Tankless water-heater & HVAC questions

[JHZR2]

Originally Posted By: rjundi
Do you have an efficient boiler in the mix? Use the boiler to heat a tank and you get nearly the same efficiency as the boiler itself. These hot water tanks are incredible as losses are something like 1/4-1/2 F degree loss/hour. You also do not run out of hot water.

I run a Buderus (German top notch) oil burner at 93% efficient which is significantly better than any tankless situation running at 75% efficiency. Hot water tanks gas or electric are worse typically for efficiency.


is 1/2 to 1/4 degree loss per hour good or bad? I assume youe implying an "indirect" fired hot water heater that uses a second connection to the furnace used for heating water, right?

I don't see how it is any more or less efficient than an equivalent HE hot water heater (Im assuming that your unit is a condensing, super HE unit, and that there is an equivalent HW heater device too). Unless your point about the 1/4-1/2 losses implies that it is a super-good insulation that is much better than other heaters...

This is really of high interest to me, as though we have radiator hot water heat and not forced air/central air, high efficiency operation of both (and making the best decision) is of really high interest.

 

[duaneb9729]

As a heating and a/c contractor myself, the right J load calculations are normally right on the money for the areas, they are using weather data that stats from the 1950's through today and are up dating the software as needed.

Plus in the program there are ways to fine tune it more.

We have been through the tankless water heater craze before in the early 80's and it wasn't good back then. parts availability being the main problem. This time around we are seeing many dangerous installations, the main problems are improper gas line sizes and lack of air for combustion.

If one is going to consider this type of water heater the installation instructions need to be followed to a "T"

Congrats on the new system, any reason why you didnt consider a heat pump?

 

[Virtuoso]

Originally Posted By: duaneb9729
If one is going to consider this type of water heater the installation instructions need to be followed to a "T"

Congrats on the new system, any reason why you didnt consider a heat pump?


The only thing I may add to the installation are some automatic drain valves, so it dumps the water in the unit when it errors or looses power. To tie it into a good line in the system, they had to add a little piping. But other than that I have no complaints about it yet.

We didn't do a heat pump mainly because of price. We're (so far) on track to have our basement project finsihed when we wanted it - but we need the extra cash to get that done. The price of the Furnace/AC/Heater pretty much tapped any excess we have. Even without the heat pump, I'd bet our utilites still drop 35-45%.