Natural Gas Pool heater Questions

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Karenyn

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May 26, 2019
12
Charleston, SC
Hello All, I have been doing some research and have gotten two quotes on a natural gas pool heater with and Pentair Screen Logic bundle. I currently have all other pentair products. My pool is fiberglass (Barrier Reef Coral Sea 31.2x15.2/ 4ft to 6'4depth) and is about 15000 gallons. Here are my questions. One quote is for 250,000 BTU Mastertemp and the other is for 300,000 mastertemp. Which unit should I go with? Is the 300,000 overkill? Price is abt 500 difference between each quote for the mastertemp (300 difference between total cost). I need to get a gas line installed and I have 3 quotes. Only one is using galvanized piping. The other two are using a mixture of flexible type and galvanized. What is your experience with either? Does the flexible type make any type of noise when gas is flowing to the heater? I am located coastal SC if that is needed for any reason.

Thanks
 
Our pool is similar in size to yours. Mastertemp 400 is what we have. We're just west of Houston, Texas. I don't think the 400 is excessive for us. It will heat the spa in the middle of winter (40's to 50's) in 30 to 40 minutes. My wife can't deal with cold water and to her cold is less than about 90 degrees! We last used the heater a week ago when rain dropped the water temp to 86. We have all iron pipe. Our meter had been upgraded earlier for a standby generator. No flex pipe.
 
A 250K heater will heat your pool 2 degrees/hour. A 300K heater will do 2.4 degrees/hour. A 400K heater will heat it 3.2 degrees/hr.

So a 400K heater will heat 50% quicker then a 250K heater.

With a smaller heater you will need to anticipate more when you want the pool to be heated and get it going.

Flex piping is normally used for underground gas lines and it alsts longer underground than galvinized. Gas is low pressure and you don't hear it flowing..
 
Karenyn said:
I am looking at the different types of 400k mastertemps. Do you any of you know the difference?
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There is:
  • Mastertemp
  • MasterTemp HD
  • MasterTemp ASME
  • MasterTemp ASME HD.
From Pentair MasterTemp Heaters - Further Reading

The commercial ASME certified performance model features include:
  • New bronze header design for easy access to the thermal regulator and bypass valve service without use of special tools
  • Upgrades to thermal regulator include a governing stainless steel sleeve for better wear protection
  • All internal components of the bronze header are plastic for lightweight, corrosion and wear protection
  • Ignition Control Module includes more diaphragm spring force for better gas control and robust operation.
  • Fuller pre-mixed system with highly efficient air and gas mixture allows for faster heat up times
  • Efficiencies up to 84%
Both the MasterTemp and MasterTemp ASME come in an HD model that has a cupro-nickel exchanger. Pentair claims the cupro-nickel exchanger stands up to the harshest of applications, like low pH, high flow or heavy use.

For almost the same price the HD unit may last longer. But then there are many reasons a heater fails not related to the heat exchanger. So you may spend the extra money for the HD and never get the benefit.

The ASME unit is about 5% more efficient and some more robust parts for commercial use.
 
Thank you for the input. I think I am going with the 400k. I do have one last question. Since the 400k will warm the pool faster does that mean that it uses the same amount of gas that a 250k/300k unit would use, but in less time? I hope that is clear because I am not sure else how to explain it.
 
Karenyn said:
Thank you for the input. I think I am going with the 400k. I do have one last question. Since the 400k will warm the pool faster does that mean that it uses the same amount of gas that a 250k/300k unit would use, but in less time? I hope that is clear because I am not sure else how to explain it.
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Yes, to heat the pool to a given temperature the 400K heater will use the same amount of gas or a bit less then a smaller heater.
 
ajw22 said:
Yes, to heat the pool to a given temperature the 400K heater will use the same amount of gas or a bit less then a smaller heater.
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Are you sure about this? This seems to defy logic to me. A therm of natural gas is equal to 100K BTUs of energy. So without taking into account efficiency, the 400K BTU would burn 4 therms per hour, and the 250K would only burn 2.5 therms per hour.

Now maybe the 400K unit is more efficient than the 250K, but I cant imagine that the efficiency difference is so large to account for 1.5 therms.
 

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Yev said:
Are you sure about this? This seems to defy logic to me. A therm of natural gas is equal to 100K BTUs of energy. So without taking into account efficiency, the 400K BTU would burn 4 therms per hour, and the 250K would only burn 2.5 therms per hour.

Now maybe the 400K unit is more efficient than the 250K, but I cant imagine that the efficiency difference is so large to account for 1.5 therms.
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I believe what he is saying is that they will burn the same amount of gas, but the 250K will do it over a longer period. For example, if your target rise is 6 degrees, the 400K will do it in 2 hrs, while the 250K will take three, with each consuming about the same amount of gas.
 
Chasarms said:
I believe what he is saying is that they will burn the same amount of gas, but the 250K will do it over a longer period. For example, if your target rise is 6 degrees, the 400K will do it in 2 hrs, while the 250K will take three, with each consuming about the same amount of gas.
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Correct.
 
Yev said:
Now maybe the 400K unit is more efficient than the 250K, but I cant imagine that the efficiency difference is so large to account for 1.5 therms.
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400K will give out 1.6X the heat of a 250K heater for 1.5X therms.
 
Another thing to consider is air temp. I don't know what temp is assumed in the heating times quoted here, but it would seem that if the air temp is lower than the target water temp, you will continuously lose water heat to the air. In that case, the slower heating small heater would take disproportionately longer to heat the pool. I find on average with my Mastertemp 400, I get 1 degree of water temp increase every 20-25 minutes, depending on air temp, and I've never tried to heat the pool when the air temp was lower than 80-82 degrees.
 
Thank you for your answers. That helped me understand the use of gas. I guess i was thinking the 400k unit would burn less gas overall because it took less time, BUT it seems my theory was wrong because it will take more gas (even though it's a shorter amount of time) to warm the pool because the unit is bigger. Either way I decided to go with the 400k unit. I just thought it would be a better option to heat the pool quicker. I am not sure if I will every use the heater in Dec-Feb unless it happens to be a warmer day (that happens sometimes in coastal SC). I am hoping to extend the season from March to Nov.
 
Karenyn said:
I have been doing some research and have gotten two quotes on a natural gas pool heater with and Pentair Screen Logic bundle. I currently have all other pentair products.
Click to expand...

Can you Create Your Signature? Do you already have an EasyTouch system? If not you might want to consider the IntelliCenter instead of getting it with ScreenLogic bundle.
 
I didn't mean to post that question twice. I just thought it would be easier to automate when the pump runs and also be able to adjust the heater. My quote says screen logic bundle. I will verify it is screen logic2. The quote is for 1k, is that a bad move to automate at this point? I am wanting it for convenience.
 

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