[MoreCowbell70]

My home is about 4k sq feet.

My gas consumers in the basement:
- Two high-efficiency (vented) furnaces
- Two traditional 40G HWTs (standard chimney vent)

A few feet from the HWTs is a large, round vent. Today we had -10F temps and I noticed copious amounts of cold air dumping from this pipe.

The two traditional HWTs are 9 years old and they are on my hit-list. I have a wife and three daughters so we occasionally run out of hot water during consecutive showers. I am planning on getting a 50 gallon "A. O. Smith Vertex power-vent and power direct-vent gas water heaters" to replace the two 40 gallon builder-grade tanks.

Two questions. The first is mostly plumbing related:

Does anyone have any experience with these types of high efficiency tanks? My family member is telling me I'll essentially never run out of hot water due to how quickly they can recover. This is the one I'm eyeing:

http://www.hotwater.com/water-heate...power-direct-vent-50-gallon-gas-water-heater/

2nd question is concerning the combustion air duct. As I understand it, the purpose of this duct is to provide fresh air for the two HWTs. If these were replaced with a powered, direct vent variety, could I simply close the vent? Or does it serve some other purpose? Would I be violating any codes if I sealed that opening after removing the two chimney HWTs?

Thanks for any insight!

 

[Jnaas2]

Is there a separate line for the 2 furnaces and the new water heater for combustion air from the exterior or do they get there combustion air from the utility room there located in

 

[MoreCowbell70]

Is there a separate line for the 2 furnaces and the new water heater for combustion air from the exterior or do they get there combustion air from the utility room there located in

The 2 furnaces each have their own separate lines (4 total)

The 2 water heaters are currently traditional style with a chimney that goes up and through the roof. I'm planning on swapping those out with a power vented setup.

 

[TheEplumber]

If all three appliances are vented like the proposed WH and you have no other appliances that need combustion air, then you should be able to do away with the duct.

Your proposed WH has a first hr. rating of 129 gal. That probably well exceeds your existing set up by a lot. You can check it against your existing set up by looking for the yellow tags on tanks. They should give you their 1 hr ratings to compare to the 129 number

BTW- your new heater is 100,000 BTU. Will your existing gas supply handle that? This can also be somewhat confirmed by comparing BTU ratings of the old system vs. new (refer to the listing labels)

 

[how]

You might also consider that when the hot water begins to cool a bit now, that shower is over.
It self regulates the hot water usage.

You are a generous man to now offer 4 women under your roof, unlimited hot water showering usage.

 

[MoreCowbell70]

I live for my ladies, don't mind spoiling then a bit.

 

[supers05]

I just put in a similar unit but smaller btu input for my own house. (50kbtu) I love it. It recovers more water then I consume, so it actually cycles off during a single shower. I've also installed them in several other locations. They really do work great, and save a bundle on gas.

Are you replacing both tanks with one? Or 2 tanks are going back in? If it's just the one, then your gas service should be OK, but if it's 2, then check that out first.

The older style HWTs use more air (combustion and dilution) then the planned new one. Locally here, if your furnaces use a 2 pipe system, and the DHWT is 50kbtu or lower, you don't need the extra combustion vent. Since you're putting in a larger tank, you'll have to follow the specific instructions for that tank, but I'm sure that you'll be able to at least partially close up the vent.

Cheers!

 

[gregzoll]

The pipe that allows for combustion air, should be inside a 5 gallon bucket or have a elbow on the end, so that it is not spilling cold outside air into that area all of the time.

Some people have it so that when there is a call for the burners to light for the water heaters, a vent will open automatically for combustion air. When the burner is done, the vent closes.

If you go with a HE water heater, keep in mind that the longer they take a shower, the higher the water bill and gas bill. Which means that you will never see any kind of savings.

I have a 50 gallon Richmond/Rheem Power Vent Water Heater, we have never ran out of hot water.

Just keep in mind that if you lose power and do not have a genset that can handle the load of the tankless unit, or the tankless unit does not play well with gensets, you are stuck with no hot water.

That is why a lot of people stick with units that do not require power, when they are in locations that see a lot of power outages.

 

[IslandGuy]

I was going to mention that - if the WH's are in good shape and do not require power to operate, you might consider keeping one of them parallel piped in to be used only in the event of a power outage.

Gregzoll, he's considering a power vent unit, not an on-demand unit.

 

[MoreCowbell70]

Thanks all - my combustion vent is up near the ceiling (9ft in basement) so I can't really do the bucket setup.

I actually have a nice generator still in a box in my garage. I bought one 5 yrs ago in anticipation of a power outage and have yet to have one last more than 20 minutes. I'm considering selling it, if only to regain a little garage space. Of course the moment I do that we'll have a week-long outage soon.

And after checking the label on my current 40G tanks I see they're rated at 68 gallons for the first hour - I suppose going to the 50G Vertex would be a downgrade in hot volume?

I go back and forth between the Vertex I linked to above and a beefy tankless. This one seems to get great reviews:

http://www.hotwater.com/water-heate...-ultra-low-nox-indoor-199,000-btu-ati-540h-n/

But I'm weary of the bad reviews I've heard of tankless units in general. Maybe this is another instance of "you get what you pay for"?

 

[supers05]

To get the efficiency and roughly regulated hot water, you'll need a fully modulating one. (non-modulating will have hot and cold flows with low flow and far more critical to size correctly)

I couldn't buy a standing pilot natural draft HWT locally anymore, well not from the normal suppliers. Anything else requires power. The power consumed by my condensing tank is very similar to a 80% power vented.

For instant HW, minerals will tend to drop out and plug every strainer in the house. (this includes the airators on the facets) With soft water, and fully modulating on demand, it's not so bad. With hard water and/or non-modulating is worse. We recommend cleaning and checking (general maintenance) the system at least once each year.

The minerals settle to the bottom of tanks, regardless of type, so they are more immune to that problem.

Cheers!

 

[MoreCowbell70]

To get the efficiency and roughly regulated hot water, you'll need a fully modulating one. (non-modulating will have hot and cold flows with low flow and far more critical to size correctly)

I couldn't buy a standing pilot natural draft HWT locally anymore, well not from the normal suppliers. Anything else requires power. The power consumed by my condensing tank is very similar to a 80% power vented.

For instant HW, minerals will tend to drop out and plug every strainer in the house. (this includes the airators on the facets) With soft water, and fully modulating on demand, it's not so bad. With hard water and/or non-modulating is worse. We recommend cleaning and checking (general maintenance) the system at least once each year.

The minerals settle to the bottom of tanks, regardless of type, so they are more immune to that problem.

Cheers!

How do you determine whether a particular unit is fully modulating or not? I don't see any reference to that phrase in the link above.

Thanks