Heat pump bypass valve

[lilpam14]

So can someone explain to me about the bypass valve for an electric heat pump pool heater. If the bypass valve is in the off position, does water still circulate thru the heater?? Does the water automatically start running thru the heater once you turn the heater switch to on? May be a dumb question but...still learning all this.
I had to finally call someone to come out and look at why the heater was not working. It ended up being the capacitor. While there he asked why the bypass valve was on. I said I thought it had to be on for the water to flow thru the heater to get hot. He said no. That by it being on, more water was flowing thru and taking longer to heat up? I don't know enough about this to question him, just took his word. So now that I have had time to think about it I am even more confused. If more water was flowing thru, wouldn't it heat up quicker. Maybe he said the opposite and I misunderstood. With the bypass valve open maybe 50% of the water does not run thru the heater and it takes longer to heat up????? :?
Thanks

 

[phipsi1237]

With the bypass valve open, less water flows through the heater. It could be 50%, more, or less, depending on the setting of the valve. It was explained to me the same way being the heater is more efficient heating the smaller water passing through at once. Apparently, this is better for the heater as well. Not sure why though.

 

[ps0303]

Not all pools with heaters, gas or electric, have by-pass valves plumbed into it. A bypass does allow you to divert water past the heater for several reasons but I have never heard anyone say that if you bypass some of the water it would heat up the pool faster. That doesn't make logical sense. It should take longer to heat that way as you are allowing the cool water to flow back to the pool without even slightly heating it.

Some times you add a bypass to divert some of the water because the flow is too great and causes issues with the heater. They are also added in case you might need to perform a stain treatment of which you don't want acidic water flowing thru the copper in the heater.

 

[rdhetrick]

Interesting thoughts, I don't have the answers but:

The heater will generate a fixed amount of energy (BTU) whenever it is heating. Heat transfer to the water is a function of the temperature difference of the heated pipe and water, and the contact time. If the bypass valve is open, this will reduce the flow through the heater which will reduce the water velocity through the heater, thus increasing the residence time in the heater. This means more heat gets transferred to the water instead of wasted to the atmosphere.

I'm not sure if this is the reason for the bypass valve, but I don't have any other explanation.

 

[lilpam14]

Thanks guys.