New house, Bisai Heating System

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Hi All,

I have recently moved into a house that had a combi boiler fitted approximately 6/7 years ago.

Rather unfortunately, the combi boiler is a Biasi Riva Compact (M96.28SM/C2), which I know have a bit of a reputation for being “bottom of the barrel”.

There are a few things concerning me about the heating system.

1. Immediately following its annual service the boiler ignition electrodes have gone crazy! Prior to the service they would click once, the flame would ignite and all was well. However since the service the boiler ignites on the first click still, however the clicking continues after the flame is visible for approx 10 seconds (20-30 ticks in total?). I understand that this particular boiler has two spark electrodes and a detection electrode. Could the flame detection electrode have been accidentally knocked during the last service or be on its last legs? The plumber that did the service has basically said that he hasn’t done anything that would affect the electrodes it and is rather unwilling to check it!

2. All of the radiators have TRV’s fitted. Whilst I understand that the boiler has a built in bypass to protect the heat exchanger when the TRV’s close, I am of the opinion that a secondary bypass is also required with this model of boiler? Presumably this is easily gotten around by removing, say the TRV’s from the hallway and bathroom?

3. Loud knocking noise from bedroom radiator when boiler fires up from cold. I’m assuming that this is thermal expansion, causing one of the pipes to rub against a joist or something as when I have lifted the radiator slightly the ticking seems to stop. Is there anything else I could try to bottom it out further?

Apologies for all the questions but I’m starting to think that this heating system was put in by a non competent person!

Lee
 
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How did you know they worked well prior to the service? Did you sit there everyday watching it, then after the annual service, sit there and think that's different?

TRVs, no separate bypass required, although if run off a room stat no need for one on the rad closest.

Take floorboards up, just to be an arse I hope it's chipboard. Good luck.
 
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How did you know they worked well prior to the service? Did you sit there everyday watching it, then after the annual service, sit there and think that's different?

TRVs, no separate bypass required, although if run off a room stat no need for one on the rad closest.

Take floorboards up, just to be an a**e I hope it's chipboard. Good luck.

Thanks for the reply.

The boiler has one of those remote programmable thermostats. I re-programmed it the day I moved in to suit our heating times etc and physically stood by the boiler to watch it switch on and off, to check the signal was being received correctly - so I know for a fact that the electrodes were not like this previously.

The biasi manual seems to recommend an additional bypass if using TRV's or microbore pipework. Is this just a get out clause in their manual?

Will definateley lift the floor boards - fortunately they are proper ones (screwed down too)!
:p
 
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Yes I understand what you're saying, rectification can be a nuisance. At the time you were testing it may have been ok, but not always, you wouldn't notice. What did the plumber do? If he removed fan, burner etc then maybe he's disturbed something, but I doubt he did, could be wrong of course. If it's clicking now on every attempt then get him back.

How many rads have you got? It's very unlikely all TRVs shut to basically overheat the boiler even with it's own bypass.
 
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Yes I understand what you're saying, rectification can be a nuisance. At the time you were testing it may have been ok, but not always, you wouldn't notice. What did the plumber do? If he removed fan, burner etc then maybe he's disturbed something, but I doubt he did, could be wrong of course. If it's clicking now on every attempt then get him back.

How many rads have you got? It's very unlikely all TRVs shut to basically overheat the boiler even with it's own bypass.

He basically just hoovered the combustion chamber out! What is interesting is that the flame detection electrode sits right next to the combustion chamber in the manual. Presumably if this got slightly knocked it may not detect the flame accurately?

I've tried to get him back, but he has no interest. I may even report him to gas safe through work.

9 radiators in total.
 
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Report him for what? So you watched him just hoover this out and that was it? Don't open a can of worms without a tin opener my friend. Get somebody else in, have them check the problem, it's not a major fault.
 
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Report him for what? So you watched him just hoover this out and that was it? Don't open a can of worms without a tin opener my friend. Get somebody else in, have them check the problem, it's not a major fault.

In a nut shell yes, that's all he did.

He could have at least checked it could he not?
 
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Then who's to blame :rolleyes: Try picking a better engineer next time and not a plumber.
 
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Then who's to blame :rolleyes: Try picking a better engineer next time and not a plumber.

Unfortunately this is a sign of the times. I'm actually a Building Services Design Engineer myself, however I'm not qualified to physically install much.

However someone who has down a 3 week City and Guilds plumbing course is allowed to run havok? The whole system needs a rethink IMHO

As you say, pick better next time.[/u]
 
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2) You shouldn't need an extra bypass, because the rad(s) near the room stat shouldn't have TRVs on, otherwise the TRVs and stat can conflict with each other. If there is a TRV on rad near stat, make sure it's always on max.

3) If it's a loud, metallic ticking/clicking, it's poss the rad's location mounting on rear of rad rubbing on the wall bracket as the rad expands and contracts. Lifting the rad means the two are no longer in contact and stops the noise. The wall bracket would poss have originally had small plastic spacers to avoid this, but the get brittle, break and fall off. Either get some more spacers or poss put a strip of plastic, etc along the bottom of the rad's mounting.

http://www.ebay.co.uk/itm/PACK-OF-4...DIY_Materials_Plumbing_MJ&hash=item2a33a503cc
 
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2) You shouldn't need an extra bypass, because the rad(s) near the room stat shouldn't have TRVs on, otherwise the TRVs and stat can conflict with each other. If there is a TRV on rad near stat, make sure it's always on max.

3) If it's a loud, metallic ticking/clicking, it's poss the rad' location mounting on rear of rad rubbing on the wall bracket as the rad expands and contracts. Lifting the rad means the two are no longer in contact and stops the noise. The wall bracket would poss have originally had a small plastic spacer to avoid this, but the get brittle, break and fall off. Either get some more spacers or poss put a strip of plastic, etc along the bottom of the rad's mounting.

http://www.ebay.co.uk/itm/PACK-OF-4...rials_Plumbing_MJ&hash=item2a33a503cc[/QUOTE]

Brilliant suggestion, I had overlooked the possibility of the inserts being knackered on the brackets :D
 

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