Fast recovery cylinder questions

[KS]

We've decided to abandon our major heating overhaul, until such time as our kitchen needs re-doing - otherwise kitchen would nee major work and we would need to demolish a chimney and re-site the boiler, which is a major PITA given the access problems we have. Would also have real problems siting the consending pipe for a new boiler

As a short-medium term solution, we were thinking of keeping the current Thorn floorstanding boiler (touch wood, it's 20 years old but it works fine) and replacing the standard copper cylinder with a fast recovery one, like an Albion superduty. Plumbcentre also do one called a Centercyl.

The current problem is that in depths of winter, two people can't shower as hot water runs out (its a 36 * 18 copper cylinder). It's a pumped shower. Will a fast recovery make much of a difference. Max BTU of boiler is 40,000.

Also, is =A3350 a decent price to change the cylinder - including a flush through and new inhibitor.=20

Thanks

KS

[Andy Hall]

This is approx. a 10kW boiler (BTUs are deprecated units :-) )

If it is currently connected via gravity circulation and not pumped, then converting to pumped would help and pumped with the larger coil area a little more.

However, the first fundamental problem is that the boiler is too small to take much advantage of a fast recovery cylinder - they can usually take at least 20kW.

The second is that the cylinder is too small. Even if you could take all of the output of the boiler, 10kW will not produce anything close to the amount of heat required to reheat the water fast enough. If you were able to heat it at a rate of 20-30kW by having a larger boiler, you could possibly get away with this size.

Given that you don't want to change the boiler right now, since you are replacing the cylinder, then going for a 160 or even 180 litre fast recovery one would be the way around this problem. The footprint is the same, just higher.

[Christian McArdle]

Make sure that you go for a larger cylinder than you already have. With only a diddy boiler, the coil size will make little difference to your problem, although it will be useful when the new boiler arrives.

If you have a good mains water supply, then consider fitting either an unvented cylinder or a heat bank instead. These provide mains pressure showers and rapid bath filling without the need for a noisy shower pump, although it will cost more to do, being more of a Rolls Royce option.

Christian.

[KS]

pressure

Thanks for the feedback.

If it is not going to make that much difference, I wonder if it is worth doing. We only have one bathroom so I would have thought the current 120l tank was sufficient - but as you say, the boiler just really isn't up to the job!

We did think about unvented or a combi but our flow rate yesterday was

18 lpm, and that was Sunday afternoon. The plumber reckoned it would drop to below 15 on a busy morning with everyone using water and that was very much borderline. He did want to come back and check pressure but suspected it was a bit low.

He said it would be best to upgrade the mains to get the full benefit of an unvested cylinder or a combi.

KS

[Christian McArdle]

Well, 120L clearly isn't sufficient, because you are running out!

Fair enough.

BTW, the water is running cold rather than actually stopping isn't it? If it is running cold, it is your hot water cylinder running out of capacity. If it stops running altogether, then your cold cistern is too small. This can happen when using a 25 gallon tank with a poor mains water feed.

Christian.

[Alan]

Is the current cylinder plumbed properly, with the cold feed into the bottom, and hot out of the top? I've seen one plumbed the wrong way round with the result of very little hot water before it goes cold! My cylinder is similar size to yours (36" x 18") and I can easily get 2 showers back-to-back from it, or a shower and (reasonably filled!) bath. Or do you like loooong showers?

Alan.

[Dave Plowman (News)]

I doubt it - the boiler is simply too small to heat the water fast enough regardless of the type of cylinder. And your cylinder is rather smaller than ideal, too.

I've got a 100,000 BTU boiler older than yours with a fast recovery 160 litre cylinder, and feeding a shower gravity fed via 22mm pipe, it's impossible to run it cold in practice. Of course if an entire football team were using it one after another without the pause for undressing, drying and dressing then yes. ;-)