# Condensing boiler versus conventional comparisons



## villa 1 (12 Jan 2011)

This is a question for all the tekkies out there.

What are your views on the mandatory installation of new condensing gas/oil fired boilers. Are these boilers really saving the householder/building owner money?
How much saving is there when these boilers are required to heat high output radiators up to design working temperatures. Surely this negate the oppurtunity to return low temperature water to the boiler thus cutting down on efficiences. Is it not better to return the coolest water possible to these boilers. 
This can be done with underfloor/buffer tanks systems but i'm dubious on the gains to be achieved with general space heating high output convector radiators. Is it on heating start up that the efficiencies are gained?
You have to ask the question, Is there much of a difference between these new(troublesome?) condensing boilers and their previous conventional uncles?


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## DGOBS (12 Jan 2011)

Gas and Oil boiler would be 2 different discussions

As condensing oil boilers do require the 20deg diff. to get into condensing mode and
get the most out of the fuel, slow a flow temp of 70deg and return of 50deg is really 
required to get the most out of it, a standard 11deg diff. will only condense on heat up only but stop once the flow/return reaches temp. 


On gas the same rule apply, but there is 2 distinct types of gas boiler (band b and band a) band b are in truth a standard boiler with a secondary heat exchanger (similar to the
oil boiler) but the band A are 'pre-mix' boilers so there is an added gain of a reduction in excess air, which means we are moving much closer to the stoichiometric air to gas ratio leading to efficiency gains regardless of condensing


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## esox (3 Feb 2011)

"stoichiometric"... that reminds me must take a look at my GI notes


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## Shane007 (4 Feb 2011)

villa 1 said:


> What are your views on the mandatory installation of new condensing gas/oil fired boilers. Are these boilers really saving the householder/building owner money?


 
To put it in simple terms, I can give a fairly relevant example:

I have a client with a substantial boiler, a Firebird 250 (yes, 250,000Btu). The boiler was set to 225,000 output with a nozzle size of 2.0 US Gal/hour. He has two 1,300 litre oil tanks feeding it. I done a heat loss calculation on the house and the boiler output was bang on for the house in question. Whoever installed it was right on the money.

I have changed the boiler to a Grant Vortex 240 condensing boiler. To obtain an output of 218,000 from this boiler, a nozzle size of 1.65 US Gal/hour is required. This is an automatic saving of approx 18% of fuel to obtain the same power output.

In addition, I had previously achieved a combustion gross efficiency of 81% from the Firebird 250 and the Grant Vortex is currently giving a nett efficiency of 99.1%. This is a considerable difference of 18% also.

The client informs me that from his calculations through his pocket, he is achieving a saving of approx 25%.

So is it worth it? You betcha it is!


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## DGOBS (4 Feb 2011)

All down to good sizing though Shane, and maybe would even try derating a little further put it under some pressure, see if it improves even more by condensing 100% of the time (gotta love the vortex though) 

Problem I find is most boilers are grossly oversized and short cycles wayyyy too much
one temp is achieved, may aswell have stayed with the old appliance, one was so bad the fuel consumption for the customer had actually gone up since the instaler put in a condenser (a 90k, was replaced with a 120k???)


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## Shane007 (4 Feb 2011)

Once nice tool I use to help keep running at optimum efficiency is the Grundfos Alpha2 Circulating Pump. Open all circuits, set the flow rate to achieve the ∆T you require, set this flow rate as the template on the pump, put into Auto Mode and no matter how many circuits open or close, the pump will increase or decrease its speed to maintain this flow rate, therefore ensuring a consistent ∆T. 

Especially useful for UFH.


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## villa 1 (5 Feb 2011)

Just a thought, Is there not a good reason for fitting a grundfos alpha variable speed pump and lever type zoning valves and dispense with costly automatic controls that will break. Explained properly to the householder I can't see why this system of control would not well.


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## Shane007 (5 Feb 2011)

That would not be acceptable at all because:

1. The homeowner tells their teenage son to not turn on heating without opening a valve, he grunts and turns it on anyhow. I have yet to see an automatic bypass valve fitted between the flow and return in this situation for safety. I fit them as standard on every installation and especially if there is a frost stat installed.
2. There's is no convenience factor.
3. There will be no boiler interlock.
4. You will be relying on the boiler's thermostat to turn on and off the boiler, causing short cycling, instead of the room stat telling the motorized valve that is does not require heat and the motorized valve then turns off the circuit and the boiler.
5. The cylinder stat will be of no use as it cannot turn off a lever valve when the cylinder water temperature has reached it's desired temperature and then much energy is pumped into the cylinder when not required. 
6. The cylinder will be always heated whenever the heating is on. With a motorized valve, in conjunction with a 7 day electronic timeclock, the cylinder can be heated at required intervals.
7. Each zone cannot be independently controlled in conjunction with a timeclock. In reality, people will use manual lever valves twice a year, once to turn off rads after winter and the time to turn them back on again after summer. With motorized valves, zones can be heated automatically generally upto 3 times per day independent of eachother. 

With regard to costly controls that will break, I would say I have replaced one or two Myson motorized valves in the past two years. They cost approx €65 incl VAT (€55 if only the head is required). I agree that the cheaper ones do break down frequently.


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## salaried (5 Feb 2011)

I am sitting at home at the moment waiting on a plumber to have a look at our oil burner. It is the old type with the flue going up through the garage roof. I can actually see the flame through the top of the boiler at this stage so might just replace it with a condensed boiler, Does anyone have a suggestion as to which boiler is more efficient and apprx how much it costs, and roughly how much would I be looking at to get one fitted, I have read the above posts and find them interesting but if anyone has any basic info I would appreciate it, Thanks Salaried.


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## villa 1 (5 Feb 2011)

I do not think there is anything wrong with giving a customer the option of operating lever valves to control zones, if they understand the system. For example a simple gate valve will work as an auto bypass valve when fitted at the boiler.

While I have no problem with zoning and these heating controls do give an automated system but at what expense,
I have said it before and I will say it again, people spend far too much money on heating and plumbing systems in houses. They will never re-coup this unnessary expense. Proper levels of insulation will cut down on extravagant spend on heating system design.
I wouldn't be informing the teenager to operate any switch because you'd need a limitless supply of fuel if they had their way!!
To the last poster, fit a Grant Vortex condensing boiler.


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## salaried (5 Feb 2011)

Thanks for that Villa1.


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## Shane007 (5 Feb 2011)

salaried said:


> I am sitting at home at the moment waiting on a plumber to have a look at our oil burner. It is the old type with the flue going up through the garage roof. I can actually see the flame through the top of the boiler at this stage so might just replace it with a condensed boiler, Does anyone have a suggestion as to which boiler is more efficient and apprx how much it costs, and roughly how much would I be looking at to get one fitted, I have read the above posts and find them interesting but if anyone has any basic info I would appreciate it, Thanks Salaried.


 
For a list of the most efficient boilers on the market, go to www.sedbuk.com. You will see that Grant Vortex model wins the top 20 on the market. It is by far the best boiler. If cost of boiler is an issue, then my second choice would be Grant Euroflame Condensing boiler.

With regard to your existing boiler, make sure that the flue is sealed before using it again, otherwise *you are* *in danger of carbon monoxide poisoning*. Also if you install a new condensing boiler, ensure it is commissioned and installed to the manufacturer's & OFTEC's specification and that the Boiler Passport is filled out with a printed flue gas analysis attached to it. As of 1st September 2010, Grant, Firebird and Warmflow will no longer accept any warranty calls without it.

You can obtain a list of OFTEC certified technician's from http://www.ofteconline.com/locatecompanyIreland.asphttp://www.ofteconline.com/locatecompanyIreland in your local area. You can also obtain further information regarding boilers, etc. from http://www.oftec.org/ireland.asp.

Cost of boiler:

Grant Vortex 26kW Boiler House Model: €1,100 Incl Vat
Low Level Balanced Flue Kit: €140 Incl Vat
Grant Vortex 35kW Boiler House Model: €1,200 Incl Vat
Low Level Balanced Flue Kit: €160 Incl VAT
Plume Diverter Kit if required: €200 Incl Vat

You will also require remote acting fire valve, condensate pipe, insulation (thickness equal to pipe diameter & armaflex sticky insulation on joints), frost stat if in unheated garage, AAV's (1 on flow and 1 on return), auto bypass valve, 3 bar safety valve piped to outside and to minimum 100mm from ground, 2 x 3amp fused switches with neons, heat resistant flex, permanent live to stat, pipework, fittings, etc. Heating system should be flushed and an suitable inhibitor must be added to the system. I would normally install a new circulating pump and 2 new gate type pump valves when fitting a new boiler.
Oh and labour cost also!


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## DGOBS (5 Feb 2011)

that pump sounds spot on Shane will look into them, cheers


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## salaried (6 Feb 2011)

Shane, Thanks for the info, I appreciate your time and effort , Cheers Salaried.


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## TLC (3 Mar 2011)

Just been told our oil burner (type with no big flue burns kerosene ??) What recommendations & costs involved in replacing?  Also would we be able to apply for a grant?  As you will see from the first sentence - not in the least bit technically minded, so if anyone does have advice keep it simple - thanks


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## DGOBS (3 Mar 2011)

what you mean, type with no big flue?

Replacing any non-condensing appliance with condensing type can get a grant but the system controls would have to be upgraded also (can add a lot to the cost)

As for getting costings, guesswork here is ok, but better to get at least 3 installers in for quotation as some replacements are more costly than others depending on the way your
house is plumbed, boiler indoors or outdoors etc.....

If you going to look into grant aided seai.ie is the website for the grant applications and 
a list of installers that are registered to the grant scheme.


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## TLC (3 Mar 2011)

DGOBS thanks for the info I'll check out the seai website.  What I meant was that the burner doesn't have a big chimney.  The boiler is outdoors.  Sorry to be so thick - but what do you mean by "system controls".


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## DGOBS (4 Mar 2011)

It's what we call an outdoor 'module' or 'cabinpac' as to no chimney, LLD (low level discharge)


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## Shane007 (6 Mar 2011)

TLC said:


> Sorry to be so thick - but what do you mean by "system controls".


 
System controls is basically having your heating system and your hot water system zoned, in that, you can have each section/zone on or off independently of all others. A typical two storey house will have 3 zones, one for heating downstairs, one for heating upstairs and the third for heating hot water. A bungalow will typically have two zones, heating and hot water, but you must also incorporate at least 3 TRV's on your radiators.

Boiler interlock must also be incorporated into the system. This means that a zone or room thermostat gets it's power from the timeclock when you want heat in that zone. It in turn gives power to a motorized valve, which then calls in the boiler and the circulating pump. The boiler and circulating pump cannot operate unless at least one zone valve is active and open.

There are many other stipulations for the SEAI grant but the above should give you an idea.


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## cathalcjb (26 Mar 2011)

Shane007 said:


> For a list of the most efficient boilers on the market, go to  You will see that Grant Vortex model wins the top 20 on the market. It is by far the best boiler. If cost of boiler is an issue, then my second choice would be Grant Euroflame Condensing boiler.
> 
> With regard to your existing boiler, make sure that the flue is sealed before using it again, otherwise *you are* *in danger of carbon monoxide poisoning*. Also if you install a new condensing boiler, ensure it is commissioned and installed to the manufacturer's & OFTEC's specification and that the Boiler Passport is filled out with a printed flue gas analysis attached to it. As of 1st September 2010, Grant, Firebird and Warmflow will no longer accept any warranty calls without it.
> 
> ...


 
Shane, this is great information. Where would the boiler be purchased at that price, Heatmerchants or any of those places?

I was quoted over 3k for fitting a condensing boiler last year, fitter suggested fitting a standard efficiency boiler instead - I was a bit dismayed. I didn't get the impression he'd e fitting all the bits you descrie. He didn't even use inhibitor after changing the rads, despite my request. 


I think I'd need a 26k version. It's a boilerhouse model needs replacing. Existing one is very, very old (30-40 years) and runs on green diesel with asbestos flue to roof height. I've been draining the tank down to switch over to kerosene in anticipation of getting new boiler fitted.

Question: Is it pointless fitting a boiler like that to GB piping where there's no separate feed for heating water only? I can't handle the disruption to flooring, I replaced all the radiators last year, have TRVs and a wall stat.

If you had any recommendation on people to supply and fit condensing oil boilers, please PM me. Price of oil is just getting too high now.


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## Shane007 (26 Mar 2011)

cathalcjb said:


> Where would the boiler be purchased at that price, Heatmerchants or any of those places?


 
I buy mine in Chadwicks. If you have any bother ordering at those prices, let me know and I will get the price fixed for you.



cathalcjb said:


> I was quoted over 3k for fitting a condensing boiler last year, fitter suggested fitting a standard efficiency boiler instead - I was a bit dismayed. I didn't get the impression he'd e fitting all the bits you descrie. He didn't even use inhibitor after changing the rads, despite my request.


 
Fitting a standard efficiency boiler is actually against regulations unless you can prove that a condensing boiler cannot be installed. Economic reasons is not a valid reason. Not using a system inhibitor after every drain down and re-fill is just very bad practice.



cathalcjb said:


> I think I'd need a 26k version. It's a boilerhouse model needs replacing. Existing one is very, very old (30-40 years) and runs on green diesel with asbestos flue to roof height. I've been draining the tank down to switch over to kerosene in anticipation of getting new boiler fitted.
> 
> Question: Is it pointless fitting a boiler like that to GB piping where there's no separate feed for heating water only? I can't handle the disruption to flooring, I replaced all the radiators last year, have TRVs and a wall stat.


 
Condensing boilers can only be run on kerosene (28 sec oil). You should completely remove all diesel from the tank, wash out all traces of bacteria from within the tank and re-fill with kerosene. Your installer should be able to do this for you without any disruption. I done a new installation in Nenagh last week where the tank was 1/3 full with diesel and the local oil company came, sucked out the diesel, waited while we cleaned out the tank and re-filled with kerosene. They even credited the homeowner with the value of the diesel they removed. Great service.

There is nothing wrong with GB as long as it is in good condition. I have seen GB systems in place for over 50 years and no problems whatsoever. What I would do is give it a powerflush with no chemical or very little, spending longer on each radiator to flush. GB will create a lot more sludge in a system, but nothing that can't be dealt with. If you have a lot of leak stains on the pipework, then it could be time to replace the system. If not, then a good quality inhibitor should keep the system in reasonable condition. If you have already replaced the rads, then it should be fine.



cathalcjb said:


> If you had any recommendation on people to supply and fit condensing oil boilers, please PM me.


 
Where in the country are you located?


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## monagt (26 Mar 2011)

Did your central heating break down in the big freeze? Here's why... 

The recent cold snap has revealed a major problem with 'condensing boilers' - they don't work in freezing weather. 

FYI!

Full Story: 
http://www.dailymail.co.uk/sciencetech/article-1342357/Central-heating-break-big-freeze-Heres-.html

28 January 2011
www.dailymail.co.uk

Also crowd in Finglas I use and they are reliable - Gas Junction ask for Sean (no connection - customer only)


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## Shane007 (26 Mar 2011)

monagt said:


> Did your central heating break down in the big freeze? Here's why...
> 
> The recent cold snap has revealed a major problem with 'condensing boilers' - they don't work in freezing weather.


 
Absolute nonsense! 

If a condensing boiler is installed correctly and as per manufacturer's instructions and as per regulation, a condensate overflow pipe will *NOT* freeze. All external pipework should be kept to a minimum and never exceed 3m in length and should be adequately insulated with external grade insulation that can withstand UV light. If it is not, then it is not installed as per regulation. How many of the boiler call outs in that article where installed as per regs? 

With regard to condensing boilers being damaged by the acidity of the condensate, this is also nonsense. The parts of a condensing boiler that come into contact with acidic discharge are made from stainless steel and plastic. Installers who fit condensate pipework in copper, steel, etc. do not understand the implications of this and therefore should not be installing one without proper training, etc. Even if they read the manufacturer's installation manual that comes with every boiler, they will understand what needs to be done. I am installing, servicing and maintaining both non-condensing and condensing oil boilers on daily basis and when installed to code, a condensing boiler will far exceed a non-condensing one, in both performance, reliability and money savings.

I will agree that if a condensing boiler is not installed correctly and is not commissioned, the results can be far more detrimental than with a non-condensing boiler. They need to be set up correctly and maintained correctly. My Vortex is running at 99.1% nett efficiency (and I've yet to install one where I could not achieve 98.0%), it did not break down in the big freeze (-17°C) and it will continue to give me years of reliability and savings in oil. 

On efficiency, a Vortex will have an average flue temperature of 45°C to 50°C whereas a standard efficiency boiler will have a flue temperature of 180°C to 400°C. This is a directly proportional to efficiency and a very good measure of how a boiler is performing, i.e. how good it is at transferring the heat from the flame chamber into the heating system. Poor, it has high temps, good has low. Less heat lost out the flue = more heat into the house and ultimately less fuel used.

Is Gas Junction OFTEC registered? Recommendation request is for an oil boiler!


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## DGOBS (26 Mar 2011)

+1 Shane

Coupled with the fact that installing non-condensing appliances is not to current building standards...ie.. illegal! and would cary no warranty either me tinks


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## monagt (27 Mar 2011)

OK Shane007,
Good 2 know. I was due to get a new boiler and put if off because of that article.

Is if cost effective to replace working boiler or better to wait until it breaks?

Is Vortex a good make?

Ooops GS is a Gas house afaik.

M


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## cathalcjb (27 Mar 2011)

Shane007 said:


> I buy mine in Chadwicks. If you have any bother ordering at those prices, let me know and I will get the price fixed for you.
> 
> Fitting a standard efficiency boiler is actually against regulations unless you can prove that a condensing boiler cannot be installed. Economic reasons is not a valid reason. Not using a system inhibitor after every drain down and re-fill is just very bad practice.
> 
> ...


 
Yeah, I think the time has come to move on from my current boiler - the heat in the shed itself is shocking - can't be efficient. Tank of diesel is nearly drained now through burning off. So I might be able to remove the last of the diesel by tipping it over. 

When you clean the tank, what do you use - power washer? Any detergent? It's a plastic tank and is there about 4 years now, I got an old metal tank replaced when I was moving in because its base was unsafe.

I'm in Dublin if you know of anyone who you would recommend.


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## Shane007 (29 Mar 2011)

cathalcjb said:


> When you clean the tank, what do you use - power washer? Any detergent? It's a plastic tank and is there about 4 years now, I got an old metal tank replaced when I was moving in because its base was unsafe.
> 
> I'm in Dublin if you know of anyone who you would recommend.


 
If the tank is only 4 years old, I would not think there is much bacteria in it. I use a mop to reach in and clean. Just ensure all the diesel is completely removed from the tank & the oil line.


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