Solar or Heat Pump?

[tcat]

I have a dilemma. I was thinking of DIY solar, but decided to call an installer to see how an installed cost compared. As soon as I told him where I lived he would only quote a DIY kit (5 Sunsaver panels and all other supplies). Supposedly in Lakeway TX you have to run any water lines inside the house, and the installer won't do that on solar panels. Now I'm afraid to install myself, since the panels will be viewable from the street (where inspectors drive by daily tagging people). So unless I run a Solar Bear on the ground, I really don't want to risk any additional investment in solar.

So... my question is about Heat Pumps. They appear to be the cheapest way to heat a pool other than solar. My pool is 15-16K gallons, 370 sq ft., I figure maybe a 120BTU unit? Are they very good at "on demand" heat (say I only want to swim from 5-6 every other day), can I turn it on at 8 AM and have +10 degrees by 5? Don't want to mess with a cover (very odd shape with 1/2 the edging raised stone walls). I used tis cost estimator: http://www.aquacal.com/heat-pump-operating-cost-estimator/3 and it's not that expensive to heat the pool from April to October.... and probably less if I only use it a few times a week. I do have a .75" propane line at the pump, but probably not large enough, and propane cost is way to high to mess with.

 

[jblizzle]

Seriously? Is that a HOA rule? I thought they could not have rules against "green" type installations. I know I added solar in my previous HOA.

 

[tcat]

No clue, I took his word for it, but will be researching it more tomorrow. No wonder I haven't seen any solar around. No HOA, just an independent "city" with lots of "rules" (and lots of drive by inspectors). Heck, when I moved in, I had my trash pick up started on a Wednesday, we moved in a week early and I put the trash can out the previous Wednesday, and an "inspector" drove by that morning and told me I wasn't scheduled until the following week and to remove the trash can (city guy not even related to the trash pick up company!).

edit: Here's the ordinance:
(d) Solar systems. No roof-mounted solar panels will exceed the maximum approved roof ridge line height. Ground-mounted solar panels will not be located within building setbacks or public utility easements. All ground-mounted solar panels must be adequately screened form view from public streets and adjoining properties. Solar panels will not be reflective. Exposed solar piping on roofs is prohibited. The solar panel contractor is responsible for all roof flashing in order to prevent water penetration. Additionally, the contractor is responsible to ensure that the roofing can support the live and dead loads. A permit from the local water district may be required if the project involves plumbing of any kind.

 

[jblizzle]

Wow. Seems like something that you could actually sue the city for since they are placing an undue hardship on installing solar which would be viewed by the federal government as environmentally friendly.

Although not likely worth the hassle.

Do they allow satellite dishes on the roof? That is something they would have to allow by federal law.

Of course I have no idea what I am talking about

 

[pwrstrk]

You would think they would love the green environmentally friendly solar. I guess they think it's unsightly. Ridiculous, but what isn't anymore.
Wonder how a windmill would go over ! ?

 

[tcat]

Yes, a dish on every other roof. I'm sure it's a visual thing (I think dishes are much uglier), you'd think adding a roof penetration would be more an issue for an inspector than a clean run of pipe outside. With our drought they are getting very anti-pool, so I doubt they'd be making any exceptions.

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[blbncsu]

I'll give my input on our heat pump we installed this year for our 2nd year of pool ownership.
No, it doesn't give on-demand type of heat. It has to be continually running to work and you can't decide that just one day when it warms up outside to fire it up and hope the water temps rise a good deal.
Its more of a slow heat-up and without a cover I think you'd lose all the heat you put into it during the day out at night.

We use a solar cover cut up into 3 sections. While its definitely a pain to use a cover it allows the heat pump to do its job and lets us swim on days it would otherwise be too cold. And you're right also, they are cheap to run, honestly haven't noticed much of an uptick on electricity costs.

 

[Poolsean]

The math related to pool heating is:
Pool Gallons x 8.33 lbs/gallons = Total weight of water (lbs). (15,000 gallons x 8.33 = 124,950 lbs)
Lbs x desired temperature rise = BTU's required. (123,900 x 10 degrees = 1,249,000 BTUS)
BTU's required / BTU output = hrs needed to increase water temperature. (1,249,000 / 120,000 = 10.4 hrs)

Having said that, keep in mind that heater output will decrease as ambient air temperatures drop, so the 10.4 hrs I calculated will actually be longer. The best use of the Heat Pump is to get it up to temperature and maintain it there. This way, your pool will be heated to your desired temperature with a low cost of maintain it there.
Since you're swimming every other day, a Heat Pump will work for you, and I would recommend, if not using a solar blanket, using a liquid blanket, which will prevent some heat loss overnight.

 

[tcat]

Since the city doesn't seem to want solar I'm leaning towards HP21404T. The south side of the house is facing a street and the city says any ground or roof solar panel needs to be hidden from street view. Also no external piping on a roof install. That makes the decision easy. Cutting the solar cover into 3 or 4 strips sounds like a good idea. Just need to check to see if I have power to add a 60 amp breaker. Is the Hayward a good HP? Seems to have a small footprint and good efficiency rating.

Is there a difference in temperature rise through a heat pump with pump running at high vs low speed? ie: is it better to run on low for 12 hours or high for 6 hours? Just curious because I currently run on low for 12 hours with no heat source.

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[suzook]

Since the city doesn't seem to want solar I'm leaning towards HP21404T. The south side of the house is facing a street and the city says any ground or roof solar panel needs to be hidden from street view. Also no external piping on a roof install. That makes the decision easy. Cutting the solar cover into 3 or 4 strips sounds like a good idea. Just need to check to see if I have power to add a 60 amp breaker. Is the Hayward a good HP? Seems to have a small footprint and good efficiency rating.

Is there a difference in temperature rise through a heat pump with pump running at high vs low speed? ie: is it better to run on low for 12 hours or high for 6 hours? Just curious because I currently run on low for 12 hours with no heat source.

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I have that same exact hp. Works Awesome!! Very quiet too.

 

[tcat]

The math related to pool heating is:
Pool Gallons x 8.33 lbs/gallons = Total weight of water (lbs). (15,000 gallons x 8.33 = 124,950 lbs)
Lbs x desired temperature rise = BTU's required. (123,900 x 10 degrees = 1,249,000 BTUS)
BTU's required / BTU output = hrs needed to increase water temperature. (1,249,000 / 120,000 = 10.4 hrs)

Having said that, keep in mind that heater output will decrease as ambient air temperatures drop, so the 10.4 hrs I calculated will actually be longer. The best use of the Heat Pump is to get it up to temperature and maintain it there. This way, your pool will be heated to your desired temperature with a low cost of maintain it there.
Since you're swimming every other day, a Heat Pump will work for you, and I would recommend, if not using a solar blanket, using a liquid blanket, which will prevent some heat loss overnight.

I'm confused about heat pump "math". Take average air temp subtract from desired water temp to get temperature rise. What outside temp is a 120btu heat pump based? If my pool is 80 and outdoor temp is 90, that's a 10 degree drop. Will it still take 10 hours to heat the pool 10 degrees? ie: if it's 70 or 90 out it will still take 10 hr's too heat the pool from 80 to 90? Odds are most of the summer pool is at 84 and I'll only need 3 or 4 degrees. Right now it's 72 and water is 72 and I need 10 degrees. Curious about time at various outdoor temps.

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