Alpha Combi Boiler Pressure Issue

S

Sysman_MK

Hello all, I have done a quick search but couldn’t find anything that matched all of my problems. Well here goes.

The problem is the boiler is constantly loosing pressure and causing the warning lights to flash meaning no hot water. This happens when just using the hot water or hot water + CHs. After speaking to a chap at Alpha I went through the following:

Bag over PRV – no water coming out.

Closed flow and return valves on boiler to isolate CH – pressure loss still occurs.

Now after opening the filling loop to reset the pressure the loss can occur after a few hours, or almost straight away. Sometimes you can watch the needle go from the green into the red.

I have had the person who installed the boiler take a look. He replaced the PRV and filling loop and gave it the all clear but it still has the same issue, and now he says that it is just air in the system that is causing the problem and that I need to bleed the rads.

Well yesterday evening I turned up the CH, turned off all the rads, and then opened each one fully intern and bled them (5). After I done this the boiler pressure gauge was in the middle of the green and every radiator was red hot. Left it like this for a few hours and all was ok.

At bout 10ish I turned the thermostat for the CH down and went to bed. Woke up this morning with the boiler pressure valve on zero, but no warning lights. Ran a hot tap and the warning lights came on. Back to square one.

I am at a loss at what to do. I need to get it fixed but am loathed to call out said engineer as he seems to think the boiler is fine when is obviously isn’t.

Cheers
 
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Is it a condensing boiler? If so perhaps the heat exchanger has failed and the water is leaking into the condensate pipework.

Alternatively the expansion vessel may have failed and the air is gradually leaking from it or the diapraghm is perished. Its not easy to access on the newer Alphas - so have the installer check its ok.

Since the pressure drops so quick with the isolating valves close I would imagine any other leak on the boiler would have become apparent by now.
 
S

Sysman_MK

Hiya Gasguru

It is a Alpha HE CB25 and is approx 18 months old.

Are the heat exchanger / expansion vessel falults easy to spot?

Cheers
 
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The expansion vessel is checked by having the system pressure showing 0 Bar. The vessel is located behind the boiler. A metal plate on top of the boiler at the rear must be removed to access the air valve on the vessel. With a rear flue connection its a pain but if you have pipework running up behind the boiler its very difficult.

The tyre valve cap is removed and the air pressure checked - it should be aboput 0.7 - 1 Bar. Read FAQ's for more details. As I said the air can leak through the metal seam or through into the water side (where it may be vented off through the automatic air vent). Pumping up the vessel will show these faults.

If the leak is on the heat exchanger then with the pressure at 1 Bar, isolate the flow and return valves. Now locate the condensate drain pipework and collect any water as the pressure drops. With the boiler off there should be no water eminating from the pipe.
 
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If the pressure loss is from the boiler then its either from the PRV or the condensate drain if you cannot see water dripping underneath.

The boiler should still be under warranty so dont go damaging it but certainly check the condensate pipe.

Minor issue, are you quite sure PRV vent pipe really does go through the wall? There have been some which dont!!! If in any doubt I disconnect it under the boiler to check.

Tony
 
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Agile said:
If the pressure loss is from the boiler then its either from the PRV or the condensate drain if you cannot see water dripping underneath.

The boiler should still be under warranty so dont go damaging it but certainly check the condensate pipe.

Minor issue, are you quite sure PRV vent pipe really does go through the wall? There have been some which dont!!! If in any doubt I disconnect it under the boiler to check.

Tony

or putting the condensate drain in to the cavity of a wall....
 
S

Sysman_MK

Cheers for the input guys. I have again isolated the the flow and return valves to see if the CH is causing the issue as advised by my engineer to see if it will still loose pressure since the new parts have been fitted.

So the boiler is now olny heating taps. Going to leave it like this till sunday (48h) and see if the pressure drops. If it stays the same, and begins to drop again I am guessing that I have a leak with my CH?

@Agile The Boiler is no longer in warranty, ony supplied with one year :(

Is the condensate pipe easy to find?
 
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as you face the boiler it be on your left under the boiler. usually have a white plastic overflow pipe of it but in reality it could be anything the installer had to hand.

check where it is going and see if there is a lot of water. in normal operation when it is on there will be a few drips. if you have the boiler switched off and the boiler isolated there should be no water coming out.
 
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Sysman_MK said:
Well yesterday evening I turned up the CH, turned off all the rads, and then opened each one fully intern and bled them (5). After I done this the boiler pressure gauge was in the middle of the green and every radiator was red hot. Left it like this for a few hours and all was ok.

At bout 10ish I turned the thermostat for the CH down and went to bed. Woke up this morning with the boiler pressure valve on zero, but no warning lights. Ran a hot tap and the warning lights came on. Back to square one.


Cheers

You need to set the pressure of the system when it is cold, not while running it hot it will give a false reading and naturally will drop while cooling down.
 
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The three year warranty only applies if they are professionally fitted by a CORGI registered installer! Also needs an annual service to keep it going.

Tony
 
S

Sysman_MK

Well the flow + return valves have been closed since Friday and the same is still happening. In the morning (8:00) while the boiler is cold I use the filling loop to top up the pressure to the middle of the green (1bar) by the evening it has droped to the bottom edge of the green, then by the next morning it is zero and warning lights are flashing.

So if I understand right the CH isn't the casue, as my instller thinks, but with the boiler?

I am going to put a bag over the pvr outlet again today to check that again, and will take alook at the condensate pipe.
 

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