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Central Heating

Two radiators start fiery hot then go barely warm. New boiler, rads & flush 6 months ago

Anonymous user 03/03/2024 - 3.40 PM

Hi all, I have a baffling issue. I have a single story 2 bed flat with a brand new Vaillant boiler, 6 new rads & power flush all done 7 months ago. When I start up my CH, all rads heat up brilliantly. However, the 3rd and 4th rads on the circuit cool down to barely lukewarm after about 40 min of CH being on. The first two rads - and incidentally, the other 2 rads which run down the separate side of my flat (not sure if these are on a separate circuit) all remain hot. However, if I turn down the heat to one or both of the first two rads, then the 3rd and 4th start to heat up again, but once again begin to come down to lukewarm after half an hour. I've noticed the top of the 3rd radiator remains hotter than the bottom, but have tried bleeding this to no avail. I've noticed the flow & return pipes vary in temperature the longer I leave my CH on. I can initially trace the super hot flow across all the radiators when I first turn on CH, but after about an hour, I notice the flow becomes much less hot sort of halfway beneath the second radiator. It's very hot until then - but then suddenly feels lukewarm. The return pipe is also almost as hot as the flow initially, but then cools down. The flow and return right before the first rad always seem to be very hot. Thermostat temp is almost never reached due to poorly sealed windows, & thermostat is in a separate room from the 2 misbehaving rads. What can be the issue? With a new boiler, new rads and flush done just months ago, I can't figure out how to get the 3rd & 4th radiators to be constantly hot. It can't be a full blockage in the pipe as they're capable of getting very hot when CH is first turned on.

Are you a tradesperson and able to answer this question?

4 Answers

Internal Repairs

Rating: 5 out of 5

Epsom

Balancing. One radiator valve can be controlled manually as you know. The other has to be adjusted with a spanner. This is the balancing valve. I'm sure someone else can guide you better than I as to how to balance them, otherwise you could call a plumber in? There's probably a youtube tutorial about rad balancing. It allows hot water to flow at equal pressures to all radiators.

Answered23 October 2021

County Boilers Ltd

Rating: 5 out of 5

Crawley

A good heating engineer will find the answer within the hour, just by looking and feeling the circulation as it heats up. You should get a price for an hour visit (or 2 hours if it will be required). I doubt you will get the diagnosis by your explanation because it could be a number of things. The biggest question is where is the installer? Was he/she gas safe? Is there evidence that a flush was carried out? Why can’t you get them back to sort it ? All the best

Answered23 October 2021

White Heating and Plumbing

Rating: 5 out of 5

Swindon

System may require balancing to give even heat distribution around the ch system

Answered23 October 2021

Boss Gas Installations Ltd

Rating: 4.9 out of 5

Hornchurch

As you have taken all necessary steps in achieving a clean system this sounds like the system needs balancing...

Answered23 October 2021