Help with heating system

[barakka]

Hi, looking for some assistance with our heating system problems, i've done a few searches but not sure as the problems are quite strange.

System is 5 years old, Baxi Solo 3 boiler in kitchen, hot water tank in upstairs cupboard, feed tank in loft.

History of system...
New build house in 2005
Heat exchanger cracked in 2007 - while on holiday - fixed by 1st engineer in phone book (mistake)
6 months later heat exchanger failed again - replaced under warranty - think wasn't fitted properly.
2009 - three-way valve replaced (heating but no hot water)

Current problems -
During cold winter (-5 and more) noticed strip of ice running down wall outside from boiler vent. Approx 5 foot long and 3in wide/1in thick at top near vent. No other houses seemed to have this.

Heating would not heat house to anywhere near thermostat temp - getting up to about 19 deg C until boiler turned up to nearly max temp - then boiler started overheating.

One radiator not working - TRV looks OK - now two radiators not working - second one is the one with no TRV. Don't need bleeding, water comes out immediately - tried bleeding small (non-TRV) one - about 2 pints out of it, and radiator got almost luke warm.

When heating comes on it runs for about 30-40 mins then goes off for about 5 mins, then on for 5-10 mins, then off for 5 mins etc etc

After running for a couple of hours you can hear when it goes off a kind of "fizzing" noise from the boiler - bit like a kettle boiling with little water, and excessive steam from vent.

Feed tank in loft checked, water in it, ball-cock working fine.

Side note - heating pump runs 24/7 - always has from day 1

No problems with Hot Water.

Would love some ideas of what to check, had an engineer look at it, but it worked fine for him, need more info before getting him back.

TIA

 

[D_Hailsham]

Is the pump external or internal to the boiler?

The pump is supposed to run on for a few minutes after the boiler goes out. If it runs continuously, then either the control board is faulty or (external only) it is wired wrongly.

normally a boiler thermostat would be left at or near max and the house temperature controlled by a wall thermostat. Do you have a wall thermostat?

The ice will be water vapour condensing and freezing when it comes into contact with the cold air outside.

Remove the head from the TRV and make sure the pin moves up and down. It should spring up when pressed down and released.

Did you turn the heating off and let the water cool down before bleeding?

Did you bleed the downstairs rads first?

When heating comes on it runs for about 30-40 mins then goes off for about 5 mins, then on for 5-10 mins, then off for 5 mins etc etc

That's normal. The first 30-40 minute session is bringing the water temperature up to 70deg+ from about 20deg, at which point it turns off. The water will then cool down about 10deg before the boiler lights (that's the 5 mins off) when it relights to bring the water back up to temperature (thats the 5-10 minutes on).

Feed tank in loft checked, water in it, ball-cock working fine.

That means water can get into the tank (I assume you mean the small tank), but not that it can get out of the tank to make up for any losses in the system. You need to open a drain tap (hose type connection on ground floor normally near a rad) and check that the water level in the tank goes down as some water is drained out.

 

[barakka]

Thanks for your reply...

Is the pump external or internal to the boiler?

The pump is External - WILO Gold 60

The pump is supposed to run on for a few minutes after the boiler goes out. If it runs continuously, then either the control board is faulty or (external only) it is wired wrongly.

I thought this would be the case, but as it's always been this way we never questioned it. Must be wired wrongly.

normally a boiler thermostat would be left at or near max and the house temperature controlled by a wall thermostat. Do you have a wall thermostat?

Yes, there's a wall thermostat in the downstairs hall opposite the radiator without a TRV.

The ice will be water vapour condensing and freezing when it comes into contact with the cold air outside.

It just seems excessive, when it froze it was the full length from the vent to the floor, and at least an inch thick - probably 3-4 inches wide at the top, and as I said, no other houses on the street (all same age/boiler) had anything like this. Now the temp is about 2-3 deg C and when the boiler runs it puts out big thick billows of steam from the vent. Could this just be the vent not being angled up enough ? There is movement in the vent itself...

Remove the head from the TRV and make sure the pin moves up and down. It should spring up when pressed down and released.

One of the radiators not working has a TRV and the pin looks fine and springy, the other non-working radiator is the non-TRV one.

Did you turn the heating off and let the water cool down before bleeding?

Did you bleed the downstairs rads first?

It was a downstairs one I tried, but I did it with the heating on, will try with it off.

Feed tank in loft checked, water in it, ball-cock working fine.

That means water can get into the tank (I assume you mean the small tank), but not that it can get out of the tank to make up for any losses in the system. You need to open a drain tap (hose type connection on ground floor normally near a rad) and check that the water level in the tank goes down as some water is drained out.

How do I tell if the tank level goes down ?

Many Thanks

 

[D_Hailsham]

The pump is supposed to run on for a few minutes after the boiler goes out. If it runs continuously, then either the control board is faulty or (external only) it is wired wrongly.

I thought this would be the case, but as it's always been this way we never questioned it. Must be wired wrongly.

Not necessarily. Although it is external, it is still wired to the boiler, so it could be that the PCB is faulty. This is quite common, with the same symptoms as yours.

It just seems excessive, when it froze it was the full length from the vent to the floor, and at least an inch thick - probably 3-4 inches wide at the top, and as I said, no other houses on the street (all same age/boiler) had anything like this. Now the temp is about 2-3 deg C and when the boiler runs it puts out big thick billows of steam from the vent. Could this just be the vent not being angled up enough ? There is movement in the vent itself...

Can you give more details about your boiler - there are several versions of the Solo 3? The GC (Gas Council) Number is the best identifier.

It was a downstairs one I tried, but I did it with the heating on, will try with it off.

OK

How do I tell if the tank level goes down ?

You need an assistant in the loft to inform you!

Turn the heating off.
Set the motorized valve to the MAN position using the lever in the slot.
Send you mate/partner into the loft
Put a container under the drain point or connect a hose to the outside.
Open the drain tap
Water should come out
The level in the small tank should go down and then the ball valve open
If it does - shut the drain tap. Your feed is OK
If it does not - shut the drain tap. The feed pipe from the tank is blocked.

If you have a magnet, you should be able to locate the blockage (magnet will stick to the copper pipe) and replace just that bit of pipe. You should also do the magnet test on the vent pipe and the pipes around the motorized valves, pump and HW cylinder.

 

[barakka]

Can you give more details about your boiler - there are several versions of the Solo 3? The GC (Gas Council) Number is the best identifier.

GC Number on the boiler is 41-075-21

 

[D_Hailsham]

GC Number on the boiler is 41-075-21

So you have the Solo 3 40 Pfl, which is not a condensing boiler. In that case the flue should go through the wall horizontally, with no slope on it.

The clouds of steam you see is just the water vapour in the exhaust gases. Condensing boilers extract the energy from the water vapour. Why you should be creating more "steam" is the mystery, which I can't answer.

As your neighbours don't have the same problem, it might be worth asking them how their boilers are set up - temperatures etc.