BTU rating

[PinkFloyd]

I've got two radiators to replace and have used an online BTU calculator. It gives the following results:

Room 1 2350 - 2825

Room 2 1775 - 2125

Both are bedrooms. I'm looking at Kudox radiators through Screwfix as they have a sale (20% off) The single panel type are obviously cheaper which is a bonus. However I'm not sure if they'll meet the BTU requirements. The maximum of both are 2802 and 2101 respectively which is just below the maximum recommendations.

What's the general consensus on this? Is is better to over estimate and go for a radiator that easily meets the max recommendation, or can you get away with it? The difference in price is quite considerable........

 

[Agile]

Heat outputs have been measured in kW for the last 40 years!

Calaulators are hardly accurate to 10% so the odd 1-2% makes no difference.

Although over sizing is always better as it enables a condensing boiler to operate more efficiently.

Tony

 

[Whitespirit66]

As those values are only just short of the maximum requirements, they should be OK.

It is usually advisable to slightly oversize if you can. If a rad is oversized, rooms reach temp quicker, and if your coiler is a condenser, larger rads help the boiler to run in sondensing mode thus saving energy. Also, oversized rads can be turned down, but undersized there is no spare capacity for very cold spells. Fitting TRVs will help run rads efficiently, in conjunction with a room stat.

 

[HERTS P&D]

Don't forget you will also have TRV's fitted to these radiators and normally these will be set between 2 & 3 as you don't want to have the bedroom too hot. Normally about 18 C.

Andy

 

[Whitespirit66]

Good British thermal units are fine.

Or maybe Tony is going out later for a 2 kilometre stroll to his local, for a quick 0.568261 of a litre or two.

 

[Agile]

I like a cool bedroom but Nigerians like 30 C !

 

[Whitespirit66]

86 farenheit, if you don't mind!

 

[PinkFloyd]

Thanks guys.

Currently all radiators just have lockshields on them, there's no TRVs I can see. I have a Bosch Worster Greenstar Combi boiler with a digital thermostat. I'm undecided yet on whether I'll fit TRVs or not?

 

[HERTS P&D]

Fit TRV's all around except where the wall thermostat is. It will save you money and you will have better control of your heating.

Andy

 

[PinkFloyd]

Thanks guys.

With regards to changing the valve it looks like I have 10mm pipe. So my plan is to:

1. Turn off combi

2. Isolate all radiators (Bar the two that are currently removed)

3. Drain down using the drain point which I've found. It's located on the other side of the wall to my hall radiator so goes straight outside.

4. Wait until the water stops.

5. Change valves to 10mm TRVs on right? Hand side.

6. Fit the two new radiators

7. Open up all radiators

8. Refill system using filling loop

Does this sound correct? I'll obviously fit TRVs to the other radiators as I progress to other rooms.

 

[Whitespirit66]

2) Leave all rad valves open (with the obvious exception of the ones where rads have been removed) to completely drain all water in the system, and any debris that is in it. Check the water as it comes out. If it is dirty, you may need a flush too. As soon as the system starts draining, open a couple of bleed valves on the highest rads to speed up the process.

Also, between steps 6 and 8, you forgot the vital addition of corrosion inhibitor.

 

[PinkFloyd]

2) Leave all rad valves open (with the obvious exception of the ones where rads have been removed) to completely drain all water in the system, and any debris that is in it. Check the water as it comes out. If it is dirty, you may need a flush too. As soon as the system starts draining, open a couple of bleed valves on the highest rads to speed up the process.

Also, between steps 6 and 8, you forgot the vital addition of corrosion inhibitor.

Thanks. I'm going to stick that in my bathroom towel rail radiator as it appears the easiest one to put it in having the drain plug on the top. With regard to flushing what's the easiest way to do this? I was thinking connecting a piece of pipe onto a radiator then to my outside tap and letting it come back through the drain pipe until clear, or by connecting a feed to one side of a radiator and a drain at the other.

The problem is I don't want to go forcing water into the Combi the wrong way if that makes sense?

 

[Whitespirit66]

2) Leave all rad valves open (with the obvious exception of the ones where rads have been removed) to completely drain all water in the system, and any debris that is in it. Check the water as it comes out. If it is dirty, you may need a flush too. As soon as the system starts draining, open a couple of bleed valves on the highest rads to speed up the process.

Also, between steps 6 and 8, you forgot the vital addition of corrosion inhibitor.

Thanks. I'm going to stick that in my bathroom towel rail radiator as it appears the easiest one to put it in having the drain plug on the top. With regard to flushing what's the easiest way to do this? I was thinking connecting a piece of pipe onto a radiator then to my outside tap and letting it come back through the drain pipe until clear, or by connecting a feed to one side of a radiator and a drain at the other.

The problem is I don't want to go forcing water into the Combi the wrong way if that makes sense?

I shouldn't get too worried about it, unless the water is dirty, and has lots of rust particles in it.

You could circulate some X400 for a day, then drain out, refill and drain with water once or twice, then refill remembering to add inhibitor.


http://www.sentinel-solutions.net/product/detail/central-heating/liquids/x400-system-restorer/

Tom advocates a DIY flushing method, but I can't vouch for it's effectiveness.

http://www.youtube.com/watch?v=PJWlPDxMnCM&feature=plcp

 

[Agile]

You could circulate some X400 for a day, then drain out, refill and drain with water once or twice, then refill remembering to add inhibitor.

X400 is not going to do much in just a day! It needs 4-6 weeks!

For one day action then you need to use X800 !

Tony

 

[Whitespirit66]

Yes, well spotted, meant to say a week.

4 weeks would only be for a very dirty system.