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Plumberpro
Plumberpro, Home Appliance Technician
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Experience:  Heating and hot water heating appliances experienced
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I have a Vailant ecoTec plus 428 boiler. On heating it overshoots

Resolved Question:

I have a Vailant ecoTec plus 428 boiler. On heating it overshoots and trips. It keeps cycling in this manner
Submitted: 2 years ago.
Category: Appliance
Expert:  Plumberpro replied 2 years ago.
Plumberpro :

Hi , do you mean it trips the power or is overheating?

Customer:

The indicated temperature rises steadily to about 5C below the set point. Power decreases and temperature reduces slightly before a surge of heating occurs. This causes the temperature to exceed the set temperature and the heating trips out. This system cools to about 45C (with radiator symbol flashing) and then restarts and repeats the cycle

Plumberpro :

Hi , is the pump wired directly into the boiler, for the pump over run to kick in? In the boiler wiring the pump should be wired directly

Plumberpro :

.

Customer: Yes
Plumberpro :

Hi , you may have a fault with one of the temperature the temperature stats .either the flow or return. Best to change both at the same time

Customer: I also have problem when the system wakes up. Instead of heating up to the set point quickly it just lights at minimum output and only warms up slowly. Is this a related problem?
Plumberpro :

No , I don't think so the boilers have modulating gas valves that start low before going to high

Customer: So how long should that low power period be? Is it controlled by a timer on the control PCB or what. Do you think the problems lie with the control circuit and the gas control valve?
Plumberpro :

Why are you convinced that it is a PCB or gas control problem?

Plumberpro :

Are you speaking from experience?

Customer:

No I have no experience of gas control systems but if the gas valve is controlled to initially deliver low power and then switches to a higher power it seems reasonable to ask what causes that change of mode.

Customer:

I also understand that the controller is a proportional controller in which case you would expect a high power input when the difference between operating and set-point temperatures is large and this should decrease as set-point is approached. In my case there seems to be a surge in power as the set point is approached. There just seem to be a whole ot of illogical actions.

Plumberpro :

Sorry , I am just a simple boiler engineer, working to diagnose boiler faults . will opt out to see if you can get an electronics engineer who can explain all your need to know .

Plumberpro :

As I originally told you , you may have a fault with your temp thermistors. These are variable with temperature change and control when and how the boiler fires up

Plumberpro :

Hi , could you please rate your answer , thanks

Customer:

Hi,

Customer:

Your advice is proving helpful thank you.

Customer:

I have tried to click on a smiley face but get no response. Do you need to sign off to say you have finished this enquiry?

Customer:

Thanks

Plumberpro :

Hi , I'm not too sure will check with cust services ,all the best

Plumberpro, Home Appliance Technician
Category: Appliance
Satisfied Customers: 634
Experience: Heating and hot water heating appliances experienced
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Expert:  Andrew Smith replied 2 years ago.
Hi, just checking - has this question been solved now?

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