Pressure changes in combi boiler heating system - normal ?

TheNewMe

Hi,

I recently changed my heating system to use a combi boiler (Ariston CLAS HE) and changed all the rads bar one to TRVs. The system is now pressurised (it wasn't before) and the guy installing it told me that it should be kept around 1.5 bar.

I have noticed a couple of times that the pressure gauge falls away from 1.5bar. Today it was at 1.2 so I increased it back to 1.5 while the system was off and now the boiler is switched on the gauge shows 1.7 bar. Is this within the limits of expected behaviour ?

At the start I also had to tighten some of the old rad connectors when I saw a couple of leaks and that seemed to fix the leaks but over a period of about a month or so the pressure fell from the 1.5bar target to <1bar. I'm wondering whether there might still be a slow leak at one of the connectors I tightened that evaporates so no water pool forms. If this was the case how might I prove this out ?

thanks

TheNewMe

TheNewMe wrote: »

I have noticed a couple of times that the pressure gauge falls away from 1.5bar. Today it was at 1.2 so I increased it back to 1.5 while the system was off and now the boiler is switched on the gauge shows 1.7 bar. Is this within the limits of expected behaviour ?

You can see movement upwards of a needle due to the pump kicking in and a temperature increase.

Always take your reading with the boiler off and the system cold, if you find the pressure drops from the cold setting, then it's either air in the system from the install or a leak.

TheNewMe wrote: »

At the start I also had to tighten some of the old rad connectors when I saw a couple of leaks and that seemed to fix the leaks but over a period of about a month or so the pressure fell from the 1.5bar target to <1bar.

It's dependent on the size of your heating system, sometimes a pressure drop can seem quite dramatic, but when you look at how much water your putting in to repressurise then sometimes it's not a lot of water.

I would keep doing what your doing, keep a diary of pressure loss and top ups, wrap tissue paper around suspect joints. It's still possible the system is settling down, monitoring things will prove if you have a problem and how big it is.

TheNewMe

thanks - I'll try and keep track of it for the next few months and see how things go

the tissue paper is a nice idea

heinbloed

Pressure changes plus/minus 0.2 bar within a standard household system are normal. These must occure because water and air and material expands and contracts.