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Hi All

Well I bought this house in Brugge and the central heating is a bit on the old side, cast iron radiators and the house has 2 systems with 3 boilers, here's the problem.

The first system is now working OK but makes a terrible noise when running, sounds like air in the pump which seems to vibrate throughout the whole system, I've spent hours bleeding the pump, system running and system not running. The pump is a Grunfos UPS 200, big pump I know but it's a big house :) my question is about the size of the feed pipe to the pump, at some time in the past the pipework has been changed and the pump is now feed by a 1" iron pipe, considering the size of the pump is this big enough and could this be the cause of the noise problem ???????

Any help would be most appreciated.

Thanks
 
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Whats the size of the pipe either side of the pump, after the 1" that is.
 
the pipe that feeds the pump comes from the boiler at 1.5" then into 1" where theres been a repair of some sort then just before the pump it goes into 2" after the pump the pipework in in 2" for the main pipe runs
 
Shouldn't be a problem and it's quite normal to reduce the pipe size through the pump.

The noise will be associated with the pump but will be more to do with pipe sizes and design, so explain the noise if possible
 
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the noise is like a buzzing noise, can be heard all over the house, in the boiler room the pump sounds like it has some stones or grit in it but when disconnected fom the pipework it runs silent. I have bled the whole system taking some 20 gallons of water out and replacing with the loop at the same time, good practice?
The pipework is very old and some of it has been fabricated on site ie welded into place, can't imagine that this system always made this noise as the house was once owned by a famous doctor who had his medical practice here, unless of course he was deaf :)

The system hasn't been used for some 3 years but the pressure still holds good at 1.2bar and all TRV's are open and free.

The pump is fairly new replaced I think within the last 5 years
 
Just a quick thought, what if the pump is way over size for the job, would this make noise, when TRV's are opened there is quite a loud rushing noise from the valve. Too much pump pressure?

Seems that everything is way oversize for the job, 2 boilers at 53Kw each running in tandem, now only using 1 boiler which seems to give good heat output all around the house.
 
Fit an autobypass set it to come in as trv's begin shut down, not when it's too late, report back.
 
whats this autobypass, point me in the right direction for some tech help
 
belgiumboy said:
the noise is like a buzzing noise, can be heard all over the house, in the boiler room the pump sounds like it has some stones or grit in it but when disconnected fom the pipework it runs silent.

A classic description of the sound of cavitation. If so, it won't make the noise with cooler water.

Excessive resistance on the pump inlet, or the pump is too big. The resistance causes a pressure drop. The hot water boils due to the low pressure at the inlet to the impeller. As the steam bubbles pass through the pump impeller, the presure increases and the steam bubbles implode.
Check all the valves on the pump inlet are fully open.

It sounds like this is just one of many problems & you'll need someone competent to design and install a new system from scratch.

belgiumboy said:
I have bled the whole system taking some 20 gallons of water out and replacing with the loop at the same time, good practice?

What?
 
any chance it could be an old gravity system with a pump retro-fitted :?: that`s my two pennworth ;)
 
Nige F said:
any chance it could be an old gravity system with a pump retro-fitted :?: that`s my two pennworth ;)

Almost certainly I would agree it was an old gravity system NigeF

The buzzing noise is probably electrical not water, so look at the controls.
 
Thanks for the input so far, here's some more info based on your comments.

Can't see any signs of the system being an old gravity system, ie no old tank in the attic or pipework leading to that sort of thing, or any signs of capping off.

System tempreture at the boiler is set to 70C is this OK???

After removing the pump yesterday and replacing it again the system run perfectly quietly for 2-3 mins then air seemed to rush into the pump and the normal noise was back.

The noise is definately not electrical.

Possiblity of a pro looking at the system in Belgium is NIL, everyone is too busy, best quote we got for looking at and working on the system is May 07.
 
belgiumboy said:
After removing the pump yesterday and replacing it again the system run perfectly quietly for 2-3 mins then air seemed to rush into the pump and the normal noise was back.


Still think it's cavitation. Pressure too low at the pump inlet, due to excessive pressure loss &/or bad system design.

Try turning the boiler off or turning the thermostat right down, so the boiler's burner is off & the pump runs. Cavitation is temperature dependent, anything else will happen whether or not the water is hot.

Where is the expansion tank (or cold feed) connection in relation to the pump and boiler?

Let me hazard a guess;
pump outlet; expansion tank connection; boiler?
 
OK guys looks like I got a whole day in front of the boiler :)

Onetap: what you say makes sense to me but there are some differences, layout: Boiler, pump, cold feed (top up), expansion tank.

With boiler burner off pump has an overun of 10 mins so water cools quickly but the noise still continues, is it worth taking the pump off and then replacing it again, the boiler and pump will only start when needed ie tempreture drops below thermostat setting which triggers the pump, then turn boiler off so system runs with cold water for 10 mins this should prove your theory of cavitaion if there is no noise. What do you think????
 

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