Hi , I am looking to change my old Glowworm 100 boiler , which is situated in a confined space, with an Ideal Isar "A" rated boiler which is much smaller . But the plumber i have spoken to does not recommend "A" rated boilers because they are less reliable than "B" rated boilers, is this true ?
"A" rated boiler V "B" rated boiler .
- Thread starter topturner
- Start date
No its rubbish......
it is a very old tale that condensing boilers don't last as long as standard boilers. This is total nonsese. Maybe comparing the first condensing boilers to the old conventional cast iron boiler maybe as they used to last 20 years plus. But nowadays you are looking at approx 10 years+ out of a combi boiler and if it is condensing it won't make the life span any shorter.
I would stay away from the Ideal Isar as they are a poor boiler IMO
I would stay away from the Ideal Isar as they are a poor boiler IMO
These guys are right, what he is really saying is "I don't understand how 'A' rated boilers work and I am much happier working on the simpler 'B' rated boilers"!
A rated boilers usually have slightly more complicated/more efficient controls to acheive extra efficiency but it just raises the bar for heating engineers, which is good! More skill, more money!
A rated boilers usually have slightly more complicated/more efficient controls to acheive extra efficiency but it just raises the bar for heating engineers, which is good! More skill, more money!
I have to disagree with Harrogate above.
Most "B" rated boilers use a conventional boiler and add a second heat exchanger to do the condensing bit.
All "A" rated boilers are premix burners which are quite sensitive to adjustment and require a well performing gas supply and correct commissioning.
A band "B" can be worked on with simple cheap tools using knowledge learnt over many years. The burners are insensitive to gas supply variations and can tolerate perhaps 20% of mal adjustment.
Band"A" boilers require an instrument called a flue gas analyser to set them up and fault find on them. They have only been used in large numbers in the domestic market for the last few years and many installers are not familiar with them and have not bought the FGA which costs from £400-£1000. A much higher level of skill and training is required and in my experience in London less than 5% of installers have this and even fewer have the FGA.
Tony Glazier
Most "B" rated boilers use a conventional boiler and add a second heat exchanger to do the condensing bit.
All "A" rated boilers are premix burners which are quite sensitive to adjustment and require a well performing gas supply and correct commissioning.
A band "B" can be worked on with simple cheap tools using knowledge learnt over many years. The burners are insensitive to gas supply variations and can tolerate perhaps 20% of mal adjustment.
Band"A" boilers require an instrument called a flue gas analyser to set them up and fault find on them. They have only been used in large numbers in the domestic market for the last few years and many installers are not familiar with them and have not bought the FGA which costs from £400-£1000. A much higher level of skill and training is required and in my experience in London less than 5% of installers have this and even fewer have the FGA.
Tony Glazier
If you ask a company that doesn't make a band b boiler (OK I'll name them, Vaillant). They will say that is because they are not likely to last very long.
otoh some band b boilers are based on really good tried and tested doners, such as the vokera linea and the baxi 105e to name but a few.
They have to be careful that the efficiency stays in band B as they don't want any condensing to occur in the first and main original heat exchanger as that would make it very short lived.
If you buy a band b you are gambling ont the fact that they have got their sums right.
Vaillant say this is going to be a problem and we are going to be the first ones to rub your noses in it if you're wrong.
Me, I'm not sure, you could buy two quality band b's for every quality band a. Will the band a last twice as long? Depends which one. Certainly an Ideal won't, might not even last as long as a band b.
otoh some band b boilers are based on really good tried and tested doners, such as the vokera linea and the baxi 105e to name but a few.
They have to be careful that the efficiency stays in band B as they don't want any condensing to occur in the first and main original heat exchanger as that would make it very short lived.
If you buy a band b you are gambling ont the fact that they have got their sums right.
Vaillant say this is going to be a problem and we are going to be the first ones to rub your noses in it if you're wrong.
Me, I'm not sure, you could buy two quality band b's for every quality band a. Will the band a last twice as long? Depends which one. Certainly an Ideal won't, might not even last as long as a band b.
On the subject of boilers whose only saving grace is that kitchen fitters love them, and we all trust kitchen fitters.....
I had to repair an Ace High which a kitchen fitter had shoehorned into a cupboard, I couldn't get the front off without removing the cupboard door, but I couldn't remove the door in the usual way (one screw and slide it towards self) as that one screw is at the back and the Halstead front being forward of that screw, all I could do was undo the two thick screws per hinge holding the hinge to the wheetabix. Now we all know how many times we can undo a screw from wheetabix and screw it back and expect it to carry the weight of a door.
I told the customer the situation and said when I get called back to the boiler again, which is a certainty since the installer clearly didn't powerflush the old system, the door would very likely drop off, it is now hanging by a thread as it is. I suggested we use mirror screws through the front.
Still, long as the kitchen looked nice in the first place, suppose the company got their 2 or 3 grand for installing it.
My advice to you is find out what sort of boiler your kitchen fitter wants to use, and where he wants to put it, then do the opposite.
I had to repair an Ace High which a kitchen fitter had shoehorned into a cupboard, I couldn't get the front off without removing the cupboard door, but I couldn't remove the door in the usual way (one screw and slide it towards self) as that one screw is at the back and the Halstead front being forward of that screw, all I could do was undo the two thick screws per hinge holding the hinge to the wheetabix. Now we all know how many times we can undo a screw from wheetabix and screw it back and expect it to carry the weight of a door.
I told the customer the situation and said when I get called back to the boiler again, which is a certainty since the installer clearly didn't powerflush the old system, the door would very likely drop off, it is now hanging by a thread as it is. I suggested we use mirror screws through the front.
Still, long as the kitchen looked nice in the first place, suppose the company got their 2 or 3 grand for installing it.
My advice to you is find out what sort of boiler your kitchen fitter wants to use, and where he wants to put it, then do the opposite.
Paul said
And this is quite correct; on commercial boilers the idea of adding recuperators after the primary heat exchanger to increase efficiencies has been standard practice for many years.
With most band A boilers that use an axial heat exchanger most of the condensing must occur behind the baffle ie at the rear of the heat exchanger since condensate could damage the burner. So these particular problems of band B are also present with band A.
For example looking at the Giannoni band A heat exchanger it can be seen how this could be a problem.
http://www.giannoni.fr/En_pages/En_echangeurinox.html
Perhaps this also explains why the majority of band A boilers have poor turndown ratios ie only a ratio of 3 : 1 from maximum to minimum output power despite many premix burners having the capabilty of a turndown ration of up to 10 : 1.
And this is quite correct; on commercial boilers the idea of adding recuperators after the primary heat exchanger to increase efficiencies has been standard practice for many years.
With most band A boilers that use an axial heat exchanger most of the condensing must occur behind the baffle ie at the rear of the heat exchanger since condensate could damage the burner. So these particular problems of band B are also present with band A.
For example looking at the Giannoni band A heat exchanger it can be seen how this could be a problem.
http://www.giannoni.fr/En_pages/En_echangeurinox.html
Perhaps this also explains why the majority of band A boilers have poor turndown ratios ie only a ratio of 3 : 1 from maximum to minimum output power despite many premix burners having the capabilty of a turndown ration of up to 10 : 1.
I agree, there is nothing wrong in principle with secondary heat exchangers and much of the commercial high efficiency market use them successfully.
It is all down to design and testing. The Kidd boilers we recommend to those with larger houses and reluctance to use electronics have a secondary HE and manage the very top end of Band B on gas and Band A on oil. They were designed correctly and have been on the market, unchanged, from 1982.
So it's very nice of Vaillant to be so boastful, but they weren't even making condensers in 1982. We fit a lot of Vaillant boilers and I think they are excellent, but they aren't going to last as long as a Kidd in service.
It is all down to design and testing. The Kidd boilers we recommend to those with larger houses and reluctance to use electronics have a secondary HE and manage the very top end of Band B on gas and Band A on oil. They were designed correctly and have been on the market, unchanged, from 1982.
So it's very nice of Vaillant to be so boastful, but they weren't even making condensers in 1982. We fit a lot of Vaillant boilers and I think they are excellent, but they aren't going to last as long as a Kidd in service.
This feedback is great.
You see I am fitting two main types, as we have two types of customer round here. We have a huge amount of people on minimun wage who are bandb customers and just a few people who are on say 7.50 an hour upwards jobs and I try and get them to have a Buderus as I like to provide a long term quality service for those who can afford it...
I even fitted the Buderus in one of my flats.
BUT the band b's which I fit may well be economic for me to repair for 20 years, just as long as the manufacturers haven't completely miscalculated their condensing figures.
The other consideration is that the band b's are so cheap it may actually pay me to stock what the Navy call a "Christmas Tree". In a remote war like the Faulklands they use one perfectly good Harrier for spare parts.
You see I am fitting two main types, as we have two types of customer round here. We have a huge amount of people on minimun wage who are bandb customers and just a few people who are on say 7.50 an hour upwards jobs and I try and get them to have a Buderus as I like to provide a long term quality service for those who can afford it...
I even fitted the Buderus in one of my flats.
BUT the band b's which I fit may well be economic for me to repair for 20 years, just as long as the manufacturers haven't completely miscalculated their condensing figures.
The other consideration is that the band b's are so cheap it may actually pay me to stock what the Navy call a "Christmas Tree". In a remote war like the Faulklands they use one perfectly good Harrier for spare parts.
Is condensate dripping down onto the burner, especially after the fan has stopped, the reason for having a baffle and the relatively-high turndown ratio?
I can't see any other reason why the life of the boiler would be affected by low temperatures allowing condensation to occur towards the front of the HX. The material used to make the HX is the same all the way across it - stainless steel. While the burner is running, its surface temperature will be way above 56, whatever the gas rate.
And the Viessmann HX (guaranteed 10 years!) doesn't have a baffle as such. And the Vitodens 200 still has than (only!) 3:1 turndown. I don't think turndown is a single issue - there must be more to it.
I can't see any other reason why the life of the boiler would be affected by low temperatures allowing condensation to occur towards the front of the HX. The material used to make the HX is the same all the way across it - stainless steel. While the burner is running, its surface temperature will be way above 56, whatever the gas rate.
And the Viessmann HX (guaranteed 10 years!) doesn't have a baffle as such. And the Vitodens 200 still has than (only!) 3:1 turndown. I don't think turndown is a single issue - there must be more to it.
Paul perhaps you could tell Vaillant about their Band A boiler which I condemmned yesterday?
Its one of their earlier and perhaps illfated design the 236 .
18 months ago it was in a dreadful state with most of the condensate parts corroded through. In a desperate effort to keep the owner with hot water we replaced many of the bits to a value of about 136 pounds for parts but pointed out that that was a rescue operation and not a long term solution.
Now the main HE is leaking slightly and I have advised him that its not worth replacing it because the combustion chamber is now so rusted that it would need to be replaced as well.\
As far as current designs are concerned my only fear is that as they are so sensitive to combustion settings they will be much more expensive to service because it can only be done by the highest trained engineers with the right equipment. Annual calibration of the FGA is over a hundred pounds.
Tony
Its one of their earlier and perhaps illfated design the 236 .
18 months ago it was in a dreadful state with most of the condensate parts corroded through. In a desperate effort to keep the owner with hot water we replaced many of the bits to a value of about 136 pounds for parts but pointed out that that was a rescue operation and not a long term solution.
Now the main HE is leaking slightly and I have advised him that its not worth replacing it because the combustion chamber is now so rusted that it would need to be replaced as well.\
As far as current designs are concerned my only fear is that as they are so sensitive to combustion settings they will be much more expensive to service because it can only be done by the highest trained engineers with the right equipment. Annual calibration of the FGA is over a hundred pounds.
Tony
There are many different constructions of Band A heat exchangers. The Viessmans for example have a rectangular cross sectional coil compressed to provide a precise gap between the coils. Condensate run back onto the burner is reduced and perhaps this negates the baffle requirement. Vaillant appear to have differing versions on their heat exchangers - some possibly with the baffle/insulating board. It may well be the cheaper simple coiled tube heat exchangers tend towards the baffle arrangement.
I would imagine a suitable stainless steel for burner constuction ie one that can survice thousands of extreme heat cylces may not necessarily be particulaly suitable to resist condensate drips after burner shutdown.
Most condensers have a low turndown ratio typically only 3:1. My point is that the fan/gas valve/burner can often cope with a burner maximun to minimum power ration of 10:1. Perhaps if the boiler ran with a very low output there may be an increased chance of condensate forming on the front section of a baffled heat exchanger.
The only other reason I can think of may be an ignition/flame stabilty problem if the working gas pressure is particualary low. Some high end boilers do have an addition gas pressure sensor.
I would imagine a suitable stainless steel for burner constuction ie one that can survice thousands of extreme heat cylces may not necessarily be particulaly suitable to resist condensate drips after burner shutdown.
Most condensers have a low turndown ratio typically only 3:1. My point is that the fan/gas valve/burner can often cope with a burner maximun to minimum power ration of 10:1. Perhaps if the boiler ran with a very low output there may be an increased chance of condensate forming on the front section of a baffled heat exchanger.
The only other reason I can think of may be an ignition/flame stabilty problem if the working gas pressure is particualary low. Some high end boilers do have an addition gas pressure sensor.
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