Natural Gas vs Heat pumps for heating

[mspohr]

Thanks. I'll look. I'm concerned about the chlorinated water causing problems and would prefer to avoid a loop with a heat exchanger. But maybe a good way to improve the hot water in the house at the same time. I'll have to see. There are lots of titanium heat exchanges available for pool use and I could run a loop up to a hot water storage tank for domestic hot water... humm...

The other consideration is I might want to use the chilling function in the summer, which makes a pool focused solution more desirable.

I think it's best to have a heat exchanger rather than running the pool water directly through the heat pump. This could lead to problems with corrosion, growth of various algae, bacteria, etc. A heat exchanger would keep the pool water separate from the heat pump.
There are lots of heat exchangers since they are a common industrial product. For instance, these people seem to have a good selection:

HEAT-EXCHANGER USA | SHELL & TUBE HEAT EXCHANGERS

Looking For Replacement Tube Bundles? Visit Tubebundle.com VISIT NOW See our List of Materials (Alloys) How to Measure a Heat Exchanger? Check out our Online/Printable Heat exchanger Dimensions Sheet. If you are unsure if you need a new unit or a repair, ship your existing heat exchanger to us...

heat-exchangerusa.com

 

[BGbreeder]

The arctic heat pumps that @EL0NTRK mentioned use titanium heat exchangers to avoid/reduce the corrosion issues with pool/spa water.

All the best,

BG

 

[brkaus]

The arctic heat pumps that @EL0NTRK mentioned use titanium heat exchangers to avoid/reduce the corrosion issues.

All the best,

BG

I’m thinking there might still be some benefit with a remote heat pump using a second heat exchanger. I could still get by with a smaller pump for the pool circulation (it’s a swim spa) that is in use year round.

 

[BGbreeder]

Yes, I agree sometimes two smaller units that can run in their most efficient modes often beats out a big one trying to do two different things well. And sometimes you really do want the pumps somewhere other than next to the spa.

However, heat doesn't travel well in my opinion. By that I mean that insulation is not all that effective at preventing heat loss/gain, so longer pipes lose more energy. It is also the case that longer pipes have more resistance (friction) that creates more energy demands back at the pump. (So...oversizing the pipes, and using as few couplings and elbows as possible helps, as does using sweeps instead of elbows. PVC bends quite easily with heat blanks, but sweeps do take up more space.)

Of course, you could go for the Cadillac of insulation and go for vacuum insulated piping, but that gets very pricey very quickly.

All the best,

BG

 

[EL0NTRK]

While we are at it, get all the pump, motors to be variable speed.

 

[mspohr]

Yes, I agree sometimes two smaller units that can run in their most efficient modes often beats out a big one trying to do two different things well. And sometimes you really do want the pumps somewhere other than next to the spa.

However, heat doesn't travel well in my opinion. By that I mean that insulation is not all that effective at preventing heat loss/gain, so longer pipes lose more energy. It is also the case that longer pipes have more resistance (friction) that creates more energy demands back at the pump. (So...oversizing the pipes, and using as few couplings and elbows as possible helps, as does using sweeps instead of elbows. PVC bends quite easily with heat blanks, but sweeps do take up more space.)

Of course, you could go for the Cadillac of insulation and go for vacuum insulated piping, but that gets very pricey very quickly.

All the best,

BG

Fortunately my heat pump is only 10 feet from the spa and pool. Heat pumps are most efficient when running at a small temperature differential. Fortunately spa and pool target temps are low

 

[EL0NTRK]

Fortunately my heat pump is only 10 feet from the spa and pool. Heat pumps are most efficient when running at a small temperature differential. Fortunately spa and pool target temps are low

What are your target temp for pool and spa?
Are you running them 24/7 to maintain the temp once it's reached?
Or just run the HP a day or so before you plan to use the pool?

 

[brkaus]

What are your target temp for pool and spa?
Are you running them 24/7 to maintain the temp once it's reached?
Or just run the HP a day or so before you plan to use the pool?

My swim spa target is 83. The electric heater draws 17a/240v and only raises the temp 0.5 degrees per hour if it's chilly out. I have a floating bubble wrap type cover and then I put 1" pink foam boards on top of that.

With the slow heat rise, I have to keep the pool at the target.

I'm looking at 30-25ft from the pool for the heater.

The current pump I have is something like 108 watts... so I'm afraid that isn't going to cut it.

I'm hoping that a higher output heat pump could heat quicker and that itself would be a savings. I could let it drift down overnight.

 

[EL0NTRK]

My swim spa target is 83. The electric heater draws 17a/240v and only raises the temp 0.5 degrees per hour if it's chilly out. I have a floating bubble wrap type cover and then I put 1" pink foam boards on top of that.

With the slow heat rise, I have to keep the pool at the target.

I'm looking at 30-25ft from the pool for the heater.

The current pump I have is something like 108 watts... so I'm afraid that isn't going to cut it.

I'm hoping that a higher output heat pump could heat quicker and that itself would be a savings. I could let it drift down overnight.

Sound like a good candidate for the Arctic heat pump. It will heat and cool your pool and plenty of output to spare.

 

[mspohr]

What are your target temp for pool and spa?
Are you running them 24/7 to maintain the temp once it's reached?
Or just run the HP a day or so before you plan to use the pool?

Spa heater is 3kW and it runs about 5- 10% duty cycle for 103 temp. Maintain constant temp. Use it daily.

 

[tfan2018]

my hybrid water heater is in the garage (Northern California), does it make sense to duct the inlet to the attic or not worth doing? conflicted since no duct makes it a cleaner look...

 

[mspohr]

my hybrid water heater is in the garage (Northern California), does it make sense to duct the inlet to the attic or not worth doing? conflicted since no duct makes it a cleaner look...

I have a heat pump DHW in a garage under a loft apartment. No need for a vent. Garage is warmer than outdoors in summer and winter so more efficient.

 

[brkaus]

I would be careful adding air paths between attic & garage. Have to be careful of fumes & fire.

 

[BGbreeder]

My swim spa target is 83. The electric heater draws 17a/240v and only raises the temp 0.5 degrees per hour if it's chilly out. I have a floating bubble wrap type cover and then I put 1" pink foam boards on top of that.

With the slow heat rise, I have to keep the pool at the target.

I'm looking at 30-25ft from the pool for the heater.

The current pump I have is something like 108 watts... so I'm afraid that isn't going to cut it.

I'm hoping that a higher output heat pump could heat quicker and that itself would be a savings. I could let it drift down overnight.

Most power costs are lower at night, so I am not sure that it makes sense economically, but from a solar power perspective, sure.

How about direct solar pool water heating?

All the best,

BG

 

[darhall993]

We are loving our Rheem 80g hybrid water heater. For the pool, our poolbuilder installed a Jandy heat pump. One additional benefit is it can cool the pool if it gets too warm in the summer. We've only done that once - ran it in chill mode overnight and it dropped a 25,000g pool a few degrees.

@strider, Would you be willing to share which model of the Jandy Heat Pump for your pool? I am building a pool and will be convincing the local installers that Electric Heat Pump makes sense rather than NG, my rates are 1.5cents per kWh at night, was thinking I can run in low speed mode during the day and if needed heat at night when the rates are lower. I also plan on installing solar and PW2's at this location. (I already have at my weekend residence).

 

[strider]

@strider, Would you be willing to share which model of the Jandy Heat Pump for your pool? I am building a pool and will be convincing the local installers that Electric Heat Pump makes sense rather than NG, my rates are 1.5cents per kWh at night, was thinking I can run in low speed mode during the day and if needed heat at night when the rates are lower. I also plan on installing solar and PW2's at this location. (I already have at my weekend residence).

Sure! I have the JE3000TR on a 25,000 gallon pool. It looks like they have a newer model called the VersaTemp. Supposed to be a bit smaller and quieter but from a quick comparison on the website it looks less efficient at 5.8 COP for the JRT3000R vs 6.3 for the JE3000T.

I also recommend keeping the pool covered. I have one of those bubble-wrap style solar covers with a reel at the end of the pool (my pool is a rectangle w/ spa at one end). I keep it covered when not in use except for July/August.

Can you share the economics of the Solar and PW2 install? I keep running the numbers but with power so cheap here, I'm pushing 30-year paybacks. Plus power is way more stable than it was when I was a kid. I may still do it but it would be a vanity project.

 

[darhall993]

Sure! I have the JE3000TR on a 25,000 gallon pool. It looks like they have a newer model called the VersaTemp. Supposed to be a bit smaller and quieter but from a quick comparison on the website it looks less efficient at 5.8 COP for the JRT3000R vs 6.3 for the JE3000T.

I also recommend keeping the pool covered. I have one of those bubble-wrap style solar covers with a reel at the end of the pool (my pool is a rectangle w/ spa at one end). I keep it covered when not in use except for July/August.

Can you share the economics of the Solar and PW2 install? I keep running the numbers but with power so cheap here, I'm pushing 30-year paybacks. Plus power is way more stable than it was when I was a kid. I may still do it but it would be a vanity project.

I'll run the numbers again and share, we run very high usage in summer in Atlanta, very humid, I also have 3 AC units, so if I can shift usage from summer peak at 22 cents/kWh to 1.5 cents/kWh or better yet just use Solar and batteries it won't take too long justify at 35MWh's/year and that figure is before the pool and hot tub are installed.

 

[strider]

Thanks! We average 3.1MWh/month pretty consistently all year. Our place is all electric w/ geothermal for heat/AC and 2 EVs, though we don't drive very much.

My actual rate last month was $0.11/kWh that's w/ taxes and fees and everything - literally just dividing my bill amount by kWh. June-October there is ToU, 2-7pm M-F is peak - all else off-peak.

Here's some back of the napkin math for me. Supposedly, I should get 5.2 solar hours per day * 365 = 1,900 solar hours per year. With 37.6MWh/year / 1900 = 19.83kW system, so let's round to 20kW. After a random web query, I can get a 20kW system w/ ground mount and installation, for $70,490. At $283/month that's 20 years to pay back. Sure, electricity prices will continue going up. But still, that's a decent commitment and I'd want to have batteries for resiliency and to time shift usage away from off-peak.

A buddy recommended a Sense Energy monitor to start tracking our usage while would help size the system more accurately.

 

[brkaus]

Absolutely. If you are interested in high performance house and getting away from inefficient appliances, take a look a Matt Risinger on Youtube. He is a builder in Austin, TX that has a large following. I take lot of idea from his builds.

Did you get the Arctic heat pump going? Any feedback? Im about to order.

 

[iPlug]

So I took a look at the morning of January 26, 2021, when it nearly reached freezing at the San Jose Airport and almost certainly went below freezing where I am. CAISO supply for that morning shows around 2200 megawatts of nuclear, 5000 megawatts of renewables prior to the sun coming up, and 7000 megawatts of natural gas, ramping up to around 10000 megawatts around 7 am before solar started kicking in. There were also around 7000 megawatts of imports. The previous evening, natural gas was almost 11000 megawatts, the largest single source of energy, with imports at 9000 megawatts. Renewables were around 5000 megawatts. So on cold nights, there's no way we're getting that mix of power, and any incremental usage likely comes from natural gas peaker plants. If not, I can always adjust the thermostat to let the heat pump run at lower and lower temperatures if it is also cheaper to do so.

Agree costs can be one main or partial reason to decide which home heating system to go with.

But a few things to clarify regarding fossil fuel impacts/carbon footprints/efficiency:

1) Even when heat pumps are least efficient during the coldest days/hours, they are always more efficient than burning NG directly in a home furnace. So in a hypothetical grid scenario powered 100% from NG on the coldest days/hours, the homes running heat pumps still are more efficient and burn less NG. (Note efficient doesn't mean they are sufficient to warm a house adequately in some colder winter climates that don't include ours)

2) CAISO shows all of CA generation supply and imports in near real time, but we are PG&E and all 2.2GW were attributed to their customers at that time. Only a fraction of the 7-10GW of NG then was attributable to PG&E.

3) Much of CA imports in winter are from the NW import area and nearly ~100% of that is renewables as that is their precipitation season and they are exporting abundant excess hydro power then.

4) Diablo nuclear will be replaced with more than an equivalent of offshore wind power. The Morro Bay and Humboldt regions have reliable high winds.

5) Utilities and industries plan to convert much NG use to H2 in the future. (Green/Renewable generated H2)

6) Onshore wind is growing rapidly in the US and massive wind farms in Wyoming are trying (desperately) to connect to CA.