Advice on new CH system

[Dan Robinson]

Oso Super S 250 9not able to be flooded mind you) has a 20 minute reheat and nearly 400 litres of useable hot water at 42 degree draw off. Partly down to the blending valve on the outlet. The 300 is 475 litres.

Tony - two words - Diversity Factor.

The OSO RI can be flooded for extra capacity if needed, and plumbing a twin coil in with the coils in series will also increase the capacity with a coil capacity of 32 kW. If the OP went for a RI 330 twin coil that can flood to 380 litres and a combined coil capacity of 34 kW.

Frankly though, in a 4 bed house - if a 250 cylinder was insufficient i would question the water usage of the household.


To the OP - a multipoint is like a combi boiler but without the heating circuit. Very simple, very reliable. No stored water to worry about. Rinnai, Main and Vokera are the most common.

The hot water needs of the annex do not warrant anything more IMHO. The heating can just be fed from he main house as a separate zone through a programmable room stat.

 

[mrbutt]

Thanks for the help with sizing the cylinder, and recommendations on which cylinder.

With regards to the annex Dan, i think you are right, it doesn't require anymore. Only issue would be that there is no gas supply to the annex, and it would be A LOT of work getting it there. I checked the 3 manufacturers you mentioned and they were all gas operated. Do you think it would be worth just getting an electric one, if there are any decent ones with decent flow rates?

 

[Dan Robinson]

No, stick with gas - they can be converted to LPG - which for the usage you mentioned keeps it reasonable in running and maintenance costs. The appliances are the same as the NG versions, just a few minor mods to cope with the different gas.

Electric hot water means lots of local heaters for sinks plus electric showers. Running costs are not significantly more than gas, but you need a silly electric supply to cope with peak usage. Gas is more versatile. The other alternative means stored water hated by an immersion and that takes space, has long reheat times, and has implications for legionellas disease.

Back to cylinders.... time and time again, people look at the numbers of bathrooms and assume that they want to use them all at the same time. It NEVER pays size for 100% usage. In practice it is the capacity of the supply pipe that limits the amount of water that can be used at any one time, and the heat capacity of a modern, well installed cylinder and control system is secondary.

I still maintain an Atag Q38s, OSO RI250 will do you fine. I have several properties with hot water and heating requirements (albeit without an Annex) running off identical setups.

It pays to insulate.... and insulate well.

 

[mrbutt]

Lots of info there Dan! Thanks

Any reason why you specify the ATAG over the other boilers? I hear good things and read good things on here about ATAG, Viessman and Remeha.

I hear the Atag is like the Rolls Royce of boilers, but after a search on here I also read quite a lot of negative comments, many people having trouble finding reliable people to work on them as they are rare, parts being very expensive and service not being too good.

One of the reasons I was inclined to a Remeha is I have bought many Di Dietrich (sp?) stuff before and been impressed, they are the same company.

 

[Dan Robinson]

By inference a lot of posters on here will have issues - rarely do you hear from a happy camper.

If in doubt contact Atag and ask how many engineers they have in your area. They are not as common as the mainstream brands granted, but the boilers are no more complicated than any other for an engineer with the experience you would expect.

Remeha I have seldom come across, and when I have it is because of problems- I wouldn't slag them off on that basis though.

The boilers I chose I select on the grounds I have taken them apart first. And feel I can deal with the manufacturer- which with me being me channels me to smaller companies with fewer bean counters....although you cant eliminate them all sadly.

As a homeowner you have the problem of eliminating sales waffle from engineering judgement...something you won't be able to do without references, photos and research.

Also look at Atmos, and consider say two InterSystem or InterOpen boilers in cascade, even simpler than the Atag, but just as versatile. Again a small company, but nicely made boilers that can be turned to a variety of uses not in the book - back to a Combi option for sinks.

Install an InterCombi next to an InterSystem on a hearer and maintain weather compensation, hot water priority, maybe a shower hooked up to the combi too for emergencies (combi side doesn't need a working heating system to operate, just like a multipoint).

The list of possibilities is vast .

 

[mrbutt]

By inference a lot of posters on here will have issues - rarely do you hear from a happy camper.

If in doubt contact Atag and ask how many engineers they have in your area. They are not as common as the mainstream brands granted, but the boilers are no more complicated than any other for an engineer with the experience you would expect.

Remeha I have seldom come across, and when I have it is because of problems- I wouldn't slag them off on that basis though.

The boilers I chose I select on the grounds I have taken them apart first. And feel I can deal with the manufacturer- which with me being me channels me to smaller companies with fewer bean counters....although you cant eliminate them all sadly.

As a homeowner you have the problem of eliminating sales waffle from engineering judgement...something you won't be able to do without references, photos and research.

Also look at Atmos, and consider say two InterSystem or InterOpen boilers in cascade, even simpler than the Atag, but just as versatile. Again a small company, but nicely made boilers that can be turned to a variety of uses not in the book - back to a Combi option for sinks.

Install an InterCombi next to an InterSystem on a hearer and maintain weather compensation, hot water priority, maybe a shower hooked up to the combi too for emergencies (combi side doesn't need a working heating system to operate, just like a multipoint).

The list of possibilities is vast .

Points taken on board, and thanks for the long detailed post once again.

And yes, I agree, you rarely hear from a happy camper.

 

[mysteryman]

the structure of the industry is very different in Germany...partly because its a big country but also a country that takes engineering seriously..

the main differences are:

Local service centres related directly to the boiler manufacturer.
A separate profession for the installation of the chimney.

These little details have enabled the installers to keep their standards of service and prices much higher than in the UK...

People don't AFAIK shop around for the cheapest tradesmen quite like in the UK...and a german installers is as respected a doctor or a solicitor...

we are along way from that in the UK!

What a complete load of drivel Alec1. Long gone are the these days in Germany, in fact even since the days of the Berlin wall coming down has what you state been true. Now it's just like here, any CC/CCC or chancer of any kind can pick up a set of tools & call themselves a Plumber/Heating Engineer. The Eastern Europeans & mainly Turks have ripped the trade too threads there.
More nonsense & missinformed drivel that constantly pollutes this forum, by aged know-it-all non trade members.

This is not drivel; it is true. Most West European installers are much more highly trained and knowledgeable. There are compulsory annual flue inspections in several countries. Installers are better respected and paid because they know more.