Help decide: Gas or Heat Pump

[crek31]

5) A 120,000 BTU heat pump is around 4K. A 400,000 BTU gas heater is around 2k. The gas line vs the electric panel is a wash, so the cost up front for gas is less.



A 10 degree rise with 400,000 BTU heater for your size pool (use 10,000 gallons) will take 2 hours. At 78 cents per therm, that about $6.25. For a 120,000 BTU HP (and you wont get 120,000 out of it in the spring and fall, lucky if you get 80,000. So, at 80,000 BTU and 5 cents per kW/hr, it would take 10 hours and about $3 in electricity.

So about half the cost, but 5 times the time to heat. And I promise you on cool days at say 63=65 degrees, all it will do is spin the electric meter.

So, I reading this to say if I go the heat pump route getting a 120,000 btu heat pump would be the equivalent of a 400,000 btu gas heater? Or, better asked: do I need a 400,000 btu heat pump?

To recap: I want 88 degree water M-F from 5:30 pm to 9:00 pm and all day Sat and Sun from June through August. If it gets me a few days either side, so much the better.

Cost of gas line install is roughly $2000 plus a huge amount of stress to my family due to unknown damage to finished basement space (perhaps fixed by asking them to trench around the house instead, but that cost is now unknown for sure). Assuming I won't need to install a new electrical panel for heat pump (as alluded to above). Is it time to scrap gas and go heat pump? Assume a 15 x 30 oval pool.

 

[bk406]

There's no such thing as a 400,000 BTU heat pump. You can only compare BTU to BTU.
I'm not sure why he cant run the gas line outside around the foundation unless your area requires it to be buried.

Re-read the thread as well. If you want to heat the pool at a moments notice to 88 degrees, stick with the gas. A heat pump will not do the job your looking for.

 

[crek31]

Ok - well, we are committed to gas. Plumber ran the line Friday as planned, and he did not have to cut into the ceiling at all. Yay! Thanks, all.

 

[TheOne]

Not sure if I should start a new thread since so much info already here.

How does the Houston, TX climate affect if a heat pump/chiller is preferable to a gas heater? This will be for a new pool build which will have a spa. Is the heat pump only able to heat the pool water but not the spa to higher temps? I was considering a heat pump that has a cooler/chiller.

 

[Poolsean]

TheOne,

It will really depend on how you use your pool and when you want to heat your pool. For quick spot heating, gas is the way to go, because you can get them in high BTU outputs. If maintaining a certain temperature throughout the year is your goal, Heat Pumps are the way to go, because you will be able to do it much more economically.
In either case, a solar cover will help greatly to prevent excessive heat loss over night.

Most pool and spa combination systems have the spa water overflowing into the pool. What this means is that in normal pool mode, the spa water will be the same temperature as the pool water. When you go to isolate your spa, the heat pump's spa thermostat (if your heat pump is equipped with a dual thermostat), will activate the higher spa temp setting. It should not take long for the water to heat up from the pool temp to your desired spa temp. Figure for a 400 gallon spa already at 84 degrees, to get it up to 100 degrees, it will take about 30 minutes with a 100,000 BTU heat pump. About 10 minutes with a 400,000 BTU gas heater.

Regarding the chiller, you will just need to be aware of what mode your heat pump is when you switch from pool to spa....unless you're looking for a cold plunge spa. FYI... for athletes, cold water helps muscles recover faster than a hot spa.

 

[loop_pea]

You can get massively sized heat pumps that do the same job as a boiler, but they come with a massive price tag to match.

Heat pumps are rated in kW, but you can convert from one unit to the other with an online calculator.

The 220,000 BTU boiler we have in our pool now is the equivalent of 64 kW.

If we'd wanted a heat pump, we were advised to get a Calorex Pro Pac 70, which is a commercial model with the equivalent of 70kW output, and had an RRP of £16,980 (gulp) and that's before fitting. It also needed three-phase electricity, which we don't have and which would likely have cost £££ to put in.

However, I think some heat pumps are rated on their actual electricity consumption, which you then have to multiply by the COP to get the equivalent output. It's all very confusing.

Someone correct me if I'm wrong...

 

[Poolsean]

Sometimes Heat Pumps can be confused with Electric Resistance heaters, which are rated in KW. These are two different methods. An electric resistance heater uses multiple heating coils (elements), similar to what's in a electric water heater. Add more elements to get more heat. The largest that I know of for pool/spa usage is a 64 kw heater (218,368 BTUs). Heat pumps uses the natural effects of Refrigerant, such as with HVAC systems, to transfer heat from one heat exchanger (air to freon) to another (freon to water). The largest (realistic) output residential heat pump is in the 140K range. Advertised ratings higher than 150K is either a super good system, or marketing hype, at unrealistic conditions (or in the case of the Calorex PRO70 unit, a double heat exchanger commercial system). Since we're dealing with residential systems, it's not likely that a commercial heat pump would be used. Other than the Calorex commercial line of heat pumps, AquaCal is the only other company that manufacturers multiple heat exchangers in a single cabinet type heat pump... Great Big Bopper puts out approx 500,000 BTUs!
AHRI, Air Conditioning, Heating, Refrigeration Institute, is an independant U.S. organization that tests and qualifies heat pump ratings under specific conditions that they will most likely be used under (80 degrees water temperature, 50 degrees air temperature, 63% relative humidity). Some manufacturers will not join this organization because their advertised outputs will reveal the true outputs.

Heat Pumps are sometimes higher in initial costs, but in the case of having to run gas lines, can actually be the same or just slightly higher than a gas heater. As for operating costs, electric resistance heaters tend to be the most expensive method to heat a body of water. However, it is 100% efficient and is not prone to decreased BTU outputs when it is cold out. Both gas and heat pumps will reduce in efficiency when the air temperature gets cold.