Please Help ,Need to Upgrade to a combi boiler

[sherifcheto]

Hello members,
I read a lot of post and I can see that many members are gas engineers.
Very soon I will be moving to a small 2 bed terraced house in Watford which need a new boiler and a gas engineer to fit it.
Any chance any of you can give me an approximate quote for installation of a new boiler like Vaillant 837 combi ?
The house consist of 1 double and 1 single bedrooms,bath,lounge and kitchen. I believe there is a conventional system in place as the boiler is located in the kitchen and there is a cylinder tank in the landing storage area.
I am interested in upgrating the current system to a combi Vaillant 837 or any other good boiler alternative and possibility for change of 4 radiators.
I am also willing to assisst in the job for best quote and time efficiency.

Best Regards

 

[morlomanc]

ah! my home town for nearly 25 years! brings back memories! lol as regards the ball park,too many variables to get close but 3-4 k might be near. get 3 rgi,s in to get you prices. good luck.

 

[bengasman]

We don't do quotes here; it is boring, and not possible to do without seeing the situation any way. No point giving a number that could be half or double what it should be.

 

[Agile]

The cost is likely to be about £2200.

But I would never consider a change to a combi as an "upgrade".

More of a downgrade!

Tony

 

[D_Hailsham]

I am interested in upgrading the current system to a combi Vaillant 837 or any other good boiler alternative and possibility for change of 4 radiators.

I agree with Tony that a combi is not an upgrade.

Why do you think you would need such a large boiler for your house?

Have you measured the flow rate?

Have you calculated the heat loss?

 

[Mark Br]

What is the reason you want to switch to a combi and quite a large one at that?

 

[sherifcheto]

The only reason I want to switch to combi is space,need the space in the cupboard and want to get rid of the hot water cylinder. I read many of your post and I am aware about some of the pros and cons of the combi.
I chose Vaillant because is german,has stainless steel HE and many says is the best . Was told that the best one which suits me for this kind of property is 824 but I though bigger is better because don't want to loose water pressure.
I just needed approximate quote ,yet need to get the keys first. The end of the day every one want's the best and I read many posts and got the conclusion that there is many experienced gas engineers here.

 

[JohnD]

do you usually have a shower, or do you often run a bath?

do you know how many litres per minute come out of the kitchen cold tap (measure the time it takes to fill a bucket)

if you're buying an entire house, why is the half-cubic metre that the airing cupboard takes up so key? You do know that if you get an extra cupboard, all you'll do is put things in it?

 

[sherifcheto]

At the moment there is a power shower in the bath,have no idea how many litres per minute of water the kitchen tap drops but that's why I want more powerful boiler like Vaillant 837 to cope with the demand. As I said its a small 2 bed terraced house, more space available needed surely.

 

[Whitespirit66]

I want more powerful boiler like Vaillant 837 to cope with the demand.

You're putting the cart before the horse. Just chucking in a big combi won't cope with the demand, if your incoming cold main can't cope.

It's pointless getting a big combi that could produce say 18 litres of hot per minute, if the cold going into it is only 16 litres per minute.

Before specifying boilers, you need to know the max. litres per minute coming out of the kitchen tap, with all stop taps fully open. You need to speak to a plumber.

 

[JohnD]

this is also relevant to your preference for a bath or shower. If you like baths, you will need to take a book into the bathroom to read while you wait for the bath to fill.

 

[D_Hailsham]

The only reason I want to switch to combi is space,need the space in the cupboard and want to get rid of the hot water cylinder.

I can understand that.

Was told that the best one which suits me for this kind of property is 824 but I though bigger is better because don't want to loose water pressure.

The boiler output does not affect the water pressure. The important thing is the flow rate. You must realize that, once the hot and cold water tanks have been removed, every outlet - bath, shower, sink, toilet, washing machine etc - is fed from a single incoming cold mains. This means that if you are having a shower and someone flushes the toilet, you will notice it.

Combi boilers always quote a flow rate for a 35°C temperature rise. This means the water would leave the tap at 40C when the incoming water is 5°C. 40°C is approximately the recommended shower/bath temperature.

If you install a larger boiler than necessary you will be able to heat the water to a higher temperature, but that seems to be pointless as you will only have to cool it down by adding cold water. That's OK when your hot water is stored in a cylinder, as the water is maintained at about 60°C to reduce the chance of legionella bacteria thriving in the water.

The other factor to consider is the heating requirement, which will be much less than that for HW. The easiest way to do this is to use the Boiler Size Calculator. Deduct 2kW from the result (because you have a combi boiler) and you will get the CH requirement, which will be much less than the HW requirement.

Combi boiler literature will show both HW and CH outputs. For example the Vaillant 837 has a HW output of 37kW and a CH output of 12kW to 28kW. You need to ensure that the required CH output is within the range given. The lower the boiler can go, compared to your requirement, the better.

As a two bed terraced house is likely to need less than 12kW to heat it, the Vaillant 837 is not a good choice.

 

[hansthebear]

The cost is likely to be about £2200.

are you joking?

 

[moggridgeplumbing]

I agree with 'Agile' about £2200 for conversion. Additional for rads.

 

[sherifcheto]

The only reason I want to switch to combi is space,need the space in the cupboard and want to get rid of the hot water cylinder.

I can understand that.

Was told that the best one which suits me for this kind of property is 824 but I though bigger is better because don't want to loose water pressure.

The boiler output does not affect the water pressure. The important thing is the flow rate. You must realize that, once the hot and cold water tanks have been removed, every outlet - bath, shower, sink, toilet, washing machine etc - is fed from a single incoming cold mains. This means that if you are having a shower and someone flushes the toilet, you will notice it.

Combi boilers always quote a flow rate for a 35°C temperature rise. This means the water would leave the tap at 40C when the incoming water is 5°C. 40°C is approximately the recommended shower/bath temperature.

If you install a larger boiler than necessary you will be able to heat the water to a higher temperature, but that seems to be pointless as you will only have to cool it down by adding cold water. That's OK when your hot water is stored in a cylinder, as the water is maintained at about 60°C to reduce the chance of legionella bacteria thriving in the water.

The other factor to consider is the heating requirement, which will be much less than that for HW. The easiest way to do this is to use the Boiler Size Calculator. Deduct 2kW from the result (because you have a combi boiler) and you will get the CH requirement, which will be much less than the HW requirement.

Combi boiler literature will show both HW and CH outputs. For example the Vaillant 837 has a HW output of 37kW and a CH output of 12kW to 28kW. You need to ensure that the required CH output is within the range given. The lower the boiler can go, compared to your requirement, the better.

As a two bed terraced house is likely to need less than 12kW to heat it, the Vaillant 837 is not a good choice.

Thanks for all the advices.
ones I moved will check what's the water drop from the tabs.In meantime I checked the calculator you have given me and seems that even Vaillant Ecotec 824 is too large as the min output is 6.7kW. As far of my best knowledge so far the calculator shows that the output needed is around 8kW and as you said when I deduct the 2kW for combi boiler ended up with 6kW.