It does on mine:
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(right on the front edge of the silver expansion vessel on the right had side of the boiler)
[?] Worcester-Bosch Greenstar 30CDi - losing pressure
Dec 27, 2008
Last reply: 3 years ago
34 Replies
Best Answer
A slight pressure drop over time in a boiler system is not uncommon, and it may be caused by various factors such as air in the system or minor leaks. It's important to keep an eye on the pressure and bleed the radiators as needed to maintain the proper pressure.
However, if you are noticing frequent pressure drops and needing to bleed the radiators often, this could be an indication of a more significant problem such as a leak in the system. In this case, it would be best to have a professional technician come and check the system for leaks.
From an economic standpoint, it may be more cost-effective in the long run to address any potential leaks now rather than waiting for them to worsen and cause more damage to the system. The cost of a technician's visit to check for leaks would be much less than the cost of repairs or replacement of a damaged boiler.
As a DIY homeowner, you can also try to locate the leak yourself by checking the joints and connections of the system, and looking for any visible signs of leaks such as water stains or drips. If you do find a leak, it is best to call a professional to repair it.
It's worth noting that the fact that the central heating pipework in your house is at least 40 years old, it's possible that some of the joints and pipes may have become corroded over time and may need to be replaced.
To better understand and troubleshoot the issue with your Worcester-Bosch Greenstar 30CDi boiler losing pressure, you can consider the following steps:
- Check the pressure gauge on the boiler: Make sure that the pressure gauge is reading within the normal range, usually between 1-1.5 bar. If the pressure is below the normal range, you'll need to add water to the system to bring it back to the normal range.
- Bleed the radiators: If you hear gurgling noises or if one or more radiators are not getting hot, you'll need to bleed the radiators to let out any trapped air.
- Check the expansion vessel: The expansion vessel is responsible for maintaining the proper pressure in the system. If the pressure in the expansion vessel is too low, this could be the cause of the pressure drop.
- Check for leaks: Look for visible signs of leaks such as water stains or drips around the boiler or around the radiators. If you suspect a leak, it's best to call a professional technician to fix it.
- Check the system's valves: The valves in your heating system may not be functioning properly, which can cause pressure drops. Check the valves and make sure they are open and working properly.
- Check the pump: The pump is responsible for circulating hot water through the system. If the pump is not working properly, this can cause pressure drops.
By following these steps, you can get a better understanding of the issue and determine if it's something you can fix yourself or if you need to call a professional technician. It's important to keep in mind that working on a central heating system can be dangerous and if you're not comfortable with handling it yourself, it's best to consult a professional to avoid any potential damage or injury.
Thanks to you and others for this. How extraordinary and unexpected. Anyway the pressure seems within normal bounds.
Not sure why you think so. It’s an air reservoir that may need topping up. What kind of pump and valve would you expect? I can’t think of a better valve.
Did you depressurise your CH system first? If it’s around 3.5 bar then it’s probably okay. If it’s the same as the system pressure on the gauge on you boiler, then it’s probably too low.
You need to vent your CH system down to zero and then check the reservoir pressure.
Tim
I wouldn't have expected any. Before this thread I didn't know there was an air reservoir, much less that it might ever need topping up. The installer manual says almost nothing about it.
No. The installer manual doesn't say to do that that (nor has anyone else before yourself). Mind you nor does it say anything about how to measure the expansion vessel pressure either.
The relevant passage in the manual reads "At the end of the filling procedure, the filling pressure of the heating installation should be at least 0.2bar above the counter-pressure of the expansion vessel. If there is still too much air in the heating installation at the end of the check programme P.00 [described elsewhere as "purging"], repeat the check programme."
When I did this today, the water pressure was 3.6 bar and the reservoir air pressure 2.8 bar (measured with an ancient tyre gauge).
How? (Again the manual doesn't help.)
They should be equal. Or the air pressure slightly higher To have it lower means ther is no more 'give' in the system
Normally a bleed valve on the highest radiator will get the air out. Any bleed valve will lower the pressure
I would be "The boiler integral expansion vessel is precharged to 0.75 bar (equal to a static head of 7.5 meters [22 ft]). A Schraeder type valve is fitted to the expansion vessel to allow for pressure adjustment if required."
Doh! I was mixing up my expansion vessels. I’m pretty sure that the one for my mains pressure HW tank specifies 3.5 bar (which matches the main supply water pressure). As you say, the CH one will be nearer system working pressure.
Tim
Ignore my comment about 3.5 bar! See John’s reply. I was mixing up my mains pressure HW cylinder expansion vessel pressure with a CH expansion vessel which would normally be lower.
You do need to vent your CH system first though. Imagine if you only have a tiny bit of air in your expansion vessel and the water system is charged to 1 bar say. The pressure of that air will also be one bar but it will have virtually no capacity to absorb expansion. The system pressure when hot will quickly rise to the preset blow off pressure (usually 3.5 bar I believe). Excess water will be vented and when the system cools, the pressure will now be much less than 1 bar.
By depressurising the system you can now fully inflate the air containing part of the expansion vessel. Pump it up to one bar say, and now when you add water to the system, there will be much more air to cushion the expansion.
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Tim
Yup, the unvented cylinder ones can be quite a bit higher.
Have a web search for “worcester bosch greenstar 30cdi pressure relief valve” and that will show you the sort of valve that you’re looking for. It’s plumbed in to discharge water outside so you don’t need to worry about making a mess.
Depending on the valve type, you may need to lift a lever or twist a knob. It has quite a strong spring holding it closed so you need a firm grip.
Alternatively you can just bleed water out of a radiator but that’s messy and slow.
Tim
Are we talking about the primary system pressure (i.e. the water in the rads etc)? 3.6 sounds close to the emergency release pressure on most sealed systems.
You can either use the bleed valve on the boiler, or open the drain point a bit to drain off a few litres of water.
Note that if the pressure gauge is on the ground floor of an installation it will always read some pressure from the head of water above it - even when the elastic pressure from the expansion vessel is no longer adding to it.
IMHO It is usually better to not activate the PRV unless necessary since you risk getting dirt / scale / crud etc in the valve and have it not seat properly again. Thus creating a slow leak in the future.
Most CH systems have a proper drain point[1] - possibly with a hose connector on it. The boiler itself probably also has a drain valve. In many cases you can turn off the flow and return valves under the boiler, and use its own drain valve to depressurise just the boiler, and by extension, the pressure on the expansion vessel.
[1] I always hard plumb mine outside to a gully or a soakaway etc, and stick a proper leaver valve on it inside - so it is easy to use, and makes not mess in the house, and needs no rigging up with a hose etc. (depending on your pip layout you may still need other bleed points)
That's what ChatGPT's new AI Text Classifier has decided about them
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Out of interest I went and got the original question and pasted into ChatGPT. Got this:
"A pressure drop in a central heating system can be caused by a variety of factors, including air in the radiators, a leak in the system, or a problem with the expansion vessel. Since the issue has only been happening for a few months, it is possible that there may be a small leak somewhere in the system.
The gurgling noises and need to bleed the radiator may indicate that there is air in the system, which is not uncommon. However, if the pressure continues to drop over time, it may be a sign of a more serious problem, such as a leak.
In any case, it is a good idea to have a professional inspect the system to determine the cause of the problem and recommend any necessary repairs. The age of the central heating pipework and the use of a chemical treatment could have potentially caused pinholes to develop, so it is important to address the issue as soon as possible."
Which is actually a much better answer than the HOH bilge!
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