High end Combi vs. Unvented for 3-bed semi-D & 1 bath.
- Thread starter EMFTeo
- Start date
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837 is still a bit too big, bear in mind if you're going to be adding extra insulation the required output figure will go down anyway. Why has it suddenly gone up? Of the two, I'd say go for the 831, but there are more suitable boilers out there for your needs that will give you the hot water performance of the 837 but without the same issues of cycling on your heating system
I miscalculated the size of the property.
I'll talk to the plumper to stick with the 831. What other boilers do you suggest ?
We want something with 5 yrs warranty on both labour & parts.
I've already suggested - Intergas Combi Compact HRE 36/30. Don't worry about the slightly shorter warranty, the Intergas has far fewer parts in it than anything else and therefore far less to go wrong. It only has four moving parts - gas valve, fan, pump and flow switch. The first three will all last a long time, the flow switch should do as well but if it doesn't it's a very cheap part to replace. The Vaillant has several more moving parts, including a diverter that has been redesigned so many times I've lost track of which version we're on. The big expensive bit on an Intergas is the heat exchanger, but that has a 10 year warranty (something you won't find on a Vaillant, although you will find two heat exchangers on a Vaillant whereas the Intergas only needs one) and so far they have a zero failure rate.
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I'll email that link to the plumber... I assume it can be converted for LPG?
Yep.
Yes very simple conversion for LPG. This is the one you want http://www.intergasheating.co.uk/si...&intergas_lijsten_Produkten_detail=26&catid=7
Should be around 160.00+vat cheaper than the Vaillant 831 as well
Water softener definitely worth investing in but don't know what's good as we don't need them in Devon
Should be around 160.00+vat cheaper than the Vaillant 831 as well
Water softener definitely worth investing in but don't know what's good as we don't need them in Devon
Atmos' version has an internal expansion vessel though 
Here's an update from my plumber:
"Test results showed 5 Bar pressure and 24 litres/min flow rate which is very good for a combi, the appliance I have in mind is an Vaillant 837 EcoTecPlus which is a top of the range boiler which will produce 15 litres/min hot water over a 35 deg raise in water temp.
Bearing in mind that the appliance is making hot water on demand and if you are in the shower and there is another demand for hot water the water produced will be shared, this is unavoidable, however washing machines and dishwashers only have a cold feed so this will have no impact on the shower at all. You will not be able to shower and run a bath at the same time as you will have a restricted water flow to both points e.g. 15/2 = 7 litres each outlet
Combination boilers are cheaper to run than traditional heat only boilers such as the one you have at present because combis produce only what is required, your current boiler heats up the water twice a day whether you use it or not and you are paying for this. Heating would also be cheaper than existing boiler as modulating boiler will only produce Kw’s required for heating load, so although it is a 37 Kw boiler it will modulate down to 11Kw’s for heating requirements
Your loft and airing cupboard would have no visible pipe work so can be utilised as a shower room, tails could be left in the area so as to connect on to for the shower feeds"
"Test results showed 5 Bar pressure and 24 litres/min flow rate which is very good for a combi, the appliance I have in mind is an Vaillant 837 EcoTecPlus which is a top of the range boiler which will produce 15 litres/min hot water over a 35 deg raise in water temp.
Bearing in mind that the appliance is making hot water on demand and if you are in the shower and there is another demand for hot water the water produced will be shared, this is unavoidable, however washing machines and dishwashers only have a cold feed so this will have no impact on the shower at all. You will not be able to shower and run a bath at the same time as you will have a restricted water flow to both points e.g. 15/2 = 7 litres each outlet
Combination boilers are cheaper to run than traditional heat only boilers such as the one you have at present because combis produce only what is required, your current boiler heats up the water twice a day whether you use it or not and you are paying for this. Heating would also be cheaper than existing boiler as modulating boiler will only produce Kw’s required for heating load, so although it is a 37 Kw boiler it will modulate down to 11Kw’s for heating requirements
Your loft and airing cupboard would have no visible pipe work so can be utilised as a shower room, tails could be left in the area so as to connect on to for the shower feeds"
Apart from the fact that not all machines are cold fill only, that is nonsense!
When you have a combi all hot and cold outlets are fed directly from the mains: there is no longer a cold water tank to feed the toilets, washing machines etc. So you could still be affected in the shower when the washing machine is filling.
The water in the cylinder will only need heating if you have used some, which has been replaced by cold water. If you have a modern well insulated cylinder, the heat loss from a full cylinder is very low. The water temperature in a cylinder will have to drop 8-10C before the thermostat turns the boiler on. We have a HW cylinder with the water temp set to about 60C and get three showers in an evening before the boiler comes on to reheat the water.
The 837 produces 12 -28kW and your requirement is 0 - 13kW!
The rated output is 4.8 to 36?
That's pretty high? I assume it can be set to the minimum? If the house is well insulated and heated ? Is this the same for the intergas?
Out existing boiler is upto 15 kw. I guess that's all we require.
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