Alpha Boilers and Oso Cylinder

[Harden Long]

Wondering what the general concensus was about alpha boilers

My plumbing engineer is installing a 210ltr Oso unvented hot water cylinder.
The house needs a new boiler in any case and my man has suggested an
Alpha CD30S.


Can anyone give me pros/cons about the boiler and/or the oso ??? Are there "better" options to talk over with my plumber?

Thanks for your help

 

[gas4you]

Alpha seem pretty reliable, Paul on here is a service engineer for them and thinks they are generally good. Quite often it is personal preference as to what boilers installers fit.

Craig on here swears by Worcesters, whilst I only fit Vaillants and their Unistor cylinders.

I don't think you will go far wrong with the suggested set up, but I would go the Vaillant route as the boiler and cylinder can be linked electronically to talk to each othe and give the greatest performance with maximum economy.

 

[clf-gas]

Craig on here swears by Worcesters

Ho you better believe it, been swearing at two of them today

My plumbing engineer is installing a 210ltr Oso unvented hot water cylinder

Loverly piece of kit these

As for alpha boilers not heard anything bad.

I only fit Vaillants

Oh Iam tempted Dave

 

[gas4you]

Come on Craig, I thought I was being even handed and fair, perhaps not quite as far as impartial, but fair though

 

[Paul Barker]

Your installer's prefernce can be a better choice for you, but not always.

You have to guage your installer, does he measure up? What are his reasons for the boiler choice?

What will happen if it breaks down will he shrug his shoulders and say phone xyz it's guaranteed, or will he come and check it first himself as part of his initial installation service at no additional cost? ASK HIM?

Most installers of Alphas do a good job and provide good backup. Alpha themselves provide good customer service.

There are other good boilers some better, many much of a muchness. The playing field is levelling off.

 

[Breesey]

Wondering what the general concensus was about alpha boilers

My plumbing engineer is installing a 210ltr Oso unvented hot water cylinder.
The house needs a new boiler in any case and my man has suggested an
Alpha CD30S.


Can anyone give me pros/cons about the boiler and/or the oso ??? Are there "better" options to talk over with my plumber?

Thanks for your help

As others have mentioned this is a good choice but there are other good choices available. I have fitted this combination myself on several occasaions, including my own house, have rarely had any problems and never a serious one.
One thing though, do have an enourmous house? if you don't you won't need a CD30. I recently fitted a CD24 with 12 rads, an under floor manifold and a 210 litre Oso solar cylinder in a three storey town house.

 

[Harden Long]

Hi Breesey

I wouldn't say we had an enormous house-it is an old detached 5 bedroom, 3 public, 2 bath and 1 toilet so it possibly isn't much different from your town house

Is there a downside to getting a big boiler like that then?

Apart from the price I mean.

I really want to get the job done right, from the start.

3 kids with frequent baths as well as non stop washing machine and d/washer !

Appreciate your advice-thanks very much

 

[ChrisR]

Remember your Oso can swallow 25kW (iirc) from your boiler to reheat nice and quickly.

 

[Breesey]

Hi Breesey

I wouldn't say we had an enormous house-it is an old detached 5 bedroom, 3 public, 2 bath and 1 toilet so it possibly isn't much different from your town house

Is there a downside to getting a big boiler like that then?

Apart from the price I mean.

I really want to get the job done right, from the start.

3 kids with frequent baths as well as non stop washing machine and d/washer !

Appreciate your advice-thanks very much

The condensing boiler is at its most efficient when it has to work almost on its limit to provide sufficient heat to its application. This makes it easier to achieve the optimum return temperature for maximum condensing heat exchange. Even when this is not occuring the larger heat exchanger means that the boiler will be more efficient. If the boiler is oversized it will be inefficient.

At the same time as you have this installation done you should make sure that your insulation (wall and roof etc) is as good as it can be.

Carefull calculation of what would be most efficient is the only way to find out which boiler you need - rather than, as it seems, your chap has just thought "Mmm It's quite a large house I'll stick a CD30 in there coz I stuck a CD18 in that 3 bed semi last week."
Or for that matter he might always fit 30s regardless, and needlessly.

Do you have 20l/min water supply for the Oso?

 

[Paul Barker]

[The condensing boiler is at its most efficient when it has to work almost on its limit to provide sufficient heat to its application. This makes it easier to achieve the optimum return temperature for maximum condensing heat exchange. Even when this is not occuring the larger heat exchanger means that the boiler will be more efficient. If the boiler is oversized it will be inefficient.

The boiler in question can be range rated by adjusting the CHcap preset on the pcb, pull out the nylon plug middle right, adjust anticlockwise to rate down from 30kw. I don't remember off thand the minimum but about 11kw probably. Set it between the max and min and see how you get on.

Don't touch the bottom one which is Max cap.


Better to get the 30kw boiler, range rate it down, for summer I would go half way adjust on test in winter, at least then you have full power should it be required.

Band B boilers are only working on a stoichiometric mix at full output, but band A boilers like the one in discussion is stoichiometric at all outputs.

There are no performance benefits to choosing too low a powered band A boiler.

 

[gas4you]

Paul, is it just experience and guess work where to set it or is there a readout somewhere of what you set it too? (for my personal info )

 

[Breesey]

The boiler in question can be range rated by adjusting the CHcap preset on the pcb, pull out the nylon plug middle right, adjust anticlockwise to rate down from 30kw. I don't remember off thand the minimum but about 11kw probably. Set it between the max and min and see how you get on.

Don't touch the bottom one which is Max cap.


Better to get the 30kw boiler, range rate it down, for summer I would go half way adjust on test in winter, at least then you have full power should it be required.

Band B boilers are only working on a stoichiometric mix at full output, but band A boilers like the one in discussion is stoichiometric at all outputs.

True, but why not just get the best size in the first place?

There are no performance benefits to choosing too low a powered band A boiler.

Also true, if this implication was taken it wasn't intended.

 

[gas4you]

on a stoichiometric mix at full output

Hate it when you lot make me have to dig my dictionary out

 

[Agile]

There are no performance benefits to choosing too low a powered band A boiler.

Thats not always the case Paul.

The Band A is only efficient when its running and able to modulate back. Most only go down to 30-40% of their full power.

I see a lot of combis which have to operate on minimum power for CH but are still overpowered and have to cycle on/off as soon as the rads reach operating temperature.

Until the manufacturers find a way of increasing the modulation range factor this will always be the case for combis.

Even a Band A boiler is a little weaker than a stoichiometric mixture to keep CO output low. Thats why you still have unused O² in the flue gases.

Tony

 

[Breesey]

There are no performance benefits to choosing too low a powered band A boiler.

Thats not always the case Paul.

The Band A is only efficient when its running and able to modulate back. Most only go down to 30-40% of their full power.

I see a lot of combis which have to operate on minimum power for CH but are still overpowered and have to cycle on/off as soon as the rads reach operating temperature.

Until the manufacturers find a way of increasing the modulation range factor this will always be the case for combis.

Even a Band A boiler is a little weaker than a stoichiometric mixture to keep CO output low. Thats why you still have unused O² in the flue gases.

Tony

Quite, that's what I meant!