Baxi Bermuda 552 backboiler only starts for 45 seconds and stops.

[Ant1]

Hi all,

My Baxi Bermuda 552 backboiler only starts for 45 seconds and stops.

A bit of history first... for the last 2 weeks, from time to time my Sunvic MK1453 3 port valve would get stuck, therefore I decided to clean it up (after remove the actuator at the front and flushing the system). Everything worked fine for 2 days, but since then the boiler would only start for 45 seconds and stops.

I am aware this is usually a common issue with the pump, however it works fine, it turns strongly (tested with a screwdriver) with little water dripping out when removing the front screw. I thought it could be an airlock issue but I have now drained the system 3 times.

This indeed seems to be an issue with the water not circulating properly, after flushing the system it seems to take much longer than usual to refil. Note that the loft tank was replaced 2 months ago (I lived in a flat where the tank is shared) but I do not think it is the issue, after all it worked for 2 days and I get water in each of the radiators. There was some sludge in the 3 port valve and I suspect that there is a blockage somewhere in the system, may be in the cylinder.

My system is ancient and having some difficulties understanding how the cylinder and expansion vessel works , I tried my best creating a diagram of my set-up, though it is probably not 100% accurate:

Note: updated diagram with better drawing of 3 port valve

The cylinder really looks old, I already replaced the 3 port valve around 1 year ago (again due to sludge damages) hence I would be keen just to replace all of the above in the blue doted area.

I have few questions though:

1) Would you think that my boiler only working for 45 sec could be due to a blocked pipe rather than a airlock?
2) What is the minimum pressure for a Baxi 552 Backboiler to work? (there is no way I can tell how much pressure there is in the system, there is no gauge)
3) Is there a way I can test the cylinder works correctly?
4) Does my diagram above looks like a possible setup?
5) What kind of hardware could be used to replace the above kit in the dotted blue area?

Note that I cannot replace the Back Boiler (which actually works fine) as I live in listed building with no access to the external walls at the back, therefore I cannot get a combi boiler installed and would be obliged to go with an electric option which I want to avoid due to cost reasons.

Thanks,
Ant

 

[DP]

Good drawing but header tank needs redrawn as does the 3 port valve that is shown as four port

 

[picasso]

Have a look at this thread and see if you have something similar.
//www.diynot.com/diy/threads/help-identifying-this-please.199369/

 

[DaveHerns]

Blockage in pipe from feed tank ? Debris flushed into pipe from when tank was changed ?

 

[Agile]

Hi all,

A bit of history first... for the last 2 weeks, from time to time my Sunvic MK1453 3 port valve would get stuck, therefore I decided to clean it up (after remove the actuator at the front and flushing the system). Everything worked fine for 2 days, but since then the boiler would only start for 45 seconds and stops.

I am aware this is usually a common issue with the pump, however it works fine, it turns strongly (tested with a screwdriver) with little water dripping out when removing the front screw. I thought it could be an airlock issue but I have now drained the system 3 times.

Thanks,
Ant

I also think it is an airlock issue.

However, I have seen it so many times on here where a DIYer thinks its an airlock and will then drain the system! That only reinstates the airlock!

The correct solution is to remove the airlock! In fact that is the only solution.

The pump screw is part of that process but in many cases the airlock forms in other parts of the pipework. Usually as a result of a pipework design fault where there are horizontal parts or the pipework does not rise upwards towards the vent.

There are many ways experienced plumbers deal with this problem, usually by loosening compression joints at various points and the cylinder coil is a common place. Sometimes water even needs to be poured down the vent pipe.

Tony

 

[Ant1]

the 3 port valve that is shown as four port

Hi Danny,

This is definitely a 3 port valve, it is connected this way:



I have seen redrawn the above diagram to make it clearer.

header tank needs redrawn

I very much agree with you, would you have details of a Coil type double feed indirect cylinder (Dublotank 100)?

 

[Ant1]

Have a look at this thread and see if you have something similar.
//www.diynot.com/diy/threads/help-identifying-this-please.199369/

Thanks for this, very useful reading.

 

[Ant1]

There are many ways experienced plumbers deal with this problem, usually by loosening compression joints at various points and the cylinder coil is a common place.

Thanks Tony, I am going to see if I can loosen some of the compression joints.

 

[Agile]

Running the pump at full speed, then on CH only, closing all rads except one and moving that one open rad along until all have been opened is a non invasive way which sometimes works.

Alternating between CH only and HW only for say 30 sec each sometimes helps.

 

[stardanny]

First run the boiler and pump on HW only, that will clear airlock on boiler flow and return.

Do you have a air vent around above 3 port valve?

Daniel.

 

[Ant1]

First run the boiler and pump on HW only, that will clear airlock on boiler flow and return.

Hi Daniel, I tried your suggestion (as well as Tony) and no luck so far, I will give it several tries during the course of the day.

Do you have a air vent around above 3 port valve?

Here is the picture of the 3 port valve (actuator removed) with the Spartan ET50 Expansion showing an air vent connected to it:


Note I included a photo of the 3 port valve viewed from the top in an earlier post, if it helps...

 

[picasso]

The spartan et50 acts like a primatic cylinder in that is fills the heating system with the same water as the hot water cylinder, an air bubble then keeps them apart, I would drain down again and refill very slowly.

 

[Ant1]

Despite having applied all the good advice from Tony, Daniel and Picasso, my boiler still shuts off after 45 seconds.

I noticed something very suspicious though, if I open the draining valve from the flow coming back from the boiler (i.e. the bottom valve in the above diagram), I would normally hear the water coming straight from the Spartan ET50 into the draining point (as it is supposed to fill the central heating), however I can hear the water dripping down at a very slow rate. When the boiler was used to work, I could hear and feel the pipes vibrating in this sort of situations.
-> Is there a way to rule out / bypass the Spartan ET50? It is so old it is no longer being made...

PS: I still haven't put back the actuator at the front of the 3 port valve, therefore I slightly loosen the 4 front screws and air escaped (only the first time). Since then, water now escapes each time I loosen those screws, which should mean water is coming from the Spartan ET50, though at a very low pressure but not sure if this would cause the boiler to stop?

 

[Agile]

None of us like that form of filling a system.

It sounds as if yours is filling slowly presumably as a result of a blockage/scaling/gunged situation in it or the nearby pipework.

The correct solution is to fit a conventional header tank!

A professional wanting to get out of your place quickly would probably try back feeding mains water into the lower parts of your system.

If you must try that you need to be aware that you could result in water exiting from the vent pipe. Most likely when you are downstairs controlling letting the water in!

Tony

 

[Ant1]

Thanks Tony,

I am going to seek the help of a professional, I am posting an ad on mybuilder.com to get someone from the Glasgow area to look at it. I very much agree with you, I am looking getting a conventional header tank and probably replacing the cylinder. Thanks for your help.

Ant