Chattering check valve on sencodary return

[Chameleonclaude]

I'm suffering from what i believe is a chatting check valve where the secondary return meets the primary return.

I have thermostatic valves on all radiators and have a gate valve rather than an auto bypass valve!

I have now learnt that i need to swap this out but in the mean time i would like some thoughts about the chattering.

The chattering occurs when the heating circuit has reached temperature in all rooms and the secondary return pressure drops to equal the primary return pressure which is currently governed by the quater turn gate valve.

I know this because the chattering stops when i either adjust the bypass gate valve either way or if i increase the demand of one of the radiators by turning up the thermostatic valve.

My questions are as follows:

1) I don't know if the tee joint where the secondary return meets the primary return is a swept tee or not. Assuming it's a non swept tee could turbulance at equal pressures cause the chattering and if so would a swept tee resolve the issue.

2) Would an auto bypass valve resolve this chattering.

3) Could a faulty gate valve produce rattling (athough this doesn't explain why turning a radiator up eliminated the noise)


I'm not a plumber so easy on the jargon!

Thanks

P.s Homage to diy.com

 

[denso13]

Some of your descriptions are not clear but, to kick off, has the noise just appeared recently? How old is the system?

 

[Chameleonclaude]

My system had a revamp about seven years ago which involved a new hot water system and an 'S' plan setup. The boiler was replaced more recently; about three years ago. It's from this time that the noise started.

Three years of the noise driving me absolutely nuts!

 

[muggles]

Why didn't you get your installer back at the time? Secondary returns aren't ever connected to primary returns, so I think your description/understanding is a little flawed here. I would be surprised if there is a check valve on your primaries, it's not usual to have one.

If adjusting the bypass makes it go away then it could be the gate valve that's at fault, I'd get this changed first as it needs doing anyway. Increasing the rad demand will lower the force being applied to the noisy component, thus eliminating the chattering.

 

[Chameleonclaude]

Definately will swap the valve and true about the rad reducing pressure in a faulty gate. Didn't think of that, thanks.

What i was trying to explain and i could be misguided is that the non return is fiitted on the point at which the heating circuit return to the primary return. I thought the return of the heating circuit was called the secondary return?

 

[Chameleonclaude]

Having changed the pump to a modulating pump and changed the gate valve bypass to a Taconova inline flow setter the system is all balanced. When the CH circuit has reached temperature on all the thermostatic valves, the flow setter is letting water through the bypass at a rate of 2 litres per minute.

When the Room thermostat reaches temperature and closes the valve the bypass is running at 5 litres per minute which is perfect.

The problem of the chattering continues though! When the bypass is letting water through at 2 litres perminute and the pump is has slowed down to minimm speed there is a chattering sound!

The chattering is directly related to the flow through the bypass when the CH motorised valve is open.

Could the check valve where the CH circuit return to the return be chattering?

Any other thoughts?

 

[doitall]

The secondary return has nothing in common with the primary return, hopefully not even the same water.

A pic showing the problem and general layout may be good.

 

[Chameleonclaude]

I know, my terminology is wrong but what i do know is that there is a check valve where the rad circuit meets the main return pipe. It's this one i'm wondering about.

 

[doitall]

Agreed, but if the system was installed correctly it wouldn't need to be there.

An as fitted sketch or pic or two would probably highlight the problem

 

[Chameleonclaude]

Yeah, the problem is that most of the pipes to and from the clinder, including the central heating circuit is underneath my built in waredrobes so pics are difficult.

I have managed to access the 22mm check valve that heas been fitted on the central heating return. I is definately this that is chattering.

Apart from just swapping it out like for like, i am considering whether to remove it completely and just fit a straight coupling (at worst i will just close all the radiator valves in the summer) or possible fitting a doublle check valve.

Thoughts?

I guess this problem would never have occured if the ch circuit met the return with a swept tee!

 

[doitall]

without a sketch it's difficult to comment.

The heating return should only connect into the common return once, so all the rads should be connected beforehand, or you'll get reverse circulation.

There shouldn't be a need for the non return valve.

 

[Chameleonclaude]

I know that this is the case. That all the rad return converge into a 22mm which then connects back into the return.

In that case i shall remove the check valve.

On the rad returns, should i be concerned that 6 rads return to the same 15mm pipe before meeting another 15mm pipe serving 2 rads at a tee which is the 22mm back to the return. I wonder whether the 22mm should be extended so fewer radiators share the me return 15mm and more are directly connected to the 22mm ch return?

Does this make sense? If so, what do you think?

Thanks BTW, i really appreciate it.

 

[doitall]

6 rads on 15mm is pushing the luck a bit , but if it works, it works.

provided all the returns are joined, before it connects to the common return you don't need the check valve, so you should question why it was fitted.

Y

 

[Chameleonclaude]

My father-in-law who fitted it claims that the radiators might heat up from back flow in summer months.

My concern with the rads sharing the same 15mm return is that the back pressure may be causing to much of the flow pumps flow to go via the bypass. In theory, i were to extend the 22mm as i said would the by pass become more redundant during CH operation and then come into play more when the ch valve closes and the over run continues?

I know an outo bypass valve addresses this issue but from what i understand they don't work to well with a modulating pump.

 

[doitall]

Can't happen if there's no circuit, I would take it out and try it.