Delonghi Compact Convection radiatior, does it matter which pipes are connected to the flow and return at the base of the radiator, using a H valve? Cheers

They take a while to heat the oil and supply heat by natural convection, air flow over the radiator, unlike bare element heaters so Yes, they are slow.
The plus is that they pose no fire hazard and are more efficient.

In the typical installation of hot water radiators, there is a Monoflow Tee placed in the supply or return line of each radiator. This allows each radiator to be adjusted to desired temperature. This allows flow of hot water to the next without blocking the supply. I suggest you check your system to see if it is Monoflowed prior to cutting in. Google Monoflow systems for a better explaination.

usual problem ,valves in injector worn for the fuel pump.easy quick fix this one ,fit a non return valve in the inlet pipe,check flow direction on valve when fitting and evan better as well is another in the bleed off return pipe .valves available from a motor factor or a specialist garage like bosch or lucas ,cut pipe and fit the valve with a piece of rubber pipe to connect the valve in line.or listen to the people who want to milk the golden cow and have the whole injector pump overhauled .

Problem is balancing & flow. Turn down the other rads until the inlet [flow] pipe is hot but the outlet [return] is luke warm. The rads have two valves - use the one which has a non-operation cap [just turns without doing anything]. when all the rads are the same temperature the system is said to be balanced and should be left like that using the other valves [with operating cap] to turn them on or off as required

I am assuming that the radiators you want to hook up are designed for hot water? If so you will need to run two pipes to each radiator, one for supply water one for return. Radiators work well on a monoflow Tee installation ( I suggest you Google monoflow tee intstallation). Valve the supply side so you have some adjustment of water flow to regulate the amount of heat it will put out. From your boiler you will need to install a main supply pipe all the way around the perimeter of the house (in the basement). I suggest a 1" diameter copper pipe. Then you will need to locate your radiators. Install a supply tee in the 1" pipe and go up to your radiator with either 1/2" or 3/4" copper pipe. Install a valve in this line to regulate flow. Connect to the radiator using the correct fitting. On the return side, connect to the same diameter pipe as the supply and take that down to a monoflow tee installed in the 1" copper pipe. Make sure you face the tee correctly or you will not get flow thru the radiator. Because there are different methods to connect radiators, this is just a suggestion. Google the net for other suggestions, talk to a heating professional and study prior to installing or it will cost you money and aggravation.

keep bleeding turn the out valve down to about 1/2 way to slow down the water flow thru rad. and keep bleeding takes a good bit of time to bleed a unit

Here's how it works....
An initial short run of the pump draws water from the reservoir into the boiler where it is heated by an electrical heating coil. There are two outputs from the boiler, one from the top runs through a pipe to a steam valve. When the steamer handle is turned, the steam valve opens and steam is piped out through the steam tube for frothing milk. The second output from the boiler is on the underside and is stopped by the normally closed flow valve. When the water in the boiler reaches the right temperature, a sensor switches on the OK light. When the light is on, the user pushes the pump switch and more water is pumped from the reservoir. The pressure in the boiler increases because the pump is trying to push in more water and this forces the spring loaded boiler flow valve to open allowing hot water to run out. As the sump filled with ground coffee is fitted to the boiler output, the water is forced through the coffee and out of the sump where it pours into a waiting cup.
When enough coffee has been poured, the user switches off the pump. The boiler pressure falls and the spring on the flow valve pushes the valve shut again. ------------ The first three steps aren't strictly necessary for disassembly however if you're using a long handle screwdriver then removing the base makes it easier to gain better access to some of the screws.
Step 1. Remove the screw on each base arm.
Step 2. ... then lift and remove the arms.
Step 3. Remove the two screws on the base of the unit. Unlike in this photo I would recommend you avoid resting the machine on its back unless you are sure it has been completely drained. The black plastic base can now be pulled away allowing easier access to some of the screws that will be removed later.
Step 4. Undo the two screws on the top rear.
Step 5. Remove the coffee tamper by pulling and twisting.
Step 6. Remove the three screws. These are anti tamper screws and are star shaped with a nipple in the middle.
Step 7. With these screws removed, the top may be lifted away. The hotplate on the top section is still connected by a couple of thin wires so lift it carefully.
Step 8. To help with shifting the top out of the way, disconnect the hot plate/boiler heater connection. This will allow you to push the top of the unit away giving you the room you need to get inside.
Step 9. Unscrew the electrical safety earth and move the earth wiring out of the way.
Step 10. Use some long nose pliers to pull out the circlip that holds the boiler inlet pipe in place. Pull out the pipe to disconnect it from the boiler once the circlip has been removed.Step 11. Unscrew, remove and clean the diffuser.
Step 12. Remove the two screws . The black plastic underside casing can now be pulled away (plastic tabs need to be pushed aside ). Step 13. Pulling away the plastic underside once screws and tabs are removed.
Step 14. Loosen the four black Torx (star shaped) boiler screws . Water in the boiler may leak out at this point so ensure the unit is upright and a towel is placed underneath.
Step 15. Remove the four nuts (three arrowed) from the underside of the boiler unit.
Step 16. Lift up the top of the boiler assembly along with the steam outlet and place to one side. The two halves of the boiler assembly are sealed with a rubber gasket which should remain attached to the upper housing. Make sure this is properly in place when reassembling.
Step 17. The lower boiler assembly can now be lifted out.
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to get more detailed help click this link directly.it has all the required instructions and pictures to disassemble the unit.the model number in the link is bit different from yours but the system is very same so it will help you
http://www.r3uk.com/index.php/tech-tips/34-disassembly-guides/129-delonghi-ec710-coffee-maker-disassembly-and-repair
click on the link above directly.
This will help. Thanks please keep updated.please do rate the solution positively .thank you for using fixya.

remove radiator and flush through, knocking botton of radiator on to a heavy block of wood releases part blockage in radiator should this fal replace radiator remember to flush out rad/valves when you have radiator off best of luck

It probably has black iron piping so, you don't want to use compression caps. Get pipe caps of the proper size and use teflon tape so you can remove them when the radiator is replaced. If you have copper pipes, just slide the base nut on, put on the compression ring and then put on the cap. Whan you replace the radiator, you will have to cut the pipe off where the compression ring was. Soldering a cap on would be a better solution. There should be a system shutoff valve to prevent the boiler from refilling automatically, or trying to fill when you remove or disconnect a pipe.

Bake- Normal convection- both upper and lower heating elements.

Conv. Bake- Semi-forced convection- both upper and lower elements, heat is then distributed throughout the oven via the fan.

Broil- radiation- The heat is radiated by the ifrared broil element.

Broil & Fan- Radiation and Ventilation- The radiated heat from the infra-red broiling element is distributed throughout the oven via the fan.