Hi,
Thinking about replacing a few radiators to get my house warmer.
Am I ok to fit larger (e.g. double panel ) radiators which will effectively increase the capacity of my system?
What effects if any will this have on my CH system?
Will a double panel radiator provide noticeably more heat that the current single panel one in my bedroom?
Thanks in advance,
CM.
The system *should* have been designed to give the required temperatures in each room. Messing with individual radiators may not give you the results you require.
The first thing to check is that the system is balanced. You do this by measuring the flow and return temperatures at each rad. If the existing rad isn't achieving the correct differential, then a larger one won't make any difference.
See the FAQ for details on balancing a system.
Yes, provided the boiler has sufficient spare capacity to be able to keep up
You need to make sure that the current pipes are of an adequate size to carry the extra flow to the larger radiators - and you will need to re-balance the whole lot. You may need to run the pump on a higher speed setting - or even replace the pump with a more powerful one.
Yes. Assuming that your existing radiator doesn't have fins, there are 3 types of radiator with which you could replace it, giving progressively more heat output:
If you pick up a radiator brochure from your local plumbers merchant, you'll get an idea of the heat output from each type. Ideally, each room needs a radiator of the right output (with a bit in hand) to balance the heat losses, when the room is at the required temperature and the outside temperature is -1 degC. To calculate this, you need to use appropriate U values for each wall, ceiling, floor, window etc. depending on the exact construction of your house, and to allow for air changes.
Yes but be careful.
Try to determine the pipework layouts to the radiators in terms of the sizes, runs and branches.
The reason is that pipes of given sizes will have a limit on flow capacity. and by implication, heat output.
There is a good paper about this on the Copper Development Association web site.
You can work from knowing the capacities and desired capacities of the radiators which you can read or estimate from radiator manufacturer data sheets. Don't forget to derate the figures in the tables by mulotiplying by 0.9 if you have a conventional boiler.
Add up the heat capacities and check that the pipework will support it.
Generally 15mm is good for up to about 6kW in a typical house, but this includes all radiators that are on the branch leading from the
22mm or greater feed from the boiler.Be especially careful if you have microbore because 8mm can only support about 1.5kW.
You will need to rebalance. There are articles on this in the group FAQ.
Generally boilers are over specified by 20%+ so unless you go mad, you should be OK there.
Yes, and look at fin options as well. Single panel with fins does more than without.
If you think you might replace the boiler in the foreseeable future, you could consider redesigning the system to give the required heat output with a condensing boiler running at lower temperatures - typically 70 degrees flow and 50 return.
To do this, you need to derate the radiators to 0.6 of data sheet capacity.
I did this exercise during a boiler swap, and by replacing 4 radiators and moving others to different rooms was abloe to achieve this.
.andy
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The system is microbore with a 22mm manifold. Each run from manifold to radiator is no more than 3 metres.
Is this 1.5 KW per radiator or 1.5KW in total? I have microbore, the feeds from the boiler are 22mm and then each radiator is supplied by an 8mm pipe. I reckon on a quick calculation that my current system outputs around 3850 adding up the wattage from all of the radiators (inc my towel radiator).
I'm planning to move from a radiator outputting approx 424 watts and 1448 BTU's to one that outputs 673 watts and 2295 BTU's. This will happen on 3 radiators with the rest being replaced with similar rated ones for aesthetics only.
No plans to do this at present.
Thanks,
CM.
Thanks for the information. On the subject of my pump it seems to be making a lot of whirring noises of late with some vibration. Sounds a little like its cavitating. Any ideas? Perhaps this is the whole problem with my system?
CM.
If the radiators are individually connected via 8mm pipe into a 22mm manifold, this is 1.5kW per *radiator*. [The 22mm pipe can support 12kW or more].
[If you had 2 radiators sharing a single 8mm drop, then the two *together* shouldn't exceed 1.5kW]Hope this is clear!
Does your system have a vented primary loop - with a little fill & expansion tank in the attic? Is there some water in this tank? [It only needs a couple of inches of so, to cover the outlet - but sometimes it can evaporate and the ball valve stick, and fail to let in any water to replace it. If this happens, you get air in the system - and possible cavitation].
If there *is* water in the tank, what is the vertical distance of the water surface above the pump?
On the other hand, if you have a sealed system (with filling loop and expansion vessel, but no F&E tank) what is the static pressure when the system is cold? Does it need topping up?
You've had some very technical replies, but the answer is probably as long as your boiler and pump can support the capacity. If not you may be heating up your bedrooms at the expense of (or more quickly than) the downstairs rooms.
I am using a bedroom as an office and I have replaced the small single panel radiator with a larger double convector and a TRV. This has worked very well as I can just turn it up when I'm using the room. The room warms up very quickly. The heating in other rooms is more than adequate and I've generally run the boiler thermostat on the lowest setting all year round since installing double glazing and cavity wall insulation.
I'd certainly reccommend using TRVs where you fit larger radiators if you don't already have them throughout the house.
Clear thanks. The only thing is that this is how I *presume* its connected up. Without getting the flooring up I have no way of telling. My assumptions are as follows:
- Pipes from boiler are 22mm leading into airing cupboard and the valve that shuts either feed to hot water tank or heating. - Pipe from valve is 22mm and I find it unlikely that this would then be reduced to 8mm. - I believe that each individual radiator is fed from the 22mm "circuit" by
8mm microbore.Any thoughts?
CM.
That's correct. The main hot water tank has a small tank on top of it and then there is an expansion tank in the loft. I'll have a check of this but I am sure there is enough water in it plus the ball valve was operational.
Estimate 2 meters.
The only other thing to add is that one of my radiators has required bleeding twice in the last 6 months. Last bled on Monday - could this indicate that there is air getting into the system? I'll check the other radiators for bleeding once I get my towel radiator reinstalled this weekend.
CM.
Probably true. Mostly one or more manifolds are deployed on the 22mm feeds with the microbore running from them.
It's reasonable to work on a rule of thumb of 1500W per radiator in this case as SS says.
Remember that this is going to be the actual derated figure and not the nominal one from the manufacturer data sheets.
.andy
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Richard Porter wrote in news: snipped-for-privacy@user.minijem.plus.com:
Further to this it is also possible that you are not getting the heat away from the boiler quickly enough; do you get "short cycling" where the boiler cuts out because of it's internal thermostat, but the pump keeps running, and the room stat is still demanding?
If so , bigger rads, or upgrading piping or both will get more heat into your rooms.
mike
If it *is* air, it would suggest that air is getting in. The other possibility is that it's hydrogen - caused by corrosion if there's insufficient inhibitor in the system. [You can check for this by holding a lighted spill by the bleed valve when you bleed the rad. If the gas coming out burns, it's hydrogen.]
In article , Set Square writes
Umm... Is it safe to do that as IIRC if the water is split up into its component parts then there should be Oxygen with it so Hydrogen and Oxygen mixed together?.
Wouldn't that go back down the bleed hole, and cause a bigger bang?.....
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