Problem with oil burner and tankless coil - Need advice

BlackDogKurt

<span style="font-size:12pt">We are the second owners of a 9-year old house with an oil burner furnace and baseboard heating. There is no water heater tank and the hot water is heated by the oil burner furnace (tankless coil).</span>

<span style="font-size:12pt">In 2007, we had to replace the power vent blower motor, which cost us over $900 with labor. The repairman said that the motor probably wore out faster than normal because of the fact that it was running so frequently and year round, every time water was heated. He suggested that we might want to consider switching to a tanked water heater since he could not guarantee how long the new motor would last.</span>

<span style="font-size:12pt">This year, the transformer on the furnace needed to be replaced, which cost a few hundred more. In addition, we have found that the water does not get hot enough in the winter if more than one of the three heat zones in the house is heating at the same time. We were leaning to live with this inconvenience (I assume our tankless coil is undersized…???), but now, in the past few months, the temperature of the hot water suddenly does not get very warm ever, and it is not even winter yet. I am afraid that there is something new now wrong.</span>

<span style="font-size:12pt">Having now spent over $1,000 on the boiler in the past few years, and being wary of the power vent blower motor going again in the next few years, and now with the new problems with the hot water, I am seriously wondering if it does make sense to switch to a standard water heater tank to reduce the wear on the boiler parts and cut our losses. As I am previously unfamiliar with tankless coil system, I am looking for other opinions or suggestions before making a decision though.</span>

<span style="font-size:12pt">Thanks!</span>

Robert O'Brien

A

powerventer is a mechanical chimney and like a all mechanical devices needs maintenance and will eventually fai,.9 years is about the average lifespan. If that is unacceptable,install a chimney.The powerventer was only chosen because it was cheaper for the builder than a chimney. Since you have no chimney,a separate  direct fired water heater will require another powerventer in addition to the one you already have.

A properly wired boiler w/ tankless coil will put out basically the same amount of DHW regardless of season,that amount might be inadequate but it will be the same as long as all zones are wired through the reverse.

If it were my house,I'd put in an indirect water heater and ODR,make sure the boiler is warm start and start saving for a chimney

TonyS

Take a look at one of these

http://www.stiebel-eltron-usa.com/accelera.html. Rheem also makes one, you can check their website. With oil at 2.50 and this unit running minimal cop of 3 you would spend less than half with electric at .12 cents a kw. With you running a tankless coil you will probably be at 1/3.

Robert O'Brien

The

only problem is oil is $2/gallon here and electricity is 21cents Kwh.Math doesn''t look so good anymore.

TonyS

Watch this video

then decide  http://www.oilsmokeandmirrors.com/

Robert O'Brien

Deja Vu?

Somehow I get the feeling I've been here before!Since the OP has oilheat,it's a safe bet they're in the northeast.How is the electricity generated ? Some nuclear,some coal and some hydro but the vast majority is from oil and natural gas and will be for the foreseeable future. On a BTU basis electricity is 4-6 times the cost  of oil or NG with propane in between.

TonyS

Very little electric is made

from oil, New York being the largest at 8%. Good old American coal accounts for 57% and the rest is Gas or nuke. You are correct about electric cost per btu...if you create heat from electric, which is ridiculous to do. Heat pumps do not create heat, they simply move it from one place to another using an electric compressor. A COP is the amount of heat returned in comparison to straight electric resistance, a COP of 3 means 1 penny in 3 pennys worth out , a COP of 5 is five times the amount. When a heat pump is used in warm conditions, like summer or spring or fall to make hot water , the COP reaches 5. At that point There is no fossil fuel even in the ball park, even at 21 cent a KW.  GAME OVER. http://www.airgenerate.com/      http://www.pelletheat.org/3/residential/compareFuel.cfm  Here is a fuel calc, remember to enter electric at 300% to 500%

Robert O'Brien

How about the

6 months a year that those BTU's aren't free?They come from somewhere? I can't speak for the country as a whole,but there isn't much coal in the NY Metro area,which has the bulk of the population of the state.





http://tonto.eia.doe.gov/state/state_energy_profiles.cfm?sid=NY

TonyS

Truth is

Neither of us know where the price of fuel is going to end up. Oil ,gas or electric. The only system we sell that I can honestly tell the people how much it will cost to operate in 30 years is solar. Its free today and will be free tomorrow as long as you pay your property taxes LOL. I have a drainback vac tube system backed up with a gas tankless Navien. Today when I got home at 3 I already had 80 gallons at 140 degrees. I agree the heatpumps units have to be in the right place. If you have a damp basement and use a dehumidifier it is perfect. I have a customer right now who uses a wood stove in his basement in the winter. The basement gets really hot even with the vents he has cut in the floor and the fan circulation system. This unit is perfect in that situation. He will get high COPs summer and winter.

Robert O'Brien

I agree

with the solar w/ tankless backup.The best solution but certainly not the cheapest upfront although with the 30% federal  solar credit,30% (capped at $1500) on the tankless and another 25% solar credit if you live in NYS and  15% solar rebate from NatGrid  if you use NG to power the tankless,you have a pretty sweet deal!

TonyS

It seems New York is serious

about renewable energy. PA isn't nearly so generous.

Robert_25

Hot water

You said that you run out of hot water when more than one one in the house is calling for heat, this isn't because the tankless coil is undersized, it is because the boiler cannot maintain a high enough jacket temperature with that load.  An indirect hot water heater with a priority zone control would solve this issue.

Jean-David Beyer

An indirect hot water heater

At my house, the smallest boiler I could get is about double the heating load, so I did not allow for the additional load of my indirect fired hot water heater. This is not the disaster it would at first appear, because it is a modulating boiler that can get down to about half the maximum load if necessary without cycling. The boiler has a 5:1 turndown ratio; I.e., its input can be varied between 80K BTU/hr down to 16K BTU/hr. I calculate my heat load at between 30K BTU/hr and 40K BTU/hr depending on how I do the calculations.*



Furthermore, in the summer, it does not seem as though my boiler spends more than 5 to 10 minutes a day heating the hot water. My boiler is set up to run three zones, one of which is the hot water heater, that runs at maximum priority. It can put possibly 70K Btu/hr into the hot water under these conditions. I have not figured out how long it would take to heat 40 gallons of water from whatever the winter temperature of my cold water might be up to 120F that I want the hot water to be, but it cannot be very long.



_____

* I calculated using Slant/Fin's program, and the boiler manufacturer's worksheets, respectively. No need to get more accurate for me, since this is safely under the minimum mod|con the manufacturer makes.



A question comes up, and I think I know the answer. The manufacturers seem to list several ratings, one of which they put into their name of the boiler. So mine has 80K BTU/hr input. But the heat loss calculations probably specify the output, right? Especially for me because my boiler is in my garage, that I do not intentionally heat, so the wasted heat does not get into the building.