Indirect Vs Instantaneous Water Heater

Dale

The indirect is the more effecient choice if all you have is oil. Plenty of hot water too. If nat gas is available an on demand (don't think instaneous as you do wait a bit) at 82% is the best energy saver, if there's just 2 of you and one shower at a time the Takagi Jr. is my favorite although the Rinnai has a good reputation also. To save fuel I think it's good getting more in step with the rest of the world at least as far as gas water heaters.

Jim_109

Indirect vs Instantaneous water heater

what are the pros and cons if indirect vs instantaneous water heaters?

I have an oil fired boiler and hot water heating. Currently my domestic hot water is via a coil in my boiler. We have always had suffienct hot water. However, I realize there are more effiecient methods

We are only 2 adults.

Darrell

Do the math and make sure your expectations match the performance specifications. Lots of folks get disappointed by the on demand type units because they have the expectation of unlimited cheap hot water..thankyou Paul Harvey...the reality is that the flow rates have to fall within certain very specific parameters, usually given in the fine print. The same advice goes for any waer heater...do the math. If it says that it will give 100 degree rise at 4gpm...don't expect 120 degree rise at 5gpm. I'm a serviceman...I spend alot of time explaining this to disappointed and frustrated homeowners where the contractor or Box Store did not design or anticipate the human element properly.

Not to sound so grouchy!!! After you do the math, if the on demand unit will fill the bill go for it...I would suggest getting one that is common in your area...parts availablity is an issue. And have it installed properly.

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JackFre

On-demand

On demand water heaters are ALL about flow and temp rise. Daryl is correct that many consumers and contractors do not understand the differences from model to model. For instance, Rinnai, (whom I represent) makes a model R53i (max flow 5.3gpm) and an R85i (max flow 8.5gpm). Both will fire from 15kbtu up to 180kbtu. I frequently get calls from people wanting the "big" unit when, in fact, in the northern climates with our cold(er) ground water temps (+/-50f) at a 70F temp rise to 120f hot water temp the outputs are identical for the R53 and the R85. Each will produce 4.5gpm at a 70f temp rise. The R53 is less money. In the southern parts of the country with warmer ground water the higher flow rates are reached.

Indirects are an excellent method of heating hot water. However, in making your decision, pay attention to how many minutes a day your hot water tap is actually open. I bet you find it is significantly under 45min/day. Why would you want to make and store hot water the other 23hr and 15 min/day.

As with any purchase, you must understand the specs, which by the way are clearly printed on every piece of literature Rinnai produces. For more info I'd suggest you go to www.foreverhotwater.com

john_83

Jack i would'nt say a indirect maintains that much a day not even close.

Rich Kontny_3

Indirect

Since you already have a hydronic system in your house with a coil that provides your DHW needs I would go with the indirect. The newer indirects have very low stand by loss and you can use the fuel and existing boiler that you have.

Have someone run the #s to make sure the existing sytem has the proper size to accomodate the indirect.

Rich K.

The Wire Nut

Stick with an Indirect

... from the sounds of it, your boiler can accomodate a coil and its heating load w/o problems. It should have even fewer issues maintaining a indirect water heater. Benefits of going indirect also include being able to put the boiler on a outdoor reset controller. That should add to your savings.

Keeping the boiler warm all summer is a good thing according to many of the oil-men/women here, it reduces rust from condensation.

IMO, the indirect will turn out to be much less expensive over its life-cycle than an instantaneous heater... no moving parts, simple/no maintenance, etc. Besides the higher up-front costs of an instantaneous, the yearly maintenance, etc. you may also need a bigger gas/electrical line to accommodate the higher power/gas loads that such heaters develop. Plus, you can always continue to use the indirect in the future should you decide to switch to a gas-fired mod/con or whatever.

With just two of you in the house, I'd venture that a 40 or 50 gallon tank would do the trick, unless you have some pretty big DHW dump loads like a jacuzzi. A good professional should be able to steer you in the right direction re: tank size. I have an oil-fired system with an indirect and couldn't be happier.