Vaillant Ecotec plus 637 - Port Valve question

[RK_London]

Some background. Went from vented to unvented system 5yrs ago when I added an extension to the house. I have 15 radiators and underfloor heating. Boiler fitted was a Vaillant Ecotec plus 637. It's a S-plan system for heating, hot water and underfloor heating. Water cylinder is 290 litres.

Problem I have is when the boiler goes into pump over run, get banging in the radiator pipes. Not in pipes around boiler, just radiator pipes, happens all day when the system has heated up so it's not the normal expansion/contraction of pipes when heating switches on and off.

Need help understanding why there is banging in the radiator pipes when the port valve has closed and isolated the radiator pipes when the boiler goes into pump over run and water flows through auto by-pass.

Thanks

 

[CountryFan]

Sounds like 2 port fitted wrong way around

 

[RK_London]

Attached some pictures below. First picture shows the S plan system. Green arrows on the port valve show the direction of the arrow on the valve. The second picture shows the valve on the flow for the central heating (Top valve in first picture). Looks like the valve is the correct way round.

 

[CountryFan]

Thank you for those. Yes, they’re in the correct orientation. Could be a trv pin then or a valve not flowing the correct way.

 

[RK_London]

I did take all the TRVs off - made no difference. Maybe I'll just change the central heating port valve.

 

[Johntheo5]

Some background. Went from vented to unvented system 5yrs ago when I added an extension to the house. I have 15 radiators and underfloor heating. Boiler fitted was a Vaillant Ecotec plus 637. It's a S-plan system for heating, hot water and underfloor heating. Water cylinder is 290 litres.

Problem I have is when the boiler goes into pump over run, get banging in the radiator pipes. Not in pipes around boiler, just radiator pipes, happens all day when the system has heated up so it's not the normal expansion/contraction of pipes when heating switches on and off.

Need help understanding why there is banging in the radiator pipes when the port valve has closed and isolated the radiator pipes when the boiler goes into pump over run and water flows through auto by-pass.

Thanks

Is the banging only when the 2 port shuts and the ABV opens?, what is the indexed setting on the ABV?

 

[RK_London]

I get banging in the radiator pipes when the boiler goes in pump over-run after the central heating port valve closes. I'm assuming the auto by-pass opens. This boiler has an internal by-pass but was told by a Vaillant engineer the internal by-pass is too small for this boiler and I should fit an external one which I did. It is set at 0.3

 

[Johntheo5]

I'm not too sure if the internal bypass is too small, I see lots of complaints of these boiler return temps, D.41, being 7 to 10c higher than the actual return temp from the rads, why not screw tthat ABV to say setting 5 and then watch D.40&D.41, flow/return temps during the overrun period, you can allways increase the overrun time, might get rid of that noise.

 

[RK_London]

I will change setting of ABV to 5. Flow and return temps right now are 37C and 29C (not cold today - about 13C).

D.40 and D.41 are always the same during pump over-run. I've already increased pump-over run time of 5min to 7 min - didn't seem to be much improvement.

 

[Mister Banks]

I get the same issue with pipe banging when the motorised valve closes, I’ve never been able to fix it so now I just manually latch it open once the HW cylinder is up to temp. I keep neaning to change to a PDHW system but haven’t got around to it.