TR0301 fault?

[proxima]

Third time lucky posting this, so I'll be very brief.

I have a system controlled by a TR0301 (Steca?)

It's supposed to kick in when the panel is 8K (same as 8C?) warmer than the tank, and stop pumping when the difference falls to 4K (or the target temp is reached).

It mostly works, apart from the 8K/4K temp difference. Instead, it seems to switch on and off very rapidly while the temperature is 4K different, i.e. while the panel is first warming up in the morning. Sometimes the switching on/off is happening every second or two, which is going to break the pump sooner or later.

Is this a fault? There are no fault indications, and the rest of the system seems to work fine.

Any ideas?

Thanks.

[Mike90250]

If you posted a link to the manual, I might look at the logic they use...

[proxima]

Manual

Thanks - manual is here: http://www.stecasolar.com/index.php?Steca_TR_0301_en

Another 'guide' here: http://www.reuk.co.uk/Steca-TR-0301-...Controller.htm

They both talk about the 8K(C?) difference being when it starts, and 4K when it stops - which makes sense. But this morning it seemed to be using 4C for both - and with the inside and outside readings both fluctuating up/down a degree every second or two, that was causing a lot of switching of the pump.

Of course, as soon as the panel gets more than 4C warmer than the tank, it just stays on and works fine. Likewise when it's cold at the panel, it switches off no problem. It's just the 'in between' when it's around 4C warmer at the panel, that it does a lot of switch work...

[russ]

Degrees K have to mean Kelvin - I have no idea why they would use that though as the unusual term just causes confusion 1

[Naptown]

The last one we had a problem similar to that was with a Resol controller. It was short cycling (turning on and off rapidly)
This was on a new installation and it turned out that the collector plumbing got reversed somehow during the pipe run and the collector was plumbed backwards. (the supply feeding the top of the panels and the return coming from bottom.
Check this if this is a new installation.

[Mike90250]

I was wondering if there was a way to adjust hysteresis in the controller, there is not. Have you checked for air bubbles ? the right mode for your system ?

[proxima]

Yes, it's definitely the hysteresis that's wrong - not doing what the manual says it should. I'll keep an eye on it and see if it always does it or not, but I may be forced to manually override it 'off' until the temperature is high enough otherwise.

Thanks for your help anyway.

[LucMan]

Is the collector sensor installed in a well of the outlet header? Or strapped to the outlet pipe? Was thermal paste used when installed? If strapped to the outlet pipe some insulation wrap around the sensor and pipe may help.
Check your flow rate through the panels, it should be close to the manufacturers specified flow rate.

[tarletontim]

I known this is a long shot being about 5 years after the original post, but did you ever resolve the fault with your TR0301. I also have one that appears to have exactly the same fault?

[J.P.M.]

I known this is a long shot being about 5 years after the original post, but did you ever resolve the fault with your TR0301. I also have one that appears to have exactly the same fault?

Check out the insulation around the sensors particularly the outside (collector) sensor per LucMan's questions/comments. Without adequate insulation around them, the sensors will think the fluid temps are different and respond accordingly. For the outside (collector) sensor, use waterproof insulation, like Armaflex. Make sure it's wrapped/protected from sunlight with something like aluminum tape.

[tarletontim]

Thanks for the reply, i think i've worked it out, the tr0301 has a hidden menu which allows you to adjust the temperature difference at which the pump goes on and off. Mine was on at 4 degrees difference and off at 2 degrees. I've adjusted it to 8 and 4 like the manual says which had slowed the switching alot.