Is there a heating engineer in the house? All aspects of plumbing questions and answers, help, tips and information

[Sidspanner]

I need a bit of advice. We had a new boiler fitted a year ago, it is covered by the gas board, and it is working correctly. It operates 10 radiators within our home. Every radiator achieves the correct temperature apart from the one in our living room. This one only gets lukewarm, but the pipe at the temp controlled valve is really hot. In an effort to sort the problem we replaced the radiator with a new one a month ago. This has not sorted the problem. The system is about 20 years old and is a mixture of micro bore piping and standard piping. We had a power flush carried out 3 years ago, could it be that we need to have this done again?Any advice would be appreciated

[Skids]

Hi Sidspanner,

[b]You do not state how long this problem had been occurring? [/b]

It does sound like a blockage at the Rad, you do not say if you have TRV’s fitted, which on a system that had a boiler changed a year ago you should have them, it may be a faulty TRV, there is a pin inside that sometimes sticks when they have been dormant for a bit (summer).

If you had the system ‘power flushed’ a few years ago it may be a new blockage from the system.

There maybe an airlock, however this would be the last option, but always worth checking for.

Otherwise, if its covered by a gas board guarantee:

First check the boiler commissioning certificate, then:

Question 1 ~ were all the Rads working correctly before the new boiler was fitted? Yes go to 2 / No go to 3.

2 ~ were all the Rads working correctly after the new boiler was fitted? Y go to 4 / N go to 5

3 ~ was this pointed out to the boiler fitters? Yes go to 5 / No go to 7

4 ~ recently new problem? Y go to 6

5 ~ call the boiler fitter back and get them to sort the problem. All the Rads should have been checked before handover ~ check the boiler commissioning certificate that the boiler fitter should have signed and left with you, if you counter signed it off saying all was well ?

6 ~ call the boiler fitter and tell them you have a new problem.

7 ~ you should have stated when the new boiler was fitted that you had a problem with some of the Rads, however the boiler fitters should have picked up on the problem when they were commissioning the boiler and the CH system? check the boiler commissioning certificate to see if they have stated that all the Rads were balanced and were working correctly?

A new boiler should be sized for the dhw system and the CH circuit, thus ensure it is big enough for the house.

Regards

Skids

[htg engineer]

You say the pipe to the temperature controlled valve is hot ?

Is this a TRV ? this could be the problem, not opening fully ??

Remove the TRV head and press the pin a few times, see if it opens up anymore.

[Sidspanner]

Hi,
first of all thank you both for taking the time to reply, it is greatly appreciated.

When the boiler was replaced, all radiators were checked and the system worked as it should. Over a period of time we noticed that the radiator in the living room was not heating up like the rest of the system (lukewarm). We got a gas engineer round (under the service plan) who looked at the system and said that either we need to

a) get a power flush
or
b) renew the radiator.

I explained that we had a power flush a couple of years back, and he then said in that case you will need to change the radiator. We did this and replaced the TRV with a brand new one. Since it is a new TRV I did not think that it would be sticking (although its always a possibility and I'm not discounting it). Now the strange thing is that on the very odd occasion (no rhyme nor reason) it starts working as it should!! I am being more drawn to the conclusion that another power flush is required. Is it normal to have to power flush a system more than once?

[htg engineer]

I would suggest removing the TRV head and press the pin a few times to release it, and leave off - the valve is now fully open. If the radiator works you know it's a faulty valve.

BG service plan ?
they love powerflushes and renewing boilers.

I doubt it needs a powerflush, unless there's cold spots on the radiators particularly at the bottom where it could be a build up of sludge. Even then a flush and a dose of cleanser then inhibitor will suffice - powerflushes are easy money, I'm not saying everytime - but alot of the time that's the only reason they recommend it.

It's very unlikely the blockage is going to clear for the rad to work then block again for it not to work. My bet is on the TRV.

[Sidspanner]

Well I did as you said, and took the cover off the (brand new)TRV, pressed the pin a few times and left the cover off. However there was still no improvement. The pipe going into the TRV is really hot, and if only the water/heat would get into the radiator everything would be great, which makes me think that it is possibly blocked with sludge and that a power flush is required. Any other thoughts?

[ALDA]

S,

how far does the trv pin move when pressed?

4-5mm is normal (7-8mm showing when fully open)

if it is stuck closed(2-3mm showing) and will not move it needs replacing.

is the other rad valve sufficiently open?

has the system been balanced?

ALDA

[htg engineer]

Turn off radiator valves and remove radiator - with the heating turned off open each valve so that the water can flow into a bucket.

If there's very little water coming from the return pipe this could mean there's a blockage in this pipe, between the radiator valve and the manifold

or the radiator valve may be faulty. Sometimes the rubber washer inside the valve becomes lodged and can prevent the flow of water.

To check if it is the radiator valve, you could crack open the bottom nut on the radiator valve - but if it is the valve that's the problem there'll be alot of water and pressure here.

Is the lockshiled valve fully open ?
also have you tried turning off the other radiators in the house to see if the problem radiator will heat.