Help me understand sealed system pressure please!

[will123]

Hi,

We've moved into a new house that has a sealed central heating system with an Ideal boiler providing heat for the central heating and water cylinder.

I had a problem where I was getting air in the system and losing a little pressure, but I found a loose but on a radiator and tightened it which fixed the air problem.

I then topped the system up to 1 bar and this pressure held for just over a week before dropping to 0.8.

I thought the pressure should remain the same, so I called in a plumber. We are in a new build house so it is all under warranty. He checked for leaks and couldn't find anything. He recommended topping the system up to 1.5 bar, so we did. He then said that he expected the pressure could drop to between 1.3 and 1.4.

Well that was over three weeks ago and up until today the pressure has held at 1.5 bar. However, today it has dropped to 1.4.

Why is this? I mean I know the plumber said to expect this, but why now and why the drop?

All the pressured I mentioned above are from when the system is cold.

Thanks for listening, I'm just one of those homeowners who likes to understand what's going on!

 

[albatross]

It is not possible to teach you every aspect of a heating system. If it works, leave it alone. If it stops call an engineer. What the plumber has said is fine. Water contracts and expands with heat so the pressure will fluctuate. Fresh water has some bubbles in which will disperse, often via an auto air vent in the boiler, and some pressure will go. It is common to have to top up a system after it's first filling/usage for up to 3 weeks.

 

[Dotty]

What T'Albatross said. Don't worry about it.

 

[will123]

Thanks guys. I guess I am just overly paranoid with having both a new house and a new child!

 

[Dotty]

No probs, enjoy both.