Changing over to a combi in a bungalow.

[daveemd]

We are looking to replace a conventional boiler / cylinder / water tank with a combi. The property is a bungalow with dormer bedrooms. and there is only room for a smallish ‘belly’ cylinder in the roof space, plus it needs a pump to supply the upstairs dormer bathroom which generates unwanted noise. The hot water to the downstairs bathroom / kitchen is not pumped and has poor flow. Replacing all this with a combi should solve our noise and limited hot water problems and free up more space in the loft. I don’t believe pressure / flow would be an issue, as we have over 5 bar, and the flow measured at the garden tap is nearly 30l/min.

I done plenty of reading in these forums etc, and believe the preferred solution is always to avoid a combi if possible and go with an unvented (or conventional) cylinder and regular boiler, but space is really at a premium We have 14 radiators in the house and two bathrooms.

I am thinking along the lines of a Worcester 38Cdi or maybe 42Cdi. Also looking at storage combi – the Veissmann 111-w. The similar Vaillant 938 seems just too big a unit.

Can anyone please advise which if these may be more suitable, or an alternative? I’m not concerned about running 2 showers at the same time as that is very rare, but about 1 shower running when a tap or two is opened. I think for the heating aspect, at 35kw they are all more than is needed. The Veissmann seems to modulate down lower than the WB’s, which could be beneficial there, but I wonder if the tank in it really adds anything to my setup (and is always kept hot as far as I can tell). It there any real advantage of the 42cdi over the 38cdi? (do I even need the 38Cdi?).

Thanks!

 

[DP]

Unvented and system boiler. Simple, less to go wrong, belt and braces. Combi is NOT to King people believe them to be

I love a combi as it keeps me busy throughout the year. People I love are advised not to go combi route

 

[ianmcd]

DP has given you the correct advise, follow what he says and you will have no worries

 

[muggles]

You'll need about 10kW for your heating I expect. Personally wouldn't touch WB with a bargepole. I'd spec an Intergas boiler connected to a Joule unvented hot water cylinder

 

[AdvanceHelpline]

You might have 5 bar and 30l/min at the cold supply - this won't happen at the hot taps as there just isn't enough power in any combi to do it. Use a cylinder and system boiler.

 

[Agile]

The choice of a combi should depend on the number of bathrooms and the number of people living there!

More than one bathroom or two people and I would always recommend a stored hot water system.

Tony

 

[PullerGas]

As said don't touch WB boilers, they're over priced rubbish.
An Ideal Vogue 40 will give you 16Ltr/min at a temperature rise of 35deg C.
I fitted one a few weeks ago for a punter with two showers & they ran simultaneously, no problem.
A great non storeage combi & quality kit.

Of course your cold mains incoming dynamic pressure & flow rate would need checked.

 

[ServiceNumpty]

OK, you've had the proper advice, now if you were my customer and it's your money at the end of the day. You have 2 bathrooms although very rarely used, you don't have the space for a stored hot water system, then I would opt for the 38cdi over the 42cdi. The extra cost doesn't warrant the 42cdi. The heating output on the cdi can be range rated down. As Puller mentioned you also have the Ideal Vogue 40 which is considerably cheaper than the Worcester.
From a Worcester Accredited Guy you should get 7 years parts and labour on the boiler, if you have their magnetic heating system filter that will add an extra 12months warranty (so 8 years) and if you go for their Smart App based Thermostat - The Wave- you will receive an additional 2 years warranty on the whole package (so 10 years).
Hope this helps

 

[ServiceNumpty]

I will add the Worcester Bosch Classic is the best boiler in their range so good choice.

 

[DP]

Ideal vogue and Intergas Eco 10 year warranty

 

[PullerGas]

10 Year warranty on the Ideal Logic & a better boiler than any WB, considerably cheaper too!!

 

[bolshy]

Most makes of boiler will give years of trouble free service if carefully and correctly installed. Most 40kw combis will provide around 16 l/min without storage. Unvented cylinders are not hassle free - they require an annual service and safety check and have components which are subject to the same failure rates as any other comparable part in engineering. Your DHW delivery will obviously be affected by your pipework/outlets. The downside to combis is if it does break down, you have no heating or hot water. Some people opt for a combi boiler with zoned stored DHW, combi feeding DHW to the kitchen, stored DHW feeding the bathroom. This allows for a smaller boiler. Gledhill thermal stores have temperature controlled plate hexes with circulators and are capable of delivering more than 20l/min. Have you thought about a horizontally mounted unvented cylinder? Whatever you decide on, if it is installed poorly on a dirty or inadequate system, then you will have problems sooner rather than later regardless of make and capacity.

 

[PullerGas]

Believe me I'm not a very educated guy, but I know about the rudiments of writing English.
You must put your points over in paragraphs. If you don't, it's an illegible jumble of words!!

 

[bernardgreen]

Some people opt for a combi boiler with zoned stored DHW, combi feeding DHW to the kitchen, stored DHW feeding the bathroom.

In which case it would not meed to be a combi. A simple heat only boiler would be more than adequate heat wise and with far fewer component to gp wrong. Those essential items like pumps and valves can be located in places where they are easy to access and not crammed into the case of a combi

 

[DP]

In which case it would not meed to be a combi.

Don't see why not. 24kw combi, sufficient to heat almost every household, matched for power output to large percentage of cylinders, instant hot water where frequent hot water needed (kitchen sink), almost always a stocked appliance. Have carried out this type of installation few times