How does a wood fired hot tub coil work?

A wood fired hot tub coil is an essential component of a wood fired hot tub heating system. It allows water to be heated using a wood fire as the heat source. Understanding how a wood fired hot tub coil works helps ensure proper installation, maintenance, and operation of a wood fired hot tub.

What is a wood fired hot tub coil?

A wood fired hot tub coil is a long length of pipe, usually copper or stainless steel, that is placed inside the firebox of a wood fired hot tub. The coil has an inlet and outlet that allows water from the hot tub to flow through it. As the fire in the firebox heats up the coil, the water flowing through the coil absorbs the heat, gets hot, and returns back to heat up the water in the hot tub.

Main components of a wood fired hot tub coil

The main components of a wood fired hot tub coil include:

• Piping – This is usually type L copper or stainless steel pipe with a diameter of 3/4″ to 1″.
• Inlet and outlet fittings – These allow connection of the coil piping to the pipes coming from and returning to the hot tub. Usually threaded or soldered fittings.
• Coil shield – A metal sheet enclosing the coil piping that absorbs and evenly distributes the heat from the fire.
• Supports – Hold the coil piping and shield in place inside the firebox.
• Heat deflector – Usually a metal sheet above the coil that deflects heat downwards onto the coil.

How does a wood fired hot tub coil work?

A wood fired hot tub coil works on the basic principle of heat transfer. When a fire is lit in the firebox, the coil absorbs heat from the fire through radiation and convection. The relatively cooler water flowing through the coil piping absorbs this heat from the hot coil, gets heated up, and flows back out to heat up the hot tub water. Here is a step-by-step explanation:

1. A fire is lit in the firebox of the wood fired hot tub.
2. The fire heats up the firebox, coil shield, and heat deflector to very high temperatures.
3. The coil shield and heat deflector evenly distribute heat around the coil piping.
4. The hot coil shield and deflector radiate heat onto the cooler coil piping.
5. Hot combustion gases from the fire flow around and over the coil, heating it up through convection.
6. The cooler water from the hot tub enters the coil through the inlet fitting.
7. As the water flows through the hot coil piping, heat is transferred from the hot coil to the cooler water.
8. The now heated water flows out the coil outlet and back to the hot tub.
9. The heated water entering the hot tub raises the overall water temperature.

This heat transfer process continues as long as the fire is burning and pumping water through the coil. The fire can be maintained by adding more wood periodically.

Factors affecting heat transfer

There are several factors that affect the efficiency and rate of heat transfer from the fire to the water in a wood fired hot tub coil:

• Coil surface area – More coil surface area exposed to the fire results in faster heating.
• Water flow rate – Slower water flow allows more heat absorption but requires a larger coil.
• Insulation – Insulated firebox and coil housing improves heat transfer to the water.
• Coil shields – Improve heat distribution over coil surface for even heating.
• Firebox size – Larger firebox can accommodate larger fires to produce more heat.
• Draft – Good draft through the firebox improves combustion and heating.
• Wood fuel – Properly dried wood with good combustion characteristics produces more heat.

Getting the right balance of these factors allows efficient heat transfer from the wood fire to the hot tub water.

How long does a wood fired hot tub coil last?

With proper installation and maintenance, a wood fired hot tub coil can last for many years. Coil life expectancy depends on factors such as:

• Coil material – Stainless steel lasts longer than copper.
• Water quality – Corrosive water can shorten coil life.
• Usage – Heavy usage requires more frequent coil replacement.
• Operating temperature – Maintaining appropriate water temperature prolongs coil life.
• Buildup – Preventing soot, creosote, mineral buildup improves longevity.
• Freezing – Coils damaged by frozen water require replacement.

With ideal conditions, copper coils can last 5-10 years, while stainless steel coils can last 10-15 years or longer. Proper water treatment, draining for winter, and regular maintenance will maximize coil lifespan.

How to install a wood fired hot tub coil

Proper installation of a wood fired hot tub coil involves:

1. Selecting the right coil size to adequately heat the hot tub volume.
2. Mounting the coil on sturdy supports attached to the firebox walls.
3. Installing coil shields around and above the coil to distribute heat.
4. Connecting inlet and outlet plumbing between the coil and hot tub.
5. Insulating the firebox and coil housing.
6. Installing a heat deflector above the coil.
7. Testing water flow and checking for leaks before firing up the hot tub.

The coil should be mounted high enough above the firebox floor to allow space for ash buildup. The supports, shields, and coil housing should be made of stainless steel or other non-combustible material. All connections should be leak-tight.

Maintenance tips for wood fired hot tub coils

Regular maintenance is key to maximizing the life and performance of a wood fired hot tub coil. Recommended maintenance tips include:

• Inspect coil periodically for leaks, corrosion, mineral buildup.
• Check pipe supports and shields to ensure coil is properly positioned.
• Clean coil with specialty coil cleaner to remove creosote and soot buildup.
• Replace damaged coil supports or shields.
• Test water flow rate – clean out deposits restricting flow if needed.
• Check pipe insulation – replace if deteriorated.
• Use water treatment chemicals to prevent corrosion and mineral buildup.
• Drain the coil when draining the hot tub for winter.

Periodic coil cleaning and replacing worn parts will maximize coil lifespan. Avoiding freezing conditions prevents costly damage.

Troubleshooting common wood fired hot tub coil problems

Some common wood fired hot tub coil problems and their troubleshooting are:

Problem	Possible Causes	Troubleshooting
Poor water flow	Obstructions in pipes, pump failure, closed valves	Check pump, filters, and clear obstructions. Open all valves.
Corroded pipes	Substandard water chemistry	Improve water treatment. Replace corroded pipes.
Coil leaks	Corrosion, freezing damage, joint failure	Repair leak or replace coil. Drain coil properly.
Low heat output	Improper coil installation, poor draft, inadequate fire	Ensure proper coil position. Improve draft. Build bigger fires.

Seeking help from a wood fired hot tub specialist is recommended if DIY troubleshooting does not resolve coil problems. Replacing damaged coils promptly prevents more costly repairs.

Key takeaways on wood fired hot tub coils

– A wood fired hot tub coil absorbs heat from the fire and transfers it to the water, allowing a wood burning fire to heat the hot tub.

– Proper coil installation, water chemistry, usage, and maintenance are key to maximizing coil lifespan.

– Copper and stainless steel are common coil materials, with stainless steel lasting the longest.

– Slower water flow, more surface area, good insulation, and bigger fires improve heating performance.

– Leaks, corrosion, flow obstruction, and freezing damage are common coil problems requiring repair or replacement.

Conclusion

Understanding how a wood fired hot tub coil works allows proper installation, maintenance, and troubleshooting to maximize performance and coil lifespan. With the right coil setup and care, a wood burning hot tub provides safe, efficient, and sustainable outdoor hydromassage enjoyment for years to come. Consult a professional for choosing the right coil size and material for your hot tub, and for any major repairs. With some basic preventive maintenance, your wood fired hot tub coil can provide reliable heating season after season.