Vaillant ecotec 438 short cycling

[Johntheo5]

It was fine at 24kw??, but subsequently not at even 16kw? start at minimum and then keep increasing it while its running, the biggest problem will be if it switches off is getting it away when it fires up at say the required 24kw or whatever.

 

[noddy997]

It was fine at 24kw??, but subsequently not at even 16kw? start at minimum and then keep increasing it while its running, the biggest problem will be if it switches off is getting it away when it fires up at say the required 24kw or whatever.

Tried the 8kw and it still cycles off.

Where would an ABV would be fitted on the system and what is the purpose of it? I have the power flush tomorrow warning so could discuss with engineer.

Many thanks for your help. Much appreciated

 

[Johntheo5]

Its installed between the boiler flow and return, it provides a flow through the boiler on pump overrun when all the (if installed) motorized zone valves close and also provides a minimum flowrate through the boiler when all the rad TRVs throttle down.

 

[Harry Bloomfield]

Its installed between the boiler flow and return, it provides a flow through the boiler on pump overrun when all the (if installed) motorized zone valves close and also provides a minimum flowrate through the boiler when all the rad TRVs throttle down.

Deleted!

 

[noddy997]

Its installed between the boiler flow and return, it provides a flow through the boiler on pump overrun when all the (if installed) motorized zone valves close and also provides a minimum flowrate through the boiler when all the rad TRVs throttle down.

After the pump and motorised valve? Don't think there's much roof left there

 

[Johntheo5]

After the pump but before any motorized valve(s), may not be required if you have a Y system with a 3 way mid position valve since either the CH (as long as one rad doesn't have a TRV) or the cylinder coil will all ways be open.
Should be installed with a S system with two port motorized valves as all of these will be shut when the boiler switches off and does a pump overrun.

 

[noddy997]

After the pump but before any motorized valve(s), may not be required if you have a Y system with a 3 way mid position valve since either the CH (as long as one rad doesn't have a TRV) or the cylinder coil will all ways be open.
Should be installed with a S system with two port motorized valves as all of these will be shut when the boiler switches off and does a pump overrun.

I am sure what plan I have, I do have 3 port motorised valve. But the return pipe is not nearby in the loft for the ABV. The 3 port valve and pump are in the loft.

 

[Johntheo5]

You have Y plan so no need for a ABV once you leave one rad with both valves open as a bypass.

 

[bobby spray]

This might not be relevant to your problem but I have just solved a similar sounding issue on a 428 ecotec plus. The dreaded S.53 appearing all the time and the bolier struggling to heat a 18 radiator system. I had to de-rate the boiIer to 20kW to get anything from it. I had the system power flushed, cleaned the magnetic filter and flushed individual radiators all without any improvement and paid many plumbers for the privilege. Yesterday I took the head off my grunfos pump, which is a 5 minute job and inspected the impellor vanes. Every gallery between the high pressure and low pressure side was blocked with magnetite. After half an hour with a kirby clip and a small screwdriver I managed to clear all the vanes - the magnetite was stuck pretty well. As if by magic the system has sprung to life and is performing the best it has in years, even at full rating of 28kW. worth a look - even if you have replaced your pump recently.
good luck