Boiler pressure gauge dropping

[laguna]

Hi - I wondered if someone could explain how I can get a pressure drop on my boiler when i've done the following test.

1. Let the whole system cool down for a few hours.
2. Open the filling loop and set the pressure to 2 bar.
3. Fully close the boiler flow and return valves.
4. Turn off the boiler.
5. Place cups under the condensate pipe and pressure release pipe.
6. Leave the boiler like this for 14 hours.

When I check the boiler 14 hours later, there is no water in the cups, BUT the gauge has dropped down by at least a 1/3rd of a bar of pressure.

There are no other pipes from boiler and no other visible marks of water escaping.

Surely I should either have water in my cups or the pressure gauge still at 2 Bar.

 

[chris watkins]

Yep must be leaking or a valve letting by. (un-less the water in the boiler was still warm & then went cold)

 

[laguna]

Thanks, I let it cool down for 2 hours before isolating with the flow and return valves.

I can't see any other evidence of water.

I even tested the flow and return valves by closing them, opening the filling loop and the gauge didn't move, then reopened the valves and they gauage jumped up.

 

[Fishpond]

could be a leaking/cracked heat exchanger.

Next time the boiler is running, check to see if the the condense pipe is warm from excessive discharge

 

[Centralheatking]

I have read your post carefully - apart from a slight pressure drop you
do not explain why you are carrying out these tests.

Most combis work at 1.5 bar so why do you set it at 2 bar ?..placing a 'cup' under the condense pipe will tell you nothing, and as you state the PRV (not prp) is not passing.

1/3 of one bar is a v small drop - does it rise again when u put the heat on ?m - perhaps you might re-state ur problem -

What combi boiler, how many rads, and what is the problem ? is it dropping down to zero eg..... centralheatking

Hi - I wondered if someone could explain how I can get a pressure drop on my boiler when i've done the following test.

1. Let the whole system cool down for a few hours.
2. Open the filling loop and set the pressure to 2 bar.
3. Fully close the boiler flow and return valves.
4. Turn off the boiler.
5. Place cups under the condensate pipe and pressure release pipe.
6. Leave the boiler like this for 14 hours.

When I check the boiler 14 hours later, there is no water in the cups, BUT the gauge has dropped down by at least a 1/3rd of a bar of pressure.

There are no other pipes from boiler and no other visible marks of water escaping.

Surely I should either have water in my cups or the pressure gauge still at 2 Bar.

 

[shaunsinky]

could be as simple as a faulty gauge?

 

[laguna]

Hi and thanks for your detailed response, the issue I have is its a pressurized system, not a combi boiler, hence over the course of a week all the pressure is lost and the boiler will fail to start.

Its a Main system boiler 28KW running 14 rads.

It is normally only on 1 bar of pressure, I was just using 2 bar to exaggerate the problem a little.

I've spent a lot of money trying to get to the bottom of the pressure loss. I've even had one of these leak detection firms in who carried out a nitrogen/hydrogen gas trace in all the central heating pipework and found no leak in the system.

This is why I am testing the boiler, you say a 1/3rd of a bar isn't a lot but when I've released a 1/3rd of a bar of water from the boiler its about 300ml worth or a can of coke in volume.

I carried out another test last night, as I have 2 isolating valves on my central heating pipework (my boiler is in the garage) before the pipes enter the house. This time I left the flow and return open but closed the central heating pipework valves, so in essence I had isolated the garage/boiler from the house. Checking this morning, albeit only 8 hours later, again it had dropped over a 1/3rd of a bar.

 

[Centralheatking]

You could check if the size of the pressure vessel is adequate for the size of your system
adding another is dead cheap and easy - about £40 plus plumbers time - one just t's it in in a convenient place.

Its quite possible & normal for a pressurized system to loose 500ml water each week or 2
without ever being detected. API - my company have done loads of research, enginnering
practical and statisical into pressure systems - 64% of all home owners/renters have
pressure loss problems on a daily/weekly/monthly frequency. This year we will launch

MFD PD18 a unit that is WRas approved and answers all these problems


centralheatking

 

[Centralheatking]

What do you mean by closing the c/h pipework valves ? - under the unit will be the
boiler isolaters close them and then see what happens centralheatking

Hi and thanks for your detailed response, the issue I have is its a pressurized system, not a combi boiler, hence over the course of a week all the pressure is lost and the boiler will fail to start.

Its a Main system boiler 28KW running 14 rads.

It is normally only on 1 bar of pressure, I was just using 2 bar to exaggerate the problem a little.

I've spent a lot of money trying to get to the bottom of the pressure loss. I've even had one of these leak detection firms in who carried out a nitrogen/hydrogen gas trace in all the central heating pipework and found no leak in the system.

This is why I am testing the boiler, you say a 1/3rd of a bar isn't a lot but when I've released a 1/3rd of a bar of water from the boiler its about 300ml worth or a can of coke in volume.

I carried out another test last night, as I have 2 isolating valves on my central heating pipework (my boiler is in the garage) before the pipes enter the house. This time I left the flow and return open but closed the central heating pipework valves, so in essence I had isolated the garage/boiler from the house. Checking this morning, albeit only 8 hours later, again it had dropped over a 1/3rd of a bar.

 

[stevetheplumber]

there must be water leaking somewhere is there any buried pipework between the boiler and the iso valves you closed?

 

[jonnyboy]

put your pressure upto 2bar run heating full temp for approx 30 mins check system for leaks personnely i would remove cover and check around heat exchanger and pressure gauge pipe good luck.

 

[laguna]

Hi thanks, I have the isolating flow and return valves under the boiler, I also have another set of valve on the C/H pipework and the hot and cold water supply, all in the garage and all before the enter the house, the pipework is not buried in the garage it runs up the wall and enters the house in one of the front bedrooms.

 

[laguna]

I've checked the system 14 hours later. The boiler gauge has dropped but not as much, only about 0.1 this time. It seems introducing an external vessel has made a difference to the results. I might take out the boiler expension vessel tonight and let it run on just the new external vessel.

 

[glenno1]

Exp vessel shouldnt need to come out

 

[Centralheatking]

Do tell us the end result - its nice to read a problem resolved...
so you banged in another exp as I suggested...centralheatking

I've checked the system 14 hours later. The boiler gauge has dropped but not as much, only about 0.1 this time. It seems introducing an external vessel has made a difference to the results. I might take out the boiler expension vessel tonight and let it run on just the new external vessel.

 

[laguna]

Yes thanks, the pressure seems to be holding up at the moment, I'm also pleased I put a pressure gauge on a rad indoors, least I can keep an eye on it all the time, without trips to the garage. Thanks for your advice.

What was the device you mentioned before ? MFD PD18

 

[Ollieg]

What about the cylinder coil???

edit: didn't see that you had resolve it.