Replies

1. 
   Shoeman_ | Jan 30, 2002 10:12pm | #1

   *
   on this same subject, if space wasn't an issue, what do you all think about using a holding tank (old water heater, or other) in line BEFORE the on demand heater. thought would be expected energy savings of only have to create heat rise from room temp to useful temp rather than having to heat up from ground water temp especially in the winter - just sort of a preheater

   Any reason such a tank would be a BAD idea

1. 
   David_Thomas | Jan 30, 2002 11:43pm | #2

   *Shoeman: The pre-tank would let the water heat slowly to room temperature and would let the tankless raise a little more water to desired temperature (like 4 or 4.5 gpm instead of 3 gpm). I would use an unplugged electric tank since it is designed and approved to hold 50 gallons of water at pressure.Richard: There have been many discussions in the last years (and prior to that as well) about tankless versus tanked HWHs. So if the search function is behaving itself, there's a lot of info out there.Briefly: tankless costs more initially, reduces standby losses, and can give you a infinitely long shower. The tanked HWH can handle multiple fixtures at one time and operate fine at very low flows. Tanked are cheap, readily available, and everyone knows how to install and replace them. Tankless require a bigger flue pipe for their bigger burners so they can be tough to retrofit in. With new construction, you could have provisions to go either way. Personally, I use a direct-vent tanked HWH in my own garage. Both for domestic hot water and to heat the garage through the radiant floor. I went direct-vent ($500 versus $150 for a tradiational gas HWH) for the lower air infiltration rate and the added safety. Since indoor air is not used for combustion, it is much less likely that vapors from a leaking fuel tank, chainsaw, BBQ tank, or cleaning solvent will ignite and burn or explode.I'd think of the tankless more for the many house, especially if you got someone who wants to take very long showers. Of course then your energy costs will go UP, not down. Somebody's quality of life will too, but a tanked HWH does put a reasonable limit on those long showers.The totally luxurous approach would be to have a tankless feed a tanked, unplugged electric heater. Or just set the electric thermostat low enough so it doesn't normally come on. The tank would serve to equalize temperature, would provide hot water at low flows, and would be back-up if the tankless ever goes on the fritz. The big standby losses are from the flue of gas-fired HWH. An electric (therefore flueless) tanked heater losses some heat through its insulation, but that helps heat your house. I have a 7 month heating season, so that isn't much of a downside for me. -David

1. 
   Thomas_Sawyer | Jan 31, 2002 05:23pm | #3

   *I thought about using an on demand to save space and supply my new jacuzzi tub w/ infinite water. I called a friend who just completed a new home last year and installed one that he said cost $2,000 and was supposed to be the best since sliced bread. He offered to trade me for the $225. 55 gallon tank I put in. He said for tubs etc it is great, but he said showers have been hellish since installing. He is handy and has been tinkering w/ temp rise and flow rate for a year. He can't get it to stabilize for even water temp. Just his opinion. I'd like to hear what others w/ like systems think. Endless hot water sounds like a winter vacation to me, but hesitant.

1. 
   The_Tennis_Court_Builder_...on_t | Jan 31, 2002 06:34pm | #4

   *David... what exact direct vent models are your choices for radiant/domestic hot water use?near the stream,aj

1. 
   Wet_Head_Warrior | Jan 31, 2002 08:05pm | #5

   *Thomas, facts like you present are not allowed here. The only acceptable opinion is that these units work no matter what.>Sarcasm off<

2. 
   nigel_martin | Jan 31, 2002 10:48pm | #6

   *Sorry/glad to say the bosch Aquastar 125 in my 5 person, 2.5 bath 2400 sq.ft. home has never missed a beat and always provides none stop hot water. We did switch from electric to gas for heating and hot water and my combined bill is half my friends indentical house. (11 houses along the road & they are still all electric)

3. 
   Thomas_Sawyer | Feb 01, 2002 05:43pm | #7

   *So sorry I'm new in this neighborhood. I'll try to be more positive in the future and plant any negative info where the sun don't shine. Did I mention the friend who hates his in-line heater is a habitual crack smoker with an IQ of 50 and drools incessantly when he speaks. Oh and he smells funny in the morning too -kinda like dog farts. I wouldn't worry about his opinion. Sorry to soil this site w/ his soft headed comment. P.S. if you do have a problem later I shoulds mention he was perfectly normal until he repeatedly cooked and cooled his brain showering. OOps that was a no-no. I'm tryin but it seems hopeless

4. 
   The_Tennis_Court_Builder_...on_t | Feb 01, 2002 08:43pm | #8

   *nigel,A gas hot water tank would have the same savings verses electric and in my area and oil hot water tank would be half of LP and 1/4 of electric. near the stream,aj

5. 
   David_Thomas | Feb 01, 2002 11:01pm | #9

   *AJ: I've used Rheem's 50 gallon, 42,000 BTU/hour gross direct vent. Flue goes up about a foot, turns and exits through a wall 4" to about 15" away. Total height needed ia about 6 feet. I use them not after any exhaustive market survey but because they are available locally. They cost about $480. They include a diagram for combined space heating and domestic hot water applications. Which can get you some mileage with the inspector or the gas company, "See, the manufacturer recommends it be used this way."All of them have worked fine. One thing I learned was not to circulate really cold water through them (like RFH in an uninsulated house in 10F weather). If the tank is really cold, you get condensation in the HX, which is acidic, which generates some rust. I actually already knew that, but sometimes you have to be reminded. That unit still runs fine, even before I shop vac'd the rust out. But 6 months of such operation probably took a few years off its life.To do that temporary application again, I'd use a tempering valve with a pump pulling from the mixed port and pushing to the HWH inlet. Hot port from HWH outlet. Cold port being return from the slab. The slab would still get a net of 80% of 42,000 (gross) BTU/hour just like plumbing it the dumb way. But the HWH tank would stay whatever temp you set the tempering valve at. -David

6. 
   Wet_Head_Warrior | Feb 02, 2002 10:19am | #10

   *Thomas, you is good man.

7. 
   Thomas_Sawyer | Feb 02, 2002 07:09pm | #11

   *Thanks- Had me worried I'd made my fist enemy in building land. I'm a pacifist.

8. 
   Wet_Head_Warrior | Feb 03, 2002 09:33am | #12

   *No way dude. I was being sarcastic. All the way.

9. 
   Shoeman_ | Feb 03, 2002 09:59am | #13

   *today's tom sawyer he gets high on youwith the space he invades he gets by on youRush - Tom Sawyer

10. 
    Thomas_Sawyer | Feb 03, 2002 06:00pm | #14

    *Hey Now! Let's not get that started. At least you didn't ask "Where's Huck". Save your time I drowned the bastard on the river- got sick of the jokes.

11. 
    Luka_ | Feb 03, 2002 06:30pm | #15

    *Where's Jim ?

12. 
    roman_ | Feb 04, 2002 07:50pm | #16

    *Richard,I bought a Takagi TK-1 nat-gas ondemand waterheater.I will never use a tank again. This well made machine provides 117 degree water 24 X 7. Make sure your water is soft.Roman

13. 
    Wet_Head_Warrior | Feb 04, 2002 08:08pm | #17

    *Takagi... the very best! And the tankless that makes most of my arguements against tankless worthless. Most likely will put one of these in when I build. Will see.Best place to buy...Low Energy Systems1-800-873-3507Ask for Neal

14. 
    carl_wilk | Feb 04, 2002 08:48pm | #18

    *Think the TK-1 is the same as the Bosch 240FX just repackaged.

15. 
    Wet_Head_Warrior | Feb 04, 2002 09:02pm | #19

    *don't think... but could be wrong...call LES and ask them...

2. 
   Richard_Paddon | Feb 04, 2002 09:11pm | #20

   *
   I will be building a garage with a hobby room/studio above, possibly even two stories above the garage, and will plumb it thinking of its future use. I have been considering installing a hot water on demand system like the Bosch unit instead of wasting space, time,and money on hot water tanks. Have any of you folks used this set up or similar, and what are your opinions ?
   Thanks Richard.