replacement boiler

Most sources seem to rate Vaillant and Worcester-Bosch for reliability.

I assume you have replaced the original door with one that fills the frame completely?

When I first purchased the property the outside toilet roof had slates missing and water had been pouring in. The downpipe from the main roof discharged on to this smaller roof and then the water ran down to a second gutter and downpipe. The missing slates were just below the downpipe outlet. The neighbour told me it had been like this for at least 5 years. The wall shared with the kitchen was wet, not damp - but soaked, the roof joists were rotten as was the door and the surrounding door frame. I stripped this small roof replaced 3 joists and re-installed the slates. The plaster in the kitchen was hacked off (mainly fell off) and left for about 9 months. I replaced the door and frame were replaced so yes, the door fits the frame.

Just thought it worth checking. As a kid, I used to go on holiday to a place with an outside loo. Six inch gap under the door, 12 inch above. Cold and damp even in the summer. Should stay nicely dry with a boiler inside.

How well insulated is this outside loo ?. If it is just a single- skin construction, then you will need to protect the boiler from frost. Maybe you should consider slapping 50mm of celotex on the walls and over boarding with either Fermacell or 18mm OSB topped with plasterboard. Fermacell or OSB allows the boiler to be mounted safely. If you just used a layer of insulation topped with PB then the boiler would need to be fixed with long frame anchors or similar into the brick.

With a Diamond or Heart-shaped hole in the door too ?

Until I was four, we used to live in a place with one.

I thought a crescent moon was trad?

I can't understand the current fad (Homes under the Hammer) to get rid of outside loos. If you are outside, gardening or whatever, wearing mucky boots, an outside loo is very useful so avoid going back inside for a pee. Also useful storage if there is no decent shed.

Anyone with any sense just pisses on one of the trees etc.

F*ck all storage space in one.

I don't foresee a problem as neighbours with identical properties built at the same time have boilers in these outside loos. I already keep a plumbed in washing machine in this space and have had a resistive greenhouse type heater on a plug in frost protection thermostat for many years.

I would recommend getting a Vaillant heat-only boiler - i.e.NOT a system boiler. This will work fine with the existing controls and open-vented F&E tank. This will have a balanced flue to the outside world, and several models have an option as to whether the flue comes out of the back of the boiler or out of the top, with an elbow to take it through the wall at a higher level.

If you use a Vaillant-approved installer, you should be able to get a 10 year warranty on it. I did!

Heat-only is what I would call "system". Perhaps you meant not a "combi" boiler? (I shall certainly never buy another combi).

There?re really few downsides to converting to a sealed pressurised system and many upsides. Having lived with both, I much prefer a sealed pressurised system now.

Tim

IIRC System includes the pump and any expansion vessel inside the boiler. Heat only does not.

Keep in mind that modern condensing boiler lose very little heat from the case - and so are useless at heating the room they are in unless there is a rad in there.

No, heat only is a traditional boiler that just heats. A system boiler includes the boiler and most of the components for operation of a (typically) unvented primary circuit - so pump, expansion vessel, overtemp and overpressure stat etc.

It is pretty much a combi boiler but without the secondary plate heat exchanger and diversion valve to heat DHW "on demand".

Vaillant heat only boilers are normally 400 series, system boilers 600 series, and combis 800 series.

Minimum change would be a be something like a Vaillant 400 series vented heat only boiler. The only addition required would be a condensate pipe to connect to the pipe for the adjacent sink drain.

Having said that, I personally would take the opportunity to convert it to a sealed system so you can do away with the feed and expansion tank. Sealed systems are easier to refill (no airlocks), and suffer less corrosion (since the primary water is not constantly exposed to air in the F&E tank), no pumping over, no kettling.

If the cylinder is a few years old, then it is probably a slow recovery one. You could replace that with a modern fast recovery one, and swap the zone valve for a three port diversion valve (W plan). That will allow much faster re-heating of the cylinder since the full boiler output can be sent exclusively to it. (You can also then run split temperatures - with a hotter flow temperatures for reheating the DHW to ensure adequate energy storage, and making sure it reaches a sterilising temperature, while running the rads cooler for more system efficiency and quieter operation (less clicks and clanks from system expansion and contraction)

If the boiler is on an external wall, are you content to take the flue straight out of that wall, are do you particularly want to re-use the existing flue?

If you are planning on staying, anything particularly cheap!

The pump and magnetic filter may also

Flue out of the wall is preferred (only) option and the old flue discarded.

The chimney that the current flue runs up starts at the kitchen ceiling height. Anything below it was removed long before I purchased the property and according to my neighbour at the time possibly 60 years ago. Removing the boiler from the relatively small kitchen will free up space for a cupboard, or with a small amount of re-arranging two wall cupboards.

Price/cost is not the main consideration but I am considering moving to another part of the country (other factors to be considered at present)

I had a Worcester Bosch installed in similar circumstances. It seems fine. One issue you may face is that modern rules may require a larger diameter gas feed to the boiler. I think mine had 13mm and now 22mm is the minimum required.

Dave

Not so much the size of the pipe but the pressure drop between the meter and the boiler gas inlet. I cannot see a problem for my proposed installation.

The gas now just feeds a hob and the boiler - a short straight run from the meter in 22mm copper (the last couple of feet to the boiler are in