noise in radiators

maggie · 30 Nov 2003

I have had recently the controls on my radiators (Drayton TRV2) replaced by Mistral 10 NP bi-directional valves on all my radiators (11)in the house since 4 of the Drayton controls were faulty. Since then there is a noise of swishing water (water flow) when the controls are operating i.e. when the valve is open. It stops when the right temp. is reached and starts again when it drops.
My plumber says it is due to differential pressure, whatever it means.
My Drayton controls were 15 mm; the new ones are 10mm (both were fitted on 10mm pipes).
Is the difference between 10 and 15 mm a contributing factort o why I have noise now, where I had none before. Should the plumber have had fitted 15mm controls ?
Is there any benefit in using 15mm valve as opposed to 10mm as regards noise.
Has anyone got the details of differential pressure for Mistral 10 NP (10 mm) valves so I can compare it with my old Drayton valves?

He now suggests fitting a by-pass valve at an extra cost. Are there any other solutions??? Please help!

breezer · 30 Nov 2003

I am not a plumber or heating engineer, but if you search the forum you will find that you should have one radiator that does NOT have a trv

This acts as a by pass

as you said "replaced by Mistral 10 NP bi-directional valves on all my radiators"

oilman · 30 Nov 2003

.... there is a noise of swishing water (water flow) when the controls are operating i.e. when the valve is open. It stops when the right temp. is reached and starts again when it drops.

The swishing noise is air in the system. You will need to bleed radiators several times to get rid of it, and any other bleed points will need venting.

My plumber says it is due to differential pressure, whatever it means.

This is a collection of words to make the originator sound knowledgable. For water to flow, there must be a difference in pressure between one point and another, this is differential pressure. Static pressure is the pressure the system is under when the pump is not running. It's the pressure caused by the height of the water in the system eg header tank or the highest point on a sealed system. Sealed systems also have a charge pressure which is set when the system is commissioned.

In this case it might just be the plumber didn't bother to think how pointless the statement was.

My Drayton controls were 15 mm; the new ones are 10mm (both were fitted on 10mm pipes).

Is the difference between 10 and 15 mm a contributing factort o why I have noise now, where I had none before. Should the plumber have had fitted 15mm controls ?

Is there any benefit in using 15mm valve as opposed to 10mm as regards noise.

Has anyone got the details of differential pressure for Mistral 10 NP (10 mm) valves so I can compare it with my old Drayton valves?

The valves could give rise to some noise, but not the swishing noise IMO.

He now suggests fitting a by-pass valve at an extra cost. Are there any other solutions???

You could have a manual valve ftted on one radiator, typically a bathroom radiator or just take the head off the valve. This is so when all the thermostatic valves have shut, there is still somewhere for the water to flow. Technically the plumber may be right, but it has nothing to do with the swishing noise.

maggie · 1 Dec 2003

Thanks very much!

As regards by-pass. The solution by installing a manual valve seems to be the answer.
However, on the real need for a by-pass in my case: I have a relatively new central heating system which was installed by a very competent engineer in 1983. Also I have had TRV on all my radiators. before. Does this mean that, most likely, my central system has got a by-pass ?
But I like the idea of putting a manual valve because it sems to be solving the issue, whatever the actual state of my system is.
Does this thing about by-pass sound like 'a red hering' to detract from the real issue of why the new valves are noisy (i.e. air in radiators or simply faulty/inferior quality valves).
By the way: I have checked the radiators for air: only one needed bleeding. Is there a chance of air elsewhere in the system ????

Please let me know

oilman · 2 Dec 2003

Does this mean that, most likely, my central system has got a by-pass ?

You cannot draw this conclusion. It may have one, it may not.

Does this thing about by-pass sound like 'a red hering' to detract from the real issue of why the new valves are noisy (i.e. air in radiators or simply faulty/inferior quality valves).

As I said in my last post, "........it has nothing to do with the swishing noise."

Is there a chance of air elsewhere in the system ????

The noise, if it is air, is if the air is going through the valves, unless it is a function of the valve design. Try turning the pump speed down.

maggie · 3 Dec 2003

I've checked the pump setting: it's on 1.
I've double checked all the radiators: they heat up evenlyand only one needed bleeding.
Is it possible that there is air somewhere else in the system.

Today, as well as the hissing in the valves and the swishing noise in the radiators, the boiler flame started going really strongly, despite water temp. being just on 1 and in the pipes leading from the boiler upstairs (to the hot water cylinder, I suspect) there was loud noise of water flow (boiling and fast travelling , with ocassional whistle). I've just switched the
timer for central heating and hot water off....

oilman · 3 Dec 2003

It certainly sounds like air somewhere in the system, but where?

masona · 3 Dec 2003

Have you try bleeding air from pump ?

maggie · 3 Dec 2003

No.

Thanks for the suggestion! Will try

masona · 3 Dec 2003

Sorry forgot to say bleed the pump with the system off.

maggie · 3 Dec 2003

OK! thanks for warning!
This might take a while....

maggie · 3 Dec 2003

Can you advise me of a correct procedure for bleeding radiators and checking for air in the pump
Radiators:
1. get the radiators hot for about 15 mins. ( should the boiler be on high or medium settiing; should the TRV be high eg. 5 or average???)

2. turn the system off

3. bleed each radiators, srating from downstairs up.

Have no idea where to begin with the pump: couldn'to find the instructions (I have a Grundfos model).

Thanks

maggie · 3 Dec 2003

forgot to ask: when you say system off (airing the pump) do you mean: boiler off (i.e. no pilot light) or just heating/hot water switched off????

Thanks

oilman · 4 Dec 2003

I hope masona won't mind my replying to this.

System off is just pump not running. Pump s have a nack o getting air sucked in when you didn't expect it, and the air can get carried along with the water, and so miss the exit.

I would leave the radiators cold, as the TRVs would be open more, and open them fully. I always bleed upstairs first. I don't have much justification for this, just the way I do it. It probably doesn't matter which you do first since it sometimes takes several goes and a couple of weeks to get all the air out of a system. Don't forget any other bleed points on the system.

For the pump, there's a big chromed screw on the round face. Just undo that, and the air will come out. You can take the screw right out and only get a dribble of water, when the pump has siezed, then use a small screwdriver to free the spindle. Saves buying a new pump.

masona · 4 Dec 2003

oilman said:
I hope masona won't mind my replying to this.

Not at all,this forum is for everyone. Thought you might need a rest

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noise in radiators

breezer

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