rates enough to support the whole family. Many models can be connected in parallel to increase the hot water supply if needed.

Here is a good comparison table for both electric and gas tankless water heaters, including venting option, activation flow rates, ability to connect several units in parallel, etc.:

Buyer's Guide to Tankless Water Heaters
 
 

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