Loud clunk from motorised valve

[jo23483]

When either of the 2 port motorised valves closes, I get a loud clunk. A Honeywell automatic bypass valve was fitted a year or so back to replace a gate valve bypass. I'm happy its in the correct position & orientation, Its set to 0.2 bar. I don't believe we had this clunk last year.

I suspect the automatic bypass valve has failed?

I note when I adjust it via the knurled knob, I feel no resistance, Only when it turned to up to around 0.5 bar I now feel slight resistance. It this normal. I was expecting a little spring push back, not a loose nut. I've no means to tell if there is any flow through the valve. As it's a complete drain job to replace, I'm looking for confidence that the diagnose is reasonable.
Any would be comments appreciated

Jo

 

[Deleted member 120897]

Sounds like it could be motorised valve failure.

 

[John.g]

Are you sure that the M.valves are orientated correctly despite no clunking last year??.

 

[jo23483]

Are you sure that the M.valves are orientated correctly despite no clunking last year??.

yes, pump, and all 3 valves are correctly orientated. The fact that I can get the clunk by turning off either MV (manually by the spindle) was pointing me to the bypass valve? Also how does a normal BP V feel when adjusted - turns with absolutely no resistance , sort of sloppy or firm with some resistance, say against a spring etc?

 

[John.g]

I havn't got a ABV but would expect resistance to increase as you are increasing the index setting. I would certainly expect it (if working normally) to be passing quite alot at the 0.2, 2M setting, is the pipe on either side of the ABV very hot, if so just screw it in to 0.5, see if the pipes cool off and then reduce the setting gradually until it just starts passing, if so, then can set up correct index later.
Have you a external circ pump?, if so post the mode/setting. If a gas boiler with a internal pump, post the make/model of boiler and whether a combi boiler.

 

[jo23483]

I havn't got a ABV but would expect resistance to increase as you are increasing the index setting. I would certainly expect it (if working normally) to be passing quite alot at the 0.2, 2M setting, is the pipe on either side of the ABV very hot, if so just screw it in to 0.5, see if the pipes cool off and then reduce the setting gradually until it just starts passing, if so, then can set up correct index later.
Have you a external circ pump?, if so post the mode/setting. If a gas boiler with a internal pump, post the make/model of boiler and whether a combi boiler.

Its an ext. pump: Grundfos UPS 15-60 130, on setting 2. Boiler: Worcester Greenstar 24Ri. I'll try the temp test & report.

 

[jo23483]

and its hot on both sides, I think I can feel the vibration of the flow through it.

 

[jo23483]

I previously stated the Drayton motorised valves ZA5 are the correct way round. I'm now not so sure. The brass body has no A, B marking. The actuator housing has a slide with A B on it. Water is flowing in the direction of the side A to B. The power cable is on the water entry side. i.e. water is flowing down wards in the image attached - is this correct?

 

[jo23483]

Sorry for the dribble info. I found the A & B marking on the MV, Water is flowing into Port B. So they are in fact the wrong way round and have been so for at least 15 years. I will reverse. Question; Will they have been damaged by this? and am I better to replace them?

 

[John.g]

If they are shutting off the flow as installed, I would just reverse them.

Sorry for the dribble info. I found the A & B marking on the MV, Water is flowing into Port B. So they are in fact the wrong way round and have been so for at least 15 years. I will reverse. Question; Will they have been damaged by this? and am I better to replace them?

Increase the setting to max, index 0.5/0.6, if passing at this setting, then ABV knackered.

and its hot on both sides, I think I can feel the vibration of the flow through it.

 

[jo23483]

Exactly as was suggested (thanks all) the valves were the wrong way around. These have been reversed & the clunk is gone.

The auto bypass was replaced its low cost meant it wasn't worth not doing it.

Setting the bypass raised a question. The boiler a Greenstart 24Ri has no minimum flow rate in its specification. The pump, a Grundfos 15-60 130 needs to be on setting 2 to heat up the remotest radiators. The pump says it can generate over 0.45 bar at its lowest throughput. Practically the bypass pipes feel hot no matter what setting I use (0.2 - 0.5 bar) which seems consistent with the pumps capability.

My question, Does it seem reasonable to leave the bypass set high (say 0.4) to minimise bypass flow? My concern is this is miles away from the default 0.2 setting and presumes the boiler really has no minimum flow (even though I suspect the flow never stops at 0.4). I have no means of measuring pressure in the system.

 

[John.g]

If the pump you have is a UPS2 (5M on speed 2) then a setting of 0.45 would be quite OK IMO as the ABV will still give a bypass flow of ~ 0.3m3/hr when TRVs shut in or zone valves shut which should be quite adequate but if the system is happy with 0.4 with all rads heating then I would leave it, only downsude of this is you may be running with a higher boiler return temperature which will have a small impact on efficiency.

 

[jo23483]

I'm not sure how to read that diagram, but the pump is the older UPS with spec as below, which also seems easier to read. Its pushing 1 m3/hr at .4bar, and just misses reaching 0.5 bar hence the 0.4 ABV setting. Your answers gives me confidence that 0.4 is ok - thanks.

 

[jo23483]

n.b. I now see the new spec is just a truncated version of the old spec. I don't understand the orange lines.

 

[John.g]

The UPS2 has proportional pressure PP settings as well which reduce the pump head as TRVs throttle in or zone valves close, u fortunately all a bit low to be really useful, the big difference is the 3 constant curve settings which are partially constant pressure pressure which make setting up a ABV quite difficult, unlike your model as head falls as soon as the flowrate increases, nobody has told me yet why all A rated pumps behave like this, just have a look at the UPS 3 pump curves!!

 

[jo23483]

Thanks for explanation, If understand properly, in pp mode (where head drops as flow demand falls) I would have thought that use of an ABV to be near impossible, not difficult. As the ABV looks to relies on an increasing head to be turned on.

 

[John.g]

Yes, unless you are prepared to suffer with very high boiler return temperatures, its bad enough even on constant curve mode where you are trying to set it up effectively in constant pressure mode, I don't require a ABV with my oil fired boiler.