Plumbing - diesel central heating

[barroca grande]

Hi just been buying my radiators and on unpacking the towel rail spotted this in the instructions. What does it mean? Does it mean me? In which case I will have to take it back or what?

 

"This product is not suitable for use on direct central heating systems because a corrosion inhibitor cannot be added"

 

Basically my system will be a Mikuni MX60 (also heating the calorifier), two small low old school type radiators and the towel rail in question.

 

Is this a direct central heating system?

 

What is a direct central heating system?

 

As a separate issue does the towel rail have to be at the end of the plumbing run so that the other two rads can be turned off in the summer and only the towels warmed up? Bit tricky this as it is a) in the middle and on the opposite side of the boat from the rads and c) can't go around the bows because the bed goes in and out there!

 

Thanks in advance

 

Kath

[koukouvagia]

As a separate issue does the towel rail have to be at the end of the plumbing run so that the other two rads can be turned off in the summer and only the towels warmed up? Bit tricky this as it is a) in the middle and on the opposite side of the boat from the rads and c) can't go around the bows because the bed goes in and out there!

 

Thanks in advance

 

Kath

 

You can put the towel rail anywhere in the circuit, but you should arrange the pipework with a flow and return system ( http://tinyurl.com/asq6hl ). You can then turn any radiator on or off without it affecting the rest. I originally had my pipwork arranged on the single loop system and found that the small radiator I use as a towel rail in a similar position to the one you are planning never really got hot enough.

[chris w]

Hi just been buying my radiators and on unpacking the towel rail spotted this in the instructions. What does it mean? Does it mean me? In which case I will have to take it back or what?

 

"This product is not suitable for use on direct central heating systems because a corrosion inhibitor cannot be added"

 

Basically my system will be a Mikuni MX60 (also heating the calorifier), two small low old school type radiators and the towel rail in question.

 

Is this a direct central heating system?

 

What is a direct central heating system?

 

As a separate issue does the towel rail have to be at the end of the plumbing run so that the other two rads can be turned off in the summer and only the towels warmed up? Bit tricky this as it is a) in the middle and on the opposite side of the boat from the rads and c) can't go around the bows because the bed goes in and out there!

 

Thanks in advance

 

Kath

 

To answer your questions:

 

Let me deal with this one statement first:

 

"This product is not suitable for use on direct central heating systems because a corrosion inhibitor cannot be added"

 

The wording is slightly ambiguous as it could be read that the radiator cannot be used with a corrosion inhibitor OR that it can't be used on a direct system because a direct system does not contain a corrosion inhibitor. So which is it? Read on....

 

I will tell you what the different systems (direct and indirect) mean and then answer your orginal question about the suitability of the radiator.

 

1. A DIRECT central heating system is one in which the water that is heated by the boiler flows through the radiators AND flows directly through the cylinder making hot water. Because the water that comes out of your hot taps will have flowed also through the radiators, that water MUST NOT contain any corrossion inhibitor because you may be poisoned by it, as your hot water will be used for washing your body etc.

 

Because, therefore, the water is being continually changed (as you run off hot water) the fresh water which replaces it contains fresh amounts of oxygen and this will lead to corrosion of the whole system. So Direct systems are BAD and not used nowadays.

 

2. An INDIRECT system is one in which the water that is heated by the boiler flows through the radiators BUT does NOT flow directly through the cylinder. Instead the water flows through a sealed copper coil which is placed inside the cylinder. The water in the cylinder (with which you will wash) and the water in the coil never mix - they are sealed off from one another.

 

But as the coil gets hot, owing to the boiler heating the radiator water, the coil heats up the water in the cylinder. The coil acts just like an electric immersion heater except that instead of being heated by electricity, it is heated by the hot water inside the coil.

 

Yours will be an INDIRECT system - direct systems have not been used (domestically) for 30 years. That means that the water in the radiator is separate from the water that comes out of your hot taps as explained above. Therefore the radiator you have just bought CAN be used on your system.

 

The instructions you read mean that you MUST use a corrosion inhibitor in the radiator water to prevent corrosion of this new radiator. On a boat this is normally antifreeze which, as well as preventing freezing in winter, also acts as a corrosion inhibitor. A mixture of around 20% is normally reccommended for diesel heaters but check your own model's manual for actual figures. The antifreeze MUST be premixed with water BEFORE adding the mixture to the heating system or else the two will not mix properly if poured in separately.

 

3. Your towel rail does not go ON THE END of your system - there is no END in a real sense. The radiators are NOT plumbed in series (ie: one after the other) but in parallel. ie: you install a FLOW pipe (from the boiler) and a RETURN pipe (to the boiler) and all the radiators have one end connected to the flow pipe and their other end to the return pipe.

 

It matters then not a jot where you physically install the towel rail providing one side of it is connected to the FLOW and the other to the RETURN.

 

Hope this helps

 

Chris

Edited February 13, 2009 by chris w

[barroca grande]

To answer your questions:

 

Let me deal with this one statement first:

 

"This product is not suitable for use on direct central heating systems because a corrosion inhibitor cannot be added"

 

The wording is slightly ambiguous as it could be read that the radiator cannot be used with a corrosion inhibitor OR that it can't be used on a direct system because a direct system does not contain a corrosion inhibitor. So which is it? Read on....

 

I will tell you what the different systems (direct and indirect) mean and then answer your orginal question about the suitability of the radiator.

 

1. A DIRECT central heating system is one in which the water that is heated by the boiler flows through the radiators AND flows directly through the cylinder making hot water. Because the water that comes out of your hot taps will have flowed also through the radiators, that water MUST NOT contain any corrossion inhibitor because you may be poisoned by it, as your hot water will be used for washing your body etc.

 

Because, therefore, the water is being continually changed (as you run off hot water) the fresh water which replaces it contains fresh amounts of oxygen and this will lead to corrosion of the whole system. So Direct systems are BAD and not used nowadays.

 

2. An INDIRECT system is one in which the water that is heated by the boiler flows through the radiators BUT does NOT flow directly through the cylinder. Instead the water flows through a sealed copper coil which is placed inside the cylinder. The water in the cylinder (with which you will wash) and the water in the coil never mix - they are sealed off from one another.

 

But as the coil gets hot, owing to the boiler heating the radiator water, the coil heats up the water in the cylinder. The coil acts just like an electric immersion heater except that instead of being heated by electricity, it is heated by the hot water inside the coil.

 

Yours will be an INDIRECT system - direct systems have not been used (domestically) for 30 years. That means that the water in the radiator is separate from the water that comes out of your hot taps as explained above. Therefore the radiator you have just bought CAN be used on your system.

 

The instructions you read mean that you MUST use a corrosion inhibitor in the radiator water to prevent corrosion of this new radiator. On a boat this is normally antifreeze which, as well as preventing freezing in winter, also acts as a corrosion inhibitor. A mixture of around 20% is normally reccommended for diesel heaters but check your own model's manual for actual figures. The antifreeze MUST be premixed with water BEFORE adding the mixture to the heating system or else the two will not mix properly if poured in separately.

 

3. Your towel rail does not go ON THE END of your system - there is no END in a real sense. The radiators are NOT plumbed in series (ie: one after the other) but in parallel. ie: you install a FLOW pipe (from the boiler) and a RETURN pipe (to the boiler) and all the radiators have one end connected to the flow pipe and their other end to the return pipe.

 

It matters then not a jot where you physically install the towel rail providing one side of it is connected to the FLOW and the other to the RETURN.

 

Hope this helps

 

Chris

 

 

Brilliant you are a star. Thanks so much.

 

You can put the towel rail anywhere in the circuit, but you should arrange the pipework with a flow and return system ( http://tinyurl.com/asq6hl ). You can then turn any radiator on or off without it affecting the rest. I originally had my pipwork arranged on the single loop system and found that the small radiator I use as a towel rail in a similar position to the one you are planning never really got hot enough.

 

 

Also helpful. Thank you very much.

 

You can put the towel rail anywhere in the circuit, but you should arrange the pipework with a flow and return system ( http://tinyurl.com/asq6hl ). You can then turn any radiator on or off without it affecting the rest. I originally had my pipwork arranged on the single loop system and found that the small radiator I use as a towel rail in a similar position to the one you are planning never really got hot enough.

 

 

Also helpful. Thank you very much.

 

see I'm so excited am posting twice!

Edited February 13, 2009 by barroca grande

[kerching]

1. A DIRECT central heating system is one in which the water that is heated by the boiler flows through the radiators AND flows directly through the cylinder making hot water. Because the water that comes out of your hot taps will have flowed also through the radiators, that water MUST NOT contain any corrossion inhibitor because you may be poisoned by it, as your hot water will be used for washing your body etc.

 

Because, therefore, the water is being continually changed (as you run off hot water) the fresh water which replaces it contains fresh amounts of oxygen and this will lead to corrosion of the whole system. So Direct systems are BAD and not used nowadays.

 

I have never been aware of this type of system as you describe it. The only way you would run a radiator with this system was with the old type copper back boiler and a copper towel radiator, usually chromed, in the bathroom. Not a complete central heating system. Washing in a bath as you describe it would probably result in you ending up dirtier than when you got in.

[bottle]

Screwfix still sell a 'direct cylinder' as well as indirect.

[Dave Hannigan]

The only direct systems that I have come across are for hot water, with the boiler being a copper back boiler or gas circulator, they were never used for central heating.

 

When central heating was added to hot water systems then the indirect cylinder came into being.

 

I suspect what they are saying is not to use with a 'primatic' cylinder, or to give full title 'single feed indirect' cylinder. These used the cold water storage tank to supply the central heating circuit. They were designed so that when the system was full then the primary circuit (central heating) was separate from the secondary (domestic hot water) by an air bubble.

 

Obviously with using the cold water storage tank then inhibitor could not be added.

 

Dave