Solar Hot Water - mystery nocturnal activity

[msd123]

There is a solar h/w system installed at my house (it was put in about 10 years ago, before we bought the place). Vacuum tubes on the roof, Vaillant Auromatic 560 controller. The solar heat is routed first choice to the h/w tank and when that reaches the target temp it is diverted to a secondary heat exchanger for a swimming pool. It all seems to work pretty well, except for one thing. Sometimes, between 11pm and midnight, I hear the system operating (i.e. the same noises it makes during the day, when its working normally). The LCD panel on the controller shows the same flashing symbol as it does during a hot day to indicate heat transfer in progress. It doesn't happen every night, and it never happens after midnight. Is this some sort of maintenance routine ? How can I stop it ?

 

[Johntheo5]

Can you post a screenshot of the screen when this occurs.
Under normal operation, circ pump will only start if the collector temperature is 7C/10C > than the store temperature and stop when the collector temperature is 3C > than the store temperature. The circ pump will also start, but only for 5secs if there has been no solar output in the preceding 24 hours and in some, the circ pump will run if the collector temperature falls below say 1.3C to 3C and stop when the collector temperature rises ~ 3C higher (collector frost protection, if enabled).

 

[msd123]

Thanks for the reply. Last night there was no activity - total silence. I'll check again tonight. One thing I noticed is that there is a setup parameter in the installation manual (section 6.1) called "KOLT" (collector type). The permissible values are 1 = flat collector or 2 = tube collector. The default is 1, and that is whats set, but the collectors are actually tubes, so the setting should be 2. Is this parameter acted on ?

 

[Johntheo5]

Collector type should be set to 2.

Maybe check out anti-legionella parameters (page 34), factory setting defaults to off and also check reheat function.

 

[msd123]

Thanks - I will change it to 2.
The legionella settings are at default.
The reheating function is in "constant standby mode" (i.e. sun symbol on the LCD panel) but I have the gas boiler h/w function turned off anyway (at the boiler) . The reheating delay function is defaulted (deactivated).

 

[Johntheo5]

Is/can "no reheating" be programmed via reheating times or whatever to be inactive 24/7?.

 

[msd123]

I could put it into "moon" mode, which (i think) means it would never call on the gas boiler, but that'd mean relying on nothing but the sun for h/w which won't be tenable for long even here in sunny Dorset .
It was quiet again last night so no screenshot yet, but I looked at the panel the last 2 times it happened and both times the "solar yield" symbol was flashing which surely wouldnt be happening if it was trying to invoke the auxiliary heat source (gas boiler) ?

 

[Johntheo5]

If operating correctly its hard to imagine the differential reaching 7C or whatever, maybe your swimming pool is getting very cold at 2300 hrs on certain nights!, my fairly basic Lago SG2 controller also has Collector enable temperature & Collector disable temperature settings which I set to 30C/25C when I self installed my F.Plate array 12 years ago, I have seen the differential now and then reaching very close to the cut in point (at night if a large vol of HW is drawn off) but the collector enable setting prevents any "solar yield". maybe just check that the probes are pushed fully home in their pockets, the PT1000 probes, if installed, are very reliable and I have never had a failure in the 12 years.

 

[msd123]

The default timers are in operation for the circulating pump - i.e. it goes off at 10pm. So, even if the pool was freezing and the roof was hot, the pump shouldnt come on after 10. Maybe its not the pump I'm hearing ? It certainly sounds the same as it does during the day. I'll keep trying to get a screenshot next time it happens anyway.

 

[Johntheo5]

Hydraulic Plan 1 shows ZP as a circulation pump which provides boosted HW to shower etc and maybe also acts as a secondary circulator, a legionella protection pump, Leg/Byp, is also shown. the circulation pump associated with solar yield is called Koll-P, solar circuit pump 1, I wonder if this pump is also inhibited outside the timed period as it seems illogical to time inhibit a pump associated with the collector. You can easily check it by changing the time period while its actually running in the day time.

 

[msd123]

Well spotted ! I've been reading the manual assuming all 'circulation pump' was an alternative term for the solar pump - as I can only see one pump in the cupboard. It does say "If you only have one collector field connected, a circulation pump can be connected to the controller" so I probably don't have one. It also says
"Set up the time program so that the circulation pump only operates at times when you expect a supply of hot water demand will be needed. Otherwise the circulation pump operates unnecessarily and inadvertently cools down the cylinder." so you're right its not the solar pump.

So the evidence points to the solar pump being triggered late at night. This can't be caused by a normal temperature differential as weather conditions haven't varied much over the last week, yet the noise happened 2 nights in a row and since then silence. The fact that it has never been known to happen after midnight is also now odd, as this can't be explained away by invoking a timer.

 

[Johntheo5]

Maybe around 2300hrs check sensor readings kol1 (collector sensor1), SP2 (cylinder sensor2) and the swimming pool sensor, where ever that is. Also check the differential settings for starting/stopping the solar circuit pump. Also see below.

4.13 Solar pump kick (tube collector function)
Depending on the design of the tube collectors, the
measured value obtained for the purposes of temperature
recording may be subject to a time delay. This can
be reduced via the tube collector function.
Measured value of collector temperature with active
tube collector function:
The solar pump is switched on for 15 s (solar pump kick)
once the temperature at the collector sensor has risen
by 2 °C. The heated solar fluid is thereby transported
more quickly to the measuring point.
If the temperature difference between the collector and
cylinder temperature is at least 10 °C) the solar pump
runs for as long as is necessary to heat the cylinder up
(differential control). If two solar circuits are connected,
the tube collector function is activated for both solar
circuits.

 

[msd123]

Mystery solved !
The noise was present last night at 11pm and the readings were :

SP2 - 30
SP3 - 24
KOL1 - 28

so stored solar heat was being sent, not to the tank, but to the pool (until the KOL1-SP3 difference dropped to 3 anyway) ! This is undesirable since
1) no-one uses the pool at night
2) the pool pump goes off at 6pm so the solar heat is just going to a stationary section of water in the pipe
3) it causes noise (thats where I came in)

So how to stop it ? As I now know, there are no timers for the solar pump, but I could set different values for the activation/deactivation differences for "cylinder 2" (i.e. the pool). If I change "dON2" from 7 to 10 (say) then that wouldn't interfere with daytime operation (when the actual difference is always going to be bigger than that - right now at 11:42 a.m. KOL1 is 63 and SP3 is just 19) and it would ensure that a nighttime KOL1 value of 28 would only trigger the solar pump if SP3 dropped to 18. I'm inclined to increase "dOFF2" from 3 to 6 at the same time, though the reasoning for this is flaky.

Thanks again to Johntheo5 for the assistance

ps
As for the "tube collector function" - I've read that paragraph 5 times and I still have no idea what its on about nor where I can set it .

 

[Johntheo5]

I'm surprised that the collector temperature was 28c at 2300hrs, generally speaking, the collector temperature will reflect the ambient temperature once activity has ceased for a few hours and will fall gradually, I have seen high temperatures in collectors where the NR valve has failed which is installed in all systems to prevent reverse convection circulation from the cylinder, of course evacuated tubes will retain temperatures far longer than F.plates because of their vacuum. The pump restarted when the dT was 4C, (28-24), the 4C dT shouldn't have done this as it has to reach 7C to do so?. It's possible that the tube collector function did this although it states that it will only run the pump for 15secs on detecting a collector temperature rise of 2C and if the dT is < 10C. If you have collector temperature trending you might see what this was doing leading up to 2300hrs, if not, take a few reading tonight, and see if the temperature is rising/falling, note the ambient as well.

The collector kick function can normally be turned off like mine, or be enabled via timer, the kick time period and pause time between kicks can be set, if the collector temperature rises by 0.5C within 1 min, then the pump stops before the kick time period elapses. I have mine disabled.

 

[msd123]

I should've made it clear that the noise didn't start at 11pm - that's just when I noticed it. My assumption is that it started earlier - when the DT was 7 degrees - and the DT had fallen to 4 by the time I came on the scene.

Do you know where the kick parameters can be set ? Can't see any references in the manual.