Nibe 1145/1245 water temp sensor(BT7)

KCross · 12-11-2014 04:38PM #1

Hi
Hopefully a quick simple answer to this one from one of the service engineers out there!

I have a Nibe 1145 + a Nibe VPB300 hot water tank.

I note in the Info menu there are two hot water temperatures. The BT6(hot water charging) and BT7(hot water top).

In my case the BT7 doesnt display anything. Its just "--". It has been this way since day one (installed in 2012)

So, the question is.... is the BT7 something that has to be ordered/installed/commissioned separately when the system is put in or is it in every one of these HP's by default and its likely that it just hasnt been connected in my case?

If its just a case of it hasnt been connected, is that something that my installer should take responsibility for or would I be expetced to pay for it now?

thanks
KCross

soundskin · 13-11-2014 05:30PM

Kcross,

You only need BT6, this is the sensor that will be looked at by the heat pump when deciding to come on or not for hot water, usually located 1/3 up from the base of the tank.

BT7 would have to be installed at the towards top of your tank and once it's wired into the correct location then will appear as a temperature reading. It has no function other than to tell you the temperature at the top of the tank. There is a pocket for it on the VPB. It will not have any influence on the running of the heat pump. Nice to have it but you can live without it. All the older Nibes with external tanks had only one sensor for hot water (expect VPAS but that was for another reason)

KCross · 13-11-2014 05:42PM

soundkin
Thanks. The only outstanding question I have is should the "nice to have" be there anyway?
i.e. was this an oversight on the part of the installer or is it something that has to be specifically ordered and installed.

I note that some users do have it. Do you know if the BT7 sensor is in the VPB by default when it leaves the factory and its just a matter of connecting it back to the main unit or does the supplier/installer have to order the BT7 sensor as an extra?

Is there much involved in connecting it up? I think it would be useful.

soundskin · 05-12-2014 10:17AM

The BT7 sensor ins't in place in the VPB when it laves factory, must be installed onsite.

Very little work in connecting it up. Sensor into pocket, connected to 2 core wire, then terminate wire in heat pump along with the rest of the sensors. Details in your installation manual, also in wiring spec.

Won't make any difference to running of your heat pump but will tell you the temp higher up your tank, but you'll have a fair idea of that by the water that comes out your tap.

KCross · 05-12-2014 10:37AM

soundskin wrote: »

The BT7 sensor ins't in place in the VPB when it laves factory, must be installed onsite.

Very little work in connecting it up. Sensor into pocket, connected to 2 core wire, then terminate wire in heat pump along with the rest of the sensors. Details in your installation manual, also in wiring spec.

Won't make any difference to running of your heat pump but will tell you the temp higher up your tank, but you'll have a fair idea of that by the water that comes out your tap.

Thanks soundskin. I understand it wont affect the running of it but I would like to have it as I have noticed a few times where the temp reading I have at the moment could give the same reading on two days but the temp at the tap is different particularly if some water has been drawn off already.
I think having a 2nd temp for higher up on the tank would be useful to confirm how much actual hot water is left. Its not a big deal, as you said, a nice to have.

thanks again.

KCross · 26-12-2014 04:59PM

I got the sensor and have it installed and working. Took less than an hour to figure out and do it and it only cost €10

Just for the sake of any others that might want to do it….

The sensor has about 2ft of cable hanging off it so you need some 2-core wire to extend it from the tank to the control unit of the HP.

When you pull the front cover off the VPB300 there is a piece of hard insulation at the top that can be pulled out which reveals the slot that the sensor goes into. Its a small tube on the top of the tank. The tube doesn't go into the tank. Its across the top of the tank so its reading the temp on the outside of the tank which I suppose is the same as the temp of the water at the top of the tank.

I joined the sensor and the extension and ran the extension down the front of the insulation and across to the HP into the control panel at the front of the HP.

Looking at the wiring diagram you need to look for the AA3 input card which is labelled, so easy enough to find and then find the X6 input block on the card… again the circuit board is clearly labelled so easy to find.

Within the X6 input block you pick a spare pair of slots in the 9-18 range. All mine were free so I just put the two wires into slots 9 and 10.

There is only one other step and thats to map those two ports to the BT7 value in the menu. That is done via the service menu 5.4 where you change one of the AUX values(1-5) to BT7. I used the first two slots (9/10) in the input circuit so thats for AUX1 and I simply set that to BT7 and your done. The install manual has info on this with screenshots of the menus etc.

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Obviously as you draw water off, the hot water top value (BT7) won't drop much but the water charging value(BT6) will drop as it is 2/3rd's the way down the tank. I've noticed that after a few showers, baths etc the BT6 value could be as low as 12C and BT7 could still be at 40C showing that there is still hot water there. I didnt have this info before. I would look at the screen and it would show hot water at 12C, which wouldnt be a pleasant shower so I'm happy I put it in as I might have unnecessarily boosted it before.

Also, as a consequence of connecting BT7 the water temp on the main display screen is now the BT7 temp and not the BT6 temp. If I now want to see BT6 I have to go into the menu to see it. That's OK with me.

Nibe 1145/1245 water temp sensor(BT7)

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