Best with combi or system boiler?

[Mark Huddleston]

I’m after some advice. We are replacing our 21 year old Ideal Classic boiler and have been looking at the pros and cons of combi vs system boilers. House is a 3 bed detached, 9 radiators, 1 bath tub, 1 shower. Boiler is currently on an external wall and we will be looking to move it into the garage. There are four of us in the house. The mains water pressure is good (although I haven’t measured this with a gauge)
Are system boilers more reliable, longer lasting etc?? Any clear winner or down to personal preference? The reason I’m asking is that I’m thinking of doing an online fixed price installation with heatable or boiler central. Thanks in advance

 

[Scott_D]

Are you happy with the hot water performance now?
I think most would advise against online installations.
The fitter will be given the bare minimum time, money and materials. It will get fitted as quickly as possible and into the next.

 

[Mark Huddleston]

Are you happy with the hot water performance now?
I think most would advise against online installations.
The fitter will be given the bare minimum time, money and materials. It will get fitted as quickly as possible and into the next.

The flow of the hot water is not as good as we would like currently

 

[SimonG]

System boiler and unvented cylinder, once pressures and flow have been checked.

 

[Aquarius]

Agree with @SimonG , You really need the cold main pressure and flow rate tested, usually at peak demand, although there are different ways to test. Only then can you make an informed decision regarding your own demands and requirements. You also need to consider the fact that a combi will only heat up to a specific temperature, and deliver flow rates based on incoming temperature, pressure and flow rate. Some installers will flog a combi because they’re easy enough to fit, or maybe in a reward scheme.

The flow of the hot water is not as good as we would like currently

What is it you currently want? A decent shower? Better flow rate for a bath? Just better all round? I live in a similar setup, and mine is new build (2010) and I’m happy with my heat only boiler and gravity hot water delivery. If it’s only the hot water for a shower, you could consider a pump?

Just something for you to mull over.

 

[Mark Huddleston]

Thanks for the advice. With regards to the mains pressure is it ok to measure it with a gauge attached to the outside tap? With regards to flow rate I know it’s not very scientific but I’ve read about filling a container over 6 seconds and then doing the maths to work out the flow. I know it’s crude but will this give me a good idea? Hot water performance is ok downstairs but pretty rubbish upstairs including the shower. I believe you can fit a pump with a system boiler but not a combi. If I opted for a system boiler is the tank in the airing cupboard reused or would I need a different/new one?

 

[Aquarius]

With regards to the mains pressure is it ok to measure it with a gauge attached to the outside tap?

Yes

With regards to flow rate I know it’s not very scientific but I’ve read about filling a container over 6 seconds and then doing the maths to work out the flow. I know it’s crude but will this give me a good idea?

You can do this, but, I would flush the toilet at the same time to give a rough idea of a peak demand

If I opted for a system boiler is the tank in the airing cupboard reused or would I need a different/new one?

It sounds like your tank in the airing cupboard might be your cold feed for the cylinder, which if you went for a system boiler would do nothing for your hot water flow rate and pressure. If it is the cold feed for the cylinder and want to keep the cylinder, then look at getting the cold tank moved into the loft at a higher level, the higher up the better the pressure so to speak. Also to answer about the pump, no generally not fitted to a combi.

 

[SimonG]

Just be careful measuring from garden tap for dynamic pressure, when other things are running, as the check valve may give you a false reading.

Can keep your cylinder and as @Aquarius has said try and raise cold water feed tank or go unvented and do away with cold water feed tank.

Best thing is to get at least 3 people to have a look and give you an estimate. Post location as somebody may be close enough to give you a price.

 

[Mark Huddleston]

If I opt for a system boiler then I want rid of the tanks in the loft. The job is in Bedlington in Northumberland but unfortunately we will have to take it on finance so looking for one over 7 or 10 years.

 

[Aquarius]

If you opt for a system boiler you will only get rid of 1 tank, if you want both gone Combi boiler or unvented cylinder with a system boiler.

 

[Mark Huddleston]

Just checked mains pressure on outside tap with nothing else running and getting at least 4 bar. Slight variations in readings each time and on average between 4 and 4.5 bar. Flow rate at kitchen sink tap is 17ltrs/minute.
I’ve had a FaceTime survey with Eon today and although they are very pricey compared to others I think I’m leaning towards a combi. I’ve got 2 further quotes to wait for but these are face to face surveys in the house.
I’d appreciate it if someone could advise me how these numbers stack up?
I’ve being doing some research and been looking at the Baxi 600 36kw and the Viessman Vitodens 35kw. Decent or not based on these numbers??

 

[Scott_D]

What are Eon quoting to do the job?

 

[Mark Huddleston]

What are Eon quoting to do the job?

£4138!!! for a Worcester Greenstar 8000 life 35kw. That’s moving it into the garage too but I would consider keeping it in the kitchen just moved along the wall slightly. The Viessmann and Baxi are less than £3k on Boilercentral online fixed price.
[automerge]1597078316[/automerge]

[automerge]1597078343[/automerge]

 

[gmartine]

15 yr warranty?!!! BS, these companies won't be around make good. Pick a Viessmann approved installer to get a maximum bonafide warranty. Do you need to do it on finance?

 

[Murdoch]

FWIW if the OP ever thinks they may install solar panels for lecky, having a hot tank is the easiest way to "store" excess production.

 

[Mark Huddleston]

15 yr warranty?!!! BS, these companies won't be around make good. Pick a Viessmann approved installer to get a maximum bonafide warranty. Do you need to do it on finance?

Unfortunately yes. We are putting in a new kitchen, bifold doors as well so we’ve got loads going on. I want to take my time with the boiler though and pick the right one with an installer I’m happy with.
[automerge]1597092187[/automerge]
Thanks for all the advice today. I’ve been on Worcester Bosch and Veissmann website to source local accredited installers. There are a few companies who do finance and actually one which looks much cheaper than the online companies. I think that is definitely the best way forward.

 

[Stu-B]

Wow!! 15 years, and I thought the Ideal Vogue at 12 years was ambitious!!
A 36kw is a bit on the big side, you could probably get away with 30kw, same as others said, get your water pressure and flow rate checked and size the boiler accordingly, too many of these online firms just chucking boilers on the wall and disappearing, get a local guy in then get him to service it every year too.

 

[gmartine]

If the shower is in the bathroom and therefore unlikely to be used simultaneously then a combi should be fine however your outgoing flow rate from boiler is dependent on what's incoming hence all the recommendations about getting it measured. No complaints about the choice of Viessmann or Vaillant.