Converting Ideal Mexico Slimline 2 RS55 to sealed system

[copea]

Quick question;

We have an Ideal Mexico Slimline 2 RS55 boiler in our kitchen at the moment.
It's hooked up to an open vented system.

We're getting a loft conversion so the CWSC and the F&E tank will have to go.

We have the pressure and flow to accommodate an unvented cylinder.

Although old and inefficient, the boiler is functionally fine.
It doesn't cost the earth to run (£60pm in winter) so I'm loathe to replace it.

Is it possible / advisable to run our current boiler in a sealed configuration, hooked up to an unvented indirect cylinder?

The only stumbling block I can see is that the pressure in a sealed system will be greater than that in an open vented system (currently 8m head) and the ancient heat exchanger may not like that...

Thanks!

 

[Agile]

There was an overheat thermostat kit which has to be used on a sealed system. It needs to be fitted by a gas registered engineer.

Some and perhaps many of the rad valves will probably need to be replaced or they may leak.

That kit is probably no longer available now.

Its very simple and any competent engineer could knock one up but few would be willing to do that AND provide insurance to cover any problems.

Hopefully you don't have any plastic pipe in your system!

Most would just say the boiler is years old, pretty inefficient and overdue for replacement. There would probably be a saving of about 20% on the gas bill from a replacement boiler if its not oversized!

Tony

 

[Agile]

We have the pressure and flow to accommodate an unvented cylinder.

Thanks!

But do you really have both together?

An open pipe flow rate is not indicative of the dynamic flow rate you will get from a shower.

Generally a minimum flow of 22 litres/minute @ 1.0 bar is expected to use an unvented properly.

Tony

 

[copea]

Thanks Tony.
Sounds like it's technically possible but not advisable then.

And yes, we get 27 lpm at 3.5 bar.
Static pressure is 5 bar.

 

[Dan Robinson]

If the part is not available it is not technically possible.

 

[DP]

Copea, stick with the boiler, at £60 for winter bill, you will save £12 if what tony says is true, but what about the installation of new boiler, system cleanse, rad valve upgrade, cylinder upgrade if present cylinder is not insulated, controls upgrade and gas line possible replacement. How long is that going to take fir you to break even

Throw in high tec stuff in modern hi efficiency boiler, shortage of skilled repairers and short life expectancy of your super hi efficiency boiler that will save you 20% fuel, you will be an old man yet to see any any break even. When break even is on the horizon, a new steamer will be needed

My advice? Keep the boiler as is and upgrade and improve controls to reduce fuel usage

 

[copea]

Hmm. A mixture of opinions.

I've found the part which I'd need, so it seems it is still available (online at least).

It's just a question of whether the system would handle the pressurisation.

 

[Dan Robinson]

I've found the part which I'd need, so it seems it is still available (online at least).

That is chestnut? See if you can actually order it.

We have specific clauses that exempt us from liability when sealing old systems. More are fine than not though.

 

[copea]

Fair point, although some of the sites I've seen it advertised on have counterpart eBay sites where they list the product with a photo, so I'd assume it's actually available.
The down side is that it's quite expensive at ~£85. I imagine when it was in production it was considerably cheaper.
Not that's relevant any more!

Reassuring to know that most systems are fine.
Thanks Dan.

 

[DP]

Would it be fair to say a winter saving of £12.00 might be rounded off to £30.00 per year

A boiler replacement with minimal remedial will easily top £2100
It would take 70 years before break even is reached. Longer if boiler is to be serviced. Even longer if boiler has to be repaired.

While not suggesting a new boiler should not be fitted, but one has to take in pros and cons as well as who is making suggestions as to what should be done. for instance, it is suggested a steamer will be 95% efficient. Cannot see how that is possible if boiler is to heat rads in the winter