What boiler type to install

RavingMad

With our regular boiler coming up to 17 years old, am starting to plan on what we should replace it with next.

Are combis more efficient and cost effective than regular boilers?  Will they save me money in the long run or does it depend on the variables ie size of house/ family?

Thanks

grumbler

RavingMad said:

With our regular boiler coming up to 17 years old, am starting to plan on what we should replace it with next.

Age means nothing. If it ain't broke don't fix it - just my HO. A new boiler will be very expensive to install, service and will take years to pay back.

Are combis more efficient and cost effective than regular boilers? 

I think, condensing boilers are more efficient and, most likely, all modernt boilers are condensing, be it combi or system (with a HW tank).

CliveOfIndia

It varies.  A combi boiler has the advantage that you only heat the water you need, meaning that (a) you don't run out of hot water midway through a shower and (b) you're not heating a tankful or water that you don't need.

The downside is that the flow rate tends to be slower (particularly in winter when the incoming supply is that much colder), and it can take a long time to fill a bath, for instance.

The old rule of thumb used to be that they're great for a couple who rarely have baths (showering instead), but less practical for a larger family, especially if there are kids who prefer/need to bath rather than shower.

They may have got better these days, but the principle is the same.  They're also slightly more complex than a conventional boiler, so more expensive to fix.

Over the years I've been in houses with both sorts of boiler - a combi certainly does have advantages for the right situation, but it's not suitable for everyone.

Of course, there's this whole thing about banning oil and gas fired boilers at some point and making us all have heat pumps, but personally I wouldn't even consider that as a factor at the moment - I'll be surprised if it ever actually happens, to be honest.

All that aside, just because it's 17 years old doesn't mean it has to be replaced.  The cost of a new boiler will take a long time to pay for itself, even if it is more efficient than the old one.

RavingMad

Thanks guys.  I've no intentions of replacing it until the time comes but I did notice the water wasn't it's usual hotness this morning so will see if it fires up tonight.  Fingers crossed.

We're used to seeing the old rule of thumbs so was wondering if they still apply or has technology moved on.  Are combis better/cheaper at heating the house?

Don't think I'd consider system boilers as they're quite a bit more for the added benefit of better pressure over a regular boiler.
Condensing boiler?  Google says anything after 2005 must be condensing? So ours must be one already?

Eldi_Dos

Post up details of controls your system has, technology has certainly moved on with them in the last 17 years.
Could be area that saves money and makes your system more user friendly.

knightstyle

Our old boiler was replaced two years ago with a combi, works well and we really like the constant flow of hot water when family are staying. Plus the old airing cupboard is useful storage and the wireless control thermostat and timer can be moved around the house.

knightstyle

Plus check if you can get help with the purchase.  We did BUT because of that only got a two year warranty.

FreeBear

CliveOfIndia said:

It varies.  A combi boiler has the advantage that you only heat the water you need, meaning that (a) you don't run out of hot water midway through a shower and (b) you're not heating a tankful or water that you don't need.

The downside is that the flow rate tends to be slower (particularly in winter when the incoming supply is that much colder), and it can take a long time to fill a bath, for instance.

If you have an open vented DHW tank (without a pump), a combi will deliver a consistent flow of hot water regardless of the time of year. As long as the boiler is appropriately sized for the flow rate, you shouldn't suffer any noticeable drop in water temperature during the depths of winter.

Having recently changed from an ancient back boiler (open vented DHW), there is a significant saving in gas straight away - The boiler used to run for ~45 minutes to heat a tank of water. Some 12KWh for that. Running a bath to the same level of fill with the combi, and I'm only using ~3.5KWh of gas. During the winter months when the cold water temperature drops, the amount of gas used will increase, but it will still be less than the old Baxi. Oh, and the bath fills much quicker too

One thing to consider if installing a combi is where you need hot water most frequently. If you have a bathroom at opposite end of the house to the kitchen, you'll need to run the tap longer in one or the other to get hot water. Something you'd be used to if you currently have a hot water tank.

As for heating, a modern condensing boiler paired with a thermostat that can command the boiler to modulate down has the potential to save even more energy - Increasing the size of the radiators will also help as this means you can run at a lower flow temperature and push the boiler further in to condensing mode which means higher efficiency.

But swapping out an old boiler, fitting larger radiators, and perhaps having to replumb parts or all of the system comes at a cost - My boiler cost £2500 plus an additional ~£500 for pipework & radiators (did the bulk of the work myself). Annual gas consumption had been just under 4000KWh per year, so there isn't much scope for massive savings. What I do gain is a boiler that is under warranty for the next ten years, and something that I can get a Gas Safe certificate for without having to jump through hoops finding an engineer that understands back boilers.

CliveOfIndia

RavingMad said:

  Are combis better/cheaper at heating the house?

I'm not sure there's much in it, to be honest - it's the hot water where you can potentially make a saving.  Although, do bear in mind the higher cost and higher repair prices of a combi - plus the fact that they're a bit more complicated, so more things to go wrong in the first place.

One other thing that may be worth considering.  With a conventional setup (with a hot water tank), if the boiler goes kaput you've usually got an immersion heater in the hot water tank, so you can still get hot water.  Arguably not such an issue if you've got an an electric shower as a backup, and you can always boil a kettle for doing the washing up or whatever.  But something to think about.

On the shower front, I have to say the houses I've had where there's been a combi boiler, the shower has always been brilliant - as long as someone doesn't run a hot tap whilst you're in there !

ThisIsWeird

RavingMad said:

With our regular boiler coming up to 17 years old, am starting to plan on what we should replace it with next.

Are combis more efficient and cost effective than regular boilers?  Will they save me money in the long run or does it depend on the variables ie size of house/ family?

Thanks

What type do you have at the moment? Make, model, and does it have a pressure gauge?
If you have a hot cylinder, is it vented or mains-pressurised?

FreeBear

Just another thought - If the current boiler has a pilot light burning away 24/7, a modern boiler with auto-ignition will save you around £150 a year at current gas prices.