Gas Heater size for a 24 foot round 54" height AGP

[racket]

I don't know which brand of heat pump you own/Ed but we use 4.0 cop as a reference and it
seems to correlate with our clients bill.

Sorry about missing the 85 +/- I post often from my phone.

Reguardless 85 +/- is really 82% for most products. No body in the pool biz besides lochinvar, and Zodiacs Hi-e2 are within 4% of 90%

I did a quick analysis using 2 major manufacturers heat pump calculating software.

Now being intimately involved in many of my clients pool operations I get to see energy bills etc. I trust these calculators, because by my data we have never had to pay more than what they have said. The gas usage estimator has been spot on with what their software says.

So for Bostom, MA a 24R 42" deep pool with natural gas being $1.10 per therm; electricity @ $.15 per kwH.

The calculator has the gas usage at $1,404 per year with the pool covered half of the time 4/15-10/30.

The heat pump would be less than 1/2 of the @ $630 per year.

I think that for a northeastern/northwestern climates this time frame reasonable to call it "an extended swimming season"

Even at $500 a year savings, a heat pump can pay for itself quickly. ( especially if you buy from the net.)

You can argue that real world data is different than a calculating software, keep in mind that last years weather will be different than this years, so using a large sample of historic weather to judge heat usage seems prudent.

 

[bk406]

All i know is those calculators dont take into account a lot of variables. I live outside of boston, I have for 20 years. I know what a heat pump will and wont do here. I dont care what those calculators say, NG and a heat pump are about the same cost to run on a cost per BTU basis, at least here. The calculators dont take into account the fact you need to run a heat pump 24/7 during some periods to keep the temp up. Nor does it take into account real world BTU output. 60 degrees and rain, it just spins the meter. Up here, and in a lot of areas in the east, it doesnt get warm enough, long enough in early may and september to put enough heat in the air to allow the HP to transfer much heat. Again, thats something that those calculators dont take into account. plus, if you run a HP 24/7 you have more electricyt to pay for by running the pump more. So I still say its a wash, basically.


Seattle is a world apart in climate from the east coast. And they wont do squat in april and september here, period. It doesnt matter if you can run them for free, if they wont put heat in the pool, they are useless.

 

[Red Shirt Ensign]

So what are the generally accepted useful life of a heat pump and natural gas heater?

 

[racket]

All i know is those calculators dont take into account a lot of variables. I live outside of boston, I have for 20 years. I know what a heat pump will and wont do here. I dont care what those calculators say, NG and a heat pump are about the same cost to run on a cost per BTU basis, at least here. The calculators dont take into account the fact you need to run a heat pump 24/7 during some periods to keep the temp up. Nor does it take into account real world BTU output. 60 degrees and rain, it just spins the meter. Up here, and in a lot of areas in the east, it doesnt get warm enough, long enough in early may and september to put enough heat in the air to allow the HP to transfer much heat. Again, thats something that those calculators dont take into account. plus, if you run a HP 24/7 you have more electricyt to pay for by running the pump more. So I still say its a wash, basically.

They do take in all of those factors, as well others such as wind speed. They also calculate how much they anticipate it running on the coldest day of the planned pool operating calendar.

20 years ago, they didnt have the technology they do today. Units with scroll compressors that will hit 6.0 COP on a nice day and at 50degrees they are at 4.0 (all confirmed by AHRI). The older piston compressor units were 4.0 on a good day.

The newer heat pumps are 50% more efficient than they used to be while most gas heaters have been stuck in the low 80s since the mid 80s.

Seattle is a world apart in climate from the east coast. And they wont do squat in april and september here, period. It doesnt matter if you can run them for free, if they wont put heat in the pool, they are useless.

Check out weather undergrounds trip planner. The 2 markets weather are almost identical (sans the 90 degrees you had in april last year.)

I'm not sure why you don't have the luck we have here, but using both aquacal, and pentair heat pumps, the results have been better than expected.

 

[racket]

So what are the generally accepted useful life of a heat pump and natural gas heater?

With the humidity, and cold air temperatures here we are lucky to get 10 years out of a gas heater here. I have yet to see a heat pump that didn't make it to 10. Most heat pump manufacturers offer 10 year warranties on the compressor, and lifetime on the heat exchangers which are the 2 most expensive components to replace.

Most gas heaters offer 3 years tops but a majority are 1 year.

 

[bk406]

When i said i have lived here 20 years, I didnt mean i had a heat pump for 20 years. I've had one for 3 years.

There's no point in further discussion with you on this. I live here,and I know what a heat pump will do in the spring and fall here, which is not much. and, FWIW, Worcseter MA and seattle weather are not identical in the least.

 

[no-mas]

Red Shirt, maybe I missed it. Where are you located?

 

[bk406]

Red Shirt, maybe I missed it. Where are you located?

Cleveland. They wont work there in the early spring and fall either i'm afraid. It'll work great in late May thru labor day, though.

 

[racket]

When i said i have lived here 20 years, I didnt mean i had a heat pump for 20 years. I've had one for 3 years.

There's no point in further discussion with you on this. I live here,and I know what a heat pump will do in the spring and fall here, which is not much. and, FWIW, Worcseter MA and seattle weather are not identical in the least.

http://tinypic.com/r/2ikpcmv/7

left is Worcester, right is Seattle. You are right there has to be at least a good 1-2 degree difference.

 

[Guest]

Racket,

Why must you persist on this??? BK has made his points as have you. Quite frankly, I side with BK... His agenda is not to push Heat Pumps. You have multiple posts on this forum with your "LOVE" for heat pumps. I'm glad they work for you.

Enough said...

 

[racket]

Racket,

Why must you persist on this??? BK has made his points as have you. .

Making points and refuting points are all part of debate.

When someone makes a point on a public forum that could be casted in the internet's databases forever; wouldn't it be helpful for everyone interested in heating pools, to have access to debate so that they can make their own informed decisions?

It was said that we are worlds apart in climate. I substantiated my point that we weren't.

 

[Guest]

Gas Heater size for a 24 foot round 54" height AGP

Red Shirt is in Cleveland, OH, what does WA and MA have to do with this thread? I could make the same argument with Solar Heating. Works well in my region but not yours, unless your in Eastern WA where there are more sunny days. You made your point... So has BK... Don't beat a dead horse.

Just curious, have you spent much time in the New England region? The weather is not even close to the Northwest.

 

[racket]

Electricity is very cheap in Cleveland, OH but the weather would be prohibitive to a heat pump
I paid .114 per KWH last month alone
Nat Gas is 6.60 per MCF with del charges last month it was 11.08 per MCF total charge

Are these heaters on/off or do they work as a thermostat would?

At $1.10 per them (10.27 mcf per therm) vs .114 per kwh.

On a covered (solar blanket) you would pay ~$1,477 to heat the pool 4/15-10/30. $500 is what you would pay with a heat pump.

So lets say we assumed that the company that designs the software decided to skew the numbers by 50% and we were we'd be at $750 for the season.

The heat pump on the coldest day will run 4.5 hours a day to heat your pool.

There are "icebreaker models" that will reverse cycle to defrost if you are really worrying about the icing up. They would have to lose their efficiency 3 fold to match $ per BTU of a gas heater.

 

[bk406]

In late september and october here it doesnt get warm enough for long enough during the day to really heat up the air to transfer a lot of heat. Just comparing highs and lows is not quite accurate in terms of how many BTU you can get out of a heat pump during that time of year.

I'm not sure I ever said that those programs weren't accurate in terms of trying to compare apples to apples. I believe if you go back and re-read what I said was that they dont take into account how people use thier pool.

Assume for a minute you could get 85 degree water on october 1st with a heat pump in worcester county mass, or even cleveland. Those are designed to MAINTAIN temperature, not bring up water 10-15 degrees very quickly. On a day in late september, you might make 62-63 degrees for a high. At night, you're down in the low 50's a lot of the time. Even with a solor cover, the pool can drop to 77 or lower from 83-85 . The next morning to maintain that 85 (it wont but lets assme it does) at 100,000 BTU output, it would take 9 hours to get to 85 degrees. That $8 a day in electricity cost at 6 kw/hr at 15 cents. If you did that for 30 days (and remember a heat pump needs to run to maintain the water temp), it would run close to $250 a month to keep the water at that temp.

Most people here and elsewhere in cooler climates, use the pool sparingly in the early spring and fall. Take september for example. Last year I think was used it 3 weekends in september, and one weekend in october. If I left the HP off, the temp over the course of a week might drop to 70. The cooler the water gets the less heat it loses over time. Now, I heat it up to 85. Thats 15 degrees i need in the pool. With NG at $1.10 a therm, and a 400k heater thats 83% efficient, it will cost around $22 to heat it to 85. For that cost, I can heat the pool 15 degrees 11 times with NG and leave the heat off during the week. Most people wont heat it that many times in the fall, but there are the numbers.
For propane, you can do it 5 times for the same money. So yea, propane is pretty expensive, but as I said before, my experience is you will not get 100,000 BTU out of a HP up here for that entire 9 hours so you would probably have to run it longer.

My overall point here, again, is that the programs do not take into account HOW people may use their pool. It strictly compares on an apple to apple basis. For that kind of comparion, its does ok, the numbers dont lie. But very few people would maintain the pool at 85 degrees 24/7 that time of year. At least here they dont.

 

[bk406]

The heat pump on the coldest day will run 4.5 hours a day to heat your pool.

To what temperature? You cant make a statement like that without clarification. I promise you on a 60 degree day with night that was at 48, you cant get 10 degrees in the pool in 4.5 hours, its impossible.

Assume 120,000 constant BTU, a 14000 gallon pool, and an 8 degree rise.

14,000 gallons X 8.33 pounds=116,620 pounds of water.

116,620 pounds x 8 degrees=932960/120,000 BTU out put =

7.7 hours at best. And you wont get 120,000 BTU out of one consistantly on those kinds of cold days, no way.

 

[racket]

The heat pump on the coldest day will run 4.5 hours a day to heat your pool.

To what temperature?

We assume 85 degrees.

 

[bk406]

Ok, so for that 4.5 hours you say you run the heater on the coldest days to get it to 85 degrees.
1) how many gallons is the pool
2) Whats the average BTU output of the HP

3)what the starting temperature

Can you show your work on how you get that 4.5 hours?

 

[racket]

Ok, so for that 4.5 hours you say you run the heater on the coldest days to get it to 85 degrees.
1) how many gallons is the pool
2) Whats the average BTU output of the HP

3)what the starting temperature

Can you show your work on how you get that 4.5 hours?

The 4.5 hour is the maximum run time to maintain on a cold day.

It may take 12-14 hours to do so, over the course of a couple days. Most work at a COP of 4.0 @ 50 degrees which should be about $.50 per btu vs gas (at worst).

A heat pump is like a hybrid car. It's not going to go 0-60 in 4.5 seconds, but it will get you where you need to go efficiently.

If you heat your pool 1-2 days at a time at random times, a heat pump probably won't save you money, because you don't use much gas ( or anything else to heat the pool)

Most people start their heaters in the spring, and shut it off in the fall when they are done swimming.

Aside from a few select markets where gas is cheaper than power, heat pumps will almost always save these

 

[bk406]

The 4.5 hour is the maximum run time to maintain on a cold day.

It may take 12-14 hours to do so, over the course of a couple days.

Not sure i understand. To maintain temperature, it has to start from somewhere. So is it 80 degrees in the morning when the pump kicks on and you need a 5 degree rise? For an average size pool, thats more than a 4.5 hour run time as I've shown.

It may take 12-14 hours to do so, over the course of a couple days.

Not sure i understand this either.

If you heat your pool 1-2 days at a time at random times, a heat pump probably won't save you money, because you don't use much gas ( or anything else to heat the pool)

Thats my point. On the edges of the season, thats how most people use their pool, at least most pople i know. You also assume the COP ratings for a HP is actually real under real world conditions. I say they are not. Thats why, IMO, on average NG is about as cheap as a HP to run when you factor in how folks use the pool, etc.

If I set my heat pump at 85 degrees in on april 15th and shut it down columbus day, it would cost a fortune.

Are you assuming running the filter pump 24/7 as well? if so, that makes the cost rise significantly.


If you could show some concrete examples with BTU output, gallons of water, starting and ending temperature, and the math behind it, that would help me understand.

 

[Red Shirt Ensign]

Heck this topic is hot but still civil that's what I like about the forum here... you have a point go ahead and make it but on some other forums i go to (non pool) they would be in a major flame war by now!! Thanks for everyone' sinput, I am happy to conitneu to reading about the points fo rboth ways,
but I think for my climate a heat pump is probably out... I envision using it to keep my 1/2 shaded yard at 80 for most of the season... and maybe letting it go lower (using a solar cover the whole time) when we are using it alone, as long as the wife can tolerate it) and then spiking it up for known visits by friends and fam etc... I will definitely run it early into lapril/May and sept/october based on the seasonal factors etc...

I see a local craigslist for a 1 year old Rheem 133K BTU for 800 bucks. (Already have him down 100)

Any one have experience delaing with this via Craigslist? Our friends bought one and its seems to work out fine for them with GL but I'm worried something would be wrong with it... the claims to be moving to Texas (Perhaps he just wants to sell it off his pool so the new owner doesn't get it and he got somequick cash???)