Trouble priming solar heating pump (Sunbather SCM + Onga LTP550)

[leah.la]

Newb here. Finally given up and asking the experts. Or at least, the unpaid experts!

Pools are new to me so apologies if I don't know the right terminology or something obvious. This site has been a huge help in other pool care aspects.

We are located in Melbourne, Australia. The solar heating was working before we moved in, but hadn't run for a week or so before we took ownership.

THE ISSUE

• I can't properly prime our solar pump, which is separate from the main pump.
• I can get some water to flow through after ~3mins, but it's minimal and never fully primes. See video.
• No bubbles appear in the pool after turning it on.
• The pipe flowing towards the roof feels full, the pipe returning has water trickling through it.
• There doesn't seem to be any valves I can open. There is a clear covering where you can view the water coming from pump towards the roof. I'm not sure what its purpose is, but it's full of water and the spring latch is closed. See video.

What I've tried:

• Filling the pump housing with water, closing the lid, starting pump. Lots and lots of times.
• Replaced the o-ring, pump lid and have plenty of lube.

Equipment used:

• Solar pool heating: Sunbather SCM
• Solar pump: Onga Leisuretime LTP550

Any tips you might have I would greatly appreciated. Need more info? Just say the word and I'll get snapping.

Thanks guys

 

[Texas Splash]

Hello and welcome to TFP! While the issue may be isolated to the pump itself, the solar plumbing may also be a factor, so I'm going to tag @mas985 for some hydraulics experience.

I'll also tag some fellow members from your area such as @AUSpool and @aussieta who might like to say hello.

 

[mas985]

THE ISSUE

• I can't properly prime our solar pump, which is separate from the main pump.
• I can get some water to flow through after ~3mins, but it's minimal and never fully primes. See video.
• No bubbles appear in the pool after turning it on.
• The pipe flowing towards the roof feels full, the pipe returning has water trickling through it.
• There doesn't seem to be any valves I can open. There is a clear covering where you can view the water coming from pump towards the roof. I'm not sure what its purpose is, but it's full of water and the spring latch is closed. See video.

The valve with the clear cover on the solar supply is the check valve. The valve without a handle on the solar return is probably an isolation valve and from the picture that does not look like it is fully open.

The issue could like be one or more of several factors.

1) Check valve is damaged and will not open fully. The one you have should be serviceable. Unscrew the cover and make sure the spring is operating correctly
2) Solar return valve does not appear to be fully on. Do you have the handle for that valve? If so, post a picture with the handle installed. That one is serviceable as well so you can remove it for inspection.
3) The solar pump impeller is clogged. Remove the pump basket and make sure the impeller inlet is free from debris. You may need to disassemble the pump to make sure the impeller is free.

Also a few questions:

Do you know if the outlet of the filter is directly connected to the inlet of the solar pump?

In other words, is the solar pump always on when the main pump is on?

OR does the solar pump pull from a different suction port than the main pump so it can be on or off when the main pump is either on or off (i.e. completely independent)?

 

[AUSpool]

Geday Leah and welcome to the forums,

Mark is all over it. In a lot of applications here in AU that handleless valve will be for flow control. It’s there to reduce the flow a little to optimise efficiency. We generally have two types of setups, a booster off the main system or a stand alone with its own inlet and outlets. I believe we a looking at the latter. If it is a stand alone you should have two covered deep inlets, about the size of a side plate, and one or two outlets.

I‘m not sure that they make or supply the sunbather controller anymore and although is probably past it’s prime it’s not the cause of the problem. Checking, servicing and repairing both the check valve and the valve on the return line would be the first job. The easiest way to do that is to buy the complete valve and just use the new internals on the existing valve bodies. There is also a vacuum break on the roof that I would check and replace too.

 

[mas985]

It’s there to reduce the flow a little to optimise efficiency.

Lower flow results in lower efficiency, not higher.

 

[AUSpool]

Lower flow results in lower efficiency, not higher.

Probably the wrong word, the idea is to slow down the flow to increase the heat gain. Increasing the the size of the solar mat would be a better idea but that’s what they put it there for. The return line should drain back to the pool with the pump off so there’s no need for an isolation valve.

 

[mas985]

Probably the wrong word, the idea is to slow down the flow to increase the heat gain. Increasing the the size of the solar mat would be a better idea but that’s what they put it there for. The return line should drain back to the pool with the pump off so there’s no need for an isolation valve.

But lower flow rates don't increase heat gain, it reduces heat gain. Lower flow rates increases outlet temperature but that reduces total heat gain because losses increase. You think you are getting more heat out of the panels but in reality, the heat gain into the pool water is less.

 

[mas985]

Thinking about this some more, if the solar is on its own plumbing loop, the valve may be there to increase the pressure at the top of the panels to keep the VRV closed.