PV vs CV water heaters?

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So what do you guys think about the water heater debate? I constantly get customers who have paid big bucks to have their home audited and tested for efficiency ect...They tell the customer to replace their conventional vented water heater with a power vented one. I think a lot of people assume the power vent is high efficiency because of the plastic vent. It doesn't condense so obviously it's not. I have tested both using flue gas analyss, found they run 75-80%. The power vent needs 120v though, so I lean towards the PV actually being less efficient. Faster recovery time though, lower input...so I dunno , confused...
What do you guys think?
-CanadianHeat
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The worst thing about a atmospheric vented water heater is the HUGE standby loss. I imagine a PV WH is better in that regard. The "problem" with a PV WH is they've got to be using fairly large amount of possibly conditioned air to reduce the flue gas temp to the point to where it's not excessive for the PVC.
We see lots of boilers and use an indirect fired WH in almost every instance. Standby loss down to 1/4ΊF per hour depending on the WH.
On 22 Dec 2006 04:28:53 GMT, DANgER ( snipped-for-privacy@heat.com) wrote:

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On 22 Dec 2006 04:28:53 GMT, DANgER ( snipped-for-privacy@heat.com) wrote:

I didnt know there was a debate. Power-vented doesnt save money over atmospheric. The power-vented is usually twice as expensive as the atmospheric. Go with a tankless. .............and No, I dont have one........yet. Bubba
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Tankless gas is less efficient at heating the water. If the usage is infrequent then the savings from not having to keep the water hot outweighs that. In a normal household that is not usually the case. There is the added advantage of never running out of hot water though.
Bubba wrote:

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The endless hot water thing is hype. Any WH can run out of hot water. A 100kbtuh WH will only deliver a little over 2gpm continuous flow at a 75F temp rise.
On 22 Dec 2006 05:42:26 -0800, "jamesgangnc"

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I didn't mean to suggest it was unlimited by saying endless. Within it's gpm limitations a tankless will go on delivering hot water for as long as you want. It won't "run out" because it keeps heating new water. You can draw 2 gpm for as long as you want. You might run out of money to buy the gas though :-)
Steve Scott wrote:

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When water is heated, the minerals drop out of it. Tankless heaters get a build-up of minerals much like a persons veins do with hardening of the arteries. They should be flushed out with a vinegar solution every year(the tank, not your veins.Veins should be flushed with copious amounts of Stella Artois). This is just one more reason to stay away from them. If you place your hand on the side of a conventional type of tank ,you will notice that there is very little heat transfer due to the high insulation value of most tanks. Turn off your water heater and you'll still have hot water 8 hours later. Tankless heaters are popular in Europe mostly due to space constraints. They are not a good idea unless you need the extra room.
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Finally some good advice re tankless wtr htrs. The reason they have a problem with mineral clogging is because of how they work. They regulate the flow and pressure to ensure that the water comes out at 120 F for example. When you heat water and change the pressure, minerals tend to drop out. Ground/water source heat pumps can also have that problem.
Tankless water heaters require very high firing rates, at least in the north where the entering water temperature is 50 F or lower, to give us the amount/volume of hot water most people are used to. In many cases, around 200,000 Btuh or more is required to do that. In many existing homes the gas piping will not accommodate this along with a gas furnace and other appliances without a piping up-grade, adding further to their already high cost.
The standby losses through the tank walls for a conventional or power vented gas water heaters is about 6-7%. Most of that loss is inside the building envelope and in many areas reduces the normal heating load of the furnace. During the AC season it can add to the AC load, a minor problem in the north and a non-issue in most homes with basement installations.
It is also difficult to find a service contractor who knows how to fix the ductless units, especially since there are so many brands out there. I also imagine parts availability can be a problem in many areas. Part prices may also be very high.
Most people that try the tankless water heaters are not happy with the flow rate they get. We have often had to remove many of them and replace them with a regular PV model.
Where I live, the average family spends about $350 a year for gas hot water heating. Conventional gas water heaters can be installed for somewhere between $600 and $700. A tankless water heater might save $150 a year in this example. At that rate, the payback period will be quite long, not even counting the annual acid flush and other repairs that WILL be necessary over its life. Very little goes wrong with a conventional water heater - we ought to know as we rent out well over a million of the things.
Having said that, one day in the not to distant future, I will think we will see them become the norm in new construction, especially as the short comings get addressed.
On Fri, 22 Dec 2006 20:56:41 GMT, "Bob_Loblaw"

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You have a very good point. BUT in alot of cases for us, we have installed TWH's for unlimited hot water usage. Took out (2) 50 gal atmospheric HWT's (in a LARGE house) and installed (1) Noritz N-132M (13.2 gal per minute) The Dr wanted the biggest. He had 5 baths (3 whirlpool tubs) 5 children and the story goes on. Installed with the option flush kit and remote controller. Ended up with all hot water taps opened with 132° at all taps. Dr happy and paid the bill (cash). We have been once to flush appliance...routine maintenance. He has said his gas bill is down and the consumption is also down. Maybe a few of the kids moved out :o)

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That Noritz unit must have a whopper of a firing rate? What is the Btuh input? There was no doubt once we got past the tiny output Euro models, with good reliability and a big enough gas line, these instaneous water heaters would be the way to go. 13.2 gallon per minute at what incoming water temperature. We run about 45F or less here in winter and 50F in summer.
wrote:

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wrote:

Bubba: About 8 years ago I replaced existing gas water heater with a power vented gas water heater. Same capacity and same BTU input. Youngest daughter was senior in high school. Gas bill dropped about 15% taking degree days and such into account. When she went to college the next year gas bill dropped another 5%.
Just speaking from experience.
Cost was about $100.00 more than regular vented.
Merry Christmas
Vic
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On Fri, 22 Dec 2006 14:43:32 -0500, "Victor H Plank"

Today, a 50 gal gas water heater cost me more than what I used to sell them installed for. Im not going to argue but I dont think you could accurately calculate that 15%. When your daughter left..........certainlly Id believe a 5% savings. That goes without saying. About a yr ago, water heaters went up about $100 just to cover the new safety standards they built into them. If you purchase a 75 gal pwr vented gas water heater installed from me, you will think you just bought a new high efficiency furnace. Cost of both are about the same my cost. Water heaters are out of sight anymore. Bubba
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Here, the electric ones are quite commonplace...
Funny thing, I had packed one from an old rental place around for nearly 25 years...cause I was in a hurry to replace it....and was no time to troubleshoot at the moment...
Well, the heater recently went out in the shop, and so finally the time came--and I found a loose wire there where it attaches to the lower element.
Total cost= FREE (plus yesterday's alrerady spent dollars )....
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Goddam Canadians snipped-for-privacy@heat.com wrote:

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I've taken some training on a rinnai tankless. I wondered how well they would hold up. Japaneese seem to have built a good machine from what I saw. I have yet to get to install or service one though. Thanks for the input about them Bob. I guess maintenance will be the big issue. Vic your numbers are useless for my original question. I don't pay for gas so I never really get a chance to see LOL
-CanadianHeat
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Question: what happens with furnace when vent fails to open?????? from Dido

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My guess is Dildo's dick falls off and then he has to call his mommy? Go lick a window first. Bubba

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What furnace has a vent that closes? If you're refering to a vent damper, then you shouldn't have a license if you don't know the answer.
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wrote

No, he is talking about the return vents on the upper level that he closes to help the air conditioner cool better.
I figgered that he thinks that the "cold air return" vents will let all the cold air return to the lower level, so he wants to trap it upstairs.
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Honestly, I doubt even he knows what he means!! LOL
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