Cast Iron Radiators Frequenty Asked Questions

Some of the questions we are commonly asked

How do I know what size of radiator I require for my room?

Calculations for room heat requirements can be quite difficult; however we have a programme which can work out what your requirements are in British Thermal Units (BTU) or Kilowatts (kW). Once you have worked out what heat out puts you require OR size of radiator, please look at our styles and sizes to match which radiators are the most compatible or let us have your requirements to quote a competitive price for you. If you are unsure, we would always recommend that a final check is made on this calculation by your heating installer prior to order and to ensure your current boilers capacity is sufficient for the size of radiators being ordered.

Why are our longest standard radiators approx 1.43m long?

There are two main reasons why our longest radiators are approx 1.43 metres long. Firstly, as we sell our cast iron radiators all over the UK, Eire & Mainland Europe, in order to keep shipping costs to an absolute minimum we use a bespoke sized pallet, which is 1.0m x 1.5m in size. Anything larger incurs large surcharges and delivery prices will become too expensive. Secondly and just as important, is the actual weight of the radiator and how it is handled upon delivery. Obviously cast iron radiators are heavy and with some of our assembled cast iron radiators weighing approx 140+kg, this needs to be considered.

Are cast iron radiators more heat efficient than modern steel radiators?

Yes, although they may take a little longer to get to full operating temperature (though on any sound heating system this time should be negligible) cast iron radiators are highly efficient, with darker colours being the most efficient conducting colour and due to the ability of cast iron to retain and spread heat evenly for much longer periods than steel, even when your heating has been switched off.

What is Delta T rating and what Delta T rating do you use for your outputs?

Delta T or Dt refers to the difference in temperature between the water circulating throughout your central heating system and the room temperature.

When replacing any radiators in your home it’s important that you use the correct Delta T. This is because the same radiators can have different outputs at different water temperatures due to the heat source you are using.

As of 01.03.2019, all heat loss values shown on our website will be calculated to Delta T50 (ΔT50°C), the current European CE standard.

To calculate our radiators to other Delta T outputs, please use the following table:

Correction factor to convert our heat loss values to Delta T60 – multiply by 1.267

Correction factor to convert our heat loss values to Delta T55 – multiply by 1.132

Correction factor to convert our heat loss values to Delta T50 – multiply by 1.00

Correction factor to convert our heat loss values to Delta T45 - multiply by 0.872

Correction factor to convert our heat loss values to Delta T40 - multiply by 0.748

Correction factor to convert our heat loss values to Delta T35 - multiply by 0.629

Correction factor to convert our heat loss values to Delta T30 - multiply by 0.515

Correction factor to convert our heat loss values to Delta T25 - multiply by 0.406

Correction factor to convert our heat loss values to Delta T20 - multiply by 0.304

Can you paint my radiator?

Yes, we do offer a spray paint service for all radiators we supply you, using the colours shown on our product pages, for a modest fee in our professional spray booth. Obviously, the lighter colours such as Cream White will require more maintenance from being marked over time.

Our Radiator Castings.

All our traditional radiators are individually hand cast and assembled, thus total lengths/widths of the radiators can vary slightly. Therefore, we strongly advise that you position your radiators before installing your pipe work. The Company will not be liable for any damage or losses incurred by the purchaser or their representatives for installation of pipe work prior to the goods being placed in situ. Also, we purposely source our radiators that are not completely smooth, but with acceptable casting characteristics and blemishes to give an authentic aged look which will be highlighted more with lighter colours.

Can I paint my own radiators or get someone else to paint them?

Yes, you can arrange to paint your own radiators or we can deliver the radiators to a nominated paint shop of your choice if required. The primer we use is a cellulose based primer and so it is alright to use other cellulose based paints. We do not recommend powder coat finish as this will affect the section seal/gaskets when put in finishing oven causing your radiator to leak. DO NOT USE WATER BASED PAINTS.

What size pipe work is required?

Our radiators are prepared to accept ½” BSP. The diameter of the pipe work required to supply your cast iron radiators will be determined by the systems supply requirement, but all can be adapted by copper-brass converters, available from most plumber’s merchants, by your plumber.

Who can install cast iron radiators?

Our radiators should be installed by a qualified heating engineer or plumber. They are compatible with all modern pipe work systems & come with 15mm (1/2”) bushes - connections as standard.

Can I use your cast iron radiators with my existing heating system?

All of our cast iron radiators are compatible with normal central heating systems, and come complete with ½” British Standard fitting connections. This means you can change as many or as few radiators as you wish.

Can I use small/micro bore (10mm) or larger (22mm) pipe work?

Our radiators can be used with existing pipe work which is either narrower (10mm) or wider (22mm / ¾”), though we recommend using 15mm bore pipe as a minimum. Copper/brass Converters or Reducer fittings are freely available at little cost to enable the radiator to be fitted to smaller (10mm) or larger (22mm) pipe work. On larger radiators (those in excess of 2000 Watts) it may prove a problem in balancing the system if using microbore (10mm) pipe. Therefore, we always suggest speaking to your heating engineer or plumber to make sure your pipe work is compatible.

Where should I position cast iron radiators?

This really is up to you, however, traditionally, radiators were in the coldest part of the property. This would normally be on an outside wall or under a window; however it is perfectly acceptable to position your radiator to suit your rooms’ layout taking into account windows, doors etc. For larger rooms, it may be more beneficial to have more than one radiator to give an even heat spread for the whole area.

What valves should I use for my radiator?

You can use either a Thermostatic or Manual valve set. On larger radiators, or rooms where the radiators have been oversized we would normally recommend the fitting of a TRV (Thermostatic valve) although this is not essential. Our radiators are designed to accept both valves at the bottom for pressurised systems or if required for gravity fed systems, with the inlet valve fitted to the top on one side of the radiator, and the outlet (lock shield) to the bottom on the opposite side of the radiator. One point to remember is that if you are positioning a radiator in the same room/area where there is a central heating thermostat, it is recommended to use a manual control valve set, this will prevent the thermostat and TRV valve counter-acting each other.

What is the difference between a TRV (Thermostatic Radiator Valve) and a Manual one?

A TRV controls the room temperature, by sensing the air temperature and automatically opening and closing the flow to the radiator. A manual valve can only control the temperature of the radiator regardless of the room temperature & is usually controlled via a room or general thermostat.

How are valves fitted and cast iron radiators sealed?

It is important with our cast iron radiators that no caustic plumbing compounds are used on any part of the radiator, its valves or connections (this can react with the iron, breaking down the sealing washers in both the radiator & any ‘O’ rings in your boiler or pumps). If any compounds are used then you must return the water to Ph neutral before operating the system. All radiator joints should be dry jointed, with PTFE tape wrapped around the valve threads for tightening. We would recommend the use of a thicker gas type PTFE tape on parallel threaded valves.

I see that many of your TRV valves offer a 'Frost Protection'. What does this mean?

'Frost Protection' valves offer exactly that, protection for your heating system from the effects of frost. Most of our TRV (thermostatic) cast iron radiator valves offer this and will therefore, continue to work when in the fully turned off position. This is to ensure that if, you are away and your have turned all your valves to the fully wound in - Off position and the temperature drops to the levels above, the valves will automatically open to help prevent the heating system from freezing and causing damage. Obviously, your heating needs to be on and operating for this to work. In view of this protection, please remember that the valves may not fully shut off when in the fully wound in - Off position, so installing an inexpensive in-line isoltaion valve may be helpful when plumbing in your radiators. We also offer decorators caps under the Accesories & Spares tab above for the Bentley Range to fully shut off these valves.

Is it safe to use Inhibitors or other plumbing compounds?

It is very important that the Ph of your heating syatem is maintained between 7-8.5 at all times to prevent gaskets breakdown in valves or radiators. Failure to do so will invalidate your warranty. Ph neutral inhibitors are fine to use & MUST BE USED to the correct dosing levels, but NO caustic/corrosive/acidic plumbing compounds or liquids are to be used on or in any part of our radiators, our valves or connections and that if aggressive flushing agents are used, the water in the system MUST BE immediately neutralised correctly following their use appropriate crystals or similar and certificated as such. Where caustic and/or corrosive compounds (liquid or other) have been introduced into the radiator(s) which have caused damage to seals/gaskets, or the use of insufficent amounts of Inhibitor are found, this will invalidate any guarantee offered. PLEASE SEE OUR FITTING GUIDELINES FOR FURTHER INFORMATION.

We strongly discourage the use of a water softener on the heating system as this treatment can cause problems with the gasket seal.

Do I need a wall stay for my cast iron radiators?

We always recommend that you fit a wall stay with our cast iron radiators as they will help stop the radiator being moved and thus moving the pipe work into your valves which may then subsequently leak. As a general rule we suggest 1 stay for cast iron radiators up to 10 sections long (for the traditional 460mm range 1 stay for up to 16 sections will be fine) and 2 stays for cast iron radiators 11 - 23 sections long. We can supply stays for both solid-block walls and studded-partition walls to suit.

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Cast Iron Radiator Centre
(a Division of Mossmead Ltd)
241 Torrington Avenue
(Corner of Padstow Road)
Coventry, West Midlands
0800 294 8603 / 024 7630 3999
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