Connecting a Tankless Water Heater to a Boiler Feed
Hot water from water heater #1 feeds into #2
Both water heaters supply whole house
Purpose: Twice as much hot water available.
How to control cost:
1) Turn off heater #1 and save $40 per month
2) Use heater #1 as tempering tank to passively raise temperature to ambient room temperature
3) Install timer on heater #1 or both heaters
4) More ideas: Insulate pipes, Insulate water heaters, Turn down thermostats and save, turn up thermostats and install mixing valve to increase amount of hot water.
Buy:
Water heater installation kit
Shark bite water heater connection
Resources:
Tempering tank
Compare timers
9 ways to save
Add another thermostat to water heater
Advantages mixing valve
How to increase amount of hot water
2 separate hot water lines for different parts of house.
Purpose: Twice as much hot water available.
Turn up water heater thermostats and add mixing valve to moderate temperature on pipe going to bathroom and allow hotter water on pipe going to washing machine.
The first heater does most of the work and wears out sooner
How to control cost:
1) Turn off heater #1 and save $40 per month
2) Use heater #1 as tempering tank to passively raise temperature to ambient room temperature
3) Install timer on heater #1 or both heaters
Resources:
Mixing valve
Temperature needed to kill bacteria
Tempering tank
Compare timers
2 separate hot water lines for different parts of house.
Increase heating capacity without buying large, expensive heater
Advantage from series: one heater can be controlled by a timer, or home automation.
The first heater does most of the work. Mitigate problem by using the second heater for less-used part of home.
Plumber's note about terminology:
This is not considered parallel piping according to plumbers. This is just two water heaters sitting next to each other, but is labeled 'parallel' on this webpage for organizational purposes. Parallel option #1 shown above is an actual parallel system, and requires the piping on hot and cold to be equal for the heaters to draw down equal. Two water heaters sitting next to each other, shown on left, does not require specific lengths of pipe to work correctly.
If tanks are different size or types ... and are not identical to each other, then connecting in series, or cold into both heaters (as shown above) are best choices. This means a 50 gallon gas and 30 gallon electric, or two different size gas, or 2 different size electric can be plumbed together without problem. Two different tanks plumbed in parallel (shown below) would be a problem.
Which size tank should come first? There are no rules except what works. For example if home uses 65 gallon of hot, then install the 50 gallon heater nearest to faucets, and 30 gallon farthest from faucets. This might maximize usage out of the 30 gallon, causing less cold water to enter big tank so that big tank re-heats using less energy. Water heater formulas and terminology
How-to-adjust-water-heater-temperature
There are three ways to look at temperatures.
1) Set both heaters to same temperature and see if it supplies enough hot water. The higher the thermostat setting, the more heat energy is stored inside the tank, so you get more hot water per tank when thermostats are set higher. Ways to increase hot water
2) If you need very hot water right away then closer tank should be set higher and the farther tank can be set lower.
3) Temps over 135� pose risk of scalding ... so set close tank to safe 125-130�, and farthest tank to 150-160� will supply more hot water with low risk of scalding.
All settings are approximate, with factory accuracy +-5% more or less. Water heater thermostats come out of calibration, requiring replacement.
Open TP valve or drain valve and check actual water temperature using cooking thermometer. If drain continues to drip afterwards, install a brass hose cap.
Buy: Kitchen thermometerTemperature gauges
Buy:
Buy replacement brass drain valve
Brass hose caps
Parallel is not best choice if you have two different size heaters. Why? Because the small heater will run out of hot before the big heater, and then small heater will start adding cold water into the hot water line.
Two heaters must be same type for parallelParallel is not best choice if you have two different types of heaters, for example a gas and electric heater, or gas and indirect heater, even if both are same size. Why? Because the gas will outperform the electric, or indirect outperform the gas etc and then one heater can start putting cold water into the line.
With parallel, the temperature setting should be close to identical on both heaters. Be mindful that thermostat settings are approximate and each thermostat will have a different calibration ... or in some cases a wide difference in calibration, for example with gas heaters, the range of temperature drop before tank fires up again can be 10+� different from each other. This could be a problem, but not normally.
On electric heaters, it's cheap and easy to swap thermostats to solve a calibration issue, but gas valve thermostats are expensive replacement. Do not expect manufacturer to grant a new gas valve under warranty.
Both water heaters supply whole house.
Parallel is different than other options.
Parallel is defined as: ''Equally manifolding the inlet water pipe and outlet water pipe in multiple heater installations. Having equal number of fittings; as well as lengths of pipe.'' Both heaters are used equally.
Increase hot water capacity without buying large, high tech heater or paying premium for a large less efficient commercial grade heater.
Review Polaris condensing heater Problem with Vertex condensing heater
Review Marathon electric heater Commercial 100 gallon gas heater pdf
Disadvantage: Parallel uses both heaters equally, so you cannot turn off power to one heater to save energy unless you install shut offs on hot water line isolating one of the two heaters.
Caution: 'Balancing in parallel is tricky and often one heater does all the work and the other just sits there.' If the heaters are not piped properly, it will NOT double the capacity and the system will not be efficient. One heater will supply more than the other heater.''
Incoming cold water line should be equal length to each heater, with matching pipe diameter, and condition so same amount of cold is supplied to each heater without constriction..
''The piping on the hot must be equal for the heaters to draw down equal. Ideally you want 50% from each heater, otherwise one heater will run out of hot before the other heater, and begin to add cold water to the line.''
Pipe diameter, elbows and distance must be identical, for the Hot to be drawn equally. Obstructions in the pipe can impact outcome, so fresh plumbing should be installed on both heaters.
Note: Both water heaters must be ON, and set to same temperature. If one heater is off, then it will add cold water to the line while other water heater supplies hot. This means a malfunction in one heater will impact hot water supply ... and a timer cannot be added to one heater but not the other. Plumb heaters with valves so they can be isolated from each other.
Buy:
Ball valve
Brass gate valve
40 gallon electric water heater
40 gallon gas water heater
Parallel / piping must be equal on Hot and Cold pipes
Piping on the hot and cold must be equal for the heaters to draw down equal. Ideally you want 50% from each heater, otherwise one heater will run out of hot before the other heater, and begin to add cold water to the line.
If water heaters are different size (different heights), then measure pipes and install so both pipes are same length to the point where they meet.
Pipe diameter, elbows and distance must be identical, for the Hot to be drawn equally. Obstructions in the pipe can impact outcome, so fresh plumbing should be installed on both heaters.
The sources I've read, indicate that precise balancing is hard to do ...
One strategy might be to set the thermostat different on each water heater.
Set container under TP overflow tube, open TP valve on each heater and get baseline temperature using cooking thermometer, then average two temps.
Run Hot tap at bathtub and measure temperature... if the bath temp equals the average temp, the heaters are balanced.
How you would correct the difference, and possibly balance heater, is to keep adjusting thermostats until average is reached.
First off, Parallel is a challenge getting each water heater to balance into equal draw. It might be impossible unless heaters are identical BTU rating and gallonage, and there is no guarantee that the pair will stay balanced over time.
Does this mean Series is better?
In my opinion yes, because heater #1 can be turned off except during peak usage times. This gives Series a clearcut advantage if higher usage is just occasional, such as weekends or filling a large bathtub occasionally.
Sales manager from Lochinvar pointed out a disadvantage for Series that should be noted.
He says 'if both tanks are used continually, then tank #1 is doing most the work, and will wear out sooner than tank #2, possibly twice as fast if usage is very heavy. The continual influx of cold water into heater #1 will produce more moisture and cause more stress on the steel tank.'
AO Smith notes in their literature that undersizing a gas water heater (which Series mimics for heater #1) can cause 'excessive condensation that will corrode the heater faster. The flue tubes, baffles, and burners are susceptible to hydrocarbons in condensate (moisture created inside the vent) and carbonic acid. Continual exposure will weaken the flue tubes. Condensation can also spoil combustion and produce a carbon monoxide hazard. Read about CO detector and vent test
This means an overworked heater #1 in Series configuration will fail sooner, and need more maintenance.
Meanwhile, Parallel heaters do equal work and each heater should last equally long ... IF the Parallel heaters are balanced.
My opinion is that reducing consumption is best strategy for long term. You can add 20 gallon passive tempering tank on incoming cold water line, and/or turn down thermostat on heater #1 to mitigate some issues.
That is not always possible with high density living, or over-consuming households with Niagara-size shower heads, in which case if water heaters are in Series, then heater #1 should be expected to fail sooner, and need more maintenance.
The problem with Series also gives a choice for people who are using old heater with a new one: Use newest heater for heater #1 so the old one can last a bit longer, or use old heater for heater #1 and replace it when it gives out. The information gives options, but not an answer for which is best.
Resources
How to maintain water heater
How to troubleshoot gas water heater
Effect of water softener on two water heaters -One softener can supply soft water for two heaters, any configuration.
-Softener cannot be put on hot water. It must be installed on cold water.
-You cannot run hot water into softener. Hot water will damage softener.
-Use pressure reducing valve if water pressure is over 80psi. 50 psi is good, less pressure like 40psi and plumbing lasts longer. Use expansion tank if line has check valve or pressure reducing valve. Expansion tank is installed on cold water line. Identify and repair water heater valves
Effect of water softener on water heaters in general-Softened water will deplete the anode rod, causing rusted tank
- If you have odor problems, or tanks rust out frequently, the softener is suspect. Turn down the softening, or remove softener, or replace anode rod frequently, or install power anode rod, or deodorize by adding hydrogen peroxide frequently.
Buy: Water softener
Resource : How to replace anode rod
How to deodorize water heater with hydrogen peroxide
How to deodorize water heater with bleach Expansion tank and two or more heaters: A single expansion tank will work, if sized correctly for the pressure.
Heating water causes water to expand. Water will not compress, so pressure from heated water pushes out of tank and back into water pipes. Typically the water will expand harmlessly out to the street or to water well tank and creates no problem.
But if check valves or pressure reducing valves are installed on the incoming water line, then expanding water is blocked and has nowhere to go. This creates a 'closed system' where "temperature rise of just 10�F (increasing from 75� to 85�F), increases pressure from 50 psi to 250 psi."
Residential water heater tanks are manufactured to meet 300 psi max when new ... without any rust or defects ... but for safety, all residential tanks are rated maximum 150 psi..
If pressures exceed 150 psi, then the TP valve will release at 150 psi and drizzle water. This condition indicates if a closed system is present. The TP is not designed for continual operation in this manner, or designed to substitute for correctly-sized expansion tank. Moreover, the continual expansion and contraction of high pressure will damage tank, cause pipes to burst etc.
Do not not install a TP valve that is rated for higher pressures. Each water heater, and or storage tank or tempering tank in the water heating system must have a correctly-rated TP valve. Resource : TP valve code
To check pressure : Put a pressure gauge on the water heater drain valve to determine pressure. Any incoming water pressure over 80psi should have pressure reducing valve installed on incoming cold water line and correctly sized expansion tank located on cold water line between heater and pressure reducing valve.
Some local codes require pressure tank on all installations. Some locales have a check valve on water meter to stop backpressure coming from homes. Consult local code or plumber or city utility.
Buy:
Expansion tanks
Water pressure gauges
Temperature pressure gauge
Resources:
TP valve leak troubleshoot
Troubleshoot water heater valves
Closed system Pressure reducing valve and two or more heaters: A pressure reducing valve is used when incoming water pressure exceeds 80psi. Too much pressure can shorten life of plumbing fixtures, cause leaks, rupture pipes, and damage heater. A pressure reducing valve can create a closed system that results in water heater causing too much pressure on the hot water line, thus requiring need for expansion tank with every pressure reducing valve installation.
Buy:
Pressure reducing valves
Pressure regulating valves at Amazon
Resource: Closed system / pdf
Applies to electric water heaters only
20 gallon point of use water heaters are electric
First heater does most of the work
Typically 120 volt water heaters arrive with one element rated 1500 watt.
Element voltage and wattage shows on end of each element.
Watts divided by volts equal amps
1500 watts divided by 120 volt = 12.5 amps ... use 20 amp breaker
1500 watt will raise 6.9 gallons from 60� to 120� each hour.
Buy:
20 gallon water heater
Resources:
Figure volts amps watts for water heater
How to install point of use water heater
How to install electric water heater
Gas supply and two water heaters: When adding second gas water heater, total BTU of both heaters must be calculated. Call local gas company. Read label on side of each tank for BTU rating. For example both heaters together 80-100,000 BTU, and gas pipe length is 80 feet, then 3/4" pipe is needed.
Resources:
Gas pipe chart
How to install gas water heater
Parallel Two water heaters with circulating pump / applies to gas or electric heatersRecirculating system is handy for folks wanting faster hot water supply at distant faucets. Ideal home construction clusters usage points near water heater to increase efficiency and reduce costs, but many oversized homes and multi-dwellings are not able to meet that level of efficiency and a recirculating pump is chosen for convenience.
Note: Recirculating pumps have different installations, and piping configurations. Some pumps must be installed on vertical section of pipe, and some systems have a direct return line entering the drain valve port.
Resource:
Recirculating systems
Recirculating system for Tankless
The problem of distant faucets can be solved with a small point of use heater, plumbed in different ways to meet different needs. Resource: How to install under counter heater
Easiest choice for recirculating system is to have Parallel heaters as illustrated on left.
Recirculating system can also be used with Series heaters. However, in a series system, if Timer is used on heater #1, or heater #1 is turned off except when demand requires more hot water, then best recirculating plan is direct return line that goes into drain valve port on heater #2 and does not enter both water heaters on the common cold water line.
.
Resources
How to install gas water heater
How to install electric water heater
Recirculating systems
Note about installing 2 gas water heaters. Residential code for venting gas appliances/ pdf
Venting multiple heaters/ resource pdf
If current installation has 1 gas water heater, then venting and air requirements for 2 heaters is different.
Vent: Illustration shows basic connection for 2-3 water heaters on same vent. DO NOT ASSUME the numbers apply to every installation or your installation.
Both heaters can be connected to 1 vent, but the vent must meet specifications to meet BTU per hour operation, number of elbows, horizontal distances, vertical distances.
Air supply: New heaters cannot be installed in a dusty, dirty environment or the air intake screen can get clogged and cause FV failure. Two water heaters mean more air intake into house. The mechanical space might need a pass-thru vent fan to draw air from another part of house.
Gas supply: The gas meter is rated for certain level of BTU consumption. Gas supply line that is designed for 1 heater will not supply enough gas for a second heater without running larger gas line.. unless total BTU of 2 new heaters is equal to the BTU per hour rating of old heater. Too much BTU draw by one heater or two heaters can starve other appliances. Call gas company for specifications, or refer to gas chart pdf. Low gas pressure can be tested using manometer, or more easily, observe other appliances.
Tankless: Some folks imagine that tankless with solve all issues of hot water. And there are applications where tankless is suitable substitute. But the same problems of vent, air supply, and gas supply also apply to installing tankless to replace tank-type heater. Why? The tankless must quickly heat water as is passes in a pipe, consuming more fuel per gallon of heated water than tank-type heaters.
-The need for greater fuel consumption also produces hotter and more vent by-product, requiring larger stainless steel or PVC vent pipe and not the typical galvanized pipe used for tank type heaters. The tankless will fail to turn on if incoming cold water exceeds demand. This is especially true in winter.
-Other issues include failure of parts if water hardness exceeds 11 grains. A floor drain is needed for acidic condensation that drips down from the vent line.
-Maintenance for tankless exceeds tank-type heaters, and includes annual deliming and cleaning water filter. Unlike tank-type heaters, the tankless cannot be repaired DIY, and local technician might not be qualified to repair your model. I do not recommend tankless.
Resources:
Multiple water heater venting chart/ pdf
Troubleshoot water heater vent
Troubleshoot water heater air supply
Read about FV failure
Gas pipe sizing .pdf
Two tankless plumbed in 'reverse' Plumbed in reverse which is a type of parallel requiring identical heaters, with each heater supplying equal amount of hot water.
Can combine two or more tankless units together
Can be Manifolded together with single controller
-People generally have notion that tankless heater will solve all water heating problems ... endless hot water while saving money ... plus a 20 year warranty. Each of these is false. The warranty is 6 years.
If incoming water temps are too cold, then the amount of hot the tankless can supply drops off ... so in winter, the tankless cannot deliver same amount of hot water. It's not endless. There are limits.
Saving money? Tankless require yearly maintenance, like deliming. Tankless have 700+ parts, while a tank type heater has 20+ parts. Parts are expensive and not generic. Tankless are not DIY repair. Local technician might not be qualified to work on unit. Service manuals are near non-existent.
Resource: AO Smith tankless error codes, maintenance and parts .pdf
Tankless cannot be exposed to more than 11 grains hardness without loss of efficiency then complete failure in few years.
The installation requires larger gas line to supply enough fuel to support the huge burner. The huge burner requires larger flue pipe made of stainless or PVC to support the surge of combustion byproduct each time unit activates.
It defies common physics that you can quickly heat 'endless hot water' using a high-powered burner that requires an oversized flue pipe and use less energy vrs heating less hot water, no matter what kind of water heater. Lower consumption is only way to save energy and money.
Boilers and Polaris shown below also require large gas lines and venting, and are truly designed to deliver large amounts hot water regardless of season.
Resources:
Rheem diagram .pdf
AO Smith diagram pdf
Larger image
Four heaters plumbed in 'reverse'
Plumbed in reverse which is a type of parallel requiring identical heaters, with each heater supplying equal amount of hot water.
When heaters are plumbed in reverse, then the first heater to receive cold water is the last heater to supply hot water. Illustration shows heaters 1234 .... heater 4 receives cold water first .... so 4 supplies hot water last.
Heater 1 receives cold water last, so 1 supplies hot water first.
Note: illustration shows high efficiency and high volume gas condensing heaters, with the vertical vent and condensation drain located at bottom of heater.
Resource
High-Efficiency-Models.pdf
Larger imageLarger image with more detailed plumbing
Indirect Heater and Boiler ...
Fig 1 shows overview of boiler and indirect heater operation. Purpose: home heating plus hot water.
The boiler super-heats hot water using gas or oil at a rate of 150,000-300,000+ BTU per hour producing a temperature range that can reach near-boiling 200�F water (a fatal temperature for humans, bacteria, lobsters etc).
"A water heater is an appliance for supplying hot water for residential or commercial use other than
space heating. By code, the maximum outlet water temperature for any type water heater is 210�F (98.5�C)." including boilers, industrial heaters etc. Above 210�F risks steam explosion that will destroy building. Typical household water temperature is recommended at 120�F (with max range at 150�F) to prevent scalding. This includes indirect heater.
Typical commercial water heaters are same 120�F for pipes leading to taps used by people, but can include heaters and booster heaters set at maximum 180�F for dishwashing etc. Designing energy efficient commercial systems .pdf
1) Heat living space by circulating 200 degree water in a continuous loop (boiler loop) from the boiler, through a series of pipes and radiators located in each room, and back to boiler.
2) Heat a supply of potable (drinkable) water by circulating 200 degree water in a loop from the boiler, through the coiled heat exchanger inside indirect heater, and back to boiler.
When connected to a typical boiler, the indirect heater can supply super high volume of potable hot water (200-400 gallons per hour) depending on BTU rating of boiler, specifications of system, thermostat setting, temperature of incoming cold water, size of indirect heater, etc.
What size indirect heater is needed
There are different types of indirect water heater designs that receive hot water from external heat source .... for example a geothermal loop, rooftop solar collection system, wood burning stove-boiler, etc.
Many designs do not use indirect heater, and instead circulate potable water through a heat source and then directly back into ordinary water heater or storage tank.
Care must be taken not to exceed tank limits. Some models of Marathon storage tank are rated 170�F. Solar tanks are generally rated for 180�F water temperatures. Some water heater auxiliary storage tanks and some commercial water heaters are rated 180+�F (must check specification sheet), while ordinary residential tanks are uniformly rated 150� when new. Higher temperatures will damage tank by weakening integrity of inlet and outlet welds etc. To prevent damage, all water heaters are required to have correctly rated TP valve that release water at 210�F. Old tanks with rust would be unsafe at high temperatures and more likely to rupture violently.
Resource: TP valve code
The indirect water heater is required for any system that does not circulate clean potable drinking water, for example a rooftop solar collection system that uses glycol (deadly antifreeze) in the circulation loop to prevent freezing.Resource Read about glycol water heaters
Glycol, lead and other chemicals can never be introduced into potable drinking water supply.
Drinking water cannot pass through any pipes that are used or have been used for boiler because of chemicals (chromates, boiler seal etc) found in boiler system, and because of the dangerously high temperatures and pressures of boiler water.
Using the indirect heater ensures that drinking water and water from boiler remain separate. If the heat exchanger located inside indirect heater breaks or develops a crack, the indirect heater must be replaced.
How it works: The indirect heater has a thermostat that is set independently of boiler. The thermostat controls a circulation pump. When water inside the indirect heater drops below set point, the pump circulates hot water from the boiler, through the heat exchanger, and back to boiler in a continuous cycle.
When water temperature inside indirect heater reaches thermostat set point, for example 120�F, the circulation pump turns off, and water stops moving through the exchanger until thermostat calls for heat again.
Why use indirect tank with heat exchanger to supply hot water to home?
1) Potable hot water must be safe for drinking, and cannot be mixed with hot water used in the boiler system. The boiler is a closed system that recirculates same water, while drinking water must be introduced fresh with each draw.
2) Super heated hot water from boiler cannot be allowed into household water pipes where pressures could exceed pipe rating, and temperatures could exceed tank rating or exceed residential safety standard for scalding (maximum 150� for residential heaters). Very hot water (140-180�F +) can kill, and/or cause serious burn injuries. Typical bath shower temperature is 104�F and rarely much higher. Typical thermostat setting on indirect heater might be 120�-135�F, meaning that cold water is mixed with Hot water at the shower valve to achieve 104�F temperature. Every product manual for residential water heaters recommend 120� thermostat setting. Mixing valve should be installed for any thermostat setting above 120�F.
Resource:
Advantages mixing valve
The boiler loop is a 'closed system,' and must have safeguards to minimize high pressures and prevent explosion of tanks and pipes that contain super-heated hot water. Boiler MUST be installed, maintained etc by licensed plumber with boiler experience due to high pressure and temperatures from boiler...Not DIY household project.
Resource
Pipe diagram for 3 boilers
Typical boiler-indirect manuals:
Indirect service manual
Boiler instruction manual
Boiler installation / service manual
Commercial boiler install/ service
What size indirect heater is needed Boiler and indirect are truly an 'endless supply of hot water' ... capable of delivering 400+ gallon hot at continual draw before becoming too cool to use.
Larger imageCondensing heaters ... Since the 2015 energy standard, any household requiring GAS water heater larger than 50 gallon, must look to buying two heaters, or consider a condensing heater.
Polaris is among a class of water heaters called 'condensing' due to the amount of heat recycled from flue and the resulting output of condensed acidic water vapor that must be routed into floor drain. Polaris heater ... ... ultra low nox, power vented Polaris water heater, with 100,000-199,000 BTU per hour burner and 444 stainless tank and heat exchanger, requires no anode rod and comes in 34 and 50 gallon size.
Purpose: supply large amounts of potable hot water with secondary purpose of home heating.
The Polaris has been in use many years. It is not a new introduction.
Polaris has higher efficiency (80%) than ordinary atmospheric or power vented heater (60% efficiency).
Efficiency is combined thermal efficiency and standby cost of heater including any electricity needed for blower, flue damper etc, but does not factor purchase price, longevity, maintenance, repairs, cost of installation, home alterations etc., nor consider environment damage of high-consumption households. The 50 gallon 100,000 to 199,000 BTU per hour Polaris is about same size as ordinary residential water heater (22" diameter) but can supply more hot water than 40,000 BTU water heaters,.
For example, 50 gallon 100,000 BTU Polaris delivers estimated 100 gallon first hour ... meaning it will deliver 100 gallons hot water in single continuous draw before water temperature becomes unusable. Recovery 129 gallons per hour. (Depending on temp of incoming cold water and thermostat setting).
The 50 gallon 199,000 BTU Polaris can deliver estimated 170 gallons first hour.
Contrast with ordinary 40 gallon tank heater with first hour delivery estimate 60+ gallons usable hot water, with recovery 40-50 GPH per hour.
The trade off for condensing heaters like Polaris is higher cost, more expensive repairs, larger gas line and gas consumption, more complicated installation (power direct vent), need for clean electric power and dedicated 120 volt circuit, plus surge protection to protect complex electronic controls are susceptible to surge etc.
Polaris condensing heater uses a blower to draw air into the burner at the bottom of the water heater through an intake pipe from outdoors. A supply of natural gas or propane gas is mixed with air inside the burner located at lowest part of water tank. After burning the fuel, the blower pushes hot combustion by-product through helical-shaped heat exchanger located inside tank before pushing the exhaust by-product out of tank and up a vent pipe exiting through side-wall or rooftop terminations. Vent pipe is typical 2-3" PVC as specified in manual.
Polaris heater can be integrated with auxiliary storage heater, or integrated with air handler for whole house heating ... or used stand alone for delivering large volume potable hot water.
Resources:
Review Polaris water heater and images
Vertex condensing heater has problem keeping up with high consumption shower
Efficiency: Condensing heaters circulate hot water through helical heat exchanger, raising thermal efficiency. Polaris is rated with thermal efficiency of 94-96%
Thermal efficiency is percentage of heat from burner that is transferred into water ... add thermal efficiency with estimated standby loss = total efficiency.
Polaris has total efficiency around 81%.
Ordinary atmospheric residental gas water heater efficiency is around 60%. Remember, the EF rating of a heater is not efficiency ... it's a formula for calculating efficiency that subtracts percentage of tank volume ... with smaller tanks having less volume, and slightly higher efficiency.
Toxic byproducts. By federal standard any water heater with 100,000+ BTU must be ultra low nox. Polaris with 100,000 to 199,000 BTU burner is ultra low nox ... releasing 20 PPM (parts per million) NOx. Contrast with typical 40,000 BTU residential ultra low nox heater that releases 14 PPM. Typical 40,000 BTU residental gas water heater (if not rated for low nox) around 54 PPM.
Full image
High volume system
Shows return line installation, aquastat (thermostat) on hot water line, and 2-80 gallon heat pumps.
This illustration shows the drain vale used as entry point for both cold water and recirculated water.
The advantage might be using the open cold water port to add second anode rod and extend life of tank, or at least extend the length of time between anode rod inspections.
Buy:
Grundfos circulating pumps
Grundfos clip-on aquastats
Resource:
Recirculating system designs
Aquastat manual
Calculate first hour delivery
Calculate recovery
Replace anode rod
Plumbing for 2 water heaters and Storage tank pdf
Plumbing for 3 water heaters pdf
Plumbing for 2 water heaters and Recirculating system pdf
AO Smith pipe diagram /pdf
AO Smith pipe diagram /pdf
AO Smith pipe diagram /pdf
Larger imageSuper high volume system
Storage tank and heat pump/ DIY
Purpose to increase storage capacity to meet high volume demand.
Typically, a gas water heater is used for high volume systems, and not heat pump. Storage tanks are available in 150-200 gallon etc and rated for high temperature applications.
Tankless will stall and quit heating when demand exceeds parameters of unit. Even 3 tankless heaters can stall.
Heat pump supplies hot water that circulates into the storage tank.
Storage tank thermostat controls circulating pump, so when water drops below set point inside storage tank, the heat pump replenishes the hot water.
Storage tank can contain super-dangerous 140+�F water. The mixing valve located on top of storage tank, adds cold water to the line, so end user receives 115�F water.
This strategy increases the amount of hot water available to meet high volume demand. Typical bath-shower is 104-110�F.
Buy:
AO Smith Storage tank
Rheem thermal storage tank
Resources:
Advantages disadvantages mixing valve
Plumbing for 2 water heaters and Storage tank pdf
Larger imageTwo gas water heaters plumbed in reverse (parallel) with a storage tank
Resources:
Storage tank and booster-heater.pdf
Tank plus booster heater
AO-Smith-storage-tank.pdf
Commercial-storage-tank-specs.
Two-heaters-and-storage-tank
Two-heaters-and-storage-tank
Source: http://waterheatertimer.org/Two-water-heaters.html
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