noisy indirect cylinder when water circulating through coil?

[jimk280]

Hi anybody have any experience of this fault? There has been an ongoing problem with what can only be described as what sounds like water/air turbulence within the coil of the indirect cylinder when DHW is selected on the programmer.

The vent pipes in both the F&E and main water tank have been checked to ensure that air isn't being sucked in. If DHW and CH is selected then the noise remains but is less volatile in sound. Select CH only and the noise disappears. The pump speed is a Grundfos 15/60 on pump speed 2 and is fitted on the return next to the boiler which is on an S Plan.


I've fitted a Honeywell Auto Air Vent on the top of the DHW secondary circuit of the cylinder, and one on the flow of the primary CH circuit next to the boiler to rid the system of any suspect air but it made little difference. Still get the noise turbulence. The system was chemically powerflushed 6 months ago as the oil boiler was kettling. This cured the kettling and inhibitors were added on refill. Do you think that the coil may be pinholed within the cylinder? Or is it a possible pipework problem? I'm scratching my head on this one.

Thanks Jim

 

[jimk280]

I would add that the F&E tank water height appears to be stable when the cylinder's gurgling away.

 

[Best]

Try temporarily manually shutting auto vents off (by tightening the plastic screw in) because they can take air in.
Some cylinders require a bypass to prevent noise. Telford unvented cylinders ask this.
A bypass at boiler & set properly should help

 

[Unregistered]

Thanks. I have tried shutting the valves down when the system was purged i.e. all rads bled off. Seems to be ok for a short period then noise is back as bad as ever. I suspected the system may have been gassing but there's plenty of inhibitor in and system's as clean as possible based on it's age of around 40 years.

I understand why you suggest a bypass i.e. pump noise but this a definite gurgling noise. Although I will look to see if there's a bypass in place already when I return wednesday morning...very annoying this fault.

 

[riksony]

Have you a balancing valve on the cylinder return. I always fit one to adjust the flow through the coil. If you have, try opening it a turn it may be closed down to much.

 

[jimk280]

I don't believe there's a balancing valve on the return but I'll take a look. If there isn't what type do you recommend?

 

[kris]

I don't believe there's a balancing valve on the return but I'll take a look. If there isn't what type do you recommend?

Stick the valve next to the cylinder,

 

[jimk280]

Thanks Kris. Got it. I'll put the valve on the return of the secondary circuit next to the cylinder if that's what's required. My only concern is that this appears to be something that's developed since approx February. I'm told there wasn't a noise before. Nothings been touched valve wise? But i'll take a look

 

[joni os]

"Secondary circuit". Do you mean," Primary" ie. the one that flows through the coil.

 

[gassafe]

Does pump speed 1 make the noise quieter ?

Some unvented coils are that stainless steel type corrugated hose, can be noisy with fast flow & may need a gate valve on the return to slow down the flow as mentioned.

 

[TheHeatingGuy]

Possibly a faulty motorised valve. If it's a Honeywell 2 port valve the ball inside can swell restricting the flow. Does the noise happen as soon as the boiler fires for HW or once it's been on for a period of time?

 

[Billy Bob Bob]

having briefly read the thread through i can form the conclusion the op has pumped heating and gravity domestics,therefore i would expect it to be noisy on hot water only as the pumps not being used,if this is the case there is no fault,just system design ,either except this is"how it is"or convert to y or s plan depending on system design/load

 

[jimk280]

Hi guys been away a few days on business. I mean the coil that runs through the cylinder. I was always in the belief this was the secondary circuit as the heating was primary? Please correct me if I'm incorrect? The cylinder is copper. Pump speed has no effect on the noise. However, I returned today. On boiler fire up with dhw only selected, there's a rush of noise as the boiler fires which sounds like bubbling and surging inside the cylinder.

I turned on heating also, started bleeding radiators and the householders reported the overflow pouring. It was the F&E but by te time I got into the loft everything was in, no high levels, no pump over etc.....grrrrrrrr. the system is on an S PLAN with the pump on the return right next to the boiler,. Today I closed all auto air vents, put pump speed on no.2 and will await customer feedback. Thanks for the advice so s
far.

 

[TheHeatingGuy]

having briefly read the thread through i can form the conclusion the op has pumped heating and gravity domestics,therefore i would expect it to be noisy on hot water only as the pumps not being used,if this is the case there is no fault,just system design ,either except this is"how it is"or convert to y or s plan depending on system design/load

The OP stated It was an S plan therefore fully pumped not Gravity HW.

Jimk280 does the pump run when you select HW only?

 

[jimk280]

Hi yeah. Pump runs when selecting DHW but the air rush through the coil on startup is considerable. I've been back since to have a look at system. Bled all air from rads etc. Closed down the AAVS. Pump on the return circuit so I can only think it has been drawing air in via the AAVS? Will ask customer in a few days how the system has been?

 

[Jimbobber]

I would point the problem at the air separator being clogged not keeping equilibrium between the cold feed and open vent to the primary circuit. So it's pumping over the vent or drawing air through the vent.