Navitron Renewable Energy and Sustainability Forum

SOLAR THERMAL => Solar Thermal Systems => Topic started by: Steve Locke on October 13, 2018, 04:48:59 PM



Title: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: Steve Locke on October 13, 2018, 04:48:59 PM
System installed 2012.  After less than three months it was apparent air was in the system.  Original installer refilled the transfer fluid.  Early 2017 the system appeared to be working fine, no air gurgling and info/control panel showed the pump working.  However, inspection of the installation in the roof space there was absolutely no heat transfer to the cylinder.  The pump did not seem to be operating, no noise or vibration.  The body of the pump was very hot to the touch.  Before realising this I noticed from the control panel on really sunny days the pump would shut down and the display would show the tube temperature at around 140c+.
The installer who fitted the system has moved from the area and appears reluctant to get involved in problem solving.  Quite frankly don't want him back as it appears whenever there's a problem just makes excuses.  My impression, he's been trained to fit a new system but unable to troubleshoot even his own installs.
Thinking as the best case it's a new pump a refill of the system, it's going to take 3+ years to recoup the cost.    Given that there is a fundamental problem of air getting in the system is it even worth even considering???  Would be grateful for any recommendations for an engineer in the Epsom, Surrey.
If not viable, the forward plan would be to junk the thermal solar panels and use roof space for photovoltaic panels to offset power required to run proposed air source heat pump and use the thermal solar connections on the cylinder for log burner back boiler.


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: offthegridandy on October 13, 2018, 05:52:56 PM
Hi Steve and welcome to the forum. Sorry to hear your wows.  No expertise on solar water but plenty here that have successful systems I believe.

Bit confused by your post.  You appear to be saying system has worked fine from 2012 after system was refilled until at least 2017 but you also say there is a fundamental problem of air in the system.  Do you mean that the system has always had air in it?.

Couple of thoughts for you.

Are you sure it's the pump failed, have you tested the pump independently?  Is it possible to remove the pump from the system and bench test it before consigning it to scrap?

Good luck.

Andy


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: eabadger on October 13, 2018, 06:39:25 PM
welcome.
could it be the pump running dry due to air? hence it is hot.

steve


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: desperate on October 13, 2018, 06:45:53 PM
Second the above comments, is there a positive way to bleed air just above the pump, air is the cause of the majority of problems in systems I work on.

PS we are based in Worcester Park :)

Desp


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: todthedog on October 13, 2018, 07:06:14 PM
Hello and welcome to the forum.

Just a couple of thoughts

Is the system getting to this temperature now or in the Summer?

Any  system needs a top up from time to time easy diy with a garden sprayer.

Did these arrive on days when no hot water was used by you or the family.

Sounds like the system is stagnating going over temperature and the pump shutting down.

Is your expansion vessel empty and properly pressurised?

https://www.navitron.org.uk/forum/index.php?topic=24532.0


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: linesrg on October 13, 2018, 09:42:25 PM
Steve,

I have a similar depressing story of a solar thermal system constantly filling with air.............

Regards

Richard


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: Philip R on October 13, 2018, 10:16:40 PM
Hi Steve,welcome to the forum.
Air in system, either leaking in via expansion vessel perforated bladder ir diaphragm or incorrect precharge.
The other air ingress points will be the mechanical fittings that joint the pipework together. Even when under positive pressure, localised -ve pressure points can be created due to localised venturis within fittings/ pipework of varying cross section.
I saw how an application of silicone sealant applied to the outside of s dry compression fitting, stopped air ingrees into a pressurised stator water system. Bodgeneering, yes, but it proved a point. The goo was cleaned up, a smear left in place ro seal ingress. Until properly rectified and next short shutdown.

The satisfactory running period from 2012 - 2017 suggests to me that your EV needs investigating first
Philip R


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: merkland on October 14, 2018, 11:58:18 AM
Steve,
Going by your description it looks as if the pump impeller is stuck "info/control panel showed the pump working.  However, inspection of the installation in the roof space there was absolutely no heat transfer to the cylinder.  The pump did not seem to be operating, no noise or vibration.  The body of the pump was very hot to the touch." The pump is powered up but because the impeller is stuck it cannot pump but just heats up. Some pumps have a plug which when removed allow you to turn the impeller with a screwdriver, if yours is this type you may be able to check whether the impeller is stuck and possibly free it otherwise you will have to remove the pump and dismantle to free the impeller - a simple job if you have an isolating valve either side of the pump!
merkland.


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: kristen on October 14, 2018, 12:26:32 PM
I have a similar depressing story of a solar thermal system constantly filling with air.............

Me too, although not as bad as that.

In my case some air gets in, for a while (months maybe) the pump manages, and whilst the temperature is not too hot ... but midday, Summertime, perhaps higher temperature = more expansion of the air that is in there? there is no circulation. Temperature rises and then the system shuts off the pump. In the evening it does manage some heat-production again. Eventually there is enough air that nothing works ... all I get is temperature-rise.

Not sure about sprayer-pump to fix it, my Solar Thermal guy has a vigorous pump which he uses to force fluid around, discharge into a large bucket and recirculate, to evacuate all air.  But there must be some sort of pin-hole or somesuch ... I have two separate thermal solar (DHW and Pool) and over the decade I've had the first, and the 5 years the second, they have both needed maintenance from time to time.

I wouldn't do Solar Thermal again, I would install PV + Heat Pump.  But Heat Pump for DHW is quite a "temperature lift" of course ...

Heat Pump would mean I could run that off mains, instead of PV, if I wanted to or, if sufficient hot water, could turn Heat Pump off and just use the excess PV in the house, so more flexibility. Also, my perception is that Heat pump = less maintenance.

I read my Solar Thermal controller's "heat-output" value each week (along with reading Electricity and Water meter, and the PV) and use that to give me early warning that production is less than expected (or in case of Water / Electricity that consumption is more than expected :) )


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: desperate on October 14, 2018, 02:57:23 PM
Hi Kristen, and Richard,

have you 100% ruled out a leak across the diaphragm of the EV? if you have air constantly getting into a pressurised system it's hard to see where else it is coming from. In both cases does your guage pressure in the loop stay constant? or does it slowly drop?  PhilipR is correct that air can get into a pressurised system from the atmosphere but only if the difference is pretty small.

Desp


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: kristen on October 14, 2018, 05:02:44 PM
In my case works fine for a year or two, then needs maintenance. Currently the DHW system is fine, but needed maintenance a 12 - 18 months ago. The pool system is, again, needing service.  My father-in-law had a single vacuum-tube system installed same time as mine, for DHW, 10 years ago, and has never had a problem with it ...


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: Tinbum on October 14, 2018, 06:15:57 PM
Mine has been great for about 5 years but this year it has been loosing pressure and stagnating. I eventually traced it to a leak in the header for the tubes. As I'm going to be re jigging the whole system soon I opted for leak sealant that has solved it.

The cause:

It's always had a minuscule leak on it and I think i didn't keep my eye on it enough and it lost too much pressure and stagnated. I think the elevated temperature then caused the leak on the header.


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: DonL on October 14, 2018, 10:39:36 PM
Just for balance, my system is now over 11 years old and has never missed a beat - original installation, no repairs. I had a service a couple of times in the early years and since then it hasn't even had a top up. In terms of heating water and decreasing CO2 emmissions it is highly effective and also very satisfying to own.
Sorry to sound smug and this will probably cause it to break down tomorrow; but I wouldn't like people to be put off the technology by giving too negative an  impression.
Don


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: desperate on June 29, 2019, 10:30:46 PM
Just to round this topic off, I did diagnose and sort this system after visiting Mr Locke. It was a classic case of a fairly tidy install but no provision to properly bleed the pump, it had an auto air bleed on the roof which frankly in my opinion is a waste of time and a fault liability. The air had caused the bearings to fail and then it all stagnated.

We binned the old pump and replaced it, cut a tee with a decent upstand and gate valve on top as close to the pump as possible into the pipework, applied the trusty garden sprayer and so far it is working fine.

In thirty years and more of messing around with these systems I would say more than 75% of problems are caused by air locking and being unable to purge properly.

 Don't f**k about with a pump station, put the pump in a vertical 60cm long piece of 22mm pipe with a gate valve at the top, tee off just above the pump to the NRV and on to the panels, then you can guarantee there is no air in the pump and all should be well.

Desp


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: kristen on July 03, 2019, 10:52:15 AM
My installer has a pump and a "big bucket" that he hooks up to the loop and vigorously circulates it to purge any air.  If I have understood correctly this is to force any air tapped anywhere (e.g. a slight down-up-down section of pipe) around the system until it ends up escaping from his Big Bucket (flow taken from bucket, return [including any air] discharges into bucket)

I don't know if this is going to actually purge anything that would not also be achieved by Garden Sprayer method? or is that just to pressurise the system?


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: Pile-o-stone on July 03, 2019, 11:29:16 AM
I'd cut your losses and fit PV with an iboost type diverter to your immersion heater. Fit and forget. No leaks, no stagnation, no freezing, no pumps breaking down. Plus when you have a tank full of hot water at noon on a sunny day, you can still use the energy your panels are producing.

As I said on an earlier post, I can understand people maintaining old cars, but sticking with antiquated heating systems?


Title: Re: FAULTY NAVITRON SOLAR THERMAL INSTALLATION - STICK OR TWIST?
Post by: desperate on July 03, 2019, 07:58:31 PM
My installer has a pump and a "big bucket" that he hooks up to the loop and vigorously circulates it to purge any air.  If I have understood correctly this is to force any air tapped anywhere (e.g. a slight down-up-down section of pipe) around the system until it ends up escaping from his Big Bucket (flow taken from bucket, return [including any air] discharges into bucket)

I don't know if this is going to actually purge anything that would not also be achieved by Garden Sprayer method? or is that just to pressurise the system?

Your installers big bucket and pump will certainly shove the fluid around the system much faster than normal, so it would be better at picking up trapped air and purging it into the bucket than a hand pumped sprayer. Air bubbles though have a habit of hiding away only to emerge later and end up in the pump, it takes a very small amount of air to completely stop the pump working.

In view of that it is very important  to install a reliable method of bleeding the air out of the pump and adjacent pipework and being able to trap it to be bled as needed. If you can ensure that the pump is fully bled it will be quite capable of shifting quite large air locks around the system, if they can be encouraged to land in an upstand above the pump and then bled away it is a fairly easy operation to use the system pump itself to purge the air.  The system refered to earlier had only an auto bleed on the roof which is going to be useless at ensuring the pump is free of air.

Desp