Do I need a bypass?

[wrighty208]

Hi, I have a standard open-vented system with an old back boiler (Baxi) behind a fireplace downstairs feeding 7 radiators

I have just fitted TRV's to all radiators in the house with the exception of the hallway radiator where I have a room thermostat. I have just read on the honeywell website the following:-

"When fitting several thermostatic radiator valves, it is essential that a bypass is fitted"

Do I need to fit a bypass or is this my hallway radiator?

Thanks

 

[Breesey]

You need to by pass the valves. Fit an auto by pass valve.
Like this

 

[wrighty208]

where exactly would that be installed though? and what would it achieve?

I must admit I can't see the reason for installing one as worse case the boiler can flow via the hallway radiator?

 

[Breesey]

where exactly would that be installed though? and what would it achieve?

I must admit I can't see the reason for installing one as worse case the boiler can flow via the hallway radiator?

What if the hallway rad is off?
Strictly speaking it is required if the boiler specifies a min flow rate, ref Part L1
Fit it to by pass the valves from flow to return!

 

[gas4you]

If your BBU is really old I would assume it is gravity HW and pumped CH?

It would depend on whether your pump is in the return (probably on an old system) or the flow.

If on the flow then the auto bypass would be after the pump and link across to the heating return.

If pump is in the return then from the ch flow to the ch return before the pump.

Your easiest option is to remove the trv in the room with the room stat in, or at least just the trv head.

 

[Gasguru]

You may not require a bypass..many properties don't and function ok however it depends on pump settings, type of pump, size of system etc.

Look at the manufacturers data on TRV's. Somewhere they will quote a maximum differential pressure accross the valve...if this is exceeded the valve can become noisy.

The bypass valve connects across flow and return pipework (after the pump). It has an adjustable spring loaded valve. It is set so as the TRV's shut down the valve opens to "bypass" the water flow relieving pressure across the valves and water velocity through the uncontrolled radiator

 

[wrighty208]

Your easiest option is to remove the trv in the room with the room stat in, or at least just the trv head.

ah ha! In my first post I stated "I have just fitted TRV's to all radiators in the house with the exception of the hallway radiator where I have a room thermostat" - the hallway radiator has both valves wide open and no TRV.

Take it I shouldn't need a by-pass then?

Not sure of the terminolgy but I know how the system is connected up! Out of the boiler into a pump - then into a 3-way valve to control HW, CH or both - I don't think the return goes back into airing cupboard though from what I can see ( the boiler is downstairs)

 

[ChrisR]

As long as you don't shut the hall rad, you don't need a bypass.

 

[gas4you]

Thats the problem of only half reading a post first thing in the morning and on my way out to 3 breakdown calls (which I'm obviously running late for now )