indirect water heater vs. boiler coil

Cosmo_3

If you plan on staying in the house for more than 5 years, go for it. In fact I would go for it even if I was planning on leaving within less! Payback depends on your hot water usage, and is sometimes difficult to calculate.

Let me paint a picture.

Your current setup is a boiler that always maintains heat in the boiler so that there is heat for the hot water heat exchanger. Now look closely at the boiler, go ahead get close. Feels warm, don't it? Just think how much heat is just radiating through the thin insulation blanket. Ok, now look at the pipe from the top or side of the boiler that connects to the chimney. There is a draft that is constantly drawing cool basement air through the burner combustion air inlet through your always hot boiler, and zoom! Up your chimney! That is happening 24 hours a day, 7 days a week, 365 day a year. As the boiler cools off, the aqua-stat control sees the temperature dropping and bang... the burner burns black gold to heat the boiler again. All this happens even when you are not using heat, or hot water. While you are away at work, while you are sleeping, and while you sit at the dinner table paying the fuel oil delivery bill.

Compare that to an indirect hot water heater.

Now you have a well insulated tank that loses about a fraction of a degree F every hour. Buy a good stainless steel model with 2" of foam insulation that totally encapsulates the tank. For the most part the only time the water heater calls for heat is when you or your family actually use hot water. There is also no chimney running through it to cool off the water. Now for the boiler, the aqua-stat control that kept the boiler warm all the time gets changed out for a control that lets your boiler cool down when it is not needed. It will only run when there is an actual need for heat!

Hmmm, pretty cool eh?



Cosmo

A.Falcone

Indirect water heater vs. boiler coil

Just bought a house with original (1959) oil-fired boiler. It's 1500sqft baseboard & convector heating throughout, and the existing boiler has internal loop for hot water.
Some plumbers are suggesting to install an indirect hot water heater when I replace the boiler. Is this worth the expense vs. getting a new boiler with HW coil inside? Payback period may be excessively long, no?

Thank you. All opinions appreciated.

ALH_4

indirect

The indirect may have a shorter payback than you think. With fuel prices always increasing, and a tankless coil being the most inefficient way to produce dhw with a boiler, I would recommend an indirect. Indirect water heaters require almost no maintenance, and will not foul. Tankless coils are relics from the past when fuel was cheap.

-Andrew

mdewolfe

indirect

ok, add this to the stew....what would be better an aqua store or a on demand lp fired water heater. I currently have a oil fired boiler with an indirect coil and have propane for my grill,range,and garage heat. Our 16th aniversary is comming up we want to get somthing for the house....I kind of like the Aqua store idea...but the on demand is pretty cool........my wife needs a size 40 [gallon]....mark

Cosmo_3

the answer is simple, it depends

I would go with the tankless water heater if;


You have short piping runs from the water heater to the bathrooms. If you have a large home with 70+ foot piping runs you may be waiting too long. Recirc pumps for tankless water heaters seem to me to defeat the purpose (just my opinion).

Your wife will be able to get used to waiting a few seconds more for hot water.

Your propane is not astronomically more $ per btu than your oil.

The size of your oil fired boiler, both water capacity, and output. In other words, something 100,000 btu or less with small water capacity (low mass) is quicker to heat up and more efficient than lighting up a 200,000+ Btu behemouth with a large water capacity just to heat up a 40 gallon indirect when the extra btu's won't be useful for keeping up with a whirlpool, and high-flow shower heads.

The tankless water heater rated flow rate is up to the gallon per minute hot water demand of your family, and fixtures. Older 5 gpm showerheads exercise most tankless units to the upper limit.


I may not have covered everything to consider....



Cosmo

Constantin

We're in violent agreement...

If the heating plant is efficient, I'd vote for an indirect instead of a tankless heater in most homes. To me, tankless is something to consider in homes that do not have hydronic heating, such as FHA homes.

If there is a hydronic system begging for something to do, then an indirect can provide ample buffer storage, very low standby loss, and the possibility of recirculation (if desired). Quality indirects are pretty indestructible and many have lifetime replacement warranties.

So from a KISS perspective, I'd go with the indirect just because it eliminates another combustion appliance that has to be serviced. An indirect combined with a mod-con boiler is pretty unbeatable efficiency-wise.