Recommendation for a replacement Semi Commercial Boiler

[FozzieBear]

I am sure all plumbers and heating engineers have their favourites but can anyone recommend a condensing boiler as a replacement to an Ideal Mexico FF100 currently installed in our Village Hall?
As I understand it needs to conform to the following:-
1) Be a condensing boiler due to change in Regs
2) Ideally needs to be wall hung to gain space in the current location.
3) Needs to be A Rated
4) Have an output of at least 36Kw (125,000 btu) as the current boiler appears to be undersized (unless you are going to tell me that A Rated boilers are much more efficient and therefore I can get away with a lower rating).
5) As it is replacing a boiler on an old vented system I am told it needs to have a stainless steel heat exchanger in order not to experience corrosion with aluminium ones.
6) Capable of working as an unvented boiler if that is the way the system is redesigned.

Any help and advice would be greatfully received as there appear to be a myriad of different makes and types of boiler out there.
Fozzie

 

[Biggles..]

Broag Quinta, Vaillant Eco tec 46, Strebel,

 

[Agile]

Why do you think the boiler is undersized?

Look at FAQ and do a gas rate test on current boiler to see what power its actually consuming as a first step to seeing what power you need.

Its more efficient to make it a sealed system.

Tony

 

[FozzieBear]

Thanks Tony but if you read my previous thread //www.diynot.com/forums/viewtopic.php?p=1931181#1931181 you will see this is not a straight forward problem. Until we get the correct gas input pressure of 20mB at the boiler, which means having the meter moved or up-sizing the supply pipework, we cannot confirm if the existing Mexico 100ff boiler is sufficiently rated. As you stated in my previous post it needed a qualified heating engineer to ensure that the boiler is correctly set up. We have now had that done and the engineer has confirmed that the boiler is at it maximum output with only 16mB gas pressure, something he confirmed with the manufacturer. He also stated that our gas consumption as a result is much higher than expected.
At 16mB we are only getting 61degrees on the flow and not the expected 80 degrees which I belive is the norm.
Maybe incorrectly but I have always assumed that a boiler works most efficiently when the required heat output is within its range rather than working flat out at the top end all the time, so upsizing from 100,000btu(29Kw) to 125,0000btu (36Kw) when replacing it seemed sensible. Incidentally the load on the boiler has recently increased since it was first installed. We have just had an extension put on the hall with at least 9 more LST radiators. This was done after checking the design against the current boiler design output which was deemed to be sufficient, but at that time we were unaware of the low gas pressure.
I should also say that the current controls are very basic with only a wall thermostat in the main hall, which when it comes up to temperature turns off the whole system. It has already been agreed to install thermostatic valves on these rads and move the stat to a better location.
Agreed that a sealed system may be more efficient, and that is the preferred option for the installing plumber, however we are not sure that the existing 20 year old pipework and radiators in the older part of the hall will cope with a pressurised system?
Fozzie

 

[Agile]

That why its better to stick to posting on your original thread. The information on each thread should be self contained.

Either you have been misinformed or the engineer does not understand gas pressures.

If the supply at the boiler input is 16 mB then it can be set to deliver the rated 30 Kw and thats what I expect it is doing. That makes no difference to the efficiency. You pay for the heat you produce. A condensing boiler will be about 90% efficient compared with about 76% perhaps on your old boiler.

If you would read the FAQ and do the gas rate then we can see what current power input is and consider what size boiler you really need.

Tony

 

[D_Hailsham]

As I understand it needs to conform to the following:-
1) Be a condensing boiler due to change in Regs
2) Ideally needs to be wall hung to gain space in the current location.
3) Needs to be A Rated

Item 1: Not necessarily, provided the boiler meets the minimum efficiency requirement.

Item 2: This is not a requirement, it's down to personal preference.

Item 3: This only applies to domestic buildings, which does not include village halls.

See Non-domestic Building Services Compliance Guide 2010

4) Have an output of at least 36Kw (125,000 btu) as the current boiler appears to be undersized (unless you are going to tell me that A Rated boilers are much more efficient and therefore I can get away with a lower rating).

Efficiency is: Output ÷ Input. Input is what you pay for.

If you have a 30kW output boiler which is 75% efficient, your input is: 30 ÷ 0.75 = 40kW, which is what the gas bill will show. If you change the boiler to one which is 90% efficient, the input will be: 30 ÷ 0.9 = 33.33kW, so your bill will be lower.

5) As it is replacing a boiler on an old vented system I am told it needs to have a stainless steel heat exchanger in order not to experience corrosion with aluminium ones.

Most commercial boilers use aluminium heat exchangers as it is a better heat conductor than stainless steel.

6) Capable of working as an unvented boiler if that is the way the system is redesigned.

Is the existing system unvented? If it isn't, there is no obligation to change it. In fact it would probably be safer to leave it as a vented system.

You seem to be trying to do the job on the cheap and have only spoken to domestic heating firms. You need to talk to a commercial heating firm.

 

[Agile]

This commercial thing is a red herring!

Boilers used in houses are normally up to 36 kW.

But gas installers with a domestic rating can install boilers up to 60 kW output.

The obvious solution is a domestic style of boiler but until we know the power output of the existing boiler then guessing at a replacement rating is risky.

When the OP has measured the gas rate then we can ask him to confirm the boiler is firing constantly while providing the heating.

Tony

 

[FozzieBear]

That why its better to stick to posting on your original thread. The information on each thread should be self contained.

I started a new post because it was a different question and was asking for recommendations on a boiler with a stainless steel heat exchanger as both the servicing engineer and the Electromechanical Consulting firm who did the calculations both say stay clear of an aluminium based boiler because of the danger of corrosion when installing on an existing system.

Either you have been misinformed or the engineer does not understand gas pressures.

I can only go on what a supposedly long established and reputable local heating engineering company tells us. His findings when doing the checks were
standing pressure 28 mb
firing pressure 16 mb
He said there should be no more than a 4 mb drop between the two figures.

He also advised that the boiler operating pressure was 28.2 Kw working on 13 mB and should be a minimum of 29 kW for that boiler working on about 7 mB.
Ideal, the boiler manufacturer, stated that 29 Kw was the maximum we could get out of that model boiler, which has a self-modulating gas valve, so could not be adjusted further.

If you would read the FAQ and do the gas rate then we can see what current power input is and consider what size boiler you really need.

I assume you are talking about timing the gas meter dial and dividing the figure into 1092? I will do this once the current warm snap ends as this will have an effect on the heating.
Many thanks again

Fozzie

 

[FozzieBear]

Item 1: Not necessarily, provided the boiler meets the minimum efficiency requirement.
Item 2: This is not a requirement, it's down to personal preference.
Item 3: This only applies to domestic buildings, which does not include village halls.

These were customer requirements/aspirations as well as conforming with current regulations

4) Have an output of at least 36Kw (125,000 btu) as the current boiler appears to be undersized (unless you are going to tell me that A Rated boilers are much more efficient and therefore I can get away with a lower rating). Efficiency is: Output ÷ Input. Input is what you pay for.

If you have a 30kW output boiler which is 75% efficient, your input is: 30 ÷ 0.75 = 40kW, which is what the gas bill will show. If you change the boiler to one which is 90% efficient, the input will be: 30 ÷ 0.9 = 33.33kW, so your bill will be lower.

Understood I Think!!!!

Most commercial boilers use aluminium heat exchangers as it is a better heat conductor than stainless steel.

Agreed but other posters have recommended a number that are stainless steel hence my post has partly been answered.

Is the existing system unvented?

Yes. Again agreed although other posters have said that an unvented system is more efficient and may also resolve some of the airlock issues we are currently having.

You seem to be trying to do the job on the cheap and have only spoken to domestic heating firms. You need to talk to a commercial heating firm.

Not so the Electro Mechanical consultants only deal with commercial/industrial buildings and the Heating Engineers that did the testing also mainly do commercial.

Yes we are trying to do the job on a budget (not necessarily cheap) as we are a charity with limited funds and reliant on grants.
Thanks for your response

Fozzie

 

[D_Hailsham]

This commercial thing is a red herring!

It's not a red herring. The regulations for commercial installations are completely different from those for domestic ones and not alldomestic installers will be aware of the differences.

What a gas installer is permitted to do only relates to his Gassafe registration. It has nothing to do with his knowledge of Building Regulations.

 

[D_Hailsham]

Item 1: Not necessarily, provided the boiler meets the minimum efficiency requirement.
Item 2: This is not a requirement, it's down to personal preference.
Item 3: This only applies to domestic buildings, which does not include village halls.

These were customer requirements/aspirations as well as conforming with current regulations

There's nothing stopping you doing a "Rolls Royce" job (should it be "Maybach" now), apart from the cost.

As for the type of heat exchanger, both should last along time, provided the system is properly cleaned before the boiler is installed.

 

[Agile]

I stand by my advice that you need a domestic style boiler as the price difference for a commercial is about TWICE the cost and usually a very short warrantee, usually just ONE year!

Any good engineeer should understand the requirements. I used to have a commercial gas registration but did not renew that when it expired three years ago.

Whilst I also agree that a boiler with a stainless heat exchanger is better, Worcester use ali EXs and they have a good reputation for reliable boilers.

Probably Viessmann, Vaillant, Intergas in no particular order. The Viess and I think the Intergas have FIVE years warrantee.

The Vaillant 46 kW commercial boiler is I think just ONE year! But you are unlikely to need that power.

Those gas pressures/words are partly wrong! Only a nupty would say there should be no more than 4 mB between standing and working pressures at the boiler. A low working pressure only means the pressure drop exceeds the standard but if over 15 mB will not usually affect boiler power output which can still usually be adjusted to give the full rated power output of the boiler.

Its very likely that YOU have not stated what they told you. For example above you are saying that its an UNvented system although earlier you said it was vented. An unvented system is about 2% more efficient.

Lets hear the gas rating then we can move forward. Also check that the boiler is constantly firing when the rads reach 62° and dont get any hotter.

Unfortunately there are many people in this industry who are not as knowledgeable as they should be.

Tony

 

[Steambod]

I am sure all plumbers and heating engineers have their favourites but can anyone recommend a condensing boiler as a replacement to an Ideal Mexico FF100 currently installed in our Village Hall?
As I understand it needs to conform to the following:-
1) Be a condensing boiler due to change in Regs
2) Ideally needs to be wall hung to gain space in the current location.
3) Needs to be A Rated
4) Have an output of at least 36Kw (125,000 btu) as the current boiler appears to be undersized (unless you are going to tell me that A Rated boilers are much more efficient and therefore I can get away with a lower rating).
5) As it is replacing a boiler on an old vented system I am told it needs to have a stainless steel heat exchanger in order not to experience corrosion with aluminium ones.
6) Capable of working as an unvented boiler if that is the way the system is redesigned.

Any help and advice would be greatfully received as there appear to be a myriad of different makes and types of boiler out there.
Fozzie

Suggest Vaillant Ecotec, had a few fitted and good reports all round. If you want to keep the open vented system you'll need minimum 1m head above the boiler (according to Vaillant, but best go for more iff poss) otherwise go for the sealed system version (with a village hall you'll need somebody to remember to check the pressure now and again.
Boiler rating depends on your building heat losses. If your redesigning the system these should be checked if the place seems underheated. Are you going for radiators or fan heaters?

 

[transam]

put 2 smaller domestic boilers in & link them up ( If u have the room )

 

[ironman1]

Depending on pipework layout & materials used eg: steel , commercial boilers would fair better than domestic types , any debris left in that system (which there will be) will deem the domestic a very short service life.............i would look to installing two boilers with all necessary controls..............of all the years tendering for churches , social clubs etc , never yet actually got the job. , i don't bother wasting my time anymore.................

No disresect for the OP but that's just how it is , a good job costs ££££££s....................