Heat pump - a worthy consideration?

Jump to latest Follow Reply
K

Kwikee

0
Feb 13, 2013
102
Melbourne, Australia
I'm about to begin our pool refurb before our swim season starts in Australia. We moved into this house in December last year and the pool is fully manual chlorine with no heating other than the solar blanket.
Looking into it, my understanding is that for solar to be effective I need to have the same surface area as the pool (approx 40sq.m) on the roof, facing North. This is a problem on several fronts. The pool is probably 10m (33ft) lower than the tile roof, and the majority of the roof faces East and West, with maybe 15% facing North which is not the pool area. I would need much more surface area on these East or West faces.
So in considering other options, gas heating is out of the running due to being quite expensive and inefficient.
I hadn't really considered electric heating for the same reason, however I can get an 18kW heat pump for $3,000 (plus installation)that should do the job nicely, and it uses 1600W of power, which equals around $2 a day if it runs for 12 hrs. This seems quite reasonable to me, given the solar kit would be close to $4,000 (plus installation), plus you still need to run a pump with that.
So in summary:
PRO's: No plumbing over the roof, cheaper (or at best similar)initial outlay, can heat any time of year, simple installation, can heat a spa

CON's: Approx 3 x cost of operation compared to solar, shorter life span (10yrs)

Have I missed anything or does anyone have any comments? I'm not looking for all year swimming, just something to give the shoulder season an extension of a month or so.
Thanks for reading.
 
I don't think you are really comparing equivalent things. A solar system with the same area as the pool is a fairly large solar system, while a heat pump that draws 1600W is a fairly small heat pump. I would expect that solar system to produce several times as much heat as that heat pump, at least when it was sunny. I'm more used to comparing solar systems with half the area of the pool to heat pumps that draw 6,000 watts.
 
I actually quoted the wrong value for the heat pump, it's 2.9kW input for 13kW output at 22'C. That's around 45,000btu's. Secondly, the pool area for solar is based on being in a Southern climate (Melbourne, Australia), west facing and a long way from the pool.
I'm reading on here that gas can compare favourably to a heatpump, but if the heatpump is run off-peak, surely it would win based on efficiency alone?
I'm only new to all this so any advice or experience is appreciated.
 
Mine is a hayward heat pump rated at 110000 btu for a similar size pool, when i want to extend the season beginning of may to mid october i have to overide my pump timer in the end months to run more often because the heater might run 15 hrs a day to keep the pool at 87.during the summer months it only runs a few hrs a day at the most.If your are using a heat pump a solar cover is a must.100k in gas is probably closer to 80k actual output.but as the temp drops so does the output of my heatpump.i had a propane heater at my last house and my heatpump is far cheaper to run.
 
I sent detailed information about the pool to the potential supplier and he recommends a 13-18kW unit that draws just under 3000W. 18kW is around 62000btu's so not even close to yours. Sounds grossly inadequate?
Summer here is around 90-106'F, and the minimum for the period I want to swim (Oct-Apr) temps are around 76-82'F. Does that change things?
Last season I had only a solar cover and it actually was enough to get me to the end of March and keeping around 26'C in the pool (82'F). I reckon the heatpump won't be doing a lot of work, so maybe this will do?
My options are very limited as a solar run would have a head of 10M+(33'), and run out around 25M (80'). Great info though, very appreciated!
 
Just re-did my numbers to compare gas to electricity the heatpump. Here's how I figure: if the suggestion of 110,000btu's to heat the pool is right, for gas at a 1:1 input:eek:utput ratio that equates to 115MJ of gas from our supplier at $0.0165/MJ, is $1.89/h. Electric heatpumps operate around 1:4.5-5.5 ratio input to output (I'll use 1:4.5), so 110,000btu's becomes 32kW, for an input of 7.1kW at $0.11 per kWh which is $0.78/h. So gas is out for mine.
 
That heat pump is still smaller than what I would recommend for that pool, and smaller than the equivalent heat output of the solar (even with the less than ideal roof arraignment). Of course any heat is better than no heat. Your basic situation is good for a heat pump, they like air temperature above 50 degrees (10 C). Most gas heaters are about 80% efficient, so even more expensive than what you calculated. Heat pumps start to lose efficiency below an air temperature of about 70 degrees (21C), but it doesn't sound like that will be an issue for you.

By the by, output BTU is directly comparable between different kinds of heaters, but input BTU is not. Gas heaters are normally rated by their input BTU, with output BTU usually running at about 80% of that. Heat pumps are normally rated by their output BTU, which is often 4 to 5 times their input BTU (which they don't normally mention, but which can be found by calculating the BTU equivalent of the electricity they use if you really want to know).
 

Enjoying this content?

Support TFP with a donation.

Give Support
ok, to head off on a tangent a bit, I've been planning a pool side "summer house" and if we go ahead with it along the basics of my design, it will have around 42sq.m of roof area (pool is about 36sq.m). It will be a shallow pitch flat roof, of about 8 degrees, but will pitch toward the East. Otherwise it is basically a big, flat plane in full sun exposure, other than early in the morning it might get a bit of shade from a tree next door.
The question now is, if this is going to cost around $3000, much the same as the 18kW heat pump, which would likely give the best results?
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply