Gas Boiler has no pressure

[davidoco]

The tap in the hot-press is permanently open and the pressure remains steady at 1 bar. I've had absolutely no problems except to bleed the system -

The reason it remains at 1 bar (it must change between heating off and on) is that there is a non return valve before that valve which stops water from your heating system going backwards into the public supply so your pressure will stay at whatever the supply to the house is and in Ireland that is usually not more than 1 bar. You really should close the inlet valve and see how things go.

Good place to help identify fittings

http://www.sanbrafyffe.ie/products.html or www.rwc.co.uk

bottom of this page to see non-return valve which is usually brass [broken link removed]

 

[davidoco]

Our valve is in the hot press on one of the pipes leading into the water tank.

That valve is either the cold water feed to the tank which enters at the very bottom

or more likely the return of the heating coil in the cylinder which is about 3/4 way down. Its purpose is to balance the system. You either get loads of hot water before your rads heat or you have a bit of both.

Sometimes an air lock can develop there and opening it fully for a bit moves the air along. You should really return it to its original position (not fully closed!) to return the system to the balance that the installer set - unless of course he didn't bother to get it set right in the first place. That valve on most installations is a wheel valve which people tend not to mess with.

 

[pat127]

The reason it remains at 1 bar (it must change between heating off and on) is that there is a non return valve before that valve which stops water from your heating system going backwards into the public supply so your pressure will stay at whatever the supply to the house is and in Ireland that is usually not more than 1 bar. You really should close the inlet valve and see how things go.

Good place to help identify fittings

http://www.sanbrafyffe.ie/products.html or www.rwc.co.uk

bottom of this page to see non-return valve which is usually brass [broken link removed]

Great, thanks. The pressure falls to just over 0.5 bar when the system is off. What should happen when the valve is closed and are there any negative aspects to watch for?

 

[davidoco]

What should happen when the valve is closed and are there any negative aspects to watch for?

The water inlet valve that we're talking about should be shut unless you have to refill or top up the water.

Remember every time you find air in a rad and bleed it the pressure will drop. An idea might be to open that valve some saturday morning early when heating is off and bring the gauge up to 1. The reason for Saturday morning early is that is when you see better water pressure as there are less businesses and people using water and you might get some extra pressure at the tap to force water into the system.

Heating systems with the water inlet valve, non return valve and small red cylinder should ideally be free of air and full with water at 1 bar when cold. Heating when on will then push that to between 1 and 2 bar - depends on how hot your boiler is running. If you have to bleed a rad because it is cold at the top you will need to go back to the valve and let in a bit more water to bring the gauge back up to 1 bar when cold.

Ideally once you have filled to 1 bar you should not have to top it up more than once or twice a year. If you find that you do have to keep topping up there must be a leak somewhere. When plumbers say "it just happens that the pressure drops" this is because plastic pipe work allows air out of the system very slowly and that causes a pressure drop and not a leak of water, but that should be only noticable once a year.

Another word to complicate issues, most sealed systems will have a small "bottle" air vent fitted at the highest part of the system on top of a piece of 1/2 copper. see [broken link removed] This device will try and trap and release any air in the sytem that reaches it. So by and by during the year it is capturing air that has been hiding in the system and releases it thereby reducing the pressure in the system that needs to be topped up. Remember water contains oxygen (air) and the heating process in the boiler can seperate this air from the water but it does this relatively slowly and only if your boiler is set relatively high.

 

[collieb]

Hi,
Just noticing this post. Our boiler has a label on it saying that normal pressure should be between 1 and 2.
It also says that if below 0.3 you should contact someone.
Ours constantly remains at 0.4 ->0.5 and has NEVER been at normal pressure since we moved into the new house (2 years ago). We only noticed this when it started making strange squeeling noises and having problems with our water pressure so we immediately got someone out to look at it.
We were told it was fine.
It doesn't seem fine to me when you hear the noise and you're having a shower and the water stops coming out.
Is the boiler guy correct in saying it is ok and if so why if the pressure isn't in the normal range? Or should I get someone else out to fix the pressure?

Marty,

A lack of pressure in your heating system shouldn't have any affect on the amount of water coming out of your shower - they are 2 separate systems, and that sounds more like an air lock in the domestic water supply. If pressure is low on your boiler guage, do as advised already here on this post, open the valve in your hot press and let some water in when system is cold until pressure builds to 1 bar, then close the valve and watch what happens when the heating kicks in.

 

[davidoco]

We only noticed this when it started making strange squeeling noises and having problems with our water pressure so we immediately got someone out to look at it.
We were told it was fine.

Marty you mentioned somewhere else that you had a combi boiler but you also had a large tank in the attic. You have a pump somewhere (usually on top or beside the attic tank) that generates the pressure for the incoming water to the combi which in turn feeds your shower with hot water. Your electric shower is also fed cold water from this pump and I bet it's a Mira Sport or similar.

The next time you run out of hot water in your hot water shower and hear the pump go up to the attic and see if there is any water in the large tank. You may be running it dry, ie incoming water from the mains can't keep up with the pump. You will need to adjust the pump down a bit or else your pressure reducing valve needs adjusting or is acting up - two jobs that might be best left to a plumber.


collieb also has a good point that your combi boiler is at the incorrect bar. It may be unable to heat the shower water effectively thereby causing your thermostatic valve to lock in at the shower. Another reason to make sure you get your bars right on the combi.

 

[pat127]

Another word to complicate issues, most sealed systems will have a small "bottle" air vent fitted at the highest part of the system on top of a piece of 1/2 copper. see [broken link removed] This device will try and trap and release any air in the sytem that reaches it. So by and by during the year it is capturing air that has been hiding in the system and releases it thereby reducing the pressure in the system that needs to be topped up. Remember water contains oxygen (air) and the heating process in the boiler can seperate this air from the water but it does this relatively slowly and only if your boiler is set relatively high.

That's extremely comprehensive, thanks for all the tips. I've located the non-return valve and also the bottle air vent. There are 2 more vents above the boiler also. Is it okay to leave all these vents slightly open?

 

[davidoco]

There are 2 more vents above the boiler also. Is it okay to leave all these vents slightly open?

I'm not sure what these two vents would be. One is likely to be the pressure relief valve which is piped to the outside like a drain pipe. It is r shaped usually with a black knob on top.

I see in your first post that you said semi-sealed and I've never heard of that. What might have been said to you that your heating circuit is sealed but your hot water is vented to your attic tank therefore giving your a "semi sealed system". Most new instllations now are fully sealed pressurised hot water and central heating.

 

[pat127]

I'm not sure what these two vents would be. One is likely to be the pressure relief valve which is piped to the outside like a drain pipe. It is r shaped usually with a black knob on top.

That's there as well. I'll ask the service-man about the other 2 when he comes in March.

I see in your first post that you said semi-sealed and I've never heard of that. What might have been said to you that your heating circuit is sealed but your hot water is vented to your attic tank therefore giving your a "semi sealed system".

I'm sure you are right as the house is over 30 years old. I obviously misunderstood what I was told.

Many thanks again.

 

[marty004]

Cheers fellas for all your help.
They have been again a few times now and have decided that the tank in the attic needs replaced.
We are still having the water problems.
In fact our electric shower no longer works at all even when our other showers are working. They think it might be an air lock.
They also mentioned about "dirt" being in the combi boiler which is effecting the pressure gauge.
I just wish they get it sorted.
It's a bit embarrasing having guests come to your new house and teh shower cutting out on them after 2minutes!!
Anyway, thanks again.
I'll print this off and see if they have tried any of these things.
Don't want to tell them how to do their job though, but it is getting ridiculous at this stage.

 

[Manchesterbu]

Worked a treat!

Our boiler was working agian last night after letting more water into the system. It was most likely due to bleeding all the radiators a few evenigs before but worked a treat so thanks for advice.

My girlfriend & I just returned from holiday & had no hot water!
I'm an utter dunce when it comes to things like this.
It's a rented flat with a Potterton performa 28 boiler
I had to pull out a wooden panel to get at the tap but once I twisted it the pressure gauge bounced up & the problems solved!

Thanks guys!!!

 

[col]

Had a similar problem on my boiler with pressure dropping below 1 every night. I had to top up the water every day to get the boiler to work. I assumed I had a leak and had a plumber out to look at it. He took out an air pump (foot bicycle pump) and pressurized a chamber in the system to give a type of back pressure. No leaks , no faulty parts just air was required. System has worked perfectly ever since and stays above 1.