Heatpump flow rate question??

[jamesfr]

Hi,

I have just installed a new heatpump and it looks like its a bit under sized for my pool

My pool depth is approx 4.5ft avg so I calculate that I have approx 13200gals

The heatpump is 17k so is sized correctly for my pool according to manufacturer - they recommend upto 50m2 surface area, I have 36.4m2.

My question is they recommend a flow rate of 6m3 to 12m3 and say 6m3 is optimum. I am currenly running 12m2 as I am putting all of the water through the heatpump.

By doing this am I reducing the output of the heater?? Will the water not absorb all the heat in the coil?? Anyone good at maths to work this out?

The pump is rated at 55k btu. I have also calculated that it will take about 2hrs to raise the pool by 1f. It is taking much longer than this....

Any thoughts on this apart from buy a bigger one

 

[jamesfr]

Heatpump spec;

I have a eco 7 40

 

[jamesfr]

Possibly taking 4hr running to raise 1f...

Could this be to the max flow rate through heatpump??

Or have I got all the calculations wrong or the heatpump is not performing??

 

[jamesfr]

Anyone??

 

[chem geek]

I can understand the minimum flow rate to prevent getting the coils too hot and also to give reasonable efficiency. I can also understand a maximum flow rate to prevent erosion corrosion. However, I don't understand why the "optimum" is at the low end since the higher efficiency would be at the higher flow rate. Perhaps they are trying to reduce the risk of erosion corrosion. I don't believe you are any less efficient at the higher flow rate and if anything should be slightly higher in efficiency.

 

[jamesfr]

Thanks Chem Geek! I will go and turn the flow rate back up to max then!

Do you agree with my cals of 2hr per 1f if the pump is running at 55k btu's?? Is there anyway of testing the thermal output of a heater?

 

[JasonLion]

The efficiency of the heater will vary quite a bit with the air temperature. Heat pumps are much less efficient when the air is cold. I don't know what the weather is like where you are, but if it has been a cold spring like I have been having here then the heat pump won't be putting out anywhere near it's maximum output.

 

[jamesfr]

I have been running it when the air temp is between 14 - 20 deg C so should be in the 55k - 59k output if it is working correctly and I don't have massive losses through pipes etc...

 

[chem geek]

By the way, for those who are curious, 6 m³/h = 26.4 GPM while 12 m³/h = 52.8 GPM. The higher flow rate will also produce more head (resistance), but you'd have to look at a head curve for the heat pump to know how much.

 

[bk406]

There's nothing wrong with the flow rate i dont think. You're just trying to heat a pool, in April/early May, in canada, with a 55k heat pump, with 55-60 degree air temps. You're not getting 55k out of that heater. Its somewhere south of that. Heat pumps dont work too well until the air temp gets to around 70 degrees consistently, and there's a little humididty. But the salesman doesnt tell you that.