Vaillant ecoTec Pkus 428 - not a combi

[mverdier]

Hi,

I hope someone can help with the following issue:

Re: Vaillant ecoTec Pkus 428 - not a combi

My Vaillant ecoTec Plus boiler radiator setting is set to max 75 c. However, the the boiler will only reach approximately 45 c even though the house thermostat has not reached temperature. It just ticks along at that, but goes up for short bursts when the fan kicks in.

I have noticed the following:

1. If I turn the water heating on the boiler then heats to the correct radiator temperature i.e 75 c.

2. If I turn the water heating off the boiler will continue to meet the 75 c heating requirements working with the house thermostat.

However, as soon as the Boiler is not active for a period of time i.e The thermostat is turn right down so the boiler is not required to work for a time, I then hit the same original issue. That is, the boiler just runs at approximately 45 c and the house takes forever to heat up.

Any help on this would be really appreciated...

One final question. I noticed a post that the pump should always be set to 3 - is this correct as mine is set to 1. When I had it set to 3 the central heating was overflowing.

Thanks for any help / diagnosis.

Cheers
Matt

 

[Dan Robinson]

Inadequate or goosed pump

 

[jeff the gasman]

Sounds like it's piped up wrongly
If pump is on 1 to stop overflow that proves it.
Get a decent engineer to check the pipework over.
The boiler probably nit getting sufficient flow so won't ramp up.

 

[simond]

The ecoTEC 4 series has a tight pitch heat exchanger; in other words, a high flow resistance.

It is therefore more susceptible to exposing poor circulation.

From what you have told us here I would say there is a partial blockage in the radiator circuit.

If you get the system to 'pump over' on higher speeds, and it works satisfactorily on HW only, then this confirms that the pump is OK but there is an obstruction to flow.

More often than not there is a reason for this; often down to the cold feed and open vent arrangement being carried over from the original low hydraulic resistance boiler the ecoTEC replaced. If the system has been pumping over even a little bit since, your system will be full of corrosion by products.

 

[mverdier]

Thanks for all your helpful replies.

Simond - I think you may be right on your comment, and I concerned about the potential damage this has caused the boiler????

One final thing, when it is running at the 45 c and not getting to temperature it shows a status on the bolier of the following:

Status: S.53 “The Appliance is in the waiting period of the operation block function due to water shortage (VL-RL Spread to big)”.

Not sure what this means and if it is linked.

Cheers, Matt

 

[mogget]

It means that the temperature difference between flow and return is too great, causing the boiler to drop to minimum flame. Caused by either inadequate flow, or a slug of cold water entering the boiler.

I'm just a DIYer but I had a 418 until recently and had this problem a few times.

 

[Dan Robinson]

It is linked and covered here several times.

 

[mverdier]

Thanks again for all the Posts very helpful. I have a plumber coming tomorrow and have printed out all these comments to help with the investigation and resolution.

 

[mogget]

Which speed do you run your pump on? - usually it will need to be set to maximum speed with the larger 400 series and the auto bypass valve (if present) set accordingly.