Pump overrun is killing my heating!

[milleniumaire]

Might also be worth also checking if it keeps the zone valve opened for the overrun period (otherwise despite what I thought previously) the ext pump will have no pathway for the water, (with/if all zone valves closed), it may not do the ext pump any harm if the overrun is only for a minute or so.

I'm 99% sure the zone valve does stay open during overrun as this is what originally made me question why the external pump wasn't also running. My old system, without the external pump, would have continued to pump water around the cylinder in the morning even when in overrun mode, but the new system wasn't doing that and so the water was only being pumped around the boiler circuit.

It seemed like the system spent a lot of time in overrun mode, which is what I had assumed was causing it to take so long to heat up the hot water in the mornings. Maybe that wasn't the cause and it was due to my son having secret midnight showers and also having the hot water temp set to 65. It still seems "better" that the external pump should be running during overrun.

 

[John.g]

How long is the overrun period now, roughly?
I don't think the secret shower had anything to do with it as there was hardly 250 lires of water that needed to be heated to 65C in the morning and 1 hour should have been more than adequate, also the ext pump even on D.27 5, should have remained running except that the burner cut off due to the boiler minimum output being greater than the heat absorbed by the coil as the cylinder temperature was approaching 65C.

 

[milleniumaire]

How long is the overrun period now, roughly?
I don't think the secret shower had anything to do with it as there was hardly 250 lires of water that needed to be heated to 65C in the morning and 1 hour should have been more than adequate, also the ext pump even on D.27 5, should have remained running except that the burner cut off due to the boiler minimum output being greater than the heat absorbed by the coil as the cylinder temperature was approaching 65C.

The problem was that it was taking the whole of that hour in the morning to heat up the cylinder and therefore the house wasn't being heated, resulting in us getting out of bed to a cold house.

Currently, there's around a 4 degree C temperature drop overnight for the cylinder, which means the boiler doesn't even bother to re-heat the cylinder when it turns on in the morning and therefore spends a full hour heating the house, resulting in it being nice and warm by the time we rise.

When my son had his night time showers, there was a MUCH bigger temperature drop in the hot water (the boiler is off during the night) and therefore a large proportion of that hour in the morning was taken up re-heating the water, rather than heating the house. Plus, heating the water upto 65 deg C takes longer than heating it upto 55 deg C. It all affects the remaining time allocated to heating the house.

Agreed that the setting of d.27 for the external pump probably hasn't made that much difference, but it makes me feel much better knowing it now comes on when the internal boiler pump runs.

I haven't noticed how long the overrun period is, but will investigate.

 

[EvilDrPorkChop]

Wow, have we finally got there? 😂

 

[John.g]

Better late than never!.

 

[Lekan Shanu]

Secondary Circulation pump or “flow pump” as Vaillant refer to it, should be Wired to the orange wires of the two port valves as per the VR71 wiring diagram.
Greys permanent live as usual in S plan.

 

[Timmy D]

Secondary Circulation pump or “flow pump” as Vaillant refer to it, should be Wired to the orange wires of the two port valves as per the VR71 wiring diagram.
Greys permanent live as usual in S plan.

I hope after 6 months he’s got it sorted 😳