New two speed pump + solar

[jaysin436]

I recently installed a 2 speed pump with the intentions of running my pool 24/7 on the low speed. Everything went well except my solar threw a wrench in the plan. Despite being told the pump would have enough boost on low speed to run my solar (by the salesman) it doesn't. If the pump is on low speed and there is air in the solar panels (due to the vacuum release valve opening) then it doesn't seem to have enough juice to clear the air and get things going (salt system says "No Flow"). If I kick the pump to high and then give it a minute and switch to low it seems to work. The problem seems to be with getting that air cleared. I don't quite understand the hydrology of this... the pump is pumping... but I'm not getting any flow from the jets. Where's the force being lost here? Is the air being compressed but then just expanding back on each pump stroke?

The obvious answer is run the pump high for a few mins to get things rolling but my solar is temperature controlled via temp sensors and a Goldline actuator on a panel. This panel has no feedback to the pump so it may choose to come open/close whenever it wants to. If the pump is in low then it's not going to work.

Short of replacing the pump with a variable speed with a bit more variance for low speed setting and/or getting a Suntouch/EasyTouch/etc, is there anything clever I can do? I have an Intermatic 1353 digital timer, but without some sort of info from that solar actuator I'm not sure how to get feedback to the pump to go high.

 

[jblizzle]

I am going to be dealing with this myself soon; however I realize that low speed is not going to have the power to prime the panels. I plan to just use the pump on high when I want the solar to be running and low when I know I do not need solar ... of course having a SWG is going to make this interesting as the setting will change depending on how long I run the pump.

Unfortunately, I am also not sure if any of the automation controllers is smart enough to automatically kick the pump into high for a few minutes when solar is requested (although I have not full investigated this).

I am afraid there is no clever fix for this with the equipment you have.

 

[mas985]

There are ways to configure solar to run on low speed but it takes a little work and you will need to have a controller that can switch to high speed to prime the panels when solar is first engaged. Many solar controllers will do this automatically but check first. How are you controlling solar now?

Also, the placement of the vacuum release valve is critical. It will not close unless it is under pressure and on the roof, there is usually negative pressure on low speed which will open the valve. So to get solar to work on low speed, you also will have to drop the vacuum release valve a few feed above the pad and on the supply side of the solar system. If you configure everything correctly, it will work but it requires all of these elements.

 

[jaysin436]

My solar is controlled strictly by temperature today... It has a Heliotrope controller that will move an actuator based on the temp sensors. There's no feedback to a pump. I actually had my solar guys out today for another reason and ask them about this problem and we tried a number of things that made it better but it still can't work on low speed all the time. The solar guys did replace my vacuum valve and move it to the supply side of things as it was on the return side previously. This helped, previously the valve wouldn't even stay shut at all when on low (even after priming the system on high).

Most of the more advanced controllers have a feedback/pump control that can do what I need.... I just don't want to go so far as to buy one to solve this. If I have to go that route, I'm going to replace the entire pump with a Intelliflo VS and the EasyTouch.

 

[TheGoose]

here's a thought: See if you can swap your motor out for the next size up motor (from say a 1-HP to a 1.5) so that when you run on low your flow is higher. Of course you'll have to change out the impeller and diffuser end. Don't know how well it will work but if you really want a two speed it might be an option.

 

[Diver]

what are the negatives with running solar without a vacuum breaker?

 

[jblizzle]

what are the negatives with running solar without a vacuum breaker?

Crushing the little tubes in your panels under the vacuum created by the weight of the water when the pump is off. Problem gets worse when there is non-moving water as the water get VERY hot which softens the plastic which makes it easier to crush.

 

[Sarahdog]

The Intermatic PE153PF timer will allow you to run the 2 speed pump on high to purge air, then switch to low speed for normal running.
The timer has 3 time periods for each of 3 separate loads. (High, Low, Aux)


If you are used to the old mechanical dial timers, these are far superior.
http://www.amazon.com/Intermatic-PE153P ... B0039Q9CCO

 

[jblizzle]

The Intermatic PE153PF timer will allow you to run the 2 speed pump on high to purge air, then switch to low speed for normal running.
The timer has 3 time periods for each of 3 separate loads. (High, Low, Aux)


If you are used to the old mechanical dial timers, these are far superior.
http://www.amazon.com/Intermatic-PE153P ... B0039Q9CCO

The problem is when the solar is on and the pump is on low ... then the solar turns off ... then the solar decides to turn back on, but there is no way for the pump to know that it need to kick back up to high to re-prime the panels.

 

[jaysin436]

Correct, as I stated in my original post I already have the Intermatic 1353 digital timer (with two speed pump support) but that doesn't solve the problem that the Solar controller and Timer and pump have no communication to each other other.

I bit the bullet and returned the pump and got the Hayward Ecostar + Pro Logic controller. I went with the Pro Logic because I already have the Goldline SWCG cell so it just plugs right in.

 

[Ken Hot Sun]

I have a few comments on this topic. 2 speed pumps were invented for hot tubs because you didn't need much circulating flow and you did need a high power main speed for spa jets. They are just a full sized pump running at half speed. They end up operating efficiently at low speed if the pressure is very low and you can get away with them on some pools but not all and in fact not many. The pool industry has really faltered on this item. They were wrong to transfer this hot tub technology to pools. If you look at their pump curves they are only good for about 20 feet of head. That's only 11 psi. The key question that should have been asked here is what type of filter do you have and how high is solar? Cartridge filters don't restrict flow much so they don't require much pump pressure (until they get dirty of course). So anyone in solar should have the experience to know that a 2 speed pump on low speed is a non starter not just for solar but for any pool with more than 20 feet of head pressure requirement. Note a gas heater takes 5 psi (11 feet) and a sand filter is about 8 psi when clean so you can't use a 2 speed pump on low speed on a pool with a sand or DE filter and a gas heater. Solar one story up is about the same load as a gas heater but that's not on top of the gas heater. Solar tied in between a filter and a gas heater causes zero extra load to the pump because the water is already at solar height from the gas heater's restriction.

All of this can not be remedied with vacuum breaker placement or replacement. When a solar system starts up there will be air in it. You can't avoid that. Flushing the air out does require more pressure than just raising water to the top of the solar panels because its like pushing a balloon full of air underwater. In fact I've proven mathematically that the pressure required at the top of a solar heater to force a column of air down x feet equals x feet of head. So if a solar system is 10 feet up (4psi) then it might take 4 psi plus the height of the solar system (another 4 psi) just to start the system. If you want to reduce that start up head you install an air vent. Then the air will vent out and the column of air will disappear and the system will start if the pump can raise the water to the top of the solar panels. If it can't then you need to scrap the 2 speed pump which should probably never have been installed on the pool in the first place.

Warning, Normally 2 speed pumps are over sized on high speed for the pool plumbing and solar system they operate against. Running on high speed for solar could cause excess pump load and solar pressure. Suntouch and other controllers do allow a start up high speed followed by low speed but rather than going down that mechanically problematic road its better to just vent the start up air. If the pump can't run solar on low speed with the air vented then the high speed start up cycle won't help either. Its a better and smarter solution for a problem that shouldn't exist in the first place.

I have more to say if anyone is interested. My web site is 100 pages of this technobabble. {Contact me for the web address} This issue all stems from the fact that since the beginning of pool time pool builders have been increasing the pump power and walking away from built pools leaving owners with $100/month electricity bills. The correct solution to this was to downsize the pool pump. In this pool in question the pool pump only needed to be 1/2HP in the first place. Instead it was oversized to 1.5HP or higher. I've seen residential pools with 7.5 HP pumps and pool builders arguing with my dealers over resultant energy costs. A 1/2HP pool pump can operate efficiently at 50 feet of head. You'll never have a problem with solar starting up 2 or even 3 storeys up regardless of filter type and pipe size. A 1/2 HP pump operating around say 10 psi draws 6 times less power than a 1.5HP pump working hard against undersized pool plumbing at say 16 psi. Either one will turn the pool over in 6 hours. Variable speed pumps are good. If you want this simple so the pool industry experts can wrap their brains around it then here's the bottom line. Two speed pumps are wrong unless its a cartridge filter and solar is no more than one story up.

Edited by moderator to remove link violating forum rules, jblizzle

 

[jblizzle]

You are missing the point that at the lower flow rates of low speed, the head is drasitically reduced as well. So with no solar, low speed works fine for circulation and filteration. In fact, the VS pumps are running at even lower flow rates. Are you now going to say that VS pump are not appropriate to "most" pools?

FYI, after installing my Pro Logic with a short high speed and then mostly low speed operation, I manually turned on the solar one day, forgeting I had the timer set for low speed ... turns out the solar ran just fine on my roof (although not as efficiently as it would have on high speed). Granted it was primed with an hour of high speed running, but once primed, low was able to keep the water moving since the solar does not add much head loss once primed.

Who says 2-speeds are typically over-sized? That is a pretty blanket statement. I woudl argue that most pool builders over-size the single speed pumps as well. In fact when I replaced my single speed 2 HP pump I went with a 1HP ... runs just fine.

It seems that your negativity toward 2-speed pumps is contradictory to your approval of VS pumps? That makes no sense. If the 2-speed pump is sized appropriately to run the solar on high only, then why would running on low speed when solar is not needed be a problem?

 

[bobodaclown]

I believe the intermatic PE series PE1353 can prime in hi then switch to low, you can specify the high run time and low run time individually. So you can have it come on high for a certain run time, then switch to low for a certain time.
It will control hi/low and a swcg. Something to look at.

 

[mas985]

Boy, there are just so many things wrong with Ken's comments I don't know where to begin.

2 speed pumps were invented for hot tubs because you didn't need much circulating flow and you did need a high power main speed for spa jets. They are just a full sized pump running at half speed.

Where did you get that factoid? My understanding is two speed pumps/motor were used in the water distribution industry a long time before introduced into the pool industry.

If you look at their pump curves they are only good for about 20 feet of head. That's only 11 psi. The key question that should have been asked here is what type of filter do you have and how high is solar? Cartridge filters don't restrict flow much so they don't require much pump pressure (until they get dirty of course). So anyone in solar should have the experience to know that a 2 speed pump on low speed is a non starter not just for solar but for any pool with more than 20 feet of head pressure requirement. Note a gas heater takes 5 psi (11 feet) and a sand filter is about 8 psi when clean so you can't use a 2 speed pump on low speed on a pool with a sand or DE filter and a gas heater. Solar one story up is about the same load as a gas heater but that's not on top of the gas heater. Solar tied in between a filter and a gas heater causes zero extra load to the pump because the water is already at solar height from the gas heater's restriction.

There is one HUGE fact that you are ignoring. Dynamic head loss is proportional to the square of flow rate. So on low speed head loss drops by a factor of 4 in ALL equipment and plumbing. So a pump operating on high speed at 60' of head will have only 15' of head on low speed. Just check the out the pressure loss CURVES for sand/DE filters and heaters, they are not fixed pressure loss. There are plenty of people on this forum with DE and Sand filters running a two speed pump on low speed so I am not sure where you got this from. Also, if the VRV is placed at a height such that it remains closed on low speed, the panels can be primed on high speed and then switched to low speed and the panels will remain primed.

All of this can not be remedied with vacuum breaker placement or replacement. When a solar system starts up there will be air in it. You can't avoid that. Flushing the air out does require more pressure than just raising water to the top of the solar panels because its like pushing a balloon full of air underwater. In fact I've proven mathematically that the pressure required at the top of a solar heater to force a column of air down x feet equals x feet of head. So if a solar system is 10 feet up (4psi) then it might take 4 psi plus the height of the solar system (another 4 psi) just to start the system. If you want to reduce that start up head you install an air vent. Then the air will vent out and the column of air will disappear and the system will start if the pump can raise the water to the top of the solar panels. If it can't then you need to scrap the 2 speed pump which should probably never have been installed on the pool in the first place.

Simply not true. There are many solar installers who use this technique specifically so the PO can run solar on low speed. Also there are many pools operating this way today and many on this forum. The only caveat is that the panels must be primed on high speed before running on low speed. Also, to prime panels, it isn't just about pressure, you also need a critical flow rate to push the air downwards out of the return pipe. If the flow rate is not sufficient to overcome the rising air, the panels will not prime.


Ken, I think YOU need to speed some time reading up on hydraulic theory because there are several things that you do not understand. You might start with the first two links in my signature.