Recommendation of Vaillant boiler and Heatrae Sadia Megaflo?

[noobiediyer]

A bit of context:
I'm in the UK and putting in a new heating system (the old system has been completely removed) in my house. It's a 5 bedroom house, with 4 bathrooms; 3 with showers only, one with a bathtub and shower over tub. The house has gas for heating. It will have a wet underfloor heating on the ground floor (no radiators at all). Radiators on the first floor and the loft.

I'd like to get a Vaillant branded gas system boiler along with a Heatrae Sadia Megaflo hot water storage tank. I vaguely recall someone mentioning that some Megaflo tanks have a back-up electric immersion heating coil which can be used in a pinch to heat the water if there was some problem with the boiler. This sounds really useful so I'd like this feature.

Can anyone recommend a particular product for each that would suit me please? Also, any recommended places to purchase from which have great value for money will also be awesome.

Thanks in advance

 

[noobiediyer]

Also, I notice that for a given Megaflo of a certain size (e.g. 300 litres), there's some variants indicated by the model name e.g. 300dd 300ddd and 300dddd. From what I can find out, the number of d's correspond to the number of heating elements. But if the water is heated by the gas system boiler, what benefit will having extra heating elements? If someone is able to explain then that would be great. Thank you.

 

[muggles]

Why do you want those brands specifically? Have you done a heat loss calculation to work out what size boiler you need to heat your house? If not, use the calculator at https://www.heat-engineer.com/ What's your mains pressure and flow rate?

The D on the Megaflo means Direct, IE it's heated electrically. There's no boiler connection on these. You need the "i" variant, which has one immersion heater as standard. Or an alternative brand, which will be cheaper and won't have the stupid floating baffle system in it.

 

[noobiediyer]

Why do you want those brands specifically? Have you done a heat loss calculation to work out what size boiler you need to heat your house? If not, use the calculator at https://www.heat-engineer.com/ What's your mains pressure and flow rate?

The D on the Megaflo means Direct, IE it's heated electrically. There's no boiler connection on these. You need the "i" variant, which has one immersion heater as standard. Or an alternative brand, which will be cheaper and won't have the stupid floating baffle system in it.

When I was renting, they had a Vaillant combi and whenever it was serviced, the engineer would always say that Vaillant boilers were awesome and reliable. They would say they were the Rolls Royce of boilers. Haven't heard anything bad about Vaillant so I assumed they were a top quality brand. If that's not the case, then what brand system boiler would be? I want a good quality boiler that is going to be reliable and well supported.

I assume Heatrae Sadia Megaflo are also very good, as I have heard equally good things about them. Interesting about needing the "i" variant, the price for "i" is more expensive than the "d" ones. With fewer immersion elements, I would have thought it was cheaper.

 

[noobiediyer]

What about Viessmann Vitodens 100-W System 35kw? They seem to be highly recommended by various websites (from my recent Google searching)

 

[muggles]

Vaillant aren't bad, but a bit expensive for what you get IMHO. My own preference is for Intergas boilers and Joule cylinders.

As before though, you need to do a heat loss calculation and find out your mains pressure & flow rate before specifying anything.

 

[noobiediyer]

Vaillant aren't bad, but a bit expensive for what you get IMHO. My own preference is for Intergas boilers and Joule cylinders.

As before though, you need to do a heat loss calculation and find out your mains pressure & flow rate before specifying anything.

The house this will be going into has been completely gutted, completely new water pipes are going to be put in. The builder will be doing a pressure test to make sure it is more than sufficient. I think he will be installing 35mm pipes. How can I do a heat loss calculation?

Thoughts on Viessmann compared to Vaillant?

 

[muggles]

Letting builders get involved with plumbing is always a bad start. Better to get a heating engineer in.

You can do a heat loss calculation here https://www.heat-engineer.com/

Veissmann & Vaillant both have good options, although I'd say Viessmann are slightly better. The Viessmann 200-W is an excellent boiler

 

[noobiediyer]

Letting builders get involved with plumbing is always a bad start. Better to get a heating engineer in.

You can do a heat loss calculation here https://www.heat-engineer.com/

Veissmann & Vaillant both have good options, although I'd say Viessmann are slightly better. The Viessmann 200-W is an excellent boiler

Thanks for the info. I did some Googling to search for difference between the 100-W and the 200-W and I found this thread (https://www.diynot.com/diy/threads/viessmann-advice-pls-compare-100w-vs-200w-models.476282/) which I noticed you were also contributing on. It had some really useful info. One thing I think is true (which @pgtips said) was that if you ask 10 people about boilers, you'll get 10 different opinions. This makes it incredibly hard to work out what the best boiler is for a layperson like me.

But the thread did link to a really good page (https://www.newboiler.co.uk/best-boiler-survey/) which was a survey of 600 engineering companies. With so many different opinions from individuals, I feel more drawn towards going for a Vaillant or Worcester system boiler as per the survey.

With regards to the heat loss, I had a look but there's a huge amount of input fields that I do not know the answer to. As an example, taking a look at various Vaillant system boilers (e.g. here https://www.mrcentralheating.co.uk/...-ecotec-plus-sort-by-price-sort-direction-asc), there's a difference of £250 between the 18kW version and the 30kW. £250 is a decent chunk of money but the amount of time and effort I would have to invest to understand exactly what I need, doesn't seem worth the benefit. I'd rather go with the 30kW to be safe and if I've oversized it then there's no harm, right? If anything, doesn't it mean that if the tank is empty of hot water and I need more, then the 30kW will fill the storage tank quicker than a lower powered one? So even if I oversize it, there's still some benefit to that extra cost.

Anyway, I really appreciate the effort and help with those who have replied in this post. I'll have to keep my fingers crossed that I don't get into any issues, at least I can be somewhat reassured with the 7 year warranty period.

Also, I referred to the guy as a builder but he's not really a builder. He's the guy who owns the company that and is the single point of contact for all my work. He employs/sub contracts all the work needed. He's not exactly a project manager but he takes care of all the nitty gritty day to day stuff, and gives me a single point of contact for anything that goes on. I'm not really sure what the correct term for this kind of person is so I've just (wrongly) called him a builder.

 

[muggles]

If the boiler is oversized, it'll be inefficient and cost more to run, so yes there is much to lose by having an incorrectly sized boiler

 

[noobiediyer]

If the boiler is oversized, it'll be inefficient and cost more to run, so yes there is much to lose by having an incorrectly sized boiler

That's a fair point but I'm still not sure what the input values are for that calculator. To make things even more difficult, I'm expecting the size of the family to increase in the coming years so I have to account for that. It might be oversized initially but it could end up being just right.

 

[muggles]

The size of the family, or the size of the house? If the house is staying the same size then its heat loss will remain the same.

The fact that you don't understand this is precisely why you should be employing someone who does. It's a big investment, and best to get it right first time.

 

[dilalio]

As per @muggles get your own heating engineer in to specify and install.

Don't try to be clever with the costs, having no experience, you'll get it wrong (as will the general builder you have on board) and you will be living with the consequences.

I do this for a living, as does Andrew, and I'd also be recommending an Intergas and Joule cylinder... For all sorts of reasons.
12 year warranty on the boiler for a start!

 

[noobiediyer]

The size of the family, or the size of the house? If the house is staying the same size then its heat loss will remain the same.

The fact that you don't understand this is precisely why you should be employing someone who does. It's a big investment, and best to get it right first time.

What's the typical cost for a heating engineer to do a professional assessment?

 

[dilalio]

What's the typical cost for a heating engineer to do a professional assessment?

That's not how it works... A heating engineer will appraise and discuss with you before putting in a quote to do the work.
Please don't be tempted to call someone in on the pretence that they are quoting to get the job, only for you to be extracting advice from them.

Even though your builder is acting as a SPA for you, I would strongly recommend that you appoint your own heating engineer and even electrician because they will focus on your comfort and how you live in your home... I see it so many times where builders/project managers decide on customers' behalf and they are left wanting after handover.