Vaillant VRC 400 without Vaillant Cylinder

[richiezander]

Hi

I resently installed a Vaillant 438 with s plan. The customer had an old weather compensation unit with his old boiler and wanted the same set up with his new vaillant. I was recommended to use the VRC 400 from Vaillant themselves. I installed the VRC 400 unit as a room thermostat in the hall. I didn't change the cylinder as it had been replaced not long before the new install.I followed all instructions from Vaillant and installed the VR65 wiring centre and used a honeywell cylinder stat. Everything seemed to working fine.

But now the customer has been back in touch complaining about his hot water. Since the outside temp has increased the flow temp has lowered to around 50 degrees and as the room temp reaches the target temp the flow temp reduces even more down to 35 degrees. So when he has his heating on and his hot water on when it is a warm day and the house is almost to temp the water circulating through the cylinder cools the water down.

Has any one else had problems like this or can anyone explain more about this weather compensation unit.

Thanks

Richie

 

[gas4you]

Have you left the ch and dhw controls on the boiler set to maximum?

The flow temp should increase when the DHW kicks in.

Are you sure you have wired the VR65 correctly with all valves and stats connected to this only and this connected via ebus to the boiler?

I only ever use the VRC 400 plugged into the front of the boiler as this is the only way to get full functionality from it.

As a seperate positioned room stat its functions change slightly, can't remember exactly how at the moment

 

[KITCH10]

Would agree that the wiring needs to be checked.All Valliant timers are Hot water priority to stop the weather compensator interfering with the recovery time of the cylinder.With your set up not sure how the boiler will know your demanding for hot water.Check e-bus is wired to boiler and not the 3,4 switch wires at the boiler.The Vr65 is designed as a Valliant package.Boiler,cylinder controls.The Hot water is usually controlled via a Thermistor in the cylinder directly connected via the vr65 then E-bus to the boiler.

 

[gas4you]

Has the heating curve been set to 2.6 - 2.8?

Has the HW program been set seperately to the CH?

Whats d70 been set to? It is best to leave it factory set at 0.

 

[richiezander]

Have you left the ch and dhw controls on the boiler set to maximum?

The flow temp should increase when the DHW kicks in.

Are you sure you have wired the VR65 correctly with all valves and stats connected to this only and this connected via ebus to the boiler?

I only ever use the VRC 400 plugged into the front of the boiler as this is the only way to get full functionality from it.

As a seperate positioned room stat its functions change slightly, can't remember exactly how at the moment

Yes I have both heating and hot water controls at max.

All wiring is carried out as explained in the VR65 manual. ( Double checked )

When the compensater is used as a room stat i changed installer setting 0 -RT : 2 (factory set at 0) but this what is said in the vrc 400 instructions

Also now found out the hot water boost doesn't work in special functions.

Maybe a faulty wiring station or compensater? or perhaps the honeywell cylinder stat is not compatable?

 

[richiezander]

Would agree that the wiring needs to be checked.All Valliant timers are Hot water priority to stop the weather compensator interfering with the recovery time of the cylinder.With your set up not sure how the boiler will know your demanding for hot water.Check e-bus is wired to boiler and not the 3,4 switch wires at the boiler.The Vr65 is designed as a Valliant package.Boiler,cylinder controls.The Hot water is usually controlled via a Thermistor in the cylinder directly connected via the vr65 then E-bus to the boiler.

I am certain you can use a standard cylinder stat ( have the vr65 wiring diagram infront of me now ) and it is connected to the + and - where is says "cyl"

Have left the link in 3 and 4 in the boiler and all other wiring from vr65, vrc 400 and boiler link in ebus except pump, zone valves and cylinder stat.

 

[richiezander]

Has the heating curve been set to 2.6 - 2.8?

Has the HW program been set seperately to the CH?

Whats d70 been set to? It is best to leave it factory set at 0.

The heating curve is at 2.6 as recommend by Vaillant.

The hw and ch program overlap one another, so they are times when they are on together. When the hw program is on by itself the flow temp is fine ( 80 degrees at max temp )

With this being a open vent convectional boiler d70 is not accessible. Only on combis and system boilers with internal diverter valve you can alter this.

Vaillant techy coming tomorrow hope he has had experience with these compensaters!!

Thanks for all advice and info gas4you and kitch10

 

[gas4you]

Don't agree about d70. System boilers do not have internal DV.

d 70 is telling the VR65 what to do, not the boiler.

If d70 is set to 0 then if HW and CH are on together, then HW takes priority.

d70 is accessible in 2nd level diagnostics only.

 

[gas4you]

Have left the link in 3 and 4 in the boiler

Good that is correct

and all other wiring from vr65, vrc 400 and boiler link in ebus except pump, zone valves and cylinder stat.

Lost me here Are you saying that the zone valves are not only wired to VR65 Or perhaps I am mis-interpreting your post.

 

[richiezander]

Don't agree about d70. System boilers do not have internal DV.

d 70 is telling the VR65 what to do, not the boiler.

If d70 is set to 0 then if HW and CH are on together, then HW takes priority.

d70 is accessible in 2nd level diagnostics only.

I might be getting confused with viessmann boiler with regards to internal DV, but still can't access d.70 in boiler installer menu ( press i and + togeteher ). You mention 2nd level diagostics how do access this menu?

Also in the VR65 instructions it says that d.97 alters the operation of the zone valves, is this similar to d.70?

 

[richiezander]

Have left the link in 3 and 4 in the boiler

Good that is correct

and all other wiring from vr65, vrc 400 and boiler link in ebus except pump, zone valves and cylinder stat.

Lost me here Are you saying that the zone valves are not only wired to VR65 Or perhaps I am mis-interpreting your post.

Sorry all connection are going to the VR65 except pump and external senor which go to the boiler. The honeywell cylinder stat goes to connections cyl + and -, the ch zone valve live neutral earth to connection L,N and E CH and same respectively for HW zone valve finally ebus connection from vrc 400 link with boiler ebus connection. Everything is copied from fig 5.3 in the VR65 manual

 

[richiezander]

Don't agree about d70. System boilers do not have internal DV.

d 70 is telling the VR65 what to do, not the boiler.

If d70 is set to 0 then if HW and CH are on together, then HW takes priority.

d70 is accessible in 2nd level diagnostics only.

I might be getting confused with viessmann boiler with regards to internal DV, but still can't access d.70 in boiler installer menu ( press i and + togeteher ). You mention 2nd level diagostics how do access this menu?

Also in the VR65 instructions it says that d.97 alters the operation of the zone valves, is this similar to d.70?

Sorry just read the installer manual on how to access 2nd diagnostic level.

 

[richiezander]

Thanks Dave have now found second installer menu and changed d.70 to 0. It was on 1. The hot water now heats up on times program when heating is on as well. But the override boost on hot water still doesn't work ( press the F button 4 times ).

Vaillant techy phone in sick so no help from them until next week.

 

[gas4you]

Pretty certain this function will only work if using a Unistor fitted with the VR10 ntc.

 

[KITCH10]

I am sure that d70 is for internal divertor valves only will make no difference to external valves.
If you have connected the cylinder stat to +and- this is for ebus only and will not work.This is for the ntc.
3 and 4 should be linked.
Be carefull with second level diagonostics,there are settings you dont wont to alter.If in doubt i think in the d90s is factory reset.