Combi, System or Heat only. Which would you choose?

[patrocks]

Hello Everyone,

I am about to have a new CH system installed from scratch on a 1920 four bed semi. It has been taken back to brick and is a blank slate and I would welcome your thoughts on my thoughts.

Some background, we are a family of 4, kids are 2 and 5yrs. We plan to grow old(er) in the house. The house has a family bathroom/wc and a downstairs toilet. No plans to add an en-suite in the future.
I am not saying money is no object but I am willing to spend money to do it right (within reason, can’t afford to put UFH in. The house is being insulated, loft, walls and under the ground floor, plus new windows throughout. Hopefully the house will be well insulated for its age.

We have always had combi’s previously but now have room for a cylinder which I hope would give us better showers. I am not keen on having a tank in the loft, I can’t see a good reason to install something full of water in my loft unless I have to.

I had decided on a system boiler until I talked to my plumber. I mentioned to him I preferred the idea of a heat only boiler for reliability but didn’t want a tank so system boiler. He told me I could install a heat only boiler with a conversion kit, so I am planning on a heat only boiler with an unvented cylinder.

I am not looking for specific pieces of hardware but just your thoughts on the route I am going, some friends say why bother with a cylinder, I am not sure if having an unvented cylinder is actually going to be a pain now I am reading more on them.

Having said that I don't want specific hardware suggestions I would like to have a weather compensating controller but I am struggling to find one for a heat only boiler due to the need to heat the DHW up to a higher temp than the water in the rads. I am not sure if this is the case with all heat only boilers or specific to the boiler I am looking at, Remeha. Any advice here would be very helpful.


I know it is all a bit vague but I would welcome the opinions of people who deal with these things as you do before we start ordering bits and bobs. Thanks for reading!

Pat.

 

[Killy Bing]

System boiler will be just as reliable as a heat only, if youre starting from scratch you will have a sealed system so the pump position in the boiler will be fine.

Depending on boiler, you do some wiring magic to get the boiler to fire on full to heat the unvented first.

something to consider is some boilers have the weather comp built in so you don't need an additional controller.

also check your incoming main size, flow rates and pressure.
if you're sat at half a bar pressure or 11 litres a minutes or both!
then an unvented cylinder would be wasted.

if you have the option and as you say its a blank slate then A mains upgrade would be beneficial.

are you open to quotes from forum members?

a closing and final note.

i dislike broag/remeha boilers...

 

[Mike Jackson]

If you use an Atag system boiler you can set it up to fire on full for hot water and use the built in weather comp for heating.

 

[Centralheatking]

No way a combi - a system boiler set up is your path - hardware your choice, everybody on here
has their own opinion, BUT I would talk to Ray Stafford on here before you buy anything - his
plumbing heating emporium is huge and offers direct delivery complete with his 70 years personal experience - well he looks that old anyway. He will even send choclates I understand

he has never sent me any chocs despite my push for his business Centralheatking

 

[Killy Bing]

No way a combi - a system boiler set up is your path - hardware your choice, everybody on here
has their own opinion, BUT I would talk to Ray Stafford on here before you buy anything - his
plumbing heating emporium is huge and offers direct delivery complete with his 70 years personal experience - well he looks that old anyway. He will even send choclates I understand

he has never sent me any chocs despite my push for his business Centralheatking

Home owner and not trade.

although their chosen engineer could use ray

 

[Megaflo-Experts]

I would aim for a system boiler with an unvented cylinder. Your installer will need to ensure the mains water pressure and flow rates are suitable for an unvented system, and if not, your installer should be able to advise.

 

[patrocks]

Thanks guys. So system boiler over heat only. I can see how a system boiler could work well (easier) out of the box with a weather compensation controller, I suspect the magic wiring is DHW priority?

Interesting to hear the comment about Broag, I work around commercial plant rooms balancing heat and ventilation systems and in that world Broag is well regarded and that was my reason for going remeha. However I have never bought a boiler in my life so it isn't an opinion based on real experience and I welcome your opinion, although it just makes my head spin a little faster as I thought that bit was sorted!

Not sure where I will be buying the kit (although chocolate is something close to my heart) but I was planning to buy it via a commercial mechanical engineering firm I deal with on a bit of a reciprocal deal via my work and I was leaving it up to them to source, but I have to pick the bits.

This could be opening a massive can of worms but...
OSO Super S cylinder
Sterlad Radical radiators
Rehema boiler (??)
and in a very nerd way wifi TRV heads from Germany.

Anyone hate the above, prefer others. Selfishly not from an installers point but from an end users angle.

The installer I am going with is an ex commercial pipe fitter turned gas safe self employed plumber who comes highly recommended by a family friend, I wouldn't feel right taking the work away from him.

 

[patrocks]

I would aim for a system boiler with an unvented cylinder. Your installer will need to ensure the mains water pressure and flow rates are suitable for an unvented system, and if not, your installer should be able to advise.

Thanks, I will talk to him on Monday and have this looked at before I waste my money.

 

[Killy Bing]

Broag from what I'm also told is great commercially

World of domestic boilers is a touch different to commercial.
my choice are atag + intergas (guess what, weather comp out of the box!

You cant go wrong with an oso super series. (Place boiler above for minimal pipework depending on cylinder size)
unless you got for an ACV

yup thats the magic wiring ( well ish, depends on boiler + controls set up)

we all have our loved boilers an hated.
the next 20 guys might say they love remeha!

 

[Ermintrude]

Plus one on ACV. Get an ideal vogue system boiler and fit zone valves and rf stats not those pretend trv rubbish ideas. 2 ports and rf will always be fixable. What happens if trv breaks and it's discontinued or even the controller?

 

[Ermintrude]

Remeha are rubbish

 

[patrocks]

Plus one on ACV. Get an ideal vogue system boiler and fit zone valves and rf stats not those pretend trv rubbish ideas. 2 ports and rf will always be fixable. What happens if trv breaks and it's discontinued or even the controller?

That is just common sense talking. I have this vision of me sat on a beach with an iPhone turning my radiators off whilst women stare at me in wonder.

Time to Google ACV.

 

[efficiencyman]

I would aim for a system boiler with an unvented cylinder. Your installer will need to ensure the mains water pressure and flow rates are suitable for an unvented system, and if not, your installer should be able to advise.

I would also add optional renewable heat inputs in cylinder for wood, solar thermal or heat pump might as well have an ability to cut gas bills and have diversity. Be prepared for increasing gas prices !

 

[Killy Bing]

I would also add optional renewable heat inputs in cylinder for wood, solar thermal or heat pump might as well have an ability to cut gas bills and have diversity. Be prepared for increasing gas prices !

Heat pump isnt a great option unless he massivly over sizes rads or fits underfloor (which he cant afford)

 

[tamz]

I have this vision of me sat on a beach with an iPhone turning my radiators off whilst women stare at me in wonder.

Thats easy enough these days
iT500


Btw a combi will be cheaper to install and run. Uvhwc and system or heat only offers you no real advantage.

 

[SafeGasInstall]

System boiler+unvented hot water cylimder !have to have Insulate all pipes under the floor ,alow 20-40% for heat lost on radiators and enjoy system that will last long time ! no plastic pipes have just copper everywhere
Worcester Bosch boiler
Megaflow hot water cylinder
honeywell controls
stelrads
and
lots of insulation everywhere

 

[codcutter]

My personal choice (what i have at home) WB system boiler (I like them) santon unvented cylinder (same as Megaflo but has external expansion vessel) solar panels on roof. If you can't afford the solar at the moment put a twin coil cylinder in anyway, make it easier for solar in the future.
Combi boilers are o.k for flats

 

[Gray0689]

If you want control
Why wifi trv
Go for manifolds pipe in pipe to all rads ( and manifold for domestic water if wanted)
for rads stats in every room
Wifi option on heating can be from heat miser controls
Or a simple climote time clock

Cylinder most not a lot of difference
But the best is acv imho

If you go for a manifold system no joints underfloors anywhere and the control of every room individually
And as said already fit a cylinder with solar coil in case you do ever decide to go with solar

 

[Ermintrude]

ACV SLME is the daddy and a manifold of two ports just above boiler.

 

[smhstu]

I fit a lot of unvented systems and find if your going for Worcester best to fit there twin coil cylinder, if you are not zoning the heating you can use there internal diverter
normally if it's no zones I fit
30cdi system
int diverter
worcester twin coil cylinder
worcester system filter
and dt10rf optimiser or they do a weather comp control

if you stick to all Worcester products there all covered within the guarantee
5year plus 1year for cylinder plus 1year for filter so seven year guarantee in total on all there products.

if you are zoning then Honeywell zone valves draton +3rf stats

 

[happyflyer]

Remeha are rubbish

And parts are crazy price

 

[Killy Bing]

I fit a lot of unvented systems and find if your going for Worcester best to fit there twin coil cylinder, if you are not zoning the heating you can use there internal diverter
normally if it's no zones I fit
30cdi system
int diverter
worcester twin coil cylinder
worcester system filter
and dt10rf optimiser or they do a weather comp control

if you stick to all Worcester products there all covered within the guarantee
5year plus 1year for cylinder plus 1year for filter so seven year guarantee in total on all there products.

if you are zoning then Honeywell zone valves draton +3rf stats

Running in the wrong direction fitting a worcester cylinder over an oso!

also if hes back to bricks and morter then hard wire the lot. Far more reliable

how much is the weather comp work out for them then?
atag is far more attractive
......and a better product *giggles*

 

[Killy Bing]

And parts are crazy price

And they have so many damn intermittent faults!