Adding solar heater to my indoor pool

[Jenmachen]

Good afternoon guys! I have some questions about adding a solar heating system to my existing set up. I have not talked to anyone local YET about this, because I live in a smallish town, and there won't be a contractor here that has ever done a job on an indoor pool before, so I would MUCH rather get you guy's advice first. That way I will be able to tell my contractor the way I want it done, instead of being at the mercy of a solar guy that knows very little about pools in general, and nothing about indoor pools.

I have done some research, but there is not a lot of information online available specifically for indoor residential pools. For instance can I used unglazed panels? Of course we use the pool year round, so will the warm water constantly running thru the panels be enough to keep the panels from freezing on the maybe 10 total freezing days a year we have in North Louisiana?

I will still be using my Pentair gas heater fairly regularly for the spillover hot tub. Is it ok to just let that run thru the panels at the 5 degree bump up? Or do I divert that first?

Where do I add this in the line of the system? After filter I know, so then before the gas heater?

And how do I calculate how many panels I need? The regular calculators are designed for outdoor pools.

I have a choice of two different roof lines for the panels, as my home is split level. The pool equipment is equal distance between the levels. The single story level gets some partial shade early and late in the day. But if it is ok for the panels to rise 2-1/2 stories up, that roof line gets full sun almost all day.

My goal with the panels is to #1 lower my fuel costs. I would have done this years ago, but I just found out this was an option (where have I been?). I had no idea. My gas bill last month was $780. That is not unusual. Ouch. And #2 I would love to not be totally down every single time the Pentair heater breaks down, which is all the time. Sure, I can fix it myself after I get the part in. I keep a few parts handy, for the ones that blow every few months. I hate this heater. But it's no worse than the one before it, or the one before that one. The one that I bought 25 years ago lasted for 18 years.....those were the good old days. I'm lucky if I get 3-4 years out of one now. Shameful.

 

[mas985]

Good afternoon guys! I have some questions about adding a solar heating system to my existing set up. I have not talked to anyone local YET about this, because I live in a smallish town, and there won't be a contractor here that has ever done a job on an indoor pool before, so I would MUCH rather get you guy's advice first. That way I will be able to tell my contractor the way I want it done, instead of being at the mercy of a solar guy that knows very little about pools in general, and nothing about indoor pools.

I have done some research, but there is not a lot of information online available specifically for indoor residential pools. For instance can I used unglazed panels? Of course we use the pool year round, so will the warm water constantly running thru the panels be enough to keep the panels from freezing on the maybe 10 total freezing days a year we have in North Louisiana?

It will prevent the panels from freezing but it will also cool the pool down which is why I don't think you really want to do that. Instead, you can just design the setup so that when solar is off, there is no water in the panels and therefore cannot freeze. This is done by installing a vacuum release valve at the top of the panels and for further protection, installing isolation valves in the solar supply and return pipes so water cannot reach the panels during these freezing conditions.

I will still be using my Pentair gas heater fairly regularly for the spillover hot tub. Is it ok to just let that run thru the panels at the 5 degree bump up? Or do I divert that first?

Generally, solar is installed before any other type of heater because the panel efficiency depends on water temperature. The higher the water temperature, the more is lost to the environment.

Where do I add this in the line of the system? After filter I know, so then before the gas heater?

Yes, after the filter and before the heater.

And how do I calculate how many panels I need? The regular calculators are designed for outdoor pools.

That will depend on how many BTUs you think you will need. Most rule of thumb examples are between 50%-100% of pool surface area coverage. So with a 500 sq-ft pool, you want somewhere between 250-500 sq-ft. The more square footage, the more heat that can be added in a given period of time.

I have a choice of two different roof lines for the panels, as my home is split level. The pool equipment is equal distance between the levels. The single story level gets some partial shade early and late in the day. But if it is ok for the panels to rise 2-1/2 stories up, that roof line gets full sun almost all day.

Late day exposure is usually always better than early morning exposure due to air temperature. The warmer the air temperature, the higher the efficiency of the panels.

My goal with the panels is to #1 lower my fuel costs. I would have done this years ago, but I just found out this was an option (where have I been?). I had no idea. My gas bill last month was $780. That is not unusual. Ouch. And #2 I would love to not be totally down every single time the Pentair heater breaks down, which is all the time. Sure, I can fix it myself after I get the part in. I keep a few parts handy, for the ones that blow every few months. I hate this heater. But it's no worse than the one before it, or the one before that one. The one that I bought 25 years ago lasted for 18 years.....those were the good old days. I'm lucky if I get 3-4 years out of one now. Shameful.

Do you want heat in winter? That will be almost impossible with an unglazed solar panel system. However, glazed panels are less efficient in warmer weather so more panels will be needed for the same temperature rise.

 

[Srqpoolguy]

After doing this for almost 16 years as a pool contractor I will be 100% honest. Solar will give you TOPS on a clear sunny day 8-10 degrees in heat period. So if the pool is 65 you will if lucky and conditions perfect 75. Being inside helps retain heat but the sun also helps heat the water so it's kind of a moot point. Just wanted to let you know. The sales people will throw crazy stuff at you and I live in south Florida where the sun is blazing. It's 76 right now in febuary and no one with solar here is swimming. Lol.

 

[Jenmachen]

It will prevent the panels from freezing but it will also cool the pool down which is why I don't think you really want to do that. Instead, you can just design the setup so that when solar is off, there is no water in the panels and therefore cannot freeze. This is done by installing a vacuum release valve at the top of the panels and for further protection, installing isolation valves in the solar supply and return pipes so water cannot reach the panels during these freezing conditions.


Generally, solar is installed before any other type of heater because the panel efficiency depends on water temperature. The higher the water temperature, the more is lost to the environment.


Yes, after the filter and before the heater.


That will depend on how many BTUs you think you will need. Most rule of thumb examples are between 50%-100% of pool surface area coverage. So with a 500 sq-ft pool, you want somewhere between 250-500 sq-ft. The more square footage, the more heat that can be added in a given period of time.


Late day exposure is usually always better than early morning exposure due to air temperature. The warmer the air temperature, the higher the efficiency of the panels.


Do you want heat in winter? That will be almost impossible with an unglazed solar panel system. However, glazed panels are less efficient in warmer weather so more panels will be needed for the same temperature rise.

Yes, I want heat in the winter? I actually use heat year round. Although a lot less in the summer. So, you are saying unglazed panels supply much less heat than glazed panels? The pool does not lose heat rapidly if the heater is turned off. So, I"m wondering why the question is how much the solar panels can raise the temperature? I want to know, how long can the solar panels maintain the temperature if the heater goes out? Sure maybe not for a week in winter if we happened to have rare zero sun for that week.

 

[Jenmachen]

After doing this for almost 16 years as a pool contractor I will be 100% honest. Solar will give you TOPS on a clear sunny day 8-10 degrees in heat period. So if the pool is 65 you will if lucky and conditions perfect 75. Being inside helps retain heat but the sun also helps heat the water so it's kind of a moot point. Just wanted to let you know. The sales people will throw crazy stuff at you and I live in south Florida where the sun is blazing. It's 76 right now in febuary and no one with solar here is swimming. Lol.

Thank you. However, I don't need these panels to raise the temperature. For instance, right now my pool is 89 degrees. If I installed solar panels tomorrow and had sunny days this week, I presume those panels would give my gas pool heater a break during the day. I am not asking the panels to raise the temp. I am asking the panels to maintain the temp. And then, when the heater goes out, the pool temp will slowly begin to drop. If I were having fairly sunny days, how long do you think the panels would be able to maintain the current temp?

 

[mas985]

Yes, I want heat in the winter? I actually use heat year round. Although a lot less in the summer. So, you are saying unglazed panels supply much less heat than glazed panels?

It depends on the conditions. Glazed panels do better when it is colder outside but worse when it is warmer. In very cold weather standard solar panels will gain more heat than glazed panels but the heat loss is also higher so the net heat gain ends up being worse. The following chart gives you a feel where the crossover point is:



The flat panel line is quite steep so a lot more panels are need when Tm-Ta gets large. However, the cost may still not be as high as glazed given the cost difference per sq-ft. You need to get some pricing on the cost of each panel type and adjust for the efficiency to see where the true cost crossover point is.

The pool does not lose heat rapidly if the heater is turned off. So, I"m wondering why the question is how much the solar panels can raise the temperature? I want to know, how long can the solar panels maintain the temperature if the heater goes out? Sure maybe not for a week in winter if we happened to have rare zero sun for that week.

It all comes down to the type of panel chosen and the amount of square footage.

Personally, I would plan for 100% solar usage and only augment with the heater when needed during very cold spells. The savings on heating costs should eventually pay for the solar plus the heater will last longer too.

How well insulated is the building that the pool is housed?

If you don't heat the pool in January, what is the approximate water temperature?

Do you know how many therms the heater uses for the pool in each month?

 

[Jenmachen]

It depends on the conditions. Glazed panels do better when it is colder outside but worse when it is warmer. In very cold weather standard solar panels will gain more heat than glazed panels but the heat loss is also higher so the net heat gain ends up being worse. The following chart gives you a feel where the crossover point is:

View attachment 554004

The flat panel line is quite steep so a lot more panels are need when Tm-Ta gets large. However, the cost may still not be as high as glazed given the cost difference per sq-ft. You need to get some pricing on the cost of each panel type and adjust for the efficiency to see where the true cost crossover point is.

It all comes down to the type of panel chosen and the amount of square footage.

Personally, I would plan for 100% solar usage and only augment with the heater when needed during very cold spells. The savings on heating costs should eventually pay for the solar plus the heater will last longer too.

How well insulated is the building that the pool is housed?

If you don't heat the pool in January, what is the approximate water temperature?

Do you know how many therms the heater uses for the pool in each month?

I heat the pool all the time. But, I think once the pool heater was down for over a week in the month of January and the water drifted down to maybe 78. The pool is on the ground floor of a two story portion of my home, so it is insulated well from above. It walls themselves are vinyl inside and outside, with standard insulation between. A total of four double paned glass patio doors. So, the walls are not as insulated as the ceiling. It only shares one common wall with the rest of the house.

The gas bill in the summer is about $120. Last month it was $788. The tankless hot water heater and one of my three furnaces is run on gas, along with the pool heater. Of course, I am in the South. We've had about 10 days total of truly cold weather. Currently it is 60 degrees.

 

[Srqpoolguy]

Ther

Thank you. However, I don't need these panels to raise the temperature. For instance, right now my pool is 89 degrees. If I installed solar panels tomorrow and had sunny days this week, I presume those panels would give my gas pool heater a break during the day. I am not asking the panels to raise the temp. I am asking the panels to maintain the temp. And then, when the heater goes out, the pool temp will slowly begin to drop. If I were having fairly sunny days, how long do you think the panels would be able to maintain the current temp?

 

[Srqpoolguy]

There are so many variables to this as far as maintaining temp. Personally I have only worked on 2 indoor pools where I live. One had solar and the guy was absolutely frustrated with it. He was told a lot of bs and also didn't realize the maintenance end. Solar leaks quite a bit

 

[mas985]

While I will agree that some manufacturer's panels are prone to leaking, over the past 18 years, my solar panels have never leaked. It all depends on your choice of panel.

I heat the pool all the time. But, I think once the pool heater was down for over a week in the month of January and the water drifted down to maybe 78. The pool is on the ground floor of a two story portion of my home, so it is insulated well from above. It walls themselves are vinyl inside and outside, with standard insulation between. A total of four double paned glass patio doors. So, the walls are not as insulated as the ceiling. It only shares one common wall with the rest of the house.

The gas bill in the summer is about $120. Last month it was $788. The tankless hot water heater and one of my three furnaces is run on gas, along with the pool heater. Of course, I am in the South. We've had about 10 days total of truly cold weather. Currently it is 60 degrees.

Where are you planning to put the panels and how much surface is there for panels?

GIven your location and temperature range, I think standard flat panels are going to be more cost effective than glazed.

 

[Srqpoolguy]

While I will agree that some manufacturer's panels are prone to leaking, over the past 18 years, my solar panels have never leaked. It all depends on your choice of panel.


Where are you planning to put the panels and how much surface is there for panels?

GIven your location and temperature range, I think standard flat panels are going to be more cost effective than glazed.

Well here in south Florida our summer Sun will cook pvc and warp it just from exposure. We get over 100 temps often for months. I agree quality panels are worth it. I believe most around here go a budget route. Have you ever tried a product called cover free? It helps keep your heat in the water and evaporation levels. It's a liquid solar blanket per se. It actually works. Not as well as an actual blanket but for the cost of adding 2oz every other week it certainly helps retain heat. Google natural chemistry Cover Free. It's not a gimmick. Just follow the instructions and don't add a whole bottle like I've had clients do. You won't even know it's there. Just a small tip. Best of luck with the solar.

 

[mas985]

We get well over 100F here as well.

Yes, I have tried liquid solar covers and they are worthless in areas with high winds like mine. This has been the experience of others on the forum as well so we generally do not recommend those products on the forum.

 

[Newdude]

Yes, I have tried liquid solar covers and they are worthless in areas with high winds like mine. This has been the experience of others on the forum as well so we generally do not recommend those products on the forum.

100% agree, i'd even go so far as to say a small waft of wind will push it all to the side. But in an indoor pool that barely needs any filtering / pump runtime it might have some value.

 

[Jenmachen]

Ok, I will pick some up and try that.

 

[Jenmachen]

While I will agree that some manufacturer's panels are prone to leaking, over the past 18 years, my solar panels have never leaked. It all depends on your choice of panel.


Where are you planning to put the panels and how much surface is there for panels?

GIven your location and temperature range, I think standard flat panels are going to be more cost effective than glazed.

The roof that is directly above the pool is totally available for panels, but is 2-1/2 stories high. I can also put them on the roof right next to the that roof that is single story. That elevation is partially shaded morning and evening. But if they need periodic maintenance, then it's a lot easier for me to hop onto that roof to deal with the panels. Would the distance of the rise make a difference on the pump? Probably a dumb question, so forgive me .

 

[mas985]

What is the pump make/model? Exactly how high would the panels be? I interpret 2 1/2 stories as 30 ft which shouldn't be an issue for most pumps.