Boiler circuit pressure?

[morsing]

Hi,

I recently had my water system upgraded to mains pressure and heated via an ELJAN 6 unit on my hot air heater. After installation, the installer showed me a pressure gauge in the loft and two valves and said the first week I would have to open the valves a couple of times to keep the pressure above 1.5 bar, but after that it shouldn't be necessary to do anymore.

It has now been 4 months and the gauge it pretty much at 1 bar every weekend. I have attached a photo below. Looking at the pipe work, It's a pressurised expansion vessel for the boiler circuit.

Why does this keep dropping? If it's dropping, where does the excess water go? Everything looks dry to me...

 

[Darren Jackson]

It is not necessarily going anywhere, a lot of air is introduced to the closed circuit when any work is done and can take a few weeks to disperse so keeping an eye on the pressure is the norm, it could also be hydrogen gases in the system due to a buildup of sludge etc and may require power flushing and new inhibitors introducing.. and of course the water temperature makes a difference as when the water is hot the expansion is greater leading to a pressure reading increase, and when cold lower pressure readings. It is best to top up the system when it is cold to give a more accurate pressure reading, and a 1bar reading is not realy a problem if the system is stone cold that is. If it drops much lower in a short period of time then you have a leak or flat/faulty expansion vessel.

 

[Azzer1704]

Have you noticed any water dripping from the pressure relief pipe outside? It could be a passing valve?

 

[chris watkins]

One bar is fine as it is at the top of the system.

Have you notices what the pressure goes up to when the system gets hot if you do charge it up to 1.5, only the vessel is small, how big is the heating system?

As above, have you checked the black plastic tun dish on the left of your photo to see if it is wet in side, at all?

Strongly recommend you get all that exposed pipework insulated ready for the winter, that cold mains to your un-vented cylinder will freeze in your cold loft if not.

 

[Darren Jackson]

And disconnect that filling loop after you have topped it up, it is only meant to be temporarily connected to charge the system. Many pressure problems are related to the filling loop been permanently connected and the valves letting by or not quite shut off properly.

 

[Last Plumber]

Why is your installer not explaining things to you ?

 

[morsing]

Hi,

Thanks for all the suggestions. I suppose from the installer's point of view, people have varying degrees of knowledge and he needs to keep things simple. As it's a brand new system though, I doubt it will be sludge, and the pressure relief system looks dry.

I hadn't actually thought of whether it was cold or hot when I check, I will make a note of it.

The circuit itself is about 10m of 22mm pipe, so won't hold that much water. I always close both valves after topping up. I will disconnect it as well this time.

Pipes are nearly all insulated, I will get it completed before winter.

Still not sure I understand why the pressure keeps dropping though.

 

[chris watkins]

Always check for staining on rad valves as it is a sign of micro leaks.

The higher the cold fill pressure the more chance these will leak (& the less effective the expansion vessel is)

Its not so much the pipe volume but the size & amount of rads that effect the water content.

 

[morsing]

Always check for staining on rad valves as it is a sign of micro leaks.

The higher the cold fill pressure the more chance these will leak (& the less effective the expansion vessel is)

Its not so much the pipe volume but the size & amount of rads that effect the water content.

Hi,

We don't have radiators.

Thanks

 

[Last Plumber]

As this is warm air heating and you're now using the circulator to warm the new unvented cylinder ( that's seems to be what you're describing), you'd be correct in thinking that there is a very small amount of water in that circuit.

The vessel ( red ) pressure needs to be around 0.8 - 1.0 bar ( in my opinion ) and you need to pressurise the system to around the same maybe a wee bit over so 1.0 -1.2 bar respectively.

The system will not corrode if it is all copper or stainless, not enough to be releasing hydrogen at any rate. You either have a leak ( tiny one is enough in your case ) or you're loosing through expanding water or PRV. Is faulty.

My advice is to first release the water pressure inside the system and then check the pressure in the air side ( dry side ) of that red vessel. Bike pump and pressure guage or foot pump etc. It has a valve on top.