Is this Wiring Correct?

[pete1875]

Hi Everyone,

Was looking for some advice on the below. Boiler is working and controlling the heating however the hot water diverter valve is not talking to the nest and has been put onto manual override which is causing the hot water to be permanently on and extremely hot. All new parts as new install.

Components of the install are:

• Boiler - Worcester Bosch Cdi Classic System
• Cylinder - Main Unvented 210 Ltr
• Fuse - 3 Amp
• Nest - 3rd Generation
• HW Diverter - Flomasta 2 port Automatic Valve
• CH Diverter - Honeywell 2 port Automatic Valve

Problems:

• Hot water is constantly on
• Cannot control the temperature of the water (even after reducing the temp on the cylinder)
• Nest not talking to the boiler for Hot Water

Existing Wiring:

Boiler Wiring picture attached

Looking at the design wiring plan, I think that the boiler should be the lead power and that there should be a Live return to the boiler to control the switches however this doesn't appear to be the case on the actual wiring.

Also I think that there should be some control of the cylinder temperature in the boiler but again there doesn't appear to be any cables connecting the cylinder temp sensor to the boiler.

Appreciate this is like an exam question, however Im trying to resolve but need some advice.

Thanks in advance
Pete

 

[ShaunCorbs]

No not wired correctly I would say

 

[Murdoch]

Who did the wiring?
.

 

[EvilDrPorkChop]

No doesn't look right, but tbh I don't think your diagram is helping matters.....

 

[John.g]

Hi Everyone,

Was looking for some advice on the below. Boiler is working and controlling the heating however the hot water diverter valve is not talking to the nest and has been put onto manual override which is causing the hot water to be permanently on and extremely hot. All new parts as new install.

Components of the install are:

• Boiler - Worcester Bosch Cdi Classic System
• Cylinder - Main Unvented 210 Ltr
• Fuse - 3 Amp
• Nest - 3rd Generation
• HW Diverter - Flomasta 2 port Automatic Valve
• CH Diverter - Honeywell 2 port Automatic Valve

Problems:

• Hot water is constantly on
• Cannot control the temperature of the water (even after reducing the temp on the cylinder)
• Nest not talking to the boiler for Hot Water

Existing Wiring:

Boiler Wiring picture attached

Looking at the design wiring plan, I think that the boiler should be the lead power and that there should be a Live return to the boiler to control the switches however this doesn't appear to be the case on the actual wiring.

Also I think that there should be some control of the cylinder temperature in the boiler but again there doesn't appear to be any cables connecting the cylinder temp sensor to the boiler.

Appreciate this is like an exam question, however Im trying to resolve but need some advice.

Thanks in advance
Pete

Normal S plan is power switched from programmer/timer to roomstat/cylinder stat then to open zone valve, zone valve end switch then switches boiler on. I would imagine nest is some variation of this very basic system whereby it takes the place of the programmer/timer and may also change the roomstat/cylinder stat setpoints, I wouldn,t have thought that it would talk directly to the boiler but maybe it can alter the boiler stat setpoint.
I presume it is not just a one zone nest? if such exists.

I see its a third generation nest so should be able to control hot water OK.

 

[Ziggie]

As far as I remember each zone needs a Nest.

the gen 3 nest controls one zone heating and hot water and you need a zone valve for each zone and one for hot water

here is a response to a similar question
(Not on this forum)

Your boiler should have a valve for each zone. I have two heat links, each one connects to a zone valve rather than directly to the boiler. Then each of the thermostats connects to its respective heat link.

When you call for heat, the heat link activates the valve. The valve opening then activates the boiler.
[automerge]1579129587[/automerge]
Another method to achieve this is to use wireless TRVs but these are not supported by Nest

 

[Brambles]

Pete,

If you hand drawn as built diagram is correct - your boiler is operating completely independently to your control system.

If the boiler is on and the dhw and or ch control valves are manually opened - you will get heat and water - but it is only controlled by manually switching the boiler on or off.

It is not a safe way to manage you dhw (you have no effective temperature control in place), particularly if you have children and / or old people resident in the house.

If this was installed by a plumber you need to get him / her back to wire it correctly.

Your diagram indicates that your DHW is unvented, I would switch the boiler off until the matter is properly resolved. The two thermostats for the UV Dhw cylinder need to be wired in series between the control feed and dhw control valve. That is the first level of protection for the cylinder. At the moment you inly are relying on the mechanical P and T valve ( the second level of protection) to protect the cylinder from overheating / over pressurising.

 

[Ziggie]

This is the example in the Nest install manual for an Splan
Shows one heating and one hot water zone.
The extra heating zone could be added by copying the documented heating zone using a new Next thermometer and link

hope this helps

 

[John.g]

As far as I remember each zone needs a Nest.

the gen 3 nest controls one zone heating and hot water and you need a zone valve for each zone and one for hot water

here is a response to a similar question
(Not on this forum)

Your boiler should have a valve for each zone. I have two heat links, each one connects to a zone valve rather than directly to the boiler. Then each of the thermostats connects to its respective heat link.

When you call for heat, the heat link activates the valve. The valve opening then activates the boiler.
[automerge]1579129587[/automerge]
Another method to achieve this is to use wireless TRVs but these are not supported by Nest

The zone valve actuator activation should/must be the at the end of any system request no matter how clever
[automerge]1579187473[/automerge]
Since a UV HW cylinder has 3 levels of protection, Cylinder control stat (say, 60 to 65C), Hi limit stat (80C to 85C) and a T&P safety valve (90C to 95C) & (6/7 bar), can a remote (Nest) settable stat be substituted for the normal control stat and if so does it have a high limit setting?. Or does it have to be in series with the existing two stats?.

 

[Ziggie]

The zone valve actuator activation should/must be the at the end of any system request no matter how clever
[automerge]1579187473[/automerge]
Since a UV HW cylinder has 3 levels of protection, Cylinder control stat (say, 60 to 65C), Hi limit stat (80C to 85C) and a T&P safety valve (90C to 95C) & (6/7 bar), can a remote (Nest) settable stat be substituted for the normal control stat and if so does it have a high limit setting?. Or does it have to be in series with the existing two stats?.

The Nest uses its device to measure the room temperature and does not control the water temperature. The nest works as a heating timer and room temperature and a timer for the water . It does not measure the temp from the boiler.

 

[John.g]

I was referring to the HW Cylinder temperature and not the boiler water temperature but I think that's what you mean anyhow so that's fine, thanks.