Strange noises

[Anonymous]

Hi, Please can anyone explain some strange grinding sounding noises that appear to be coming from our water pump on the central heating.
Scenario: Boiler heating water, boiler turns off, grinding noise, then boiler restarts again.

Please can anyone tell me any possible causes for the noise, and why the boiler would switch off, have the noise and then re-start.

Thanks,
Tony

[SylvanLMPParticipant]

If this boiler a steam set up where the “pump” is a condensate return system?

The grinding could be a defect impeller or sediment build up and the boiler going off then firing up again sometimes is a low water cut of doing its job.

As the water level drops the probe senses it and cuts off the main flame then as the water lever risers to a safe level the burner again fires up.

Either way have someone pull apart the pump and examine it for a worn or blocked impeller.

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SylvanLMP

» This message has been edited by SylvanLMP on 21 September 2001

[tonyparkParticipant]

Thanks for your response.

The pump looks to be around 10-15 years old, probably as old as the central heating system.

I have noticed that the noise only seems to appear when the hot water is on, rather than the heating – does this change anything? I have also noticed that I need to bleed to air vents in the airing cupboard on a fairly regular basis, one is directly above the motorised valves (after the main pipe enters the hot water cyclinder) – this is the air valve that needs bleeding most frequently. The other air vent is just above the pump.

Why would the water level fall (assuming that the pump is switching off for the falling water level) – what could cause this problem?

Thanks,
Tony

[GuestParticipant]

It taks some time for the pump to heet up the water tank, but tha boiler ony needs to heet water up to the water tank tempurtur so it turns on an off wen the pump sends water throug the heatchangr. The water temurtur is high so the water pumped from the botum of the boiler boils inside the cirulatur making noises. Yu need to set the water tempurtur lower for the boiler water so the water wont boil in the ciculatur. Wen the boiler cool down it sucks air in the pips an yuo have to bleed it.

[GuestParticipant]

After reviewing the information given and having transferred to the site in question through an out-of-body experience, I have determined that the system is a small commercial steam boiler system with an indirect heating tank using heated boiler water from below the water line. Nick is most correct in this instance. However, the boiler controls are set to bring the water through the water heating tank exchanger only after the water has heated sufficiently to activate the reverse-acting circulator switch, so while the burner cycles, the circulator may run steadily. However, the circulator is making noise from wear due to sediment running through the inmpeller and cavitation from periodic approach to the boiling temperature. The boiler and piping need flushing and the boiler water temperature upon hot water demand needs to be lowered somewhat to prevent cavitation. However, this can not be avoided during the heating season, so more frequent circulator repair or replacement is necessary. The water level will naturally rise and fall as bubbles occupy some of the water space as the water approaches boiling, especially at the suction side of the pump where the pressure drops inducing boiling at that point as bubbles take more space than water.

[Author]

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