Combi VS Standard Boiler

[richardhill84]

Hi,
I think my CH system is coming to the end of it's life. The rads aren't getting very warm (even after numerous manual flushes, sludge removers, new pump etc...) and the gas bills seem very steep! I could also do with replacing the cylinder as it's the type with a red jacket!.

I want to replace it with an efficient new boiler but i'm not sure which way to go (Combi or Standard)

I' swaying towards a combi but my only concern with a combi is the flow rate. People used to say "Don't get a combi if you like lots of hot water" "baths take ages to run" etc....

Is this true for mondern combi's?

Also, my current shower is a manual gravity feed type. (i.e. Hot water from cylinder and cold water from the tank in the loft. Could this be replumbed to run from the combi and would the flow rate be acceptable?

Thanks.

 

[DP]

Resist the temptation. Upgrade controls and the cylinder. Fit a new boiler only if there is no other option.

Old boiler may not be efficient ( control will improve efficiency), but it is not costing you much in repairs (which a modern boiler by the bucket load)

 

[richardhill84]

Resist the temptation. Upgrade controls and the cylinder. Fit a new boiler only if there is no other option.

Old boiler may not be efficient ( control will improve efficiency), but it is not costing you much in repairs (which a modern boiler by the bucket load)

Really? Is that because modern boilers are unreliable and expensive to repair?

 

[gas4you]

What ever boiler you go for fit a good quality one like a Vaillant.

Modern combis are available i outputs to meet your needs. Always size a combi for your hot water requirements, not the rad side. I never fit less than a 31Kw (30 in other makes) if you have baths instead of showers all the time then I recommend the 37 Kw. Whatever combi you go for it is best to assume it will only supply one hot outlet efficiently at once.

 

[richardhill84]

What ever boiler you go for fit a good quality one like a Vaillant.

Modern combis are available i outputs to meet your needs. Always size a combi for your hot water requirements, not the rad side. I never fit less than a 31Kw (30 in other makes) if you have baths instead of showers all the time then I recommend the 37 Kw. Whatever combi you go for it is best to assume it will only supply one hot outlet efficiently at once.

Thansk for the reply.
Could a 37KW Valliant drive a manual shower at an acceptable flow rate?

 

[gas4you]

with good cold mains pressure a 37Kw vaillant will 'sand blast' you clean

31 Kw are v good for showers. Only advise 37 if mainly baths used

 

[gas4you]

with good cold mains pressure a 37Kw vaillant will 'sand blast' you clean

31 Kw are v good for showers. Only advise 37 if mainly baths used

 

[Paul Barker]

This is true, but to be devil's advocate the gas supply pipe and the meter govenor may require amendment for anything from 35kw band A. They suck gas out of the pipe, and if you or your govenor starve them A/ it doesn;t do the heat exchanger a lot of good, and in very rare but possible scenario can be fatal. (gas hob is on heating pans, boiler fires for hot water sucks the life out of the inadequate gas supply ring on hob goes out, person shuts hot tap having had a shave, comes down to kitchen turns on light, BOOM!)

Secondly, combi boilers go through ignition sequence every time someone runs a tap no matter for how short a length of time. It cannot descriminate. It isn't necessarily any longer an issue that combis are unreliable, it is simpler than that. Ignition components, compressors, and pumps have so many starts in them, once you have used them up they will need replacing. Frequent nuisance firing of the normal household water demand behaviour will ensure that the combi is in need of repair prior to the system boiler.

I am not dead against combis, I am trying to provide OP with the information from which to make an informed choice.

 

[gas4you]

I agree Paul. Late as this I forget about pipe sizing. I never go more than 9M equivalent length for a 37Kw. 37Kw needs 4m3/hr gas flow.

Combis are good for their purpose, but not for large multi bedroom properties

 

[richardhill84]

Thanks for your replies.....

I don't think i'll need a 37KW unit. It's only a three bed semi!

 

[gas4you]

I've never had any complaints about a 31Kw installed after questioning customer about their hot water usage