That sounds like a good idea if metal pipes are involved.

I know this would require a heat-load analysis, but would one of these water heaters be capable of heating a 1800 sqft house hypothetically? (1930's, zone 6) I am in the difficult position of needing a water heater for domestic now but I have a 1960's slantfin 60-odd% efficient boiler that is on its last legs. So, I was thinking of using a Vertex as a near-term solution and adding pumps and external heat-exchanger later when the slantfin erupts.

Would it be more efficient just to do a heat-load analysis now and replace the entire system with a mod-con with domestic hot water aux tank? (Understand no "final" answer just looking for opinons from the experts here).

Posted By ibilisi on 24 Jul 2012 04:14 PM
I know this would require a heat-load analysis, but would one of these water heaters be capable of heating a 1800 sqft house hypothetically? (1930's, zone 6) I am in the difficult position of needing a water heater for domestic now but I have a 1960's slantfin 60-odd% efficient boiler that is on its last legs. So, I was thinking of using a Vertex as a near-term solution and adding pumps and external heat-exchanger later when the slantfin erupts.

Would it be more efficient just to do a heat-load analysis now and replace the entire system with a mod-con with domestic hot water aux tank? (Understand no "final" answer just looking for opinons from the experts here).

biggest difference between the boiler and hot water heating systems is design temp. If you have a radiation system designed for 180 degrees (i.e. baseboard) a boiler is likely the best fit. If you have infloor radiant or something else that permits lower water temps, a water heater may work.

Next thing is code. The IBC has applications where you may use some water heaters for space heating, but there are requirements.

Finally, it's water you drink so you want to consider how to keep it safe.

Good Luck,
j

Most systems designed in the 1960s for 180F water were over-built from the get-go on both radiation and burner sizing. With any kind of insulation and window upgrades that are likely to have been implemented in the last 50 years most of those systems would be able to deliver design-day heat with 130F or 140F water, making it likely that a Vertex or Polaris could be used, provided the whole house heat load was within the burner's BTU output range (which it almost certainly is, if it's 1800' with OK windows or tight storms and at least some insulation).

Whether a condensing tank heater is the RIGHT solution kinda depends, but doing the room-by-room heat load calc and figuring out the water temp(s) required for the radiation to deliver the heat at the outside design temperature is an important first step no matter what you do for the heat source. Doing the calculations and deciding ahead of time, before the SlantFin craps out, makes it more likely you'll end up with an efficient & effective system.

When using a tank HW heater for space heating it's always advisable to use a heat exchanger even in places where "open" systems are legal, keeping the heating system water separate from the potable for both safety and system longevity. Using fresh water in hydronic heating systems introduces oxygen into the heating system increasing the rate of corrosion many-fold. With a heat exchanger it takes two pumps, a non corroding bronze-impeller pump on the potable loop side, and a standard heating system pump on the other side. But unless you're willing to do the math and really design it it's probably better to pay a pro to design it for you.

One advantage to using a condensing tank HW heater in a low-load house is that you can micro-zone it as much as you like sipping even very low BTU rates without short-cycling the burner the way a mod-con would, since the thermal mass of the water in the tank guarantees a minimum burn time. But if the room-to-room heat balance is already pretty good, keeping it to a small number of zones works, as long as the heat load of the smallest zone is a large fraction of the minimum-fire output of a mod-con solution.

The other thing to remember is most manufacturers that will certify their heater for space heating will state the heat load be below X% of the burner output in order to leave sufficient DHW capacity. I recall one BradfordWhite 75 gal/ 75Mbtu unit had a max space heating load of 40Mbtu so it makes sense that the Vertex or Polaris would allow perhaps 60Mbtu for space heating.

BTW, I see the Vertex sold on the web in the US for $1450+. Here, the best price I can get, as a contractor, is about $2400. Almost everything is more expensive here but not usually by that much.

A valve for load shedding make more sense to me. Ie, let the house go without heat for the short and rare periods when max DHW is needed.

I wonder why conventional air furnaces don't include some water or concrete mass to help with the short cycling issue.

Conventional hot air furnace systems rely on the thermal mass of the house/zone they're heating and haveing at least some hysteresis on the thermostat. There are no efficiency losses related to the short-cycle the way there can be with short-cycling high-mass boilers, but a rapidly cycling temperature hysteresis isn't the hallmark of comfort. (Fortunately, in a high-R house only the T-rise portion of the hysteresis is rapid.) It would be a very rare house indeed that didn't have enough thermal mass to have burn times of the smallest gas burners in excess of 5 mintutes with 1C of hysteresis.

The better-class mini-splits do it one better though, using the rate of change in temperature on incoming air at the interior head to sense how far the room air is from the setpoint, and modulate the BTU-rate down, locking into a much tighter temperature range than with traditional bang-bang hot air furnaces (or cruder mini-splits.)

I agree - best would be if furnaces had variable speed burners and blowers and could match the required load instead of the wear and discomfort of bang-bang on/off cycles.

There are a (very) few out variable-speed multi-stage hot air furnaces out there- great for comfort in conventional houses, but kinda overkill for the nuthin' heat load of a superinsulated house.

The NTI Matrix seems to have the widest modulation range, which is sort of a tankless-combi with fan-coil output and HRV all in a crate: http://www.ntimatrix.com/solution.html

I have the SLP98v from Lennox in my current home, and will probably put it in the new build instead of minis like I was thinking. It is a variable speed multi-stage unit. Super quiet, variable speed covers from 22k to 70k btu. It ramps up and down so you rarely hear it run. Most of the time I just set it to circulate so it keeps the temp pretty even. Since we have added another bedroom on the main level, it puts us around 3600 total conditioned space, split half with the basement so I feel more comfortable with the gas furnce with the bigger size now.

Tankless water heater is convenient and energy-saved, it may cost you more at first, but you will find it is a good investment for a long run. I think we should choose a best tankless water heater, Ecosmart ECO27 is my recommendation.

Posted By quyixudu on 05 Jun 2014 07:44 PM
Tankless water heater is convenient and energy-saved, it may cost you more at first, but you will find it is a good investment for a long run. I think we should choose a best tankless water heater, Ecosmart ECO27 is my recommendation.

Worthless. Warranty rarely has anything to do with quality. And the map is a joke. Think the ground water in Aspen is the same as Kansas City? Typical web "research". Long yawn... Almost as bad as enduring recitation of technical books, day after day...

With the previous talk of the vertex and polaris I wanted to get a opinion. I have a old AO Smith FSG 40 232 that came with the house built in 1997. Previous owners may have not have used the water softner over the years (on well, softened and a hazlite/charcoal whole house) so the inside may be trashed. I attempeted to put a new anode in to maybe lengthen the life but the old is frozen in. Never had a lack of hot water thus far with me and the wife a 4 year old and a new baby. But i think we will in the future and im assumeing failure of this old unit any time. And we just finished the basement so id really dislike a leak!

Were 2150 sqft clonial in Michigan White Lake/Northern Oakland county. 2.5 baths. And i want it setup lije out 96% eff 2 stage variable Payne furnace the PVC combustion/exhaust so I can eliminate the old flue pipe and block off/foam that final rimjoist space (around the flue we get a huge rush of ice cold airdown the chimney run all winter becuase the rest of basement is air tight w 2" foam and 3" spray foamed rims)

My installer is my cousin whos been doing this for 20 odd years and can get State brand. I saw someone mention they have a version of the Vertex any idea on that model number so i can look into it? Their website is very lacking.

I assume if we got the polaris we could stick w the 35 gallon since the 40 old draft has never done us wrong and the recovery rate on the new ones are high. But i think the vertexs smallest is 50 gallon.

Any ideas or advice? Maily what is the State model number for the relabeled vertex?

Once the ACCA Manual 'J' confirms the heat load in the proper range for a combi- storage water heater such as the Polaris or Vertex, (State makes there own seldom sold model), Both look the same from a performance perspective, but one is glass-lined with a 6 year warranty and the other stainless steel with a 10 year warranty.

The Polaris has been built since 1987, the Vertex not.

We design combi water and space heating systems daily, but all is speculation until the Manual J is performed.

Ok i just wanted to get a State model number before calling him for further. And to see if the state is built the same as/a re-labled AO Smith vertex. I am slightly parinoid of the glass lined tank vs the SSteel and longevity due to well water though it is softened and filtered..... id rather pay more to get 5 to 10 years more life with the polaris. But with his installer priceing if the State is more like $1500 installed that would be a good price. Vs the $2100+install for vertex and $3100+ install for polaris.

Regarding an existing heater, I'd 1) use an impact wrench on the anode - replacing them is important and 2) put a water alarm under it and 3) try lower flow shower heads.

Used many impact wrenches on older glass-lined water heaters jonr?

It is true that a good anode, or two, will prolong the life of a water heater.

Stainless steel is the answer nearly regardless of application. For electric water heaters we use, and I own Marathon/Rheem. Plastic will last if properly installed, rare.

Used many impact wrenches on older glass-lined water heaters jonr?

One - I turned the air pressure up slowly and many years later, the water heater is still working well. Many others report similar results.

I looked yesterday the entire head and exposed threads are rusty and nasty I dont feel comfortable hitting it with a impact years of being a backyard mechanic tells me it will snap off in the tank.....

And I know many thinks its silly to upgrade for upgrade sake but we bought this house almost 4 years ago and you can tell it was upper middle class yuppy types that dident get their hands dirty the house was all mid 90's builder grade and we want to start fresh if you will. Weve done a new GAF HD shingled roof, new 96% 2 stage furnace and AC, New Sunrise windows, a 160 sqft shed, finished the basement.

The HW Heater I want to Upgrade for #1 less energy use (I realize the long payback) #2  to eliminate the basement flue up the chimney (its only used by HW now) because the rim space where it runs up is a much larger square opening so we essentially have a small window open all year with the velocity the air rushes in during winter and being the same chase I assume their is a possibility of drawing the HW exhaust back in. I will use leftover 2" XPS to seal that hole/rim like the rest of basement after. #3 Assuming the HW heater wasent maintained properly, i.e. the tanks in bad shape and had hard water all these years (Water softener was broken when we moved in,  did not have a whole house filter, lawn sprinkler heads/system wasn't working and other indicators the house wasn't keep up too well)

So I really have little interest in keeping the old one much longer, just looking for the best option. Vertex, Polaris or the State version of the Vertex

I am all for upgrading the HW heater, especially if it is now the only thing in a chimney designed for a larger heating appliance It is what we call an orphaned water heater. At a minimum I would switch to a powered draft conventional gas water heater. What I would caution you is on your plan to use foam to seal around the basement chimney. The building code generally requires 2” clearance to flammables ie framing. Foam does not cut it. Even if you are not going to use this chimney, the next owner may, and won’t realize what has been done The way to seal this is to use Roxul (stonewool) insulation to fill the opening for insulation, and then use aluminum flashing to seal the gaps. Use high temp firesafe caulk to seal joints and the flasing to the brick chimney. Cheers, Eric