direct or indirect water heater?

My hot water boiler is over 30 years old, and my hot water heater is 12. Although my boiler is working fine i'm not sure if its more efficent to change both to a inderct system or just install new direct fired unit. I have a family of 5 and sometimes hot water gets scarce. I currently have a 50 gal. HWH.

An indirect system, using the boiler, will probably be a more expensive installation, initially, and since you still have to pay for the fuel to heat it, (which could be more during the summer when you do not need the unit for heating purposes), so your choice will depend on which you consider best for you.

Some older systems were actually fairly efficient so it's hard to say how much improvement you might get with a new one. New mod-con boilers can be quite efficient - in the mid-90% range. They also are designed for cold starts, so aren't maintaining a high set point during the summer to keep the indirect hot. The better indirects have exceptional standby efficiency - some only lose 1/4-degree per hour, so may not need to refire the boiler except after a large use. Installation and equipment are moderately expensive. Some of the indirects are SS, and should last for a very long time, but nearly any one will typically last longer than a stand-alone unit. You get the full output of the boiler to keep water in the indirect hot if you set it up as a priority zone, so you can often get by with a smaller tank, which also minimizes standby losses. Payback could take a long time, if it ever happens. Hard to tell, as it depends on the local rates, and the improvement. Keep in mind that often, there is a rebate from the local utility company. You're probably too late (only one day left!) to qualify for the federal energy credit, but that would have given you up to $1500 (30%) of the cost back on your taxes.

My parents 50 year old boiler went bad the day after Christmas this year. They had an older Weil McClain boiler with an integrated hot water heating coil. The contractor offered a heating boiler plus a choice of hot water heater (GE, Whirlpool, AO Smith). Since I have previously posted here under a similar name (forgot my password), I knew to look into indirect water heating or to specify a Bradford White water heater.

The new boiler is only an 82% unit due to the use of the existing clay tile chimney liner.

Anyhow, this is the indirect tank that I chose. It will run on a new priority zone. $500 rebate (that expires 12/31/2010) from local untility on the indirect tank connected to any boiler. Without the rebate the indirect was a non starter.

http://www.usboiler.burnham.com/products/residential-boilers-indirect-water-heaters/alliance-sl

The contractor is still doing the install, so we will see how it all works out in the end.

Thanks, very helpful info. The cost is difnitly a big consideration, but not sure of problems with these new mod-con boilers being their fairly new. Any info? (Boiler problems = no hot water)

Mod-cons have been around for awhile...a lot longer in Europe than here (and many of the designs are takeoffs of theirs, or they came from there directly). I have a Buderus that has been working great now for about 4-years. When I was looking, the local distributor didn't have any confidence in the Weil-McCain condensing unit...he'd had too many problems with the heat exchanger and stopped selling it. It's hard to keep aluminum/steel joints intact. It didn't hurt that Buderus' US distributor is about 15-miles away from where I live, but it got good reviews, was used by the installer in his home, and personal experience has been good.

jadnashua said:

Mod-cons have been around for awhile...a lot longer in Europe than here (and many of the designs are takeoffs of theirs, or they came from there directly). I have a Buderus that has been working great now for about 4-years. When I was looking, the local distributor didn't have any confidence in the Weil-McCain condensing unit...he'd had too many problems with the heat exchanger and stopped selling it. It's hard to keep aluminum/steel joints intact. It didn't hurt that Buderus' US distributor is about 15-miles away from where I live, but it got good reviews, was used by the installer in his home, and personal experience has been good.

Click to expand...

All though the aluminum exchanges may conduct heat better, I agree stainless is more durabale and less likely to have problems. The Buderus is a good choice.