CDS

It’s not the boiler size. If the boiler was undersized the whole heating system would under preform rather than individual radiators.

The probable causes are:

1) Stuck Thermostatic Radiator Valve (TRV). TRV's can stick closed if left shut for a long period, try taking off the TRV head and see if the pin is moving freely. If not you can use a pair of pliers to gently free the pin but be careful not to pull the pin all the way out.

2) The radiators are blocked by sludge. This often results in the outside and top of the radiator getting warm but the central area remaining cold. Did you have the system flushed when the new boiler was installed? If not sludge could be the problem. You will need to take the radiator off to check (the sludge will be black and will stain floor covering etc. so be careful). If it is blocked then the system will need flushing.

3) Air lock in the pipework feeding these radiators. It is sometimes possible to shift such an airlock by closing all the other radiators TRV's as this will force the flow around the offending radiator/pipework.

The hot and cold pipes do feed the outlets. The secondary return creates a loop of hot water pipe so that hot water can be circulated from the hot water cylinder around the hot water pipework and back to the cylinder. This means that when the secondary return pump is running there will be hot water at the hot outlet within a few seconds rather than having to wait.

The secondary return should be connected to the hot pipework at the farthest (practical) point from the cylinder.

If the total hot water run is less than 14 m then you may not need the secondary return.

The secondary return pump must be made from bronze or stainless steel (not a standard central heating pump which is made from mild steel).

Hope this helps.

Condensation is caused when warm humid air meets a cold surface. To stop condensation you need to reduce the amount of moisture in the air and if possible remove the cold surface.

To reduce the moisture in the air make sure there is adequate ventilation and limit the amount of moisture generated. Drying washing and portable gas heaters are probably the worst offenders but also make sure that bathrooms are ventilated after a bath or shower.

As for removing the cold surface this is not going to be possible in your case.

Hi

It is possible that the boiler overheat stat has activated and need resetting (check with the boiler instructions).

I would suggest that with your limited understanding of heating systems that you take the plunge and get a heating engineer in to look at the problem and service the system.

It is going to depend on the construction of the "room" but your first step will be to add as much insulation as is possible. This will reduce the heatloss from the room.

You then need to add a heat source.

What you use will depend on lots of factors such as how often the room is used and for how long, how important it is to protect the room contents when not in use.

The simplest (assuming you have electrical power in the room) is a suitable sized electrical panel heater run from a thermostat. The stat can be set to maintain a low temperature when the room is not being used and can be turned up when it is being used.

Other options could include a wood burner or a portable gas heater (although these can result in condensation problems).

There used to be a real problem with putting Thermostatic Radiators Valves (TRV’s) on the return. As the TRV just opening or closing the dynamics of the flow would cause the valve to snap shut and then open repeatedly, this sounded like a machine gun.

Most TRV’s are now bi-directional (as yours is) that is they can be fitted on the flow or the return. In your case pipe the radiator as is and put the TRV on the side with the best air flow.

I know this is an old post but just in case anyone looks at this in the future:

All underfloor heating pipework MUST be pressure tested before the screed is installed (see BS EN 1264 Part 4). This is to check that it is water tight.

From the screed point of view: There is no need to maintain the pressure in the pipe during screeding. The pipe will not expand/contract or anything else. The only discrepancy to this is if the UFH pipe is Rubber in which case it will collapse But I would not use this type of pipe.

From the Underfloor Heating Point of View: I always advice that the pressure is maintained during screeding and most if not all UFH manufactures will do the same. The reason is that if any damage occurs to the pipe and it is punctured the pressure will drop and action can be taken.

So whilst screeding maintain the pressure test and check that the pressure is holding after each area has been screeded. If the pressure drops (ignore small fluctuations) then stop screeding and investigate.

To resolve problems with condensate pipes consider the following:

1) Re-route the pipe so that it is all internal. This will resolve the problem completely. If this is not possible try to reduce the length of pipework outside.

2) Increase the size of the pipework. This allows the condensate to drain quicker and thus less likely to freeze.

3) Insulate the pipework.

4) Raychem do a trace heating tape/wire for Condensate pipe.

This could be due to a few things, air locks, blocked or restricted pipework, system out of balance or faulty valves.

Try the following:

1) Close all radiators Thermostatic Radiator Valves (TRV’s) except on one of the problem radiators. If the radiator then gets hot this will rule out a problem with the valves or a blockage. Repeat with the other problem radiators.

2) If the radiators worked then it is either an air lock which is moving around the system or it is a problem with balancing. If it is an air lock with a little persistence you should be able to eventually clear it by bleeding the radiators. If this does not work it might be necessary to drain and refill the system. If this is not successful then it is most likely a balancing problem which could include an undersized pump. You need to have the system balanced.

3) If the radiators did not work then it could be a blockage, faulty valve or an air lock. Out of these it is more likely to be an air lock which is not moving. You will need to have the system drained and carefully refilled. If this fails to resolve the problem then further investigation will be required.