Should I replace old radiators with smaller one?

[jameswillo]

I'm thinking of switching an old 1400 for a 900. There's plenty of BTUs but my question is this.
If I put a smaller one in, will that over time become less efficient and then be pretty much useless in the future, or because it's a new design and more efficient than old ones it'll be fine for the lifetime of the radiator?

If that makes sense?

 

[PrenticeBoyofDerry]

You need to do heat loss calculation, for each room. Then you can size your radiators.

 

[jameswillo]

I'm not talking about sizing the radiators. They will be the right size to start with, but what I'm saying is as the years go by will my radiator become less efficient and need replacing earlier than if I put a radiator in that was oversized for the size of room?

Basically I don't want to put a smaller radiator in now which is perfect for a brand new radiator but as the years go on, wish I'd put in a bigger one cos of the build up of sludge or whatever lowering the hear output over time.

 

[denso13]

will my radiator become less efficient

No, unless something isn't working properly. I wouldn't oversize it just because you might get sludge in it at a future date. Cleaning the sludge out (if it happens) would be a better option.

 

[jameswillo]

Are there other reasons the efficiency could be reduced?

 

[denso13]

Not really

 

[muggles]

Smaller radiators run at a higher temperature cost more to heat with a condensing boiler than large radiators run cooler, but radiators themselves don't lose efficiency unless you've got muck in your system

 

[bernardgreen]

Are there other reasons the efficiency could be reduced?

Several layers of paint added over the years.

 

[Hot&Cold]

Are there other reasons the efficiency could be reduced?

Your system could already be under preforming with regard to efficiency so cant comment on efficiency,best practice is to size the radiator's output to match the room requirements.

Plenty of free radiator size calculators on the internet,get 3 calculations and work out the average.
google,heatloss calculator cityplumbing
https://www.cityplumbing.co.uk/heatlossCalculator

 

[PrenticeBoyofDerry]

I'm saying is as the years go by will my radiator become less efficient and need replacing earlier?

Providing the system is serviced and cleaned every 3 years or when any alterations or additions are made and then inhibitors introduced.
The radiators will not loose efficiently, but you must size the radiators correctly. It is not the bigger the room the bigger the radiator, heat loss calculations are required, as they will vary room to room, even if the rooms are the same cubic size.

 

[Agile]

An over sized radiator makes for more efficient boiler operation on a condensing boiler.

So just why would you want to fit a smaller radiator?

I would always fit the same size rad as a replacement unless there were significant reasons not to.


Hopefully you are not concerned just with the cost of the rad?

When the lockshield and TRV are included the difference between 1400 mm and 900 mm rads would be very small.

If you really must downsize then at least fit a 1200 mm.

All that said on the assumption that you will be fitting finned rads to replace ones without fins.

Condensing boilers are designed for a max flow temp of 70 C whereas old boiler were made for a flow temperature of 80 C.

Tony