I have a Hunter 36 and want to purchase an inverter large enough to use my water heater. Is there a recommendation?? Thanks
correct inverter
- Thread starter gregm
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DON'T
You'll kill even a HUGE battery bank in no time. A typical water heater will draw 10+ amps at 110VAC - that's 1100watts At 12 VDC, that 1100 watts will drain your battery bank at 90 amps. If you had a 400 amp bank, it would be essentially dead in less than 2 hours (bank discharged 50% requiring recharge) and the water will still be cool. Only practical way to heat water at anchor is run the engine or buy a genset.
You'll kill even a HUGE battery bank in no time. A typical water heater will draw 10+ amps at 110VAC - that's 1100watts At 12 VDC, that 1100 watts will drain your battery bank at 90 amps. If you had a 400 amp bank, it would be essentially dead in less than 2 hours (bank discharged 50% requiring recharge) and the water will still be cool. Only practical way to heat water at anchor is run the engine or buy a genset.
The math
Your hot water heater is AC and will typically draw 10 amps. That means 10 amps X 120 volts = 1200 watts. So you would need at least a 1200 watt inverter to keep up. The problem arises when you use 12 volts to drive the inverter. Forgetting battery storage and inverter losses, 1200 watts at 12 volts is 1200/12=100 amps!!! That is a lot of amps. Your starter probably only draws 50 amps for a reference. So if you have a 200 AH battery bank and you TOTALLY kill the batteries you could run the heater for 200/100= 2 hours. A more realistic battery usage (50%) results in 1 hour of use. Assuming it takes 20 minutes of "on" time to get the water up to temp and the heater cycles on once every 10-15 minutes for about 4-5 minutes 1 hour "on" time figures out to: 20 min + number of cycles X 5 min = 60 min ---> number of cycles = (60-20)/5 = 8 cycles. A cycle is 15 min off + 5 min on = 20 min and you will get 8 of them or 20 min X 8 cycles = 160 min. Add the initial 20 min cycle to bring the water up to temp and you get 180 minutes of life in the batteries once you turn on the water heater circuit breaker. If you just run the water heater to get the water up to temp (20 min) then you will be using 33.3 AH out of the batteries. The question then is will the inverter actually operate at that power level for that amount of time with out going over temp and shutting down. You might want to mount the inverter underneath the water heater to recycle some of the heat ;-) Most just take a shower after running the motor to charge the batteries. You have to do that anyway after your first shower as when you turned on the water heater you drained the batteries.
Your hot water heater is AC and will typically draw 10 amps. That means 10 amps X 120 volts = 1200 watts. So you would need at least a 1200 watt inverter to keep up. The problem arises when you use 12 volts to drive the inverter. Forgetting battery storage and inverter losses, 1200 watts at 12 volts is 1200/12=100 amps!!! That is a lot of amps. Your starter probably only draws 50 amps for a reference. So if you have a 200 AH battery bank and you TOTALLY kill the batteries you could run the heater for 200/100= 2 hours. A more realistic battery usage (50%) results in 1 hour of use. Assuming it takes 20 minutes of "on" time to get the water up to temp and the heater cycles on once every 10-15 minutes for about 4-5 minutes 1 hour "on" time figures out to: 20 min + number of cycles X 5 min = 60 min ---> number of cycles = (60-20)/5 = 8 cycles. A cycle is 15 min off + 5 min on = 20 min and you will get 8 of them or 20 min X 8 cycles = 160 min. Add the initial 20 min cycle to bring the water up to temp and you get 180 minutes of life in the batteries once you turn on the water heater circuit breaker. If you just run the water heater to get the water up to temp (20 min) then you will be using 33.3 AH out of the batteries. The question then is will the inverter actually operate at that power level for that amount of time with out going over temp and shutting down. You might want to mount the inverter underneath the water heater to recycle some of the heat ;-) Most just take a shower after running the motor to charge the batteries. You have to do that anyway after your first shower as when you turned on the water heater you drained the batteries.
Engine
Actually Greg, if you just run your engine for a little while at a time, you'll have plenty of hot water without the expense.
Actually Greg, if you just run your engine for a little while at a time, you'll have plenty of hot water without the expense.
Run your engine
Just run your engine for a short while and you'll have all the HOT H2O you need for showers, dishes, yadda yadda...
Just run your engine for a short while and you'll have all the HOT H2O you need for showers, dishes, yadda yadda...
On-Demand Propane Heater
I installed a non-marine on-demand propane water heater over 2 years ago on my Passage 450. It is HANDS DOWN the best mod I've done. I bought a ventless Excel propane water heater from an EBay store and plumbed it into the outlet hose from my electric water heater. When my electric heater goes cold I turn a lever that routes the water through the on-demand unit and back into the regular circuit for the boat. It operates at around 80% efficiency and allows for a scorching hot shower on its low setting. The high setting would surely burn my skin right off. Keep in mind that if you go with anything other than an on-demand system you will need to schedule showers and other hot water tasks around your water-heating schedule, which is a pain and can lead to much unhappiness. It's nice to know that EVERY time I return to the boat after a long, cold dive I have a hot shower waiting - even if my girlfriend or a guest decided to wash her hair while I was hunting dinner.
I installed a non-marine on-demand propane water heater over 2 years ago on my Passage 450. It is HANDS DOWN the best mod I've done. I bought a ventless Excel propane water heater from an EBay store and plumbed it into the outlet hose from my electric water heater. When my electric heater goes cold I turn a lever that routes the water through the on-demand unit and back into the regular circuit for the boat. It operates at around 80% efficiency and allows for a scorching hot shower on its low setting. The high setting would surely burn my skin right off. Keep in mind that if you go with anything other than an on-demand system you will need to schedule showers and other hot water tasks around your water-heating schedule, which is a pain and can lead to much unhappiness. It's nice to know that EVERY time I return to the boat after a long, cold dive I have a hot shower waiting - even if my girlfriend or a guest decided to wash her hair while I was hunting dinner.
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