New Radiators Questions.

GForce2010 · 20 October 2018 at 9:51AM

Hi all.

I am just in the planing stage to replace all 7 of my radiators. They are all old, too small for the purpose and the bleed nipple have seized up and are not replaceable of my current rads.

I have used an online calculator to work out what BTU's i need but I have a couple of questions I am hoping you can help me with.

Is it worthwhile getting a larger BTU than needed? As I understand it a larger BTU rad with a TRV would heat the room faster but the TRV would mean than when the room is up to temp it would use the same amount of energy to keep the room warm as a smaller unit.

Would that mean my boiler would have to work less hard reducing energy use?

Right now my system doesn't have a thermostat so when the heating is on it is just on max, the house is still very cold because the rads are full of air and, I would assume, sludge. I am planning on getting a smart heating controller that has smart TRV's so I can just heat certain rooms as and when I need them.

I assume this would reduce energy use as when my bedroom and bathroom got warm in the morning, for example, the boiler would shut off for a while?

Am i getting anything wrong in the above or are there other factors I should consider in choosing the appropriate rads for my home?

FYI my boiler is a lot younger than my rads and is powerful enough to run the proper size rads for my home.

Thanks.

System · 20 October 2018 at 10:07AM

How young is your boiler? If it is a modern condensing boiler, then there are efficiency advantages in fitting oversized radiators. Low boiler operating temperatures are the aim with condensing boilers. As far as smart controls are concerned, do not believe all the hype. The savings figures quoted are based on a property with no heating controls. The Govt and BRE assess savings through zoning to be in the order of 1 to 2%. That said, they do offer a greater level of comfort and convenience than standard controls. It is also not a good idea to leave unused rooms without any heat if you want to avoid damp and mould. With just seven radiators you would get much improved efficiency with a standard thermostat and manual TRVs.

Finally, it sounds like your system needs a full power flush. You cannot just replace radiators and expect the sludge in the boiler and pipes to go away.

paul1964mccarthy · 29 October 2018 at 4:58PM

Hi GeForce

Everyone will have a different opinion, here's my 2p worth.

I have oversized my radiators. It means my house heats up quicker and I can run the boiler at a lower temperature. The return flow temperature does effect the efficiency of a condensing boiler. the lower the temperature, the more efficient it is. It's not huge, but around 5 - 10% if running a return temperature of 40c vs 60c.
It also means your radiators aren't running red hot, less stuffy air, more even heat.
If you have pipes running under the house, make sure they are well insulated, or you're just throwing money away.

Secondly, I use smart TRV's. I'm not sure if they save any money, but I don't care. I have every room at a temperature I want, when I want. It's brilliant, and I'd never want to go back to standard TRV's.

PS: I have an old 3 bed semi in the SW. Gas consumption is around 7,000kw a year. About half the average I believe.

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