Bypass Valve on Plumbing System

eggerb

I'm very unclear about whether I should be leaving one of the valves on my plumbing open or closed. I don't want to cause any damage to my boiler. See pic below >>



There is a vertical pipe in the middle joining the coil in and the coil out. It has a valve in the middle. I recently added the white cylinder thermostatic valve back on as I figured there wasn't much point in the boiler constantly sending hot water to the cylinder if there was already hot water there.

So, my dilemma ... if the rads are off (using the motorised valves) and the cylinder thermostatic valve is off, is this scenario putting pressure on the boiler? The boiler is an Ideal SE 18 and the manual states "a bypass circuit must be fitted with an automatic bypass valve to ensure a flow of water should all valves be in the closed position".

Therefore, should I have the valve on the vertical pipe open? Is this the bypass Ideal are referring to?

However, if it is open, will enough hot water flow through the coil?

Any light anybody can shed would be much appreciated.

youtheman

My central heating system had a similar manual bypass valve when installed. I recently put in a new condensing boiler and there is an automatic bypass valve built into the boiler itself. You could replace the manual valve with an automatic valve.

Regarding the TRV you fitted, this senses AIR TEMPERATURE, not water temperature. And you've a well insulated cylinder (which is designed to keep the heat in). So you're controlling the input to the cylinder based upon the surrounding air temperature in the hot press. It will work (in a fashion), but not nearly as effective as a cylinder thermostat and motorised valve.

youtheman

Forgot to say that the manual valve you refer to should be partially open, just allowing a minimum amount of water to bypass.

eggerb

Cheers for the reply youtheman

youtheman wrote: »

My central heating system had a similar manual bypass valve when installed. I recently put in a new condensing boiler and there is an automatic bypass valve built into the boiler itself. You could replace the manual valve with an automatic valve.

It seems like it is a manual bypass valve then. I'll have a look around the boiler to see if there is an automatic bypas fitted near it. Some City & Guild book I came across suggested that it should be located near the boiler. If this doesn't exist I'll just leve the bypass partially open then.

youtheman wrote: »

Regarding the TRV you fitted, this senses AIR TEMPERATURE, not water temperature. And you've a well insulated cylinder (which is designed to keep the heat in). So you're controlling the input to the cylinder based upon the surrounding air temperature in the hot press. It will work (in a fashion), but not nearly as effective as a cylinder thermostat and motorised valve.

It looks like a TRV but there is a remote temp sensor on it joined to the valve by a coil of silver wire. The remote temp sensor is touching off the cylinder wall as a small strip of insulation has been removed. Sorry, should have made this clear as the silver wire and sensor can't be seen too readily on the picture.

youtheman

Given the information you've supplied it would appear that your system is set up o.k. You just need to check that the manual bypass valve is not fully closed.

If there is an automatic bypass valve fitted to your boiler then it may not be visible. I had to look at the manual for my new boiler to see reference to it (it can also be seen on the parts diagram).

It is unlikely to be installed if your plumber fitted a manual facility (unless you've installed a new boiler since the original installation).

youtheman

If you look at the bottom of page 9 of the manual (the link you supplied) you'll see the following:

" However, if the system employs thermostatic radiator valves on all radiators, or two port valves without end switches, then a bypass circuit must be fitted with an automatic bypass valve to ensure a flow of water should all valves be in the closed position."

You have the bypass valve, but it's not automatic.

eggerb

Thanks for the reply again.

I turned the manual valve a few times towards closed.

I took off my boiler housing and see there does seem to be a valve on top that says "3 bar" ... here is a pic ... does it look like an automatic bypass valve I wonder?




As an aside, what's this guage for ? ... and should it be showing something other than zero?
(the thin copper wire running from the valve above seems to run to this guage)

youtheman

The valve you refer to is a Pressure Relief Valve, designed to relieve the pressure at 3 bar. This is not the same as the bypass valve.

The outlet from this PRV valve should be to drain. If you look at page 11 of the manual it is referred to as a Safety Valve.

I haven't seem a PRV with a pressure gauge. I would have thought that it should read around 1 bar. But if the boiler is working ok then I would suspect that the gauge if faulty. " if it ain't broke then don't fix it".

eggerb

Cheers again youtheman. Getting to know my plumbing a bit better!

Guys I hope that you won't mind me ressurecting this thread to ask a follow on question. I have almost the same setup, but with the addition of some sort of pressure vessel, which I will come back to in a mo.





With the boiler on and both hot water and downstairs rads selected on the programmer, I sometimes get a "banging" or "throbbing" or whirring sound which emanates from the hot press and which can immediately be resolved by turning the TRV one way or the other. We have the bypass valve open about three turns, by the way. Could anyone help with a more permanent cure for the throbbing (if you get what I mean!)

Also, I take it that this (in picture below) is some sort of relief valve??



Also, what does the red pressure vessel do, please???

slavetothegrind

Sounds like you have air in your system. or partial blockage.

There is an autobleed valve at the topmost point of your pipework which may not be working.
Have you had to fill the system regularly?

The pressure vessel you refer to is there to allow for expansion of water in the system as it heats up.
It consists of an internal bladder pre-pressurised with air.

Should this bladder fail ( as they can and do) this red 25litre vessel fills with water and weighs 25kilos instead of 2 and so should be properly supported which it doesn't seem to be here!
Test it by unscrewing the black cap on it and depressing the valve therein.
Should be a hiss of air.

sullzz

if turning the thermostatic cylinder valve (tcv) stops the noise it is usually because it is sticking , which would mean replacing the head and probe .simple. another thing to check is if it is fitted correctly - there is an arrow on the side of the brass body which should be pointing towards the cylinder.
what you refer to as a relief valve is an automatic air vent , it is fitted to release air from the heating system on sealed systems.
the "pressure vessel" or expansion vessel is also fitted on sealed systems inside it there is a diaphram with one sde air and the other side water , it takes the expansion of water / pressure within the system when the temperature rises, open heating systems would not use one of these but instead have an expansion pipe going into the attic and over the headder thank . if the vessel was to fail you would know as the pressure within the system would increase suddenly you culd tell y looking at the gauge at your boiler.
hope this helps.

Thanks for that slavetothegrind - the house is new and we moved in about three months ago - we haven't had to bleed/top up the system so far. Is the device at the top of the pipe (just below and to the left of the gate valve on another pipe) in picture 3 the autobleed device??

And thanks for the info about the pressure vessel. I'll do something to support it (in case!)

sullzz

sullzz wrote: »

if turning the thermostatic cylinder valve (tcv) stops the noise it is usually because it is sticking , which would mean replacing the head and probe .simple. another thing to check is if it is fitted correctly - there is an arrow on the side of the brass body which should be pointing towards the cylinder.
what you refer to as a relief valve is an automatic air vent , it is fitted to release air from the heating system on sealed systems.
the "pressure vessel" or expansion vessel is also fitted on sealed systems inside it there is a diaphram with one sde air and the other side water , it takes the expansion of water / pressure within the system when the temperature rises, open heating systems would not use one of these but instead have an expansion pipe going into the attic and over the headder thank . if the vessel was to fail you would know as the pressure within the system would increase suddenly you culd tell y looking at the gauge at your boiler.
hope this helps.

Many thanks indeed, I'll check the valve for sticking and the flow direction

After you have checked things, as a test try opening your bypass wheel head valve all the way instead of the 3 turns it is at the moment, this will allow more water to bypass the valve taking pressure away from the valve, try it for a day, if you find things improve you need to fit a automatic bypass, Gary

gary71

gary71 wrote: »

After you have checked things, as a test try opening your bypass wheel head valve all the way instead of the 3 turns it is at the moment, this will allow more water to bypass the valve taking pressure away from the valve, try it for a day, if you find things improve you need to fit a automatic bypass, Gary

Thanks Gary, we're trying that now