Boiler powerful enough?

[spaceyy]

Hi,

I'm hoping someone could help. We recently purchased a 4b detached house which we pretty much completely renovated, including changing all the radiators, most of which are now collumn radiators, and adding additional ones. We've used the existing boiler which is a Greenstar 18i System boiler (18kw) with a large tank.

We are having issues, (even when the flow temp is to 75-80 degrees), the radiators never seem to get that hot, and in some instances some radiators dont heat atall. With the cold weather, its almost like the heating system struggles to get the house up to >17degrees, despite being on for a considerable amount of continual time >4h. The house is quite long, so there is a fair amount of distance for the water to travel - if that makes any difference?

We've tried balancing them, and checked enough water/pressure in the system

Most of the pipework along with the radiators are new, and the system has been flushed, and checked for air in the system.

We have 18 radiators which equates to (kw ive used an online calculator)

TOTAL BTU	62889
KW	18.43

Most of the videos i have seen online have said for an average radiator you want to be looking at 1.5kw per radiator.

My question is, is the boiler underpowered for the radiators/setup we have? I didnt want to look at replacing the boiler, if this isnt the likely culprit

Appreciate any advice - Thanks

 

[livingstoned]

when the flow temp is to 75-80 degrees), the radiators never seem to get that hot,

Water's going straight back to the boiler perhaps, then.
find the first couple of radiators from the boiler/pump, and shut them. See if the rest get hotter. It's often the first one, like a towel rail in a bathroom, too far open. Rads only need a dribble of water.
Does the Hot Water get too hot? If so the valve ( you probably have two, two port vales??) may be "letting by".

You could check the actual gas usage, though that can be a mission with some meters. What sort do you have?
The boiler should be on a high percentage of the time if all is OK, but they modulate (turn their flame down) so it's harder to tell than it used to be.

If the flow temperature is high 70°'s though, it doesn't sound like the boiler's faulty. (Unless it has an internal bypass). Though "renovated" rings alarm bells - if a builder did it, the gas pipe may be too skinny.
DO try to measure the gas usage. Post a pic of your meter.
If it's not a smart or moderne thing,
If Analog (dials with needles), time for 1 cu ft, then take 1096 (iirc) divided by that time gives kW
If digital (numbers), take the count for 2 minutes, multiply by .323 for kW.
It should come up about 20kW if the boiler's flat out.

 

[Agile]

A lot of vertical rads have obstructions inside which have to be correctly located.

They do not give out the heat in the same way and many people are not very happy with them!

 

[JohnD]

Chosen for style, not performance

 

[polesapart]

heating pipework undersized or incorrectly connected to emitters

Chosen for style, not performance

+1


Unlikely to be boiler problem.

 

[Madrab]

most of which are now column radiators

as mentioned by other - Unfortunately that was the first mistake, they are purely form over function.

How was the system piped - 22mm backbone to a centralised location(s) and then 15mm branches out to the rads?

As also mentioned - a lot of these rads have to be piped a specific way, was that considered/checked for? BTU or KW ratings do not translate to adequate space heating when it comes to modern column/tubed rads, they work differently to convecting rads and are a lot less efficient at heating spaces, the large the space the more inefficient they are.

If the radiator capacity is a min of ~18.5kw then I would be of the opinion that an 18i boiler isn't really large enough as that's right at the top of it's capacity without taking the loss through pipework and other losses into consideration. I would always spec headroom into the boiler to ensure it isn't running flat out all the time.

How was the system designed?