Vailliant sustain 418 heat only problem
- Thread starter diycooper
- Start date
Yes, exactly. That’s what I believe the Vaillant engineer is saying. At the moment it isn’t wired like your diagram in post #24, and it needs to be, with the 3-port valve/Y-plan switched live going to SL at the boiler and PL from the boiler going to the pump.
I have been to numerous vaillants that have no pump overrun and these heat onlys don't like any heat hanging about in them.
Usually easy enough to run a cable to the pump... On the occasions where you can't then a wireless relay can be used and also vaillant do a kit which enables overrun but I didn't want to use that at it seemed a bit Heath Robinson!
Usually easy enough to run a cable to the pump... On the occasions where you can't then a wireless relay can be used and also vaillant do a kit which enables overrun but I didn't want to use that at it seemed a bit Heath Robinson!
I’ve got a spark running a new cable from the boiler in the kitchen, up through the bedroom above, into the loft, then across and down into the upstairs bedroom where the cylinder and pump are. That will allow the boiler to control the pump properly and give it the pump overrun it needs.
Is or are the boiler and pump just starting and stopping together now?, if so, can't really see this causing a F83, it obviously needs to be wired correctly. its likely that the boiler logic will (when wired correctly) start the pump a few seconds before starting the boiler, the overrun time will then ensure that it stops well after the boiler has stopped firing.
Which? 3rd party or vaillant kit?
Vaillant 3 wire installation kit | Wolseley
Looking for a Vaillant Installation kit 0020244337? Order from Wolseley today - free delivery or click and collect available nationwide.
www.wolseley.co.uk
I spoke to Vailliant engineer he said that is for sonething else and I would still need wire regardless.Vaillant 3 wire installation kit | Wolseley
Looking for a Vaillant Installation kit 0020244337? Order from Wolseley today - free delivery or click and collect available nationwide.
Well I'm a vaillant engineer and I say different.
Also, area manager told me about them years ago, they were developed for British Gas to use in this exact situation.
Solutions/Kits: Specialized 3-wire installation adapters (such as Vaillant-compatible accessory components like part 0020244337) or external relay/stats are used when upgrading older setups that lack the necessary core wiring channels.
However... I do prefer hard wired with a proper cable and have sometimes run one externally and then back in to the cylinder cupboard, where internal would have meant shifting loads of furniture!
Last edited:
Isn't a permanent live, switched by the above, still required at the pump, to drive it?.
Yes, which can most often be taken from the wiring centre.
Granted there are setups where pump is elsewhere, but not often.
Other boilers such as Main do not require a permanent live and/or pump overrun as their hex dissipates heat via the fan or just doesn't get too hot.
Vaillant have pcb firmware that requires very tight limits from NTCs to protect the hex which is vulnerable due to design and construction.
Motorised valves start the pump when m/switch activated and then stop it when released.
That's why it's necessary to have a bypass before the MVs.
A S plan does have motorized valves but where pump overrun is required then the same logic should apply as above, ie the switched live goes to the boiler only, the logic then fires the boiler and sends the start and (delayed) stop demand to the circ pump but because the pump overruns with the all the motorized valves shut, a ABV (automatic bypass valve) is required. A Y plan, where the 3 way valve ensures that there is always a flow pathway through either the CH or HW system generally does not.
Correct.
But the 3 way kit utilises the existing 3 core if there is one between boiler and cylinder... Whereas you'd otherwise need triple.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
