Pump overrun is killing my heating!

[milleniumaire]

It should be easy enough to pick up a N&E somewhere, I wonder what logic the boiler uses to determine if any of the zone valves are open if it doesn't get a input back from them?. Why do you say ("and the DHW, which isn't applicable in my case)", don't you need a feed back from the orange wire on that Mot.valve as well.?

Of course, you are correct. For some reason I was thinking the DHW symbol was for a circulation pump, but it is obviously for the cylinder zone valve, so yes, the live from R6 would also need to be included.

Couldn't resist taking the front off the VR 71 wiring centre to see what the engineer had done with the orange wires. He' has simply cut them off as only the brown, blue and green/yellow wires are connected for the Honeywell zone valves. Also, the two UFH thermal valves only have brown and blue wires, plus the cable from a more remote zone valve is only 3 core, even though the zone valve itself has more cores than this (they have also been cut off).

So, it would appear the instructions to connect up the orange wires won't work! What is the difference between the orange wire and brown live wire? Is it that the orange is switched live (whenever the brown is live)? In which case it looks like it can't be done for my setup due to the UFH valves not having a switched live wire!

 

[ShaunCorbs]

Yes when port valves are open the oranges become live on 2 ports

 

[milleniumaire]

Yes when port valves are open the oranges become live on 2 ports

So somehow, he would need to connect the brown cables to the live on the pump, but this doesn't seem to be possible without each zone valve causing all the others to open i.e. if all the live connections are connected together to the pump live!

Sounds like maybe an electrician and some sort of device that mimics the "switch live" functionality for the two UFH thermal valves would be required to achieve this, rather than my heating engineer?

Or, as I think you were alluding to in your earlier message, is there a relay or something on the wiring centre that could be used for the pump? If so, I would have thought Vaillant would have mentioned it.

 

[ShaunCorbs]

Pump normally is connected to the oranges I think basically your turning your system into an s plan

 

[John.g]

No, not the brown, the orange wires, are you sure those actuators had orange wires as I think you could, in some cases buy them with no end switches/orange wires.
Why don't you get back to them and ask them can they give you any contact on the boiler from its own circ pump, all you need then is a external relay to switch your UPS pump, there has to be a switched wire to the internal pump in the boiler, surely it should be easy enough to wire into this??, even though the UPS will also run then if/with pump overrun it doesn't matter as it wont deadhead and will just circulate water in its own half of the LLH.

 

[ShaunCorbs]

Might be worth emailing Kirby

https://mobile.twitter.com/2starkirbs?lang=en

 

[milleniumaire]

No, not the brown, the orange wires, are you sure those actuators had orange wires as I think you could, in some cases buy them with no end switches/orange wires.
Why don't you get back to them and ask them can they give you any contact on the boiler from its own circ pump, all you need then is a external relay to switch your UPS pump, there has to be a switched wire to the internal pump in the boiler, surely it should be easy enough to wire into this??, even though the UPS will also run then if/with pump overrun it doesn't matter as it wont deadhead and will just circulate water in its own half of the LLH.

The two Honeywell zone valves have orange wires, but both are cut back and only brown, blue and green/yellow are used.
The two thermal valves only have brown and blue, not sure how these could be connected up to the pump!

I have sent an email to Vaillant asking them the question, so will have to wait a few days for the reply, but I'm guessing some sort of relay switch will be required to "simulate" the switched live for the thermal valves.

I'm sure if there was a connection on the boiler or the wiring centre that could be used to control the pump, whenever any of the zones were switched on, then Vaillant would have mentioned this, or at least you would have hoped they would!

 

[milleniumaire]

....even though the UPS will also run then if/with pump overrun it doesn't matter as it wont deadhead and will just circulate water in its own half of the LLH.

This would be my preference anyway, for the external system pump to be on during overrun i.e. at ANY time the internal pump is running. This way, you would expect the water in the boiler circuit would cool down faster, plus the hot water is being put to use either heating the cylinder or the heating.

In the early days of my contact with Vaillant they issued the following statement:

"The pump on the secondary circuit only needs to operate When any of the valves are open, and does not require a pump overrun after the demand. Only the primary side requires the overrun (the Boiler side) this is to dissipate the excess heat in the heat exchanger inside the boiler after the burn process is completes and demand is no longer required."

I'm a little confused about this statement as I'm sure when the boiler was in overrun mode, the zone valves were open, which suggests that the external pump would be on if it was wired up to them. I'll need to try to catch the boiler in overrun mode to confirm the valves are definitely open.

As I don't have a switched live wire on the two thermal valves used for the UFH, I obviously need some mechanism to switch live for these. I did wonder about the other connections on the VR 71; R7/8, R9/1, R11/12 and R13. These aren't currently being used and in the schema diagram they show motorised mixer valves (for each zone) being connected to them. Because the schema diagram also shows the use of zone pumps, wouldn't you therefore expect the mixer valves and the pumps to be switched on or off at the same time? If so, doesn't this suggest that R7/R8 will be live when R1 is live etc, so couldn't these therefore be used to wire up the pump?

 

[EvilDrPorkChop]

Personally I think it needs to be connected the the boiler, this is how I've done it in all the systems I've done with additional pumps on Vaillants.

I think their first answer was correct.

 

[milleniumaire]

Personally I think it needs to be connected the the boiler, this is how I've done it in all the systems I've done with additional pumps on Vaillants.

I think their first answer was correct.

Can you please confirm how you usually connect it up? Is it the same as my setup:
- Pump is wired into Rel 1 on the VR 40 and d.27 is set to 5

Due to the value of 5, the external pump only works when the burner is on, so it doesn't work in pump overrun, or any other mode where the internal boiler pump is working but the burner is off.

Based on their suggestion to wire it up to the zone valves, I would assume this would cause the pump to work whenever any of the zones are open, which I believe would include pump overrun etc. If not, I wonder what the differences would be.