Author Topic: Solar hot water system problem (Read 18223 times)

Corylus · « **on:** May 09, 2013, 03:14:29 PM »

Our solar water heater suddenly went nuts. Cold water is getting across the 5way valve instead of taking water from the bottom of the HWC which causes water to shoot out the header pipe and cooling of collector -->pump going on and off all day like this, banging noises on roof, air bubbles in the system.
Replaced the Ajax-->no change. And nothing wrong with the old one.So not a pressure problem. Replaced pump-->no change. Reducing the pressure at Ajax allows the circuit between bottom of tank and collector to be initiated but it is slow to heat and tends to lose a little water through the header pipe. Too much reduction causes failure in the circuit, overheating in the collector and steam bubbles coming down into the 5way valve and the tank. Shutting off the cold water altogether led to system rapidly filling up with air bubbles at which point I stopped the experiment. But overheating and steam bubbles would likely have been the result.

Looks like the pump is unable to extract the water from the bottom of the HWC as it should leading to a partial vacuum in system, so that at normal pressure the cold water enters instead. And at reduced pressure, what goes up to the pump is a mixture of cold and water from the bottom of the HWC? And if it can't get the cold water at all or if the pressure is reduced too far, a partial vacuum occurs sucking air in - from wherever, possibly the leak at the isolating valve at the intake end of the pump.

NB The air vent on the collector has never worked. When the temperature in the tank gets to 85 degrees, and the temperature at the collector is much higher than that, steam bubbles come down and into the tank causing shrieking noises and massive vibrations.

And all this seems to defy analysis of our local plumbers who can't seem to think beyond "it's got to be the Ajax" or "we need to see where the air is getting in". I need to know WHY the air is getting in. Is my analysis reasonable? If so what do you suggest?

Linkback: https://www.plumbers.nz/solar-heating-and-heat-pumps/9/solar-hot-water-system-problem/1456/

Plumber · « **Reply #1 on:** May 09, 2013, 05:34:09 PM »

Can you give us more details on what kind of solar system you have please? Layout and possibly a picture of the tank and panels? There are several things I can think of but want to see what you have first.

integrated · « **Reply #2 on:** May 09, 2013, 09:11:52 PM »

you have a blockage in the 5 way valve

you need to ask a plumber to take it out - clean it and check for blockages - while it is out check to make sure the baffle is drilled for the longer smaller dia flow pipe from the colector

Corylus · « **Reply #3 on:** May 10, 2013, 12:25:22 AM »

Thanks to all who replied. It is a Solar Technology Sunsaver 20 tube 58Dia/1800mmcollector. It was installed in Nov 09. We had it fitted to a new180 ltr 560x1200mm Prewired Elec HWC with a header pipe, working head 7.6 metres.

Good advice about the 5way valve - I couldn't work out what could block it. It just looks like a hefty bit of brass from the outside and I haven't been able to get anyone to tell me what the internal structure of it is like so I'd no idea what might have happened to it. I know it has the return pipe from the collector going right through the middle of it into the HWC through a sleeve through which the water from the bottom of the HWC is drawn up to the pump.

While we are on the topic, I'd love to know what normally keeps the cold water from entering the system when the pump goes on. At rest, it's all just sitting there in the cross piece of the valve and the cold water can go straight across while the HWC water has to go round a bend. It looks like it would be easier for the cold to enter than the warm. So is this right? When the pump goes on, it simultaneously pulls water out of the HWC and belts the hot water into the HWC so the warm water at the bottom of the tank gets a kick from behind and a pull from the front? (you guys are allowed to laugh! As an 80 year old female, I feel like I'm doing an apprenticeship and so far haven't found any good teachers. Finding this website was a miracle) And this brief increase in pressure is enough to also kick the water level up the header pipe? And out on the roof if the pressure isn't right at the Ajax? I tellya, this 5 way valve takes some getting your head around, what with the cold water going in through the sleeve in the opposite direction to the warm water coming out when you put a hot tap on when the pump is running.

I'd like the Ajax explained as well please. I have one sitting here in bits and can see how the diaphragm works. But there is obviously more to it than that. I can see that the outlet is wider than the inlet, which must reduce the pressure to start with? But what is the bit in the middle for - the bit under the black cap? I'm having to reduce the pressure by 5 to 6 whole turns and the screw feels pretty loose at that point. What is happening in the HWC when I do this? Does it actually reduce the pressure in the tank? I can't see why it would do that unless you run some hot water off - and I don't. Whatever it does, it lets me get the circuit operational - if I get it dead right. I've been doing it since 25 Feb, which can't be good for the screw? It looks pretty soft metal. Why so long? Because I want someone to think it out BEFORE they come and try to fix it. Have you guys any idea how scary it is to have a plumber spend a whole day scratching his head getting nowhere? I'm still saving up to pay the last one for not managing to fix it.

Thanks for the website. Wish I'd found it sooner!

Plumber · « **Reply #4 on:** May 10, 2013, 01:19:57 AM »

Hi Corylus, I'm very impressed that with 80 years you managed to dissect an apex valve

A quick thought before I go to bed (should really go now) You mentioned that your system suddenly started making these noises, running the pump on/off etc.. In many cases this can relate back to the the freeze protection settings on your controller. Now that the weather is getting colder the system is naturally protecting the panels creating a reverse function. This will cause the pump to go on and off randomly and in the middle of the night. Check the settings and adjust to the panel manufacturers recommendations. If you had a power outage the controller settings could have reset causing this. I don't believe in air vents on an open loop system and would get in touch with the manufacturer in this regard. The open vent flood level should be well above the panels. As you say these levels should be investigated and possibly adjusted. Might add a few more comments tomorrow.. OK bed now.. long day tomorrow. night..

Plumber · « **Reply #5 on:** May 10, 2013, 01:27:31 AM »

One more question, I can see a yellow pressure relief valve on your solar circuit, being 7.6 meter open vented system I would be interested to know what its rated to. OK off now!

Corylus · « **Reply #6 on:** May 10, 2013, 06:21:44 PM »

I see I am labelled a "newbie". Well that's the truth! Please remember guys that I don't talk "plumb". Think of me as a complete ignoramus. That would be true too. So Integrated (reply 2) I'm not sure what the baffle is in the 5 way valve. I'm hopeful that it is in fact a way of discouraging cold water from entering when it shouldn't? It seemed to me that without a way of separating the two flows, it was operating on fond hopes rather than good design. But I was assured it was just empty space in there. If you could send me a link that would show me the internal structure of this bit of brass, I'd be very grateful. I've been trying to find out for weeks.

Similarly Karma (number 4) Open loop? open vent flood level? Is this what I've been calling the level in the header pipe? If so, the top of it is well above the panels - but maybe not far enough. I assume you are saying that in your opinion an air vent on the collector isn't compatible with a header pipe? ('scuse my newbie vocab). It certainly doesn't work. Neither it nor the thingie with the yellow cap have ever seen action as far as I can tell. Which tells me my safety mechanisms aren't functional. You can see then why I called a halt when instead of identifying the cause of this sudden change, it was suggested that a valve be put in the header pipe, which I gather was supposed to increase the pressure in the tank? This was apparently like extending the height of the header pipe and would give me more pressure in the hot water system ( and stop the water from escaping out onto the roof). Having experience 180 litres of scalding hot water dancing about in my airing cupboard as steam bubbles fought to get out the header pipe, I wasn't keen to make it any more difficult for them to get out.

I can't answer your question about rating right away. But I will try to find out.

The settings on the collector have all been checked. However, since it is totally unable to keep time, I have no faith in its other functions. This is a sticking point with the installer as yet unresolved. He has a tendency just to not answer awkward questions.

The sudden change occurred on the morning of a hot sunny day. OK at breakfast. Loopy by lunchtime.

We get heaps of power cuts. But I always reset the controller. And since it is a rotten timekeeper and I'm forever putting the thing off and on as I try to get the circuit operating without just dribbling it out the roof, it is reset timewise several times a day. Perhaps it is as confused as I am.

I've checked fairly carefully that what is happening is that cold water is entering when it should not. At normal pressure, when the pump goes on, Cold water enters the 5way valve and cools the collector quickly, reducing the temperature differential and putting the pump off. It also increases the pressure in the HWC and shoots water out the header pipe. The diff. picks up quickly, starts the pump and the whole thing repeats. I'm trying to persuade the solar guy to send this controller to wherever they go when they go psycho and let me have another in the meantime.

Thanks guys.

Teatime. Cooking calls.

integrated · « **Reply #7 on:** May 10, 2013, 06:43:40 PM »

Quote from: Corylus on May 10, 2013, 12:25:22 AM

Thanks to all who replied. It is a Solar Technology Sunsaver 20 tube 58Dia/1800mmcollector. It was installed in Nov 09. We had it fitted to a new180 ltr 560x1200mm Prewired Elec HWC with a header pipe, working head 7.6 metres.

Good advice about the 5way valve - I couldn't work out what could block it. It just looks like a hefty bit of brass from the outside and I haven't been able to get anyone to tell me what the internal structure of it is like so I'd no idea what might have happened to it. I know it has the return pipe from the collector going right through the middle of it into the HWC through a sleeve through which the water from the bottom of the HWC is drawn up to the pump.

While we are on the topic, I'd love to know what normally keeps the cold water from entering the system when the pump goes on. At rest, it's all just sitting there in the cross piece of the valve and the cold water can go straight across while the HWC water has to go round a bend. It looks like it would be easier for the cold to enter than the warm. So is this right? When the pump goes on, it simultaneously pulls water out of the HWC and belts the hot water into the HWC so the warm water at the bottom of the tank gets a kick from behind and a pull from the front? (you guys are allowed to laugh! As an 80 year old female, I feel like I'm doing an apprenticeship and so far haven't found any good teachers. Finding this website was a miracle) And this brief increase in pressure is enough to also kick the water level up the header pipe? And out on the roof if the pressure isn't right at the Ajax? I tellya, this 5 way valve takes some getting your head around, what with the cold water going in through the sleeve in the opposite direction to the warm water coming out when you put a hot tap on when the pump is running.

I'd like the Ajax explained as well please. I have one sitting here in bits and can see how the diaphragm works. But there is obviously more to it than that. I can see that the outlet is wider than the inlet, which must reduce the pressure to start with? But what is the bit in the middle for - the bit under the black cap? I'm having to reduce the pressure by 5 to 6 whole turns and the screw feels pretty loose at that point. What is happening in the HWC when I do this? Does it actually reduce the pressure in the tank? I can't see why it would do that unless you run some hot water off - and I don't. Whatever it does, it lets me get the circuit operational - if I get it dead right. I've been doing it since 25 Feb, which can't be good for the screw? It looks pretty soft metal. Why so long? Because I want someone to think it out BEFORE they come and try to fix it. Have you guys any idea how scary it is to have a plumber spend a whole day scratching his head getting nowhere? I'm still saving up to pay the last one for not managing to fix it.

Thanks for the website. Wish I'd found it sooner!

due to pump being of the circulating/flow type it is sucking and creating flow below the working pressure of the hot water system - whatever positive pressure that is created is balanced out by the negative pressure that it is also creating at the same time - technically the pump creates the vacuum prior to anything else happening

to a certain extent your observations are correct - the FLOW - ie hot water from the collector runs straight up the guts through a smaller diametre pipe 3/8"? maybe 1/4? - the key to this is that it is longer and penetrates the cylinder maybe a foot - it has the end blanked off with a series of small holes to distribute heat effectively minimising disturbance to the stratification within the hwc

withing the inlet to the hwc there is a baffle - the objective of this is to minimise startification also, by disrupting and directing flow in a uni-directional manner - it is this baffle that must be drilled to allow the 5-way to locate and function properly within the hwc.

so the idea of the 5-way is that cooler water is drawn from the bottom of the hwc - in and around the inlet/baffle - and the hotter heated water is returned back to the hwc past/higher than the drawn water - I ALWAYS put a curve/bend in my smaller diameter flow pipe from the collector to discharge towards the upper portion of the hwc on side entrys as this increases efficiency

the only time efficiency really drops off with 5-way valves is when there are large draw offs within the household creating a cold water sandwich due to the cold water inlet to the hwc being in the same location

it will be at this point that you will find a blockage - and it must be a partial blockage as you said if you wound the pressure right out on the ajax it comes right? by doing this you are restricting the flow to the hwc to match the restricted oriface/opening within the 5-way - so the problem lies in the return section of the 5-way - when the collector is up to temp it is switching the pump on which would normally draw from the bottom of hwc but this is partially blocked so the next best place for it to draw from is the cold water inlet, so it does but then the system is out of balnce so the pump keeps pumping but out the only oriface it can - your hwc exhaust

the collector is stagnating - resulting in steam/air in system

there must be a service rep somewhere handy - most of the solar tech stuff is Solarcity, check for those in your area - if not let us know what area you are in and I could help - I am an agent for the aforementioned

integrated · « **Reply #8 on:** May 10, 2013, 07:07:47 PM »

Quote from: Corylus on May 10, 2013, 06:21:44 PM

I see I am labelled a "newbie". Well that's the truth! Please remember guys that I don't talk "plumb". Think of me as a complete ignoramus. That would be true too. So Integrated (reply 2) I'm not sure what the baffle is in the 5 way valve. I'm hopeful that it is in fact a way of discouraging cold water from entering when it shouldn't? It seemed to me that without a way of separating the two flows, it was operating on fond hopes rather than good design. But I was assured it was just empty space in there. If you could send me a link that would show me the internal structure of this bit of brass, I'd be very grateful. I've been trying to find out for weeks.

Similarly Karma (number 4) Open loop? open vent flood level? Is this what I've been calling the level in the header pipe? If so, the top of it is well above the panels - but maybe not far enough. I assume you are saying that in your opinion an air vent on the collector isn't compatible with a header pipe? ('scuse my newbie vocab). It certainly doesn't work. Neither it nor the thingie with the yellow cap have ever seen action as far as I can tell. Which tells me my safety mechanisms aren't functional. You can see then why I called a halt when instead of identifying the cause of this sudden change, it was suggested that a valve be put in the header pipe, which I gather was supposed to increase the pressure in the tank? This was apparently like extending the height of the header pipe and would give me more pressure in the hot water system ( and stop the water from escaping out onto the roof). Having experience 180 litres of scalding hot water dancing about in my airing cupboard as steam bubbles fought to get out the header pipe, I wasn't keen to make it any more difficult for them to get out.

I can't answer your question about rating right away. But I will try to find out.

The settings on the collector have all been checked. However, since it is totally unable to keep time, I have no faith in its other functions. This is a sticking point with the installer as yet unresolved. He has a tendency just to not answer awkward questions.

The sudden change occurred on the morning of a hot sunny day. OK at breakfast. Loopy by lunchtime.

We get heaps of power cuts. But I always reset the controller. And since it is a rotten timekeeper and I'm forever putting the thing off and on as I try to get the circuit operating without just dribbling it out the roof, it is reset timewise several times a day. Perhaps it is as confused as I am.

I've checked fairly carefully that what is happening is that cold water is entering when it should not. At normal pressure, when the pump goes on, Cold water enters the 5way valve and cools the collector quickly, reducing the temperature differential and putting the pump off. It also increases the pressure in the HWC and shoots water out the header pipe. The diff. picks up quickly, starts the pump and the whole thing repeats. I'm trying to persuade the solar guy to send this controller to wherever they go when they go psycho and let me have another in the meantime.

Thanks guys.

Teatime. Cooking calls.

1 - yes generally 1metre is enough standing height above the highest point of collector
2 - the air vent has a wee dial that should be loosened and left - how can you tell if air is or isnt being released?
3 - technically these features are not required as you have an open vent system - these are installed as per manufacturers/suppliers instructions as part of the agreement with councils for streamlined consent processes, quite often you get the inspector who knows diddly about solar and/or alternative heat sources or hot water systems in general who loves to wave his stick around, much easier to just install them as a standard measure to avoid this, also get you into the habit of thinking about safety valving in general at a precautionary level
4 - was it installed through solarcity or independant? there are one or two others that use solar tech as well - is the controller a resol unit?
5 - this has been answered

if you have problems with power going on and off all the time you should have a surge protector in place, as this will fry the controller - invest in a ups - uninterupted power supply

thanks - good luck!!

the contro

Plumber · « **Reply #9 on:** May 10, 2013, 07:34:56 PM »

Quote from: Corylus on May 10, 2013, 12:25:22 AM

I'd like the Ajax explained as well please. I have one sitting here in bits and can see how the diaphragm works. But there is obviously more to it than that. I can see that the outlet is wider than the inlet, which must reduce the pressure to start with? But what is the bit in the middle for - the bit under the black cap?
Thanks for the website. Wish I'd found it sooner!

Have attached an image for you that explains it pretty well.

Corylus · « **Reply #10 on:** May 10, 2013, 08:19:17 PM »

Hey thanks everybody. I'll study the content and get back to you later. Have guests. Your replies are truly appreciated.

Corylus · « **Reply #11 on:** May 11, 2013, 01:28:25 PM »

Hi folks. I see my carefully considered rely has not turned up. Am I allowed to say "bugger!"? Must be doing something wrong. I'll do them in short bits next time.

I'll start with Integrated. Point 2. Air vent. I can tell if it is working by going up on the roof to look when the tank is trying to jump out of the airing cupboard. Diddly. No sound. No steam. Also, steam would not be coming down the return pipe if it could get out the vent huh?

I've had a look at one of those. It's a Caleffi Solar.Tmax 180degreesC P max(can't read this clearly) 10bar 150 psi. It is apparently the only one the solar chap has ever seen used locally.

Not being able to see inside it, I'm wondering if this might be a point where air can get into a system that has developed a partial vacuum? Is it a one way valve? Just had the solar chap come to replace it with another anyway. He has checked up there and everything appears to be in order.

point 3. Yeah, I rather thought as much. A great length of expensive copper tubing for no great reason other than a penpusher signing a chitty. Loved your description.

Thanks Integrated.

4. The solar chap has his own business, the name of which includes the words Solar Technology Systems, because historically he was involved with the Nelson lot that was bought out by Solarcity. But he wasn't. Confusing? tell me about it! He has already replaced the pump to eliminate it from the puzzle. He's OK. Just difficult to pin down.

resol? Is this an anagram of Sorel? TDC 2. Undoubtedly fried. No computer can take the on/off treatment this one has had. When the plumbing is dealt with we will exchange it for another one and send this one off to rehab.

Corylus · « **Reply #12 on:** May 11, 2013, 01:39:52 PM »

Reply to Plumber. Thanks for the pics. They don't look a lot like the UFO I have in the airing cupboard. I'll have to study them to see if I can relate them to this dismembered bit of brass in front of me.

I have to confess that my husband did the dissection of our Ajax - and binned it before I got a chance to see it. So I think what we dug out again might have a bit missing. Hence the puzzle.

The yellow thingie on the quite unnecessary? discharge pipe is rated "Low bar"

Can I ask the reason why you are not a fan of air vents with an "open loop" sytem?

Plumber · « **Reply #13 on:** May 11, 2013, 03:57:54 PM »

Air vents are usually used on closed loop systems, in your case once flooded if should not be necessary. I assume the yellow relief valve is on the solar loop because they put ball valves on the flow and return (actually not approved), if anyone isolated both the panels would over pressurize, hence maybe the relief valve. You mentioned before that someone recommended putting a vacuum valve (relief valve) on the open vent to increase pressure, this would also not comply being a solar system it is still considered an uncontrolled heat source with some councils. I would strongly recommend getting another opinion on the setup and problems you are describing. With regards to the image the top one is the UFO. Good luck

Corylus · « **Reply #14 on:** May 11, 2013, 06:15:59 PM »

Hello Plumber. Thank you for your post. I had a sneaky feeling that the air vent was more to look after the panel than it was to look after me! Fair enough. One must look after one's assets. I'm presuming a ball valve is a non return valve? Yup. I think the idea is to allow you to isolate the panel temporarily while you investigate what the **** is wrong with the rest of it.

So could the air vent be the source the air bubbles? If there was a vacuum in the circuit? Otherwise, there is a slight leak at the isolating valve on the flow pipe to the pump, I sometimes think there might be air bubbles in the cold water coming into the system. I hope not. That pipe is under the house and I can't access it. I can't imagine a slight leak in a mains pressure pipe could let air in??

You seem to be slightly alarmed about the problems I am experiencing. Join the club! Second opinion? That's why I'm asking you guys. And very glad to have found you.I can't find anyone here who is prepared to actually think. Mind you, I'm going on what the solar guy is saying. He has been asking all the plumbers he can find and I don't know what he is telling them. The one who was recommended by various sources simply hasn't bothered to read the logical summary I sent him, which had no input from me other than observations. I wanted to know what the observations meant to him. He just hasn't bothered to read them. All he can come up with is a quote for $1000 to come and install his own controller and to have a look. Other than that he has set the solar guy looking for where air could be getting in. I'd like him to do his thinking before he comes - is that unreasonable? Sigh. It doesn't pay to be female. You tend to be ignored - written off as a panic merchant who hasn't a clue what is going on. And being ancient doesn't help - what would an old woman know about anything huh??? (I once taught 6th form physics, but am the first to confess, it doesn't always relate to things like 5 way valves etc. when you can' find out what they look like inside)

UFO? Yup. I realise that it was the top one. But I have to tellya, it comes from a different planet from mine!

Time to cook. Us females have our uses. PS The irony is, my husband was head physics teacher for years at the local girls' college. But he has had a stroke and his knowledge is not accessible to me. I'm just a biologist with Physics as an 01 subject, and I didn't do it at school. so it's not my best shot by any means.

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Author Topic: Solar hot water system problem (Read 18223 times)

Corylus

Solar hot water system problem

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