The oil boiler is an ageing 100,000 odd BTU thing for both hot water and heating, and I am thinking of changing it. The Aga also heats the water in the summer.
First quote said "the DHW cylinder also needed changing" - I can't understand why. Is it these new regs that say when you change the boiler, the cylinder also has to be changed ? Or is he trying to take me for a ride ? Do I have to change the Aga as well ? Should I get a new car as well ?
The cylinder is only a few years old and showing no signs of failing, but when it does it will be replaced with the current spec item conforming to the new regs - fair enough!
I get the feeling the job is being glossed up to extract more money by doing unnecessary work.
Not as far as I have read in the relevant parts of the building regulations (Part J and Part L1). Part J deals with installation of fuel burning appliances, while Part L1 is about domestic energy efficiency. You can find Approved Documents (which are guidelines to the law) on the ODPM web site.
It would be useful to know how this is all hooked up since you have two heat sources for the DHW. Can you provide some more detail?
It is possible that the specific hookup is not suitable for a new boiler, but I can't think of a generic reason why the cylinder should require replacement.
The only things that immediately occur is if the cylinder is direct rather than having a heating coil - this is generally not a good idea anyway - or if the proposed boiler has a high heat output to hot water and requires a high transfer rate of the coil as in a fast recovery cylinder. A 30kW boiler is not especially high powered although if the coil is particularly poor this could be an issue of boiler cycling because the boiler is producing heat much faster than the cylinder can accept it.
I would suggest getting the technical documentation or installation guide for the proposed boiler, then ask the installer back and ask him to explain his reasons. Also, get another quote or two anyway.
Definitely not. How on earth would you make your toast?
If you are doing a major plumbing exercise, it may be worth taking the Aga out of the work of heating the cylinder. Its rate of heat production to the hot water is pretty low so I am not sure that it really adds any value if you have a thermostatically controlled main boiler. However do call Aga-Rayburn's technical department and ask about decommissioning if you want to do this. AFAIK, it is simply a case of disconnecting, rather than needing to disassemble and swap the water jacket components.
Its not a good idea BTW to simply disconnect the Aga hot water circuit. I think you need to talk to aga about that - frankly if the gravity fed pipework is in placve, and it works, I'd leave it generating hot water. My aga costs an estmated £300 a year to run pluis servicing if left on through the summer, and you might as well see some benfit.
I'd ask the plumber for a clear exaplantion of WHY a new cylinder is needed. Then post it here. If it makes sense, well fine. If it doesn't, then get another plumber.
I can think of reasons - maybe you have a gravity fed system and pumped is indicated etc.
There are several heating experts here. Why not get the plumbers opinion and compare with others thoughts?
It may be because the complications of the Aga and old gravity circulated boiler might make installing a modern boiler impossible. It is likely that a modern boiler and an Aga have very different ideas of what a primary circuit should look like.
If so, this is one type of system that would seriously benefit from a heat bank rather than traditional cylinder. They allow multiple heat sources to be used very simply, including a gravity circulated direct system (like what the Aga might like) and a pressurised sealed indirect coil (just what the modern boiler ordered). As an extra benefit, they also supply lashings of mains pressure hot water. (If your mains isn't good enough, you could always feed it from a cold cistern instead).
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