Change from System and tank to Combi

[Tally101]

Hi All,
Over the years we have had loads of problems with our boilers and tanks and now want to rip it out and get a combi. Any recommendations for a combo for a 5 bed house with 17 rads. Looking for a quality brand if possible,reliable and cheap top run if thats possible. We have had Vaillant Eco Tea for last 3 boilers. Not stuck to Vaillant.
Thanks

 

[Madrab]

How many bathrooms, showers, baths etc and how many would be used at the same time?

 

[Tally101]

1 bath with shower , 1 shower and not usually used at the same time. 3 adults , Thanks

 

[denso13]

Consider the Vokera Pinnacle 35c, great modulation rates and warranty.

 

[DP]

Regardless of the brand, it is paramount that the boiler gets proper service instead of brand as every boiler is there to do the job. Some are better built making service a comfortable task, others are like a pigs ear and service is a pain. Know from experience as I have boiler hitting 40 year mark still working. Might use a bit more gas but parts ( is required and available) are not eye watering making total run and maintenance cost not prohibitive as some singing dancing condensing boilers

Have a client who wanted a new boiler. Suggested she refrain and go for better controls. Year later she reported back that fuel consumption was down 25%

You do not say what model you have and what the issue is. Recently learnt of a breakdown which was simple to diagnose but two additional parts were fitted which were totally not necessary. Furthermore, I would stick with the brand you have and have the same make and model fitted and retain the existing boiler for future spares. Not much to go wrong with an unvented cylinder.

A combi is a bad choice as when that option fails, all is lost whereas with cylinder you can heat the water electrically.

 

[Harry Bloomfield]

Over the years we have had loads of problems with our boilers and tanks and now want to rip it out and get a combi. Any recommendations for a combo for a 5 bed house with 17 rads.

Think carefully, before committing to a combi boiler system, there are numerous negatives, compared to a heat only system, but dependent on how you use a boiler.

They are much more complex, more to go wrong, and most of what can go wrong, will need a gas engineer to fix, versus a plumber. Delivery of HW will also be slower, much longer to fill a bath. Also a less efficient boiler, because it needs to be sized to heat the water, rather than the house it is in.

 

[Madrab]

Over the years we have had loads of problems with our boilers and tanks and now want to rip it out and get a combi.

Only reason that has happened is if it wasn't installed properly to start with or it hasn't been properly maintained by a resource that actually knows how to look after it correctly. These types of system have been in place, trouble free, for decades so there's no reason yours shouldn't be fault free either.

With a 5 bedroom house then going to a combi is not a great idea when it comes to future proofing and selling on. You also have to understand what your cold mains can deliver as far as dynamic pressure and flow is concerned, if that isn't know then the system could end up being worse than any better. That and if baths are enjoyed then be prepared to go and make the dinner while waiting for the bath to fill from a combi.

As suggested too, there is no form of HW backup if the boiler fails.

 

[ericmark]

I now have solar panels, and an off-peak supply, so using the immersion heater is much cheaper to using in my case oil. So I would question if getting rid of the tank is a good idea.

 

[Harry Bloomfield]

So I would question if getting rid of the tank is a good idea.

I'll say it - It's a cylinder!

 

[denso13]

So I would question if getting rid of the tank is a good idea.

No, not in your case. Horses for courses...

 

[ericmark]

I'll say it - It's a cylinder!

Does the shape matter?

great modulation rates

I wish I could get my head around that.

My house, living room has two radiators of around 2 kW each, what ever boiler I have, can't see it modulating to 4 kW. So boiler works on a mark/space ratio.

Now mother had a boiler with a reservoir built in, so it did not matter if tap at a dribble or full bore, we got hot water, but the response time was too slow, take a shower and the reservoir would run out, before the boiler was hot enough to take over. Put it on Eco setting, and then turn the tap on anything but full, and no hot water.

As to efficiency, can't see how one can work it out. There must be a quantity of water used, where it breaks even, but every home will be different. Getting domestic hot water (DHW) from a boiler with a cylinder, the slewing range of temperature is important, set at 30°C it may only fire up once a day, set to 1°C it will be turning on/off all the time.

So it is near impossible to work out a happy medium as also depends on distance boiler to tank.

No, not in your case. Horses for courses...

That is the problem, there is no one answer fits all. When I had a Main 7 fitted, must be 30 years ago now, before combi boiler were main stream, it was to save space, and it did, the airing cupboard became first a bedroom, then an office. But the pipe work boiler to kitchen taps was unchanged, and the delay getting hot water to the taps was quite long.

Two delaying factors added together, one how long the boiler takes to fire up and get hot, and two how long it takes that water to get through the pipes, so boiler in kitchen, and main hot water use in kitchen, and the delay is acceptable, boiler in garage, and then the delay becomes a problem, I could nearly fill a bowl with cold water before the hot arrived.

I have considered under counter 7 litres water heaters, to reduce the delay, but every home is different, I have two kitchens front and back, two shower rooms, plus a bathroom so 5 places I want hot water. Last house I have lived in, only had 2 places, bathroom and kitchen, mothers house 3 places shower room, bathroom and kitchen.

 

[Harry Bloomfield]

I wish I could get my head around that.

My house, living room has two radiators of around 2 kW each, what ever boiler I have, can't see it modulating to 4 kW. So boiler works on a mark/space ratio.

The longer a boiler runs, the more efficient, just like driving your car. Drive it in runs of a few miles, it will have very poor mpg. Modulation means the heat output can turn down, so it can continue to burn for much longer, much more efficiently, avoiding the inefficient on/off.

 

[denso13]

My house, living room has two radiators of around 2 kW each, what ever boiler I have, can't see it modulating to 4 kW.

Depends on the boiler output, but perfectly achievable.

That is the problem, there is no one answer fits all.

Of course there isn't, but why is it a problem?