TDC3 Variant for simple heat dump with new software?

[Grimsby Ranger]

Hi All

Apologies for another thread on heat dumps but I'm getting a bit confused (not hard I know  )

Just about completed my Navitron install and I'm trying to set up the heat dump, I thought it would be easy after reading threads that said use HV2. That must have been for old software as this is for a thermostat setting, there is no option for the hysteresis to be set as a negative value and there is times to set up for the thermostat. All I need to do is move the divertor valve once a temperature on S2 is reached and send the flow through a dump rad, I'd like a bit of flexibility on the temperature the heat dump starts and stops if possible for variation on winter and summer use.

I've set the TDC3 to HV9 at the moment but can't see what tells the heat dump to stop and revert back to charging the store again. I'm also a little confused over the 'load time' and 'increase' settings. I was wondering if there was an easier variant to use?

My settings at the moment are:
TMin S1 20
TMax S2 80
TMax S3 99
DTR1 10/3
Sensor Priority S2
Priority Temp 65
Load time 90 mins
Increase 1deg/min

My thoughts are that the store would warm until 65 deg then the heat dump would start, when would the heat dump stop again though? Thanks in advance for your help and advice.

Kerry

[KLD]

Hi Kerri,

HV9 might be a way to get around the missing "negative hysteresis" problem. The way the loop is switched back to the cylinder is by firstly defining the cylinder as the "priority" tank. Now, once the temperature at S2 climbs above T_priority, the tank is deemed "full" and relay 2 switches the valve over to "tank 2", ie. your heat dump radiator. The way to switch back is slightly more complex, because you have to assess whether the "full" condition is still met AND whether the panel produces enough heat for re-loading the main tank if it's no longer "full". The way to do this is to every so often ("loading time") stop the solar pump, and watch the temperature rise in the panel (so many degrees per minute, "increase", badly translated from German Steigung, "slope"). The temperature rise gives an approximation of how much heat the panel is harvesting at this moment -- you can't use the temperature difference of panel minus tank because the second tank can be at a lower temp. If it turns out that T_S2 is now below T_priority, AND the temperature increase in the panel is sufficiently large to indicate enough solar power, then you switch back to tank1. I believe there is a secondary loop in the "increase" assessment, so that if it's nearly enough you continue the "increase" measurement for another minute. Easy, isn't it? 

So, I'd try for your system:
TmaxS2 = 85°C
S_priority = S2
T_priority = 80°C
Load time = 10min
increase = well, this needs experimentation !

It'll be a while before you'll have enough sun to test it ...

Klaus

[Grimsby Ranger]

Hi Klaus

Thanks so much for your clear explanation, that has helped massively. Just need to wait until next summer now for a good test of it!

Kerry

[micko]

Hi,

I used this http://www.navitron.org.uk/forum/index.php/topic,10483.0.html

Dont understand it as I'm not too sharp but it works fine.

[Grimsby Ranger]

Hi Micko

Thanks for the link, I'd read that thread (it was one that got me using the variant I am) but with me having (seemingly) newer software and not fully understanding how the heat dump stops thought I'd ask the qestion. Good to know yours works fine though.

Kerry

[micko]

Kerry,
There are pages and pages of heat dump solutions, the TD3/ TD2 are not very user friendly and as you know there is no options to set up a heat dump radiator. If I was fitting again I would not have gone with this type of TDC, I would have done some research in to other makes. There has to be a more user friendly type out there you could set up without a degree in logic

[Grimsby Ranger]

It does seem more complicated than it needs to be, a simple system of valve opens when S2 is at 80deg and closes when it drops to 70deg (or whatever temps are required) can't be too hard to do. A shame most pages on the subject seem to be with the old software version.