Is my boiler's pressure too high?

Ellie83

Hello everyone. We had some problems over Christmas with our boiler and the Estate Agent sent a man from the boiler company to sort it out. While he was testing hot water, he told us he would add some water to the system.

Before he did this, the pressure was at 1.5 bar when hot water wasn't in use and at 2.0 bars when we were using hot water.

Now the pressure is at 2.3 at its lowest and 3.5 at its highest. He told us it was completely normal, even if the pressure indicator is in the red when we are using hot water (it is some kind of little clock that moves according to the pressure).

Now, I would normally trust a person's professional judgement but, after reading the boiler's manual a second time, it says that the indicator should not be in the red.

Do any of you know if this is normal? He seemed so sure of himself that I am thinking I may be too cautious!

I tried to explain things as accurately as possible, I hope it is clear enough, I am really not good with this sort of DIY

Thank you

djheath

No that's not normal. When you heat the water (for central heating) the pressure will increase and fill an expansion vessel in the boiler. The system should be filled with water to a pressure of about 1.1 bar. Check the manual it will tell you. When the heating is on, the pressure will rise to about 2 or so bar. If it goes over 3 bar, there should be a pressure release valve which will release water out of the boiler. This is a safety feature to stop the boiler going bang. If the pressure is released, the release valves can sometimes start leaking which is annoying and they will need to be replaced.

You should reduce the pressure of the boiler to what the manufacturer says is the correct level. This will mean draining some of the water out of the central heating system when the system is cold. Drain from a radiator bleed valve or a drain point. You shouldn't have to drain off too much.

The pressure is really for the central heating and will fluctuate a bit when the hot water is used too, but will return to a normal pressure very soon after turning off the hot tap. I wouldn't expect the pressure to rise by masses amounts when the hot water is used. My boiler has a cold pressure of 1.1 bar. It rises to about 1.5 when only the hot water is used.

lolarentt

djheath has said it all really. Our installer/service guy is happy for the boiler to even run under 1 bar, it needs occasional boosts to put it back to something over 1, but this is only necessary about every 6 months. It never gets anywhere near the red!

Ellie83

Thank you so much djheat! I have emailed the Estate Agent to tell them what happened as I don't want to be responsible for any damage it might have caused!

I will ask o/h to bleed a radiator

Ellie83

Well I had to turn the whole thing off as I read in the manual that, should the pressure go above 3 bars, the valve and the "air charge in the expension vessel" have to be checked by a qualified engineer. It looks like another weekend without hot water/heating

We are tenants so the boiler does not belong to us.

red_devil

we have a combination boiler and seem to have to check the pressure quite abit in the cold weather otherwise there is no hot water. The person who installed the boiler should show you what to do.

espresso

Ellie83 wrote: »

Well I had to turn the whole thing off as I read in the manual that, should the pressure go above 3 bars, the valve and the "air charge in the expension vessel" have to be checked by a qualified engineer. It looks like another weekend without hot water/heating

We are tenants so the boiler does not belong to us.

That sounds a bit drastic. Simply get your OH to reduce the pressure to that recommended in the manual and see how it goes. It sounds like this guy wasn't 'a man from the boiler company' if he increased the pressure unnecessarily!

Ellie83

He certainly had all the paperwork + van from the company, so I trusted him

My OH will be home this afternoon and I have NO idea how to bleed a radiator. I should have listened to my dad when he wanted to show me! OH knows how to do it though, so I can still learn :rotfl:

ic

If the estate agent can't get you sorted for the weekend, get your own plumber out and then withhold the charge from the next months rent payment. You shouldn't have to live without heat in this weather. Make sure you give the estate agents the option of sorting it today first - but make the ultimatum.

Ellie83

Thank you all very much for your advice. Got a call back from the plumber and I was told to bleed the radiator and call again tomorrow if the pressure rises as it may mean that water is added to the boiler continuously.

I also noticed that the pipe going out of the boiler to the outside wall has been dripping (it is not dripping now that I have turn the boiler off). Am I right to think this is the boiler's way to get rid of the surplus of water?

And how much water should we release when we bleed the radiator? I will of course be staying near the boiler to check the pressure but I wonder how much water we should be expected to remove, ie a tiny bit or a fair amount (a bucket would be needed?)?

roger196

The boiler dripping outside is most likely caused by the pressure relief ( or blow off) valve lifting at 3bar to release the excess pressure. Continuous pressure build up is sometimes caused by leaving the filing loop connected and the valve on it leaking water at mains presure into the boiler. The filling loop is disconnected to prevent contamination between the central heating water (often black with ferric oxide) and drinking water in the household mains( water by-laws). The pressure relief valve should be checked at each service that it releases water and then fully closes again.
The boiler should not be pressured to more than 1.5 bar( a few models 1bar so check manual) when cold. I would have serious doubts about this persons competence...did you check that he personally was gassafe registered and that his registration was up to date. Do not let the pressure fall below 0.8 bar ( depends on model) as boiler will not work due to low pressure.
Go on the manufacturers website and order/download a copy of the users manual (about 4 pages) and the manufacturers instructions ( about 50 pages)( not sure which one you have). I am not suggesting you work on the boiler but they will give insight into what should be done. I assume you have a current gas safety certificate from your landlord.