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How
does a boiler and indirect heater work? E-mail: geno03245w@gmail.com |
 Larger imageAnother image Larger image with more detailed plumbing Indirect Heater and Boiler Fig 1 shows boiler and indirect heater operation. Purpose is for home heating plus large amount of potable hot water for faucets, shower, drinking etc. Indirect heater can supply 200-400+ gallons first hour delivery of potable (drinkable) hot water for high usage homes and business.  High heatBoilers are not DIY. Boiler MUST be installed and maintained by licensed plumber with boiler experience due to high pressures and temperatures from boiler. A boiler super-heats hot water using gas or oil at a rate of 150,000- 300,000+ BTU per hour producing near-boiling 200°F water temperature (a fatal temperature). "By code, the maximum outlet water temperature for any type water heater is 210°F (98.5°C)," including boilers, household heaters, commercial heaters, industrial heaters, indirect heaters, storage tank, booster heater etc. Above 210°F risks steam explosion that will destroy building. The boiler thermostat limits temperature to less than 210°F, and in event of malfunction, then a correctly-rated TP pressure-temperature release valve will release enough hot water to match the maximum BTU output produced by that specific water heater. To prevent explosions, all water heaters, of any type or size, must have a TP valve with a BTU rating that exceeds BTU rating of heater. The TP must be installed within 6" inches of top of heater, and TP cannot be capped off. The boiler performs two functions. 1) Heat living space by circulating 200°F hot 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 water inside the indirect heater. It does this by circulating 200°F water in a loop from the boiler, through the coiled heat exchanger located inside indirect heater, and back to boiler. Water from boiler is confined inside the loop, and contains rust inhibitor, and possibly antifreeze etc. The chemical-laden boiler water is never mixed with the potable (drinkable) water inside the indirect heater. Resource: Greestar boiler chemistry pdf How it works: -Note that an indirect heater does NOT heat water on its own ... instead the indirect heater has a heat exchange coil that receives hot water (or other hot fluid) from a boiler, geothermal, or solar collector etc. -The indirect heater has it's own thermostat, separate from thermostat on boiler. The indirect thermostat controls the circulation pump, so when water inside the indirect drops below set point, the pump circulates hot water from the boiler, through the heat exchanger, and back to boiler in a continuous loop. -When water temperature inside indirect heater reaches thermostat set point, for example 120°F, the circulation pump turns off, and water stops circulating from boiler until indirect thermostat calls for heat again. Resources: add-fan-to-boiler.html Typical boiler-indirect manuals: Indirect service manual Boiler instruction manual Boiler installation / service manual Commercial boiler install/ service |
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| Indirect
heater supplies potable (drinkable), DHW domestic hot water to home. When an indirect heater is heated by a boiler, the indirect heater can supply very high volume of 120°F potable hot water for faucets, shower etc (up to 400+ gallons per hour) depending on size of indirect tank, BTU rating of boiler, thermostat setting, temperature of incoming cold water, etc. What size indirect heater is needed Boiler water vs potable (drinkable) water. 1) Water inside a boiler loop contains chemicals to protect pipes and radiators etc. These chemicals are unsafe to drink. 2) The boiler recirculates the same chemical-laden water over and over, while drinking water is introduced fresh with each draw. 3) The potable water or DHW (domestic hot water) contained inside indirect heater is never mixed with water from boiler. To prevent contamination, the heat exchange coil is a sealed unit. Some indirect heaters have a double wall coil for extra protection. 4) Super heated 200°F hot water from boiler cannot be allowed into household water pipes where the recommended safe maximum for potable water used by people is 120°F. Typical indirect heater has maximum tank temperature of 150°F. 5) 200°F hot water from boiler would cause pressures that exceed residential rating, and exceed indirect tank rating, and might cause TP valve on indirect heater to release water. This explains why the indirect heater must have an independent thermostat that stops circulation of 200°F boiler water before it overheats water inside indirect heater. |
| Alternative
for household is a Combi-Boiler that does both jobs with
one heater ... it heats
home and supplies drinking water, and does not need indirect heater. Combi boiler quick install manual Disadvantage is home heating is stopped when shower/bath is running, and Combi might experience shortage of hot for showers depending on model and temperature of incoming cold water etc. Advantage of Combi is compact size, and possibly simpler installation, which is good for residence with small footprint. Advantage of boiler and indirect heater is both pieces of equipment can be repaired/replaced separately, and home heating and bath/shower can happen at same time, plus large volume of hot water for household and commercial applications. |
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 First hour delivery from Indirect
HeaterFig 2 shows typical first hour delivery for indirect heater with boiler. -For example a 30 gallon size indirect heater would be able to supply 199 gallons hot water ... assuming incoming cold water from city or water well is 58°F, and thermostat is set at 135°F, which is 77°F higher than incoming water temperature. The heater must be able to raise water temperature 77°F. -If thermostat setting or incoming water temperatures are higher or lower, then the first hour delivery would be different. -30 gallon size would have less standby cost than larger heater because there is less surface area to lose heat. What is first hour delivery -First hour delivery is the amount of hot water that can be consumed at one time by a family before the water turns too cool to shower.It does not mean hot water will last 1 hour. |
 What size indirect heater is
neededFig 3 is the 'recommended' first hour rating that is needed per person in home A 30 gallon indirect heater would be enough hot water for 12-14 people because a boiler consumes so many BTUs and heats to such high temperatures, that it can easily keep up with demand as it occurs. Boiler and indirect heater are truly 'unlimited' hot water. |
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