Mistral Oil Combi Boiler

[wcavanagh]

Had a plumber in today to look at my project, he is recomemding Mistral HE 35 - 41 kW
He says they are British made and have an immersion heater built in for backup.

Has anyone got any experience of these?

He seems to think the DHW is very good on these.

Any thoughts?

Cheers

 

[oilhead]

Have a look at the Manufacturer's specification. On a 35-41kw the hot water the hot water should be brilliant, but is dependent on the size of the heat exchanger. Mistral are a good range boiler, but without knowing the application, I wonder whether a Combi is the right choice for a property that needs 41kw heating. I would be thinking of a more conventional set-up with a mains hot water cylinder.

 

[wcavanagh]

Thank you. The website is not that great. They say DHW is XXL. Application will be 160 sq meter of Under Floor Heating. House will have 1 main bathroom, and 2 en-suit, only 2 of us here so only one bathroom used at a time. We both work full time, so not keen on keeping tank of water warm all the time. The plumber seemed to really rate this combi, he said the built in immersion heater is a good backup. It will be oil also.

 

[leakydave]

A combi will not be great with x2 showers and a bath running at the same time. What is your mains water pressure and flow rate?

 

[wcavanagh]

But they will never be running the same time, we have always had combi's and never had issues. We hardly bath, just a morning shower, and we always shower different times. So I don't see the demand being an issue.
Flow is 27 l per min, and static pressure is between 10 and 12 bar depending in time of day.

 

[leakydave]

If you sell the house to a family with different showering habits it would be crap... consider an unvented cylinder instead.

 

[muggles]

If you sell the house to a family with different showering habits it would be crap... consider an unvented cylinder instead.

This
Heat only boiler and unvented cylinder is the way to go

 

[wcavanagh]

Thanks for input. Will get another plumber into quote see what he thinks.

Always had combi so like the idea of sticking with what I know, but guess it comes down to what the plumber wants to install in the end.

 

[leakydave]

... but guess it comes down to what the plumber wants to install in the end.

It should come down to what suits you and your property really.

 

[muggles]

Thanks for input. Will get another plumber into quote see what he thinks.

Always had combi so like the idea of sticking with what I know, but guess it comes down to what the plumber wants to install in the end.

Not at all, it's your house and you can have what you like, but you should match the boiler to the needs of the house, and in your house anyone worth their salt will tell you that a combi would be an error.

 

[oilhead]

Another point to bear in mind is the location of the boiler in relation to the hot water outlets. If the boiler is in one corner of the house, then it will take an awful long time and a lot of water before it runs hot. A cylinder can be sited muchmore conveniently. Also, if you are used to gas combis, you need to be aware that an oil combi works totally differently, with a permanently heated slave tank. Not quite the same as a mains unvented cylinder, but taking into account the heatloss from pipework within the boiler, there is probably not much difference.

 

[simond]

If you like the idea of an oil combi and have had one before, then why not?

The Mistral is unusual in having an immersion heater, but this is not rocket science. A bit like their web site, it's worth around £17.00.

Oil combis are generally less reliable than their standard heat only versions, mainly because there is more to go wrong. Mistral are a small volume manufacturer and I doubt they have a service team or offer a long warranty.

If you were to go for a Grant or Worcester-Bosch oil combi and choose the right installer, you could enjoy a 5 or 7yr warranty respectively.

The physics of the combustion method and the heatstore inside mean that for a given power input and heat store, there won't be any great difference in DHW output between manufacturers.

 

[wcavanagh]

Thanks everyone for the input. Very interesting. I have always had oil combi boilers and understand how they work, with the small heat store in them. We had one once that was installed at one end of the property and it indeed took quite some time for hot water to reach the other end. The layout of the new property is still be defined at the moment, I wanted the boiler located in one of the many outbuildings as the Mrs dont like them in the utility room.

So with a cylinder this could be installed in a central location? How would this work with boiler in outhouse? For UFH controls etc. I like the idea of having everything in one location, like a small plant room, that was the original idea.

Cheers again

PS. 2nd plumber also suggested combi so im not sure.

 

[Echo the husky]

If you have a particularly large property, or very long pipe runs from the hot water cylinder to the taps, consider a secondary return to allow hot water at the taps within a few seconds. Saves wasting loads of water down the drain while waiting for the hot to come through. Uses more fuel though...

 

[wcavanagh]

The cottage is about 180 sq meters.
I will get another plumber out and see what they say.
That then gives me 3 quotes and options.
Many Thanks