High end Combi vs. Unvented for 3-bed semi-D & 1 bath.

[transam]

Have a look at the raven 150 42 kw hot ater out put & adjustable out put for CH !

u could even fit it with a combi store , for the same money u would pay for other combi's , will give u a certain amount of free hw as well !

3 year warranty worth a look , may be

 

[D_Hailsham]

The rated output is 4.8 to 36?

Presumably you got that from Here.

It's very misleading as it's the lowest output of one non-combi boiler and the max output of another combi boiler.

There are three combi models in the 200W range and the outputs are:

CH - 5.9 to 23.7; HW - 5.9 to 26; flow rate 10.7 lpm @35C rise
CH - 7.9 to 27.3; HW - 7.9 to 30; flow rate 12.3 lpm @35C rise
CH - 7.9 to 31.7; HW - 7.9 to 35; flow rate 14.3 lpm @35C rise

 

[EMFTeo]

The rated output is 4.8 to 36?

Presumably you got that from Here.

It's very misleading as it's the lowest output of one non-combi boiler and the max output of another combi boiler.

There are three combi models in the 200W range and the outputs are:

CH - 5.9 to 23.7; HW - 5.9 to 26; flow rate 10.7 lpm @35C rise
CH - 7.9 to 27.3; HW - 7.9 to 30; flow rate 12.3 lpm @35C rise
CH - 7.9 to 31.7; HW - 7.9 to 35; flow rate 14.3 lpm @35C rise

Spoke to my plumber again, and he said they were of no match to the 837 on flow rate ?

 

[mehran]

a viessmann 200 combi will have at least 4 more moving parts and more parts over all(I could name them if mysteryman would like)

the only real advice I have for you is the boiler is only part of the equation. a good boiler installed badly will still do badly(integas may put up a better fight but would still lose in the hands of a Muppet)

so get an installer that you trust and fit the boiler he knows the best.

if it turns out to be valliant(a spit on the ground emotion) then you will be more likely better of with it.

btw still think intergas is the best combi boiler in the world followed by a close second by atmos(to keep dan happly)

 

[Dan Robinson]

If you are looking at hybrids the the Atmos Multi 24/80+ cocks its leg all over Veissman's offering

I need to reply to your email so will stick some info in there with some linkies.

 

[D_Hailsham]

There are three combi models in the 200W range and the outputs are:

CH - 5.9 to 23.7; HW - 5.9 to 26; flow rate 10.7 lpm @35C rise
CH - 7.9 to 27.3; HW - 7.9 to 30; flow rate 12.3 lpm @35C rise
CH - 7.9 to 31.7; HW - 7.9 to 35; flow rate 14.3 lpm @35C rise

Spoke to my plumber again, and he said they were of no match to the 837 on flow rate ?

The flow rate of the 837 is 15.2 lpm @35C rise. I doubt if any one will notice the difference between that and the 14.3 lpm of the largest Viessmann.

However, it's not the HW flow rate which is the problem, it's the CH requirement.

You said your current boiler is 15kW and the online calculator gave 13.25kW. Presumably that is with the house as it is, i.e. without the proposed insulation. If you repeat the calculation, assuming all the proposed insulation, you will find that the requirement has dropped, possibly to as little as 8kW. This would mean that the 837, with a minimum output of 12kW, was massively oversized.

You cannot select the boiler by considering the HW requirement in isolation, you must take the CH requirement into account.

 

[EMFTeo]

The flow rate of the 837 is 15.2 lpm @35C rise. I doubt if any one will notice the difference between that and the 14.3 lpm of the largest Viessmann.

However, it's not the HW flow rate which is the problem, it's the CH requirement.

You said your current boiler is 15kW and the online calculator gave 13.25kW. Presumably that is with the house as it is, i.e. without the proposed insulation. If you repeat the calculation, assuming all the proposed insulation, you will find that the requirement has dropped, possibly to as little as 8kW. This would mean that the 837, with a minimum output of 12kW, was massively oversized.

You cannot select the boiler by considering the HW requirement in isolation, you must take the CH requirement into account.

I understand that it's CH which needs to be taken into account then.. our requirements are no more than 15kW for CH and a minimum flow-rate requirement of 13++ lpm ?

Is there any combi which can supply that?

Would fitting a multi-fuel/wood burner stove (8kw) in the living room and retrofitting that to a LPG combi or unvented solution work? i.e help minimise LPG consumption in the long run?

 

[D_Hailsham]

I understand that it's CH which needs to be taken into account then.. our requirements are no more than 15kW for CH and a minimum flow-rate requirement of 13++ lpm ?

Is there any combi which can supply that?

Yes, the Remeha Avanta 35C or 39C.

35C: CH output 6kW to 29kW (the maximum can be reduced by the installer to whatever you like); HW 14.2 lpm @35C rise

39C: CH output 6kW to 33kW (the maximum can be reduced by the installer to whatever you like); HW 16.9 lpm @35C rise