Problem with sealed central heating system pressure rising

white_westie

1st poster, long time reader.

Question for the central heating experts
What is the normal operating pressure for a sealed system when the heating has been running for a while? Is 2bar too much or normal?
I know it should be 1bar when cold, and if it reaches 3bar its too high and the prv should open and release the pressure.

My problem is that pressure is rising from 1bar when heating is on - when it goes over 2 bar I release it by draining off some water from drain cock at bottom of boiler. Even when heating has been off during the night for say 8hrs there is no reduction in the pressure.
It never returns to 1bar unless I drain the system and refill it.

Because the weather has been cold over the last few weeks, I have not done any real troubleshooting except just keep it below 2 bar on a daily basis.

I reduced the water pump speed from 2 to 1 and also reduced the boiler stat to 60, but no real change except that 1 or 2 rads took longer to heat up - the pressure still rises.

At the moment the guage in the hotpress is at 2.2bar and the boiler guage is at 2.5bar
The pump is back to speed 2, and boiler stat set to 65

Is this normal?
Any comments/suggestions would be appreciated.



My setup

I have a Firebird (Heatpac) oil fired boiler fitted new 6yrs old (newly fitted as part of new extension as well as all new rads downstairs).
At that time system was converted to sealed system with expansion cyclinder, pressure valve and filling loop squeezed into hotpress.
Boiler was services last October - just cleaned out and oil jet replaced.


About 4weeks I noticed the heating was making funny noises and when I checked the hotpress pressure gauge, there was no pressure.
Could find no leaks in house and as it was late at night, I just refilled up to 1 bar and left it.
Was okay the following morning, but after heating was on for a bit, the pressure was down again.
Found problem was down to bottle valve air vent on top of boiler leaking when pressure built up.
Replaced this and refilled up to 1bar.

Since then I have been watching the pressure, and it keeps rising. As I said above I have just been releasing the pressure on a daily basis to keep it below the 2bar value. Have been doing some reading and unfortunately most peoples problems are related to low pressure not high.
There was hint that the diapharam might be damaged in the expansion cyclinder so I deceided to check the pressure properly.
Drained down system on Monday morning, opened up air vent on last radiator to release pressure further and checked cyclinder pressure.
Because I was checking for water in the expansion cyclinder I had let too much pressure out, so it was low.
I pumped it up 1bar using a foot pump, and refilled system with water to 1bar.

Fired up heating and pressure has risen to 2bar. So far its hovering around 2bar and seems okay, but not confident yet. Have heating switched off timer, and we are manually firing it up for 1hour at a time.

From reading it seems that the only way!!! the pressure can increase is if there is more water being added - ie: the filling loop is constantly open.
My filling loop is from the mains and is connected using an old manual radiator valve into the system via what looks like a pressure reducing valve with a pressure gauge on top and an adjuster screw underneath. When I open the rad valve to add water, there is a whining noise from the pressure reducing valve as the system pressure builds up.
This is the only external connection, so if the rad valve is not closing off completely, then it could be constantly adding water, but I hear no noise!

Because the system is sealed and under pressure I dont think it could be drawing in air somewhere?
When the heating is on all the rads (8 in total) heat up normally, no cold spots etc. All the rads have manual valves, except 1 which have a TRV fitted.
The system is reasonably balanced and gives enough heat where its required.

JamesM

It sound as if water is getting into the system. The valve must not be turning fully off. When the system cools down, the mains pressure must be enough to push through the valve and add some water to the system.
Jim.

white_westie

James

Was thinking of that myself. The Isolating rad valve is in the hotpress mounted in very awkward position upside down, so I dont really want to dismantle it.
Will look into adding another shutoff valve on the mains feed pipe maybe in the attic, to ensure that fill loop is shutoff.
Another test I was thinking of was to drain down system last thing at night and refill it to 1bar - if the valve is leaking the pressure should have risen by the morning.

Any comments on what is 'normal' operating pressure for a sealed system?

WW

white_westie

Just found my pressure reducing valve on the net
Its from a company called Emmeti and they call it an "Automatic Filling Valve 0.5-4bar manual shutoff c/w guage"
Cant find out how they work or how they should be adjusted.
Any ideas anyone?

BMCG100

Hi
I have a sludge problem in my heating system. I'm planning to put some Prote cleaner in and drain it off a few days later. I have 2 questions:
Is this the best thing to do?
None of my rads have a drain valve. Is it possible to drain at the boiler (Firebird Heatpac)?

your desired user name

I have recently had a Baxi Solo HE IE gas burner installed. It is in a sealed pressurised central heating system.

I suspected water loss from the system and turned of the water supply.

When cold and not in use, the system was 1 Bar. Within a few days, it had dropped to to 0.5.

I refilled it and again turned the feed off. The pressure dropped again after a few days.

Does the burner "use" water. I see steam being produced from it going outside. Is this removing water from the system.