110v vs 220v

[vetteonr]

I've heard a lot of people talk about how a 220v hook up is more economical than 110v. My tub can go both ways, so can someone enlighten me on this issue? Any help would be appreciated. Thanks.

[JohnnyK45]

Some good info from another online source you might find useful...

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"220 volt portable hot tubs will save you money on energy bills!"

The Truth: Quite the contrary - 220 volts will not save you money.

The reasoning behind the 220 volt theory is this: 220 volts allows your heater to draw more energy and will heat up your hot tub twice and quickly, so in the end, you have it running half the time of a 110 volt hot tub and you save money.

Why Is This So?: Your electric meters measure your energy use in watts as opposed to volts. The higher voltage means that more energy (watts) can move through the wires to your hot tub at a faster rate. With a 220 volt spa, you will still use the same amount of watts that you would running a 110 volt hot tub for twice as long. The same amount of watts goes to your tub, but it just takes longer.

Depending on the age of your home, you may have outdoor sockets, which makes plugging feeding electricity to your portable hot tub very easy. Installing a 220 volt outlet will require an electrician, not to mention permits and inspections depending on your county's policies.

110 volts can still power hot tub heaters, jets, lights and other features without any problems. The only concern is if you enjoy using your spa for more than an hour or two when the temperature dips down below 32 degrees. With the cover on your 110 volt hot tub, you can get the temperature up to 104 degrees Fahrenheit, but over a couple of hours in frigid temperatures, the temperature will slowly drop. Usually it drops 2 degrees each hour the cover is off-so after about 3 hours of continuous use in below freezing temperatures, the water will only be about body temperature. If the jets are on high, this cool off might happen more quickly. This usually does not present a problem with average use (soaks for 1-2 hours), but if you have parties on very cold nights where everyone wants to be in and out of the hot tub over a 5 hour period, you might find that the water is lukewarm by the end of the night.

220 volt hot tubs are able to keep water warmer in sub-zero temperatures. This quicker flow of voltage is used for appliances and other larger machines that need a higher draw of energy. While 220 volt outlets are usually accessible in areas like your kitchen, they may not be available through an outdoor outlet. If this is the case, then you will need to check with your local permit office and see what the requirements and permit prices are. Every county has a different policy about what requires a permit and what does not - often any new electrical line requires one and may also require an inspector to check the work after the new outlet is in place.

It is usually recommended that you hire an electrician to lay the new wiring for the 220 volt outlet and hook it up to the source of current, simply because one misstep for a Do-It-Yourself-er can result in a trip to the hospital

[Dr. Spa™ Ret.]

Wow. Not sure where you found that, but it's not correct.

220v will heat FOUR times faster than 110.

This could save a little bit of $ if the heating system is not part of a 24 hour recirc system, as the pump would need to run for only 1/4 the time to heat the water.

Electricity does NOT move at a "faster rate" at higher voltages...Higher voltages will allow more watts to travel through the same size wires.

Your article says, "you may have outdoor sockets, which makes plugging feeding electricity to your portable hot tub very easy". Doing so would be a violation of national electrical code as hot tubs are required to be on a separate, dedicated circuit with no other outlets or appliances (there are a few, very rare exceptions to this)..

A 220v spa can NOT be plugged into an "outlet" and must be hard wired.

[Chas]

What Doc said.

 

[vangoghsear]

Electric resistance heat is 100% efficient.  It does not matter what voltage the kW is delivered, 1 kWh = 3142 btuh of energy.

Excluding the pumping, which Dr Spa correctly pointed out as a potential for savings with 220, the potential heat losses are greater with 220. 

The quicker the energy is transferred to the water, the longer the water has to transfer the greater delta T (temperature difference between water and surrounding atmosphere) to the air through the insulation or open top when in use, if the heater does not keep up and the temperature is reduced (if the 110 heater does keep up, there is no difference 1kW 110v = 1 kW 220v = 3142 btuh). 

The greater the Delta T, the greater the amount of heat lost through the insulation or open top.  With 220 you will lose more heat longer, as the spa reaches setpoint sooner.   Once the setpoint is reached by both 110 or 220 they are equal again, so this only applies during startup and reheat after a big spa party.

I think the bigger difference will be the pumping mentioned by Dr Spa.  So 220v should have the edge on savings, depending on the control and heater/pump configuration.

[Dr. Spa™ Ret.]

Interesting facts, but I'm not sure relevant. If I understand you correctly, what your saying is;

Given a specific heating element, if 220v is applied to it, it will heat 4 times faster than if 110v is applied to it. In the amount of time it will take to heat up at 110v, the spa heated with 220v will lose more heat to the atmosphere than the 110v heated spa

As an example, lets say the 220v spa will reach temperature in 1 hour. The 110v spa would then take 4 hours. Over that four hour period of time the 220v spa will lose more heat to the atmosphere than the 110v spa.

Based upon physics and Newtons Law of Cooling, this is correct. However, the additional heat loss would be almost insignificant with a modern well insulated spa, and as you said, would only be relevant when heating the spa from cold. I'd also be willing to bet that the cost of running the pump for four times as long at 110v, would exceed the cost of the additional heat lost to the atmosphere when heating with 220v.

[vangoghsear]

Given a specific heating element, if 220v is applied to it, it will heat 4 times faster than if 110v is applied to it.

Not exactly.  The 220v spa has more elements, it doesn't push more watts through one.  Most convertible spas I've seen list two ratings such as 1 kW and 4.5 kW.  The 4.5 kW element set would only be used with 220v spa, as it would draw 40.9 amps on a 110 circuit.  It only draws 20.45 amps on a 220v circuit.

This is wrong, see below. 

[vangoghsear]

Actually, looking them up Doc, you are right.  It seems they vary the voltage pushed through the one element.

Apply ohm's law and stir. 

So I agree in full with your post. 

I just always thought it interesting that if apples to apples pump wise, the 220 would actually be a bit less energy efficient due to losses.  I went 220 on mine, I didn't want mine to struggle to heat up.  But yeah, it is not a substantial amount especially with a well insulated hot tub.

[sorebikr]

Actually, looking them up Doc, you are right.  It seems they vary the voltage pushed through the one element.

Apply ohm's law and stir. 

So I agree in full with your post. 

I just always thought it interesting that if apples to apples pump wise, the 220 would actually be a bit less energy efficient due to losses.  I went 220 on mine, I didn't want mine to struggle to heat up.  But yeah, it is not a substantial amount especially with a well insulated hot tub.

End of the day and I'm tired, but I'm pretty sure this is still an over-simplification. 
If you had 2 tubs, one 220, one 110 that were turned on for four hours, both tubs would get to the same ultimate temp and both would have been losing some heat for four hours.  So does a warmer tub lose heat faster than a cooler tub?  (My addled brain truly doesn't know).  If not, then its a wash and the 220 wins since the pumps aren't turned on as long. 

[Hot Spring Ace]

Given a specific heating element, if 220v is applied to it, it will heat 4 times faster than if 110v is applied to it.

Not exactly.  The 220v spa has more elements, it doesn't push more watts through one.  Most convertible spas I've seen list two ratings such as 1 kW and 4.5 kW.  The 4.5 kW element set would only be used with 220v spa, as it would draw 40.9 amps on a 110 circuit.  It only draws 20.45 amps on a 220v circuit.

This is wrong, see below. 

Its the same heater no matter which way you hook it up. What it comes down to is it will take 4x as long to heat at 110V but at 1/4th the energy use so its wash. The only way it matters depends on how your spa is set up. If your spa has a circ pump then its a wash because its running 24/7 anyway. If your spa uses a 2 speed pump that it turns on when it needs to heat then technically it will cost less to run 220v than 110v because the pump will be on less time.

What matters to some people is sometimes your elcectrical availability is strained and adding another 220v circuit to the house 'box" is an issue. Others may care that 110v can be cheaper to install. On the flip side, if you run at 110V you can't heat while you're in it running the jets which may matter in colder climates. Unless you have a real issue with doing so, go with 220v.

[Chas]

if you run at 110V you can't heat while you're in it running the jets which may matter in colder climates. Unless you have a real issue with doing so, go with 220v.

I've NEVER had a customer say they were sorry they went with 220 - you can run jets and heat at the same time. You need a dedicated circuit even on 110, so why not?

I have sold tons of our smaller tubs and hooked them up to 110 - dedicated outlet on it's own 20A breaker - and they work fine. Keep in mind that our tubs (HotSpring) recycle heat off of the jet pump motor, they are well insulated, AND I live in a mild climate. Change any one of those, and you will have some cooling when the jets are running on 110.

HTH

 

[vangoghsear]

End of the day and I'm tired, but I'm pretty sure this is still an over-simplification. 
If you had 2 tubs, one 220, one 110 that were turned on for four hours, both tubs would get to the same ultimate temp and both would have been losing some heat for four hours.  So does a warmer tub lose heat faster than a cooler tub?  (My addled brain truly doesn't know).  If not, then its a wash and the 220 wins since the pumps aren't turned on as long.

Let's assume for this example that there is a 24/7 circ pump to move the water through the heaters of both.

In your scenario if both reach the same ultimate temp, then the 220 reaches it in 1 hour and the insulation holds most of it during the next 3 hours.  There are some small losses through the insulation and cover during the entire 4 hour period.  3 hours of which are at maximum temperature difference between the tub and surrounding atmosphere.

The 110V tub reaches the setpoint at the end of the 4 hours.  So there is only a brief amount of time that the 110 tub is at maximum temperature difference.  As with the 220 tub there are insulation heat losses over the entire 4 hour period.  The losses will be greatest at maximum temperature difference, making the 110 the smaller loss tub.

[Chas]

BUT - most people 'set and forget' the tub. So - the tub stays at set temperature all the time, and your exercise is not applicable.

Bottom line, as far as I have experienced with thousands of tubs sold in a quarter century: choose the tub you like. If it has large pump(s) you will need 220 to run it. If you choose a convertible spa, you will have to run wire anyway (must be a dedicated circuit) so pay the extra and go 220. If for some reason you can't do 220, be SURE the tub is well insulated, has a good cover, and if possible recycles heat off the jet pump motor.

Many new tubs - esp. roto-molded (Freeflow etc) are "Plug and Play." That means they have a 1000 watt heater, can plug into an existing 15A outlet -BUT even THEY must be the only thing on that circuit: ie: 'dedicated' line. The theme here is "Dedicated Line."


 

[vangoghsear]

I agree with you Chas.  My point was purely academic.  Over the course of a 2880 hr (4 month) cleaning cycle the heat up period of 4 hrs vs 1 hr and delta T difference during that time is a moot point.  Pumping power and pump run times are the variables that matter. 

I was just making a point to those who believe that 220v power produces more heat through the heating element for less kW,  that is just not the case.  The kW/btuh ratio is always the same for resistance heat. 

[TwinCitiesHotSpring]

if your outdoors in a colder climate don't waste your time with 110v...I've had 2 customers in the last year who attempted to save money by going 110v, within 2 months time they all had the electrician come back and wire a 220v service