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Author Topic: Troubleshooting Old East-West Installation  (Read 244 times)
TwoHorsePower
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« on: September 10, 2017, 04:29:02 PM »

Dear All

I was asked to help out on this troublesome installation.

The owners of the property are both disabled and they have been plagued with repeated problems with the system since its installation in 2010. Hoping someone can suggest how i should best approach identifying the problems and any remedial action required.

The original  installer has since gone bust. Various other solar thermal tradesmen have been in and out over the years charging the occupants for multiple system top-ups.  The most recent episode was a few months back when yet another professional solar outfit charged for not only a refill but a replacement pump station. The system worked for only a few days before keeling over again. The solar guy landed in to turn everything off, and despite promises to return promptly, was never seen again. Understandably they are exasperated. I have agreed to help out on a voluntary basis - These folk are both registered blind - I've been involved in several DIY solar hot water installations over the years, systems mainly using 10mm pipe, low wattage 12v pumps  and simple homemade differential controllers, but have no experience of this plug'n play commercial kit.  

There are two HP200 (Thermomax/ Kingspan) panels in an east west configuration, both feeding into the one solar coil in a twin coil vented tank.  The other (top) coil is for the oil boiler as per expected. The cold feed from the tank coil rises up into the loft whereupon it divides in two legs, each with its own separate pump station  to drive the cold return up to its respective panel. The controller is an unbranded TR-0502   - Google informs me this is a Steca controller capable of dealing with a split system.

The HP200  is a heat pipe vacuum tube, unlike the earlier thermomax DF100 (where the solar fluid travelled inside the vac tube and gummed up if it stagnated too often). From what i can gather, the only practical difference between the HP200 and a generic chinese heat pipe is that the bulb of the HP200 incorporates some kind of safety thermostat which prevents the heat pipe from heating the manifold when the temp nears stagnation point.

See attached pic of one of the roof faces -  the other roof face is done the same way. The installer, rather than penetrating the roof at each end of the manifold, took a shortcut and tucked  the pipework for each panel in through a single lead slate/sock.  All the pipework is done in DN16 flexible SS pipe.

Inside the house there are no manual bleed valves or AAVs anywhere, unless that chunky cylinder on the left hand side of the leftmost pump station is some kind of de-aerator?  Once inside the loft, the DN16 flexi pipe rises upwards before falling and there are no bleed valves at the high points, so I am  at a loss as to how  one is supposed to bleed air out of such a system which would, at least in a DIY setup, collect at any high point and upward pointing elbows.

The system is pressurized using a zilmet solar EV (18L) and there is a PRV which blows off into a catch tank. I note there is some fluid in the catch tank but have no idea whether it is recent.

From reading the HP200 docs available online, the panels are supplied with manual bleed valves -  I think i can see these at each manifold at the end of the tees.

I don't like the way the pipework from the panel manifold(s) falls before entering the lead slate and then rises again inside the loft -  This creates a high point at each manifold and a likely spot for an air lock. If this were mine I would fit a vertical(ish) air trap pipe at each manifold, perhaps in microbore, rising upwards and then through/under a roof tile, rising up to a radiator type bleed valve inside the loft so i would not have to go onto the roof(s) again. I would also, if it were my system,  scrap the dual pump arrangement, plumb the two panels in series, & wire the controller's pump outputs in parallel so it controls just a single pump rather than the current two pump. Having said that, a perfect solution is not required, and realistically my objective is to get this up and running for the folks with some degree of reliability, keeping effort/disruption to a minimum.  


Any ideas or suggestions gratefully received re how i could diagnose and remedy this.  Hoping I can refill using my trusty Lidl 5L garden sprayer and not have to hire one of those solar filling pump affairs?
 
Thanks for your help

    




 

    





« Last Edit: September 10, 2017, 06:39:01 PM by TwoHorsePower » Logged

40X47mm tubes, 170L tank, 12V pump & controller.
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desperate
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« Reply #1 on: September 10, 2017, 06:37:46 PM »

Why two pumps?? or is one disconnected? it's not too clear from the piccy. In my experience most problems are down to either air locks which when they get to the pump stop it from moving anything, also those poxy flow meters have a habbit of getting blocked with gunge especially if the system has stagnated a couple of times. If it were mine I would first get rid of any excess valves/meters and other restrictions, insert a few strtegically placed Tees with gate valves, not air bleeds to give complete control of pumping fluid/air in and out. Make up a fitting on a flexi tap connector to fit on said gate valves and your sprayer pump, and then you can fill/bleed at various points around the system and truly get all the air out. Sixpence to a pinch of poop your problems will be over.

While you do all that you can assess how clean the fluid is, if clean-ish shove it back in and away you go, if it smells burnt/sweet/sticky get rid of it and fill with water and fernox or similar antifreeze mix, dont bother with special "heat transfer fluid" generally it's a con.

Desp
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« Reply #2 on: September 10, 2017, 06:52:20 PM »

I have a similar system. First thing I'd be looking at is topping up and bleeding those manifolds, that roof install is plain  awful. Check valves need checking, can cause strange problems on an E/W install if they stick.  It looks like those pump stations have sight glasses on the check valves which may help looking for air, flow and flow direction....

Is the system holding pressure?  Mine sits around 1 bar cold and goes up to 2 bar on a sunny day. When I commissioned my system I had a slow leak I could not locate, system pressure would drop over a 2 week period, solved by using a sealant.

The position of the PRV and the Acc isn't ideal, mine is on the return before the split to each pump.  
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« Reply #3 on: September 10, 2017, 07:40:39 PM »

Desperate - The two pumps are because there is one panel on the east roof and another on the west. The controller then decides independently when the heat is taken from each panel, so, e.g.,  it is not pumping the west facing panel unnecessarily in the early morning or the east facing panel in the late afternoon. The two hots from each panel are tee'd together on the way down to the tank coil.  i can understand the rationale for such a twin pump arrangement on a flat panel set up, as flat panels are less well insulated, but on those HP200s the fluid runs outdoors mainly inside a very well insulated manifold, so i am at a loss as to why both east and west panels were not plumbed in series and using a standard 'solar loop' and a single pump station - Such an arrangement would have required almost half the clobber  in the loft (= less to break or leak).

Take your point about using gates instead of air bleeds - Good idea -  Would those quarter turn isolation valves work instead of a gate or are they troublesome?

Westie - Thanks - I had thought the things with windows (just below each pump) were flow meters, but are you saying they are the check valves? Now that I think of it I couldn't see any NRVs anywhere else! Or are they a combined flow meter and NRV by any chance?

Thanks for your help



 
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Westie
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« Reply #4 on: September 11, 2017, 09:45:27 AM »

Desperate - The two pumps are because there is one panel on the east roof and another on the west. The controller then decides independently when the heat is taken from each panel, so, e.g.,  it is not pumping the west facing panel unnecessarily in the early morning or the east facing panel in the late afternoon. The two hots from each panel are tee'd together on the way down to the tank coil.  i can understand the rationale for such a twin pump arrangement on a flat panel set up, as flat panels are less well insulated, but on those HP200s the fluid runs outdoors mainly inside a very well insulated manifold, so i am at a loss as to why both east and west panels were not plumbed in series and using a standard 'solar loop' and a single pump station - Such an arrangement would have required almost half the clobber  in the loft (= less to break or leak).

Take your point about using gates instead of air bleeds - Good idea -  Would those quarter turn isolation valves work instead of a gate or are they troublesome?

Westie - Thanks - I had thought the things with windows (just below each pump) were flow meters, but are you saying they are the check valves? Now that I think of it I couldn't see any NRVs anywhere else! Or are they a combined flow meter and NRV by any chance?

Thanks for your help
 

I'm not familiar with those pump stations so I assumed they were flow/NRV combined. However I'm looking at the new pic you posted and wondering if there's an arrow pointing downward on what you thought was an AAB? Maybe that's an AAB combined with NRV?   Either way on an E/W system you need an NRV to block any potential thermosiphon between the hot and cold panel.  On my system I have two, on the cool side at the output of each pump.    

If you connected the panels in series on an E/W system and used one pump you would  be wasting a lot of the solar gain from the sunny side to heat up the shaded side, especially so early morning and late afternoon.

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