new boiler choice

[simon beer]

Just moved house and we think the central heating could do with a once over whilst we are redoing the kitchen, as boiler presently situated there.

We intend putting it in the garage, other side of the wall. We are going to install a new boiler as we think the old one is prob inefficient and working hard for the size of the house, although we put this down to its age. It is an Ideal E Type 60N which we have been told is an ooold boiler.

System pipe work is also all in 15mm which could do with beefing up to 22 on the main circuits if my thinking is right, any thoughts?

Any way we are looking to change the current vented system to a sealed system boiler, is this a good way to go?

A couple of contenders on the list at

are the Worcester/Bosch SBI System Boiler 24SBI RSF or the Vaillant Thermocompact RSF 624EH NG.

I would appreciate some experienced input from those that know better than me if these boilers are pretty much like for like. Do I need to buy extras with one that I wouldn't with another; I notice there is also a price for a SBI System Boiler Plug in Diverter Valve to go with the SBi do I need something like this with either of them or does the Vaillant already have it? Are there other boilers to seriously consider around this price point, I should say that I not keen to go the combie route as I like to have the stored hot water, just old fashioned I guess!! Also the time clock is old and playing up a little so thought better get one of the heating packs with easy wire up panel, room thermostat & time clock etc. any recommendations of names to go for.

We also have an SMC Comet Controller Pump fitted next to our Grundfos pump, what does that do?

I'm sure I can come up with some more questions later but help with the above will keep me going for now. I got her indoors breathing down neck to get the boiler moved so I can get on with the kitchen as we have to microwave everything at the moment!

Any body ever laid slate floor tiles?

Thank for any imput

[andrewpreece]

I've laid slate on concrete before, but I did it the wrong way! I'm telling you so you don't try it that way. I laid them on a bed of concrete, and had the idea that for full strength they should be totally in contact with the concrete below. To this end, I laid each slab on a more or less flat bed of concrete. That's a hard way to do it since all slates are of different thicknesses, so to get them to the right level, the only answer is to shimmy them around so that excess cement exudes from the gaps between slates. Cement doesn't exude very well, and if you squeeze enough of the water out of it it locks solid and shimmying no longer has any effect. Then you lift the slate and start again! If I did it again I would use the finer and stickier cement grout you can buy, and use a 5 dab pattern under each slate, so it can be manouevred into position easily - it leaves airspaces under the slates so when you drop something on them they sound a little hollow, but so what! Always start with the thickest slate first, and shuffle the slates if from different batches. To be really safe examine each slate for warping/curvature, size and squareness before use ( I found the odd rogue got through ). Cut the slates at the edges to fit with a diamond wheel flat-bed cutter ( £30 - £50 if you haven't got one ). Don't know how to lay slate on a wooden floor though. hth

Andy

[IMM]

What make?

If you have a well insulated floor, the masonry above the insulation acts as thermal mass, providing you don't cover it with carpets. Dotting and dabbing the slate tiles partially isolates you from a the thermal mass below. I would not recommend dotting and dabbing anything. BTW, slate has the highest "admittance" of any masonry material. Dense concrete is high too. Use all that thermal mass as any solar gain in the room will be stored in the thermal mass. The thermal mass prevents strong temperature swings.

[BillR]

Should be 22mm min up to the zone valves. In a very small property you can get away with 15mm.

You can use a combi boiler as a system boiler, I have, the advantage is that they are much more competitively priced. In fact when I asked Ariston about this they recommended it and sent me appropriate wiring diagrams.

[simon beer]

Can fast recovery cylinder only be fitted with a heat bank, not read about them yet. Or do they work just in cojuntion with the boiler. Any links, names or idea of prices on the fast recovery cylinder

[IMM]

Heat banks can be heated direct or indirect.

A fast recovery cylinder can be open vented or to a limited degree in unvented cylinders, the Megaflow type.

for an explanation of fast recovery cylinders. using a fast recovery cylinder you can downsize the cylinder, or fit one in the same size effectively increase the size. Travis Perkins do the Telford Typhoon at 80 litres (fine for a one bathroom house) for £99 inc VAT and 125 litre version. Best to have the heating cut out cylinder stat fitted and set to 64C whe using these cylinders.

[IMM]

Sorry, that should be approx 44c when using an unvented and open vented cylinder set to 55C water temp. For a heat bank at 80C, it shpould be 64C. For a heat bank at set at 75C it should be 59C.

[Christian McArdle]

According to my manual, the internal diverter valve option would be very good for most systems, as it appears to allow different temperatures to be set for the hot water and heating sides of the valve. Unfortunately, the maximum allowed is 75C on hot water, so is no good for a heat bank. Heating side is normally limited to 75C, but can be boosted to 85C by flipping a plastic insert.

Christian.

[Andy Hall]

Apart from the installation aspects of a heatbank (not needing a professional installer vs. a pressurised cylinder), the cylinder water is effectively storing energy for use through a heat exchanger which heats the water on demand. A stainless steel plate heat exchanger is typically used and can transfer large amounts of energy (100-200kW is not uncommon). In that sense, it does not suffer from the limitations of a combi which will be limited by its size and rate of gas use.

However, before considering any kind of direct mains hot water system, it is important to validate that the flow rate from the main is adequate. 30 litres per minute at the rising main/kitchen cold tap is reasonable.

.andy

To email, substitute .nospam with .gl

[andrewpreece]

Wickes. At any rate use it for grouting the joints as cement/sand mix is really too gritty and gives a rough finish ( I used 6mm gaps between slates ).

I can't comment on the thermal aspects, only that it is extremely difficult to bed any tile of a decent size down onto a flat bed of mortar ( I am talking 1 foot square or larger here ). Unless the amount of cement used is more or less exactly the right amount, your slate tile will sit proud or too low; using a sloppy mix to facilitate adjustment can create other problems. Bricks ( easier to lay in this respect as they are smaller ) are laid on a bed of mortar which has had a pattern chopped into it by the brickie ( with his trowel ). It is the equivalent of dot and dab, but modified for brickwork. I expect that skill in application of cement in any application will make for better results, with less or no voids, but I reckon it is very difficult to lay large tiles and adjust them to the correct depth without using at least a variant of the dob and dab method,

Andy.

[Ed Sirett]

Which you will find in the main FAQ.

Note almost all combi boilers have Sealed CH systems connected to them.

For a 24kW boiler 22mm pipe work on the 'backbone' will be good enough.

You have to get to around 35kW before 28mm is really needed.