Hot Water

[R2Build]

I recently removed an Aga cooker which supplied hot water for the house. There is a conventional oil fired boiler abt 12 yrs old and is working fine.
It is situated at one end of the building which is quite long. The 2 bathrooms are at the opposite end, one up one down, (one has an electric shower over bath) one kitchen and one cloakroom.

I considered having the boiler replaced with a new condenser placed next to the bathrooms at the end of the house and installing an unvented cylinder.

Bearing in mind there is mainly only two people in the house, my question is, would it be more cost effective and energy efficient to retain the existing heating arrangement for the CH and install an unvented pressurised cylinder purely for the hot water requirement.

This will be heated electrically by emersion on low tariff,and replace the boiler at a later date or consider an instantanious electric boiler for HW and not install an unvented cylinder or is there a combi boiler that would cope with the demand (I don't think so).

It seems wasteful to replace the existing boiler which has not come to the end of its useful life but on the other hand the expense of purchasing a new boiler and not connect it to the central heating seems daft.

Moving the existing boiler is not an option by the way, as the new one will have to be outside.

Any thoughts?

 

[kevgrim]

Grant engineering ltd offer outside combi's with a very good dhw flow rate. you could then at a later date connect the central heating to it when your existing boiler retires. oil is still competitive and reliable. (in my opinion). this is my first thought but there are other ways as well which may be better for your situation. regards.

 

[R2Build]

Thanks Kevgrim but I have been informed that the Grant boiler would not cope with the two bathrooms, shower, kitchen and cloakroom as well as central heating, furthermore, I would not be using the central heating part of the boiler for some time. I was thinking that running two boilers might not be cost effective?

 

[kevgrim]

I shall give your job some further thought, but i suggest whatever you do wants to be something which can be built on for further needs, as you are aware spending a little more now could reap less spent later, just as a bit of tech info grant combi output upto 20lts a minute (incoming mains run at average 9.1lts a minute) and it does not matter if the heating is not used now it can be opened up later when reqd. Also depends how you describe outside. is outside a store or coal shed or really outside?
Thermal store units are really good dhw producers no flow rate drop and quite efficient, theres also storage/combi boilers huge dhw flow rate very efficient but i don't know of a purpose built really outside unit, would need some type of outside store.
I'll keep thinking.

 

[R2Build]

Outside is really outside. I have built a slab ready for any change of boiler at a later date, but there is a small room (previously an outside wc) which is now incorporated within the house next to the slab and the bathrooms. This would be an ideal location for a pressurised cylinder (ready to connect to a boiler if need be) or perhaps for an electric instantanious water heater arrangement, but not really large enough for a boiler due to access for servicing etc.,
In your opinion Kevgrim, is it possible to use an indirect pressurised cylinder and cap off the coil until required and use this for hot water by an emersion or would it have to be a direct cylinder?

 

[kevgrim]

Hi
You could use an indirect pressurised cylinder then as you say at a later date connect from the boiler to the coil, try to position the coil so it's accessible later it might save some trouble later, you could even connect a couple of short bits of pipe onto the cylinder and leave in a position for connection later. what you are suggesting is the type of route and thought that is applied in the industry. an electric fed unvented cylinder will not give full performance of hot water, but it will when connected to a boiler, a couple of people using hot will manage ok.

Regards

 

[R2Build]

Thanks Kevgrim, I've been looking at the 210 ltr Megaflow, only because this can have two emersions, one as a boost, whereas the smaller ones can only have one. They say the cylinder will take 1hr 40m to 2hrs to heat up by emersion but is 99% efficient so will stay warm for 24hrs or so, but that assumes no water take off. Due you know if there is a scale or graph or formular available from the industry, so that I can compare the potential perfomance of different pressurised cylinders or do I have to calculate each one separately? Do I have to rely on the manufacurers stated figures or is there an independant review for these in the market?
I suppose this is a separate issue, but I realise installers are not necessarily users and may be tempted to promote the products they are familiar with or are easily installed or obtainable from there local stockist and therefore may not give the best advice. The same may be said of the merchants of course, so its difficult to get completely unbiased opinions, except perhaps for this forum! Regards