high water pressure on vokera 20/80 flomatic

[tonymac233]

Hello,This is tonymac I am a 1935 model human being having trouble with 1995 vokera 20/80 flowmatic boiler and i sure need your help.
My overflow pipe at the back of my house is dripping water and the water pressure is 3.5.
When i drain the system down to 1.5 the dripping stops but the pressure will still go back up to 3.5.However, if i turn off the cold water supply ton the boiler it remains at 1.5.
I have replaced the expansion vessel with a new one but the problem remains.
I do have a book on installation and servicing instructions which displays all the parts and what they do,I just need your help to point me in the right direction.
Thank you Tony mcintyre

 

[Gasguru]

The filling loop valve(s) are letting by - disconnect the loop - should be flexible hose.

 

[tonymac233]

The filling loop valve(s) are letting by - disconnect the loop - should be flexible hose.

Hi thank you for your help will give it a try tonymac

 

[tonymac233]

The filling loop valve(s) are letting by - disconnect the loop - should be flexible hose.

Hi thank you for your help will give it a try tonymac

Hi Gasgura i gave it a go and took the loop out and turned the cold water supply back on however, after 3hours with the boiler off it was
back at 3.5. I set it back to 1.5 with the loop out and turned off the cold water supply and 3 hours later it is still at 1.5 ??what do you think.

Thanks again Tony mcintyre

 

[Gasguru]

The domestic heat exchanger is probably pinholed allowing the mains to pressurise the heating side.

Occasionally it can be due to other fittings downstream of the boiler ie a faulty mixer valve.

New heat exchanger is around £100.00 - corgi job to fit as probably involves removal of gas parts to access.

 

[Agile]

If you managed to replace the expansion vessel yourself then you could probably replace the secondary heat exchanger. I dont think any gas parts have to be disconnected from memory.

What type of work have you done of a related type?

Tony

 

[tonymac233]

If you managed to replace the expansion vessel yourself then you could probably replace the secondary heat exchanger. I dont think any gas parts have to be disconnected from memory.

What type of work have you done of a related type?

Tony

I built and tested diesel engines for british rail locos.
I am looking at a picture of the dhw heat exchanger which as a rubber
diaphragm in it ,and also at the heating manifold which also as a diaphragm in it. if the diaphragrm of any of these units had holes in would this cause the problem
tonymac

 

[tonymac233]

The domestic heat exchanger is probably pinholed allowing the mains to pressurise the heating side.

Occasionally it can be due to other fittings downstream of the boiler ie a faulty mixer valve.

New heat exchanger is around £100.00 - corgi job to fit as probably involves removal of gas parts to access.

Hi gasguru, just reading about the heat exchanger in the instruction book
tonymac

 

[tonymac233]

The domestic heat exchanger is probably pinholed allowing the mains to pressurise the heating side.

Occasionally it can be due to other fittings downstream of the boiler ie a faulty mixer valve.

New heat exchanger is around £100.00 - corgi job to fit as probably involves removal of gas parts to access.

Hi gasguru, just reading about the heat exchanger in the instruction book
tonymac

Hi it Tonymac
I have three questions to ask you, so i have put some pictures on my web space so you know what i am talking http://www.zen65048.zen.co.uk/heating.html
tonymac

 

[DP]

It can, but the heat exchanger will not (or be difficult to) come out after union nuts have been slackened. Fan hood above the heat exchanger will have to be removed. You will also need new seals.

O ring is in fact an aluminium washer. No, the diverter valve does that. This valve acts as a junction among other things.

Primary water (water that heats the radiators) enters the red heat exchanger at 12 o’clock position of the diverter valve and outflows through the pipe behind the HW EV. 9 o’clock position on the valve directs water to the radiators.

During CH demand primary water flows to the rads. Port at 12 o’clock is closed by an internal spring. During HW demand, a shuttle within the diverter shuts the port at 9 o’clock and opens 12 o’clock port allowing water to flow through the red vessel. This water then enters the manifold on the left to be pumped to the main heat exchanger to pick up more heat. This water does not flow through any pipes in the HW HE- it just fills the red container. Cold water flows through a coil within this container.

 

[tonymac233]

It can, but the heat exchanger will not (or be difficult to) come out after union nuts have been slackened. Fan hood above the heat exchanger will have to be removed. You will also need new seals.

O ring is in fact an aluminium washer. No, the diverter valve does that. This valve acts as a junction among other things.

Primary water (water that heats the radiators) enters the red heat exchanger at 12 o’clock position of the diverter valve and outflows through the pipe behind the HW EV. 9 o’clock position on the valve directs water to the radiators.

During CH demand primary water flows to the rads. Port at 12 o’clock is closed by an internal spring. During HW demand, a shuttle within the diverter shuts the port at 9 o’clock and opens 12 o’clock port allowing water to flow through the red vessel. This water then enters the manifold on the left to be pumped to the main heat exchanger to pick up more heat. This water does not flow through any pipes in the HW HE- it just fills the red container. Cold water flows through a coil within this container.

THANK YOU FOR THAT INFORMATION i can now see how the dh water exchanger could cause the problem with the pressure going up if the ciol inside had holes in it.I now think this is the problem because when i turn off the cold water supply to the exchanger the pressure will
stay at 1.5 .I think it was worth putting the pictures on the net because you get a better answer when people know what your trying to find out, as soon as i read your reply on what the job of each item in the pictures was and how it worked i feel i can move on now
Thans again Tonymac

 

[DP]

Before you embark on replacement HE, I would be looking to service the three port valve. The tail end/ domestic manifold can let by secondary to primary.

Replacement of HWHE is quite tricky.

Our water has pH of 7. Cannot remember replacing one of these HEs

 

[scatmanjohn]

Before you embark on replacement HE, I would be looking to service the three port valve. The tail end/ domestic manifold can let by secondary to primary.

Replacement of HWHE is quite tricky.

Our water has pH of 7. Cannot remember replacing one of these HEs

I agree with DP on that one.

I have seen lots of these passing via the 3 way valve and pressurising the system.

Thats always my first port of call.

 

[tonymac233]

Before you embark on replacement HE, I would be looking to service the three port valve. The tail end/ domestic manifold can let by secondary to primary.

Replacement of HWHE is quite tricky.

Our water has pH of 7. Cannot remember replacing one of these HEs

I agree with DP on that one.

I have seen lots of these passing via the 3 way valve and pressurising the system.

Thats always my first port of call.

Hi Scatmanjohn could you please have a look at my wedsite http://www.zen65048.zen.co.uk and see if i am on the right road. thanks tonymac

 

[tonymac233]

Before you embark on replacement HE, I would be looking to service the three port valve. The tail end/ domestic manifold can let by secondary to primary.

Replacement of HWHE is quite tricky.

Our water has pH of 7. Cannot remember replacing one of these HEs

I agree with DP on that one.

I have seen lots of these passing via the 3 way valve and pressurising the system.

Thats always my first port of call.

Hi Scatmanjohn could you please have a look at my wedsite http://www.zen65048.zen.co.uk and see if i am on the right road. thanks tonymac

try http://www.zen65048.zen.co.uk/heating