Question about correct operating pressure for CH

gerdalt

I have a Baxi Solo 3 PFL Range town gas boiler rated at 80K btu/hr. It drives the CH and hot water and works well.
However I inspected the system yesterday and observed a pressure dial showing about 0.5 units. See attached pictures. I understand this pressure measurement should be 1.0. Should I be concerned? There is a red knob in the photo that looks like it is a user-level adjustment. Should I try rotate it to get the pressure back up to 1.0?
Ger

Billy Bunting

It is at 1 bar.

Robbie.G

gerdalt wrote: »

I have a Baxi Solo 3 PFL Range town gas boiler rated at 80K btu/hr. It drives the CH and hot water and works well.
However I inspected the system yesterday and observed a pressure dial showing about 0.5 units. See attached pictures. I understand this pressure measurement should be 1.0. Should I be concerned? There is a red knob in the photo that looks like it is a user-level adjustment. Should I try rotate it to get the pressure back up to 1.0?
Ger

Don't touch the red knob it's the pressure relief valve and that will decrease pressure.Your boiler is well capable of running at 0.5 bar.To increase the pressure you are looking for a valve that has a flexible steel braided hose it should be either under the boiler or the hotpress

gerdalt

Billy Bunting wrote: »

It is at 1 bar.

Are we looking at the same picture???

gerdalt

Robbie.G wrote: »

Don't touch the red knob it's the pressure relief valve and that will decrease pressure.Your boiler is well capable of running at 0.5 bar.To increase the pressure you are looking for a valve that has a flexible steel braided hose it should be either under the boiler or the hotpress

Thanks for that. Heading off now with the torch!!

Billy Bunting

well not anymore but it did work initially (not now) and i thought it was showing 1 bar ???

gerdalt

Billy Bunting wrote: »

well not anymore but it did work initially (not now) and i thought it was showing 1 bar ???

Have we crossed lines here? "it did work initially (not now)" - what's that all about?
I thought the pic I posted showed clearly 0.5 bar? I was simply asking how I could get it back to the recommended 1.0 bar level.
Happy Christmas!

Sparkpea

System should still run ok at half a bar but I'd top it up to 1 bar when it's cold then keep an eye on it for next few weeks to check if it drops

Billy Bunting

gerdalt wrote: »

Have we crossed lines here? "it did work initially (not now)" - what's that all about?
I thought the pic I posted showed clearly 0.5 bar? I was simply asking how I could get it back to the recommended 1.0 bar level.
Happy Christmas!

sorry my connection is playing up, yes i opened the picture initially and thought it read 1 bar, i can't recheck the picture so i'll take it i was incorrect in what i thought i read, sorry.

gerdalt

Robbie.G wrote: »

Don't touch the red knob it's the pressure relief valve and that will decrease pressure.Your boiler is well capable of running at 0.5 bar.To increase the pressure you are looking for a valve that has a flexible steel braided hose it should be either under the boiler or the hotpress

Can't find any braided pipe. I assume that's the pipe providing mains pressure to pressurise the system? The incoming pipe to the pressure meter is copper and disappears into the wall!! I hope it's heading up to the attic to pick up the mains there.
Dumb question: is it possible the pressure is being provided by a header tank in the attic? Would that be enough to pressurise a system? I am not familiar with pressure values so don't know if you can get 1 bar from an attic tank. I do realise either way a valve is required to seal the system.
Ger

Sparkpea

Yes ger that is possible, the boys down there call it a semi pressurised system I think. U may not need a braided pipe/hose to find it may be plumbed in directly with copper but will have a valve/ballofix on it somewhere if linked to the mains.

Provide more photos around the expansion vessel please (red drum)

Ignore my first sentence, u have a fully pressurised system

gerdalt

Sparkpea wrote: »

Yes ger that is possible, the boys down there call it a semi pressurised system I think. U may not need a braided pipe/hose to find it may be plumbed in directly with copper but will have a valve/ballofix on it somewhere if linked to the mains.

Provide more photos around the expansion vessel please (red drum)

Ignore my first sentence, u have a fully pressurised system

Thanks for that. Getting late!! More tomorrow

rightjob!

prob a semi sealed system,look in the hot press for a half inch feed,there will be a non return valve on it.

Sparkpea

gerdalt wrote: »

Thanks for that. Getting late!! More tomorrow

yes it was, and thats prob why I was wrong :P it is a semi sealed system... was thinking because it had an expansion vessel it was a fully pressurised system but its not, it could be semi if its fed from the header tank in loft with an non return valve on it.

gerdalt

Sparkpea wrote: »

yes it was, and thats prob why I was wrong :P it is a semi sealed system... was thinking because it had an expansion vessel it was a fully pressurised system but its not, it could be semi if its fed from the header tank in loft with an non return valve on it.

OK, does that mean that a header tank in the attic can provide 1 bar pressure? It's about a 24' head approx?
My (limited!) intuition says that's not enough - hence why my pressure gauge reads only 0.5 bar.
And another question: why would the boiler care if the system pressure is 0.5 or 1.0 bar?
AND - is it possible that the red knob in the attached image is a non-return valve? Earlier poster said it is to RELEASE pressure. How could it do that?
Sorry - confused
Ger

Sparkpea

red knob is a safety valve/pressure release, if the pressure build up is too much (the pressure rises when heat is on) then the safety valve (probably 3bar) will open and blow the excess water/heat/pressure out the pipe like an overflow. its spring operated and will work automatically however you can manually twist the top to active it yourself to drop the pressure.

I don't know alot about semi pressurised systems so I can't comment on what pressure to expect from that head.. I don't get the whole semi pressurised system at all why not just put an elbow bend on the mains thats feeding the header tank, put a valve in between and connect it onto the cold feed out of the expansion tank and do away with it? am I missing something or why is the tank being kept there?

If you do what I just suggested then i'd expect u wouldn't have any problem getting it to 1bar.

Some boilers require a certain operating pressure, mainly some gas boilers I've found but oil boilers don't have an issue..

shane0007

Completely agree with Sparkpea. Get rid of the semi-sealed system & fully pressurise it.
24ft = 7.3 meters so this would give 0.1 bar per meter of head so 0.7 bar head but you are probably measuring from floor to tank. Gauge will probably be located higher at boiler level so it will be less than 24ft.

The reason for higher pressure = better system, I suppose the easiest way of explaining is comparing with electricity. Think of pressure as voltage. Main electricity power station is 140,000 volts. Carried down lines to various step downs until it gets to out homes @ 230v. The reason is because if they sent it at 230v from the power station, the distance travelled would lose voltage through resistance of the lines, bends, etc. & we would end up with poor voltage & our kettles would take a lot longer to boil.

So pressure in our heating systems is similar, i.e. force. As the water travels through pipework, through resistance of the pipework & elbows & bends, it looses force & the distant rads in the system loose heat. So we have to create resistance in near rads to force on the heat. However, under pressure, it gives more force which aids us in getting that heat further down the pipework.

See, simples....:D

gerdalt

Apologies for delay in saying thank you to the various contributors. I now understand much better what is going on
Much appreciated.
Ger