Pump overrun is killing my heating!

[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.

 

[John.g]

If you use the "orange wire" method as suggested then you must fit relays to the UFH systems to pick up if they are running and also to any zone valve with chopped off orange wires, if too short, one relay might do the wole lotl.
Re your own suggestion above, to prove/disprove it, connect a test light across one of those relays and ensure it stays lit during both normal boiler burner on and off. For pump overrun, observe it while you switch off the last heating circuit, the boiler circ pump should/might overrun and the relay test light should stay on until pump overrun complete.

 

[EvilDrPorkChop]

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.

According to my Vaillant instructions;

d.27 Switching accessory relay 1 in the accessory module 1 = Circulation pump (default) 2 = Ext. pump 3 = Storage charging pump 4 = Flue gas flap/extractor hood 5 = External gas valve 6 = External error message

Why is it set on 5?

In my configurations I would always config to External Pump, so 2.

 

[milleniumaire]

According to my Vaillant instructions;

d.27 Switching accessory relay 1 in the accessory module 1 = Circulation pump (default) 2 = Ext. pump 3 = Storage charging pump 4 = Flue gas flap/extractor hood 5 = External gas valve 6 = External error message

Why is it set on 5?

In my configurations I would always config to External Pump, so 2.

It is set to 5 because Vaillant told my heating engineer to set it to 5! Apparently a value of 5 will cause the pump to run whenever the burner is on. Vaillant seem to be backtracking on the use of the VR 40 and I get the impression they are performing some in-house investigation to try to determine who gave the advice! I assume they record all their telephone calls.

Vaillant told me that if it is set to 2, then the pump will NOT run for hot water demand, which is no good for my system. The pump needs to run for ANY demand, heating or hot water, with DHW taking priority, as all flows (cylinder and heating zones) are from the pump.

I'm sure there are situations that would warrant two external pumps; one for the heating and one for the hot water cylinder, but it would be complete overkill for mine, especially as the cylinder is 1m from the boiler and it is DHW priority, so even if there were 2 pumps fitted, they would only ever work one at a time!

 

[EvilDrPorkChop]

It is set to 5 because Vaillant told my heating engineer to set it to 5! Apparently a value of 5 will cause the pump to run whenever the burner is on. Vaillant seem to be backtracking on the use of the VR 40 and I get the impression they are performing some in-house investigation to try to determine who gave the advice! I assume they record all their telephone calls.

Vaillant told me that if it is set to 2, then the pump will NOT run for hot water demand, which is no good for my system. The pump needs to run for ANY demand, heating or hot water, with DHW taking priority, as all flows (cylinder and heating zones) are from the pump.

I'm sure there are situations that would warrant two external pumps; one for the heating and one for the hot water cylinder, but it would be complete overkill for mine, especially as the cylinder is 1m from the boiler and it is DHW priority, so even if there were 2 pumps fitted, they would only ever work one at a time!

Have you tried setting it to 2 and actually testing it?

In my experience I'm sure it runs whenever there is a Demand.

 

[milleniumaire]

Have you tried setting it to 2 and actually testing it?

In my experience I'm sure it runs whenever there is a Demand.

I haven't, mainly because I assumed Vaillant technical knew what they were talking about when they said:

"Using the VR40 to run the secondary circuit pump run as a heating charge or a DHW cylinder charge Pump not both

Switching of relay 2 on the VR 40 "2 in 7" multi-functional module Options

1 = Circulation pump - DHW secondary Circulation pump

2 = External pump – Heating Charge pump

3 = Cylinder charging pump – DHW Charge Pump

4 = Extractor hood

5 = External solenoid valve

6 = External fault message"

I may just give it a try though if others, like yourself, are setting d.27 to 2 and it works for both heating and DHW.

 

[EvilDrPorkChop]

I haven't, mainly because I assumed Vaillant technical knew what they were talking about when they said:

"Using the VR40 to run the secondary circuit pump run as a heating charge or a DHW cylinder charge Pump not both

Switching of relay 2 on the VR 40 "2 in 7" multi-functional module Options

1 = Circulation pump - DHW secondary Circulation pump

2 = External pump – Heating Charge pump

3 = Cylinder charging pump – DHW Charge Pump

4 = Extractor hood

5 = External solenoid valve

6 = External fault message"

I may just give it a try though if others, like yourself, are setting d.27 to 2 and it works for both heating and DHW.

According to the instructions of the actual boiler, it states 1 as Circulation Pump, and 2 as External Pump. In my experience in fitting them, the boiler states this too when configing them up. Don't trust Vaillant technical, they hardly know out about their own boilers never mind wiring them

Try 2, there's no harm done. You can just change it back

 

[milleniumaire]

According to the instructions of the actual boiler, it states 1 as Circulation Pump, and 2 as External Pump. In my experience in fitting them, the boiler states this too when configing them up. Don't trust Vaillant technical, they hardly know out about their own boilers never mind wiring them

Try 2, there's no harm done. You can just change it back

So, I set d.27 to 2 this morning.

The system was in heat mode and the pump was on. This continued. I then turned up the temp of the water from 55 to 65 and it immediate switched to DHW mode. The external pump continued to run. It took around 15-20 mins to heat up to 65, then switched back to heat mode. I didn't see any pump overrunning so while this setting is obviously working for hot water as well as heating (contrary to what Vaillant suggested), I'm currently not sure if there are any situations when the external pump will run now, when it didn't before i.e. is there any difference between a setting of 2 or 5 in terms of when the pump runs.

I'll keep an eye on it throughout the day.

I'm assuming just changing the setting is enough? The boiler doesn't need to be reset to accept the new setting by power cycling it or anything?

 

[John.g]

D.27 5 is IMO only designed as a safety device, ie shuts a outside gas isolation valve when the burner shuts down or something similar, that's why the ext pump was only running with the burner on. D.27 2 works exactly as one would (now) expect, it runs a additional circ pump, period.
If you wish to check for pump overrun just decrease the wall stat setting (if on CH) until the boiler shuts down, it should then do a pump overrun, also check if it keeps the zone valve opened otherwise you may have to consider installing a ABV or a normally open mot valve in the secondary circuit.

 

[milleniumaire]

D.27 5 is IMO only designed as a safety device, ie shuts a outside gas isolation valve when the burner shuts down or something similar, that's why the ext pump was only running with the burner on. D.27 2 works exactly as one would (now) expect, it runs a additional circ pump, period.
If you wish to check for pump overrun just decrease the wall stat setting (if on CH) until the boiler shuts down, it should then do a pump overrun.

Thanks for the info on how to force pump overrun, you were spot on. As soon as I turned the temperature down for each of the heating zones, the boiler showed S.7 - pump overrun and the external system pump continued to run. Result!!!!

I think that just about solves all my issues and the external pump seems to be working at the same time as the internal boiler pump.

My heating engineer is visiting on the 25th to service the boiler so I'll have a chat with him to confirm who decided on setting d.27 to 5. I've always assumed it was as a result of advice from Vaillant as I know he was on the phone to them 2 or 3 times during the upgrade and specifically for info on wiring up the new pump. So maybe the advice to use the VR 40 was correct and the current advice to instead wire up the pump to the VR 41 is tosh! I'll play it out with Vaillant technical support and see where it goes as it appears they still think using the VR 40 was the wrong thing to do!

 

[John.g]

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.

 

[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 😳