Plumbing for a solar heater

[AUSpool]

Hi all and thanks for helping.

I'm in the process of ordering the solar pool heating and need to finalise the plumbing schematics. The system is a little unique, two rumps running independant off the same 2" suction and return line. The filter pump will run for 2 hours early morning and evening leaving the solar pump free to do it's thing during the day. I'm using a relay switch to ensure both pumps can never be on at the same time.

Excuse my rough drawing but this is the schematics.



Both pumps need to have a non return each. The schetch shows these before the pumps but would they be better after the pumps?

Do I need a non return after the filter to prevent the solar return from pushing water through the filter?

Most schematics have a non return after the solor panels or on the return line. Do I need one and where should it go? Immediatly after the solar return enters the filter area or after the bypass, just before the solar return enters the main return?

Thanks for any advise.

Cheers, Steve.

 

[happyheathen]

Why are you using two pumps?

I just did a google search for solar heating diagrams, and none (I didn't look at all) I saw proposed dual circuits such as you propose?

Never use valves which can case major problems, such as independent shut-off for both circuits - you could end up with no return at all.

When this pool was installed, the solar system was plumbed after the filter (never send unfiltered water into a solar system) and before a gas heater.

If the solar didn't get the water up to spa temp, the gas-fired unit had a thermometer to set it off.

Your proposal is duplicating the biggest (and most expensive) components. You now have two filters and pump baskets to clean (don't think of using a cheapie filter on the solar - the 'semi-clean' water will still get into the pool).

Why the added components and risk of wrong valve settings?

One-way valves will ensure no backwash will get into the other circuit.

If you really insist on making this as complicated and failure prone?

IMHO:
Use a single circuit with a by-pass valve on the solar panels. I'd suggest automation to use the pump at a lower speed if the solar is by-passed, i.e. "IF SOLAR ON, use max pump capacity ELSE use lower pump capacity".

I blindly replaced the over-sized pump with another 1 1/2 HP - I didn't realize the only reason for 1 1/2 HP was to push the water up to the roof for the solar panels (which did not survive the re-roof*).

* - if you put panels on the roof, re-roof BEFORE the install.

 

[Agent99]

Steve,

I forget your reason(s) for using two pumps from your other thread but I do agree about the placement of the filter. ALL the water entering your system should be filtered first and then you can send it to wherever you want knowing it is clean. You don't want a rock or build-up of sediment/pebbles/leaves/etc. clogging up your panels. Make sure it is filtered of all foreign objects. Reference my schematic again.

 

[AUSpool]

Thanks Dave, and thanks again Chris, I really appeciate everyones input.

I wasn't really wanting to elaborate on my reason for running the two pumps, but was concerned about the placement of the non-return valves and the need for the solar by-pass.

The two pump idea was my initial idea based on simplicity of control but mostly due to integrating the use of the pumps with the PV feed in tariffs. I was sold on the actuated control valve using the exisiting pump but my existing 3 speed eco pump has a full speed startup program that requires an expensive controller with advanced programing, so back to the two pump senerio, either independant or as a booster. The annual running costs are significantly cheaper using both pumps independantly.

I did a final measure up with the supplier and he went through my schematics. I'm comfortable with a non return on the suction side of each pump but it does seem a bit silly two have two non-returns in the main filter system. I will need a pair of the Jandy 90deg non returns but they will make servicing a challenge as I'm fitting a lot into a small area. Since the solar panels are on a single story roof he suggested I don't need the non-return on the solar hot return but will need to use one after the main filter to prevent the solar pump/system pushing water into the main filter.

I'm still undecided on the filter or strainer before the solar panels. The supplier suggested it's not needed but can supply a strainer and or cartridge filter although I doubt I'll be able to fit a cartridge fillter in.

I'm using a Jandy 3-way and 2-way for the by-pass. Most schematics for a bypass have three 2-way valves but I already had the three and I think it will do the job of two and allow me to slightly reduce the preasure in the solar panels a little if needed.

I hope that covers it all,

Cheers, Steve.

 

[AUSpool]

I've updated my schematitics to reflect the changes. Can anyone see any improvements or potential problems?

 

[pabeader]

I am unable to view that attachment. It says that it's invalid. You might have hit the attachment limit. Most folks you a photoshare site like photobucket, to post pics.

 

[AUSpool]

Thanks Bob, I did notice it looked different but the link worked for me. Hopfully I fixed it and I should start using my photobucket account.

 

[AUSpool]

* - if you put panels on the roof, re-roof BEFORE the install.

Thanks for your comments Dave, I appreciate your thoughts and have taken all your suggestions onboard.

The whole idea of salt water on my metal roof with box gutters is a little scary. I've been to my local fastener supplier and my first job is to replace just over 300 inferior quality roofing screws that are showing signs of wear. I'll have to drll through my parapets and haven't even thought of what to do about the box gutters, I seriously hate box gutters and parapets!

Steve.

 

[AUSpool]

I've spent the morning on roof and replaced some of the rusted screws. It's hot up their so down into the cool and spent the rest of the morning making my pump control. Essentially a pair of extention leads were the first controls the second. The power to the filter pump will shut off the power to the solar pump so the pumps can never be on together.

 

[pabeader]

I must say that I applaud your ingenuity. In reality there isn't anything wrong with your ideas. It's just a bit more expense then we would normally suggest. You have your reasons for doing it this way and that's what's important. The concern about debris making it up to the solar panels is one to take to heart. I see you have a filter/strainer shown on your drawing. I would for sure recommend that you use a skimmer sock or something like that in there. Have to check it often, but it will save you issues down the road.

 

[AUSpool]

Thanks Bob, I love a bit of automation but always think it is important to keep it simple. Most agree that a seperate system for the solar is the best and my proposal is close to this but I don't have the luxury of extra lines to and from the pool. The next best would be using the existing pump with an actuated valve but I've got an Eco Series pump that requires a solar controlar with a bit of extra wisardry. The most common way to do it hear in AUS seams to be with a booster pump but this is the least efficient, running two pumps. In AU$ values the annual running costs are $260 for two pumps independant, $262 for the existing pump plus an actuator and $450 for the main pump plus booster. My Eco pump currently costs me ~$70 a year plus roughly the same for the chlorinator.

I've put an extra 1000 watts of PV panels on the roof to offset the running cost and will be feeding power to the grid at $0.52 a Kwh while using grid power at $0.18 a Kwh to run the solar pump during the day, so in essence we will be paid to heat our pool. The main pump will run off the main peak tariff as it is now, early morning and evening so it dosent interfere with our feed in tariff.

- - - Updated - - -

My Jandy valves arrived today. The non-return valves do require a bit of force to overcome the force of the spring. I was thinking of removing the springs, I can't see any reason why they wouldn't still work as required as long as there're installed in the correct orientation. Has anyone successfully done this or used the Jandy non-return valves without the springs? I guess I can always put them back.

 

[AUSpool]

I spoke with my supplier today and although he didn't supply my Jandy valves he gave me a very good install tip. Remove the 'guts' of the valves for the instal so internal parts of the joints can be cleaned and avoid damage to the seal.

 

[pabeader]

Removing the 'guts' as you say, is a good idea. One that I forgot once and ended up gluing the valve in one position. Needless to say, I've not done that one again.

 

[beachinmoney]

Wow, I applaud you both. I want solar to heat my pool next year and I am worried about the cost. Anyone know of a catalog that I can find and purchase a smart man to do these things. My dad lives out of state!

 

[Agent99]

Look into Fafco panels. I've heard some folks getting them for dimes on the dollar from craigslist.

 

[AUSpool]

Wow, I applaud you both. I want solar to heat my pool next year and I am worried about the cost. Anyone know of a catalog that I can find and purchase a smart man to do these things. My dad lives out of state!

Thanks Beachinmonay, I don't know if you'll find what your after from a catalog but for me google and the yellow pages (phone book) worked a treat and both allowed me to be a bit specific to my local area and country. I had a bit of an idea of what I wanted to achieve, did a bit of research on the net then got a few local suppliers out to quote and have a look at the products available. I've been second guessing myself all the way though.

 

[AUSpool]

Things are moving on, I've finished replacing all my rusty roofing screws and given the roof a power wash. I was contemplating painting the roof before installing the panels but then two massive boxes arrived and the panels were installed. Now on to the plumbing.


Where to place the vacuum breaker(VB)? Based on the instructions from one manufacturer I initially thought the best place for a VB would be at the very top and I can see the logic in that. The manufacturers guide for my panels suggests at the beginning of the bottom or cold manifold while the guy who supplied it would rather see it on the bottom or cold manifold at the opposite end of the cold supply and raised up slightly so it is just above the height of the return manifold. I don't have a lot of fall across the roof so it doesn't need to be raised up much, maybe halve a foot.

I have a non return valve just before the solar pump so very little water will drain out through the cold feed line when the pump stops. It does make sense to me to put the VB somewhere on the bottom manifold for my system so the risers will syphon out via the top manifold and the return line. I assume at some point air will enter the top manifold, break the syphon and the remaining water will drain out via the feed line.


On pump shut down my feed line is blocked by the non return valve so to facilitate draining I'm installing a 6mm connection between the cold feed line and the return line just below the eaves. this will allow any remaining water in the feed line to slowly drain out via the return.

 

[gwegan]

Ok I'm late in here but I'm missing something. I just don't see how a two pump system can have lower operating costs than a single pump system. As I see it your pump (either one) must pump water up to the panels at a certain rate to heat the water. With one pump that can be the daily circulation for the pool. With your two pump system you must run both pumps each day to achive circulation and heating.
With the added complexities of two pumps and the fact that you are essentially running less than fully filtered water it makes little sense to me.

You panels only have a limited life, running water that has not been completely filtered through them will only shorten the life of the panels.

I have looked at a bunch of solar system diagrams on here and the interweb, never have I seen a two pump residential system.

 

[AUSpool]

Ok I'm late in here but I'm missing something. I just don't see how a two pump system can have lower operating costs than a single pump system. As I see it your pump (either one) must pump water up to the panels at a certain rate to heat the water. With one pump that can be the daily circulation for the pool. With your two pump system you must run both pumps each day to achive circulation and heating.
With the added complexities of two pumps and the fact that you are essentially running less than fully filtered water it makes little sense to me.

You panels only have a limited life, running water that has not been completely filtered through them will only shorten the life of the panels.

I have looked at a bunch of solar system diagrams on here and the interweb, never have I seen a two pump residential system.

I do admit it is a little 'out of the box' and I have been second guessing myself all the way. The idea came from what I found to be the most ideal setup which was to run a solar system as a stand alone system. Think of my system as two separate systems that just happen to share the same and existing feed and return lines, to and from the pool. Both pumps will never be on at the same time thanks to the relay switch.


I was very close to using the existing 3 speed eco pump and an automated valve but I needed an expensive controller to do that and although it is a generalisation the rate of failure increases complexity. In Aus the most common way to add solar heating to an existing domestic system is to use a solar booster pump which requires both pumps when solar heating is required.


My current eco pump only draws 180 watts on low and costs ~$70 a year to run on a peak tariff. If I used the existing pump with an actuated valve it would need to run on mid flow drawing 750 watts summer and winter. Even the most expensive controller cant drop my pump back to low is solar is not required. I've down graded my solar pump to a half hp so it's going to cost me even less to run than my projections.

 

[AUSpool]

I've been busy, very busy, two massive boxes arrived and the work began. I had contemplated re-spraying the roof but it really didn't need it and those two boxes needed to go somewhere. After several days of hard labor I'm almost finished and just about out of beer. I'm waiting on a part to finish the work on the roof and have a little paving to do.... I hate paving and I will never do another self install again!