New boiler installed, now I can only get one radiator at a time working

Mr_s

I had a new boiler installed through Boxt back in August replacing an old gravity fed system with a new combi boiler. 
 Everything seemed great until I attempted to put the heating on earlier this month. 
I'm only able to get one radiator to work fully at a time. If I have multiple radiators switched on, they either don't kick out much heat or not heat up at all. When I isolate each radiator individually and turn the TRV up to 5, they will get red hot from top to bottom.
If any of the upstairs radiators are on, none of the downstairs will get warm. 

•  I've bled the radiators and re-pressurised the system several times. 
• the pressure is where it should be (just under 1.5)
• the system was flushed during install
• I've not altered any settings but the heat for the rads is on 70 and the ch demand is on full
• I have tried to balance my radiators although with limited success as I can't get the entire system to heat together whatever I do. 
• TRVs are set on about 3 and a half for each room but it doesn't really matter what I set them on. 
• hot water works fine. Shower pressure is spot on. 
• boiler is upstairs

There's a little bit of a clunking sound coming sporadically from the diverter valve in the boiler, but I wouldn't suspect that would be faulty already? It sort of sounds like its spluttering.
It also sounds like there is a bit of air in the pipes, but I could be wrong and also cant get it out no matter how much I bleed. 

I am awaiting a call back from boxt, but they are taking their time, and getting hold of a plumber is proving not to be too easy. 

is there anything else I can try in the meantime? I'm not bad with a spanner and a bit of common sense but I seem to have exhausted my options. 

Much appreciated


Edit-
and I just want to say thanks to everyone for replying so far. I really appreciate it

Albermarle

Not an expert but have you checked the pump is working, that pumps the hot water around the CH system.
Usually there are three settings for the speed of the pump. Try putting it on the fastest setting. 

Mr_s

Albermarle said:

Not an expert but have you checked the pump is working, that pumps the hot water around the CH system.
Usually there are three settings for the speed of the pump. Try putting it on the fastest setting. 

yeh! that's on 5. full speed

housebuyer143

It could just be badly balanced or air in the system. When I moved into my new house half the radiators didn't work and I spent many hours tweaking the lock shield getting them to all work together. They all did eventually. It's a very fine balance though as a small turn on one would completely knock out a different one 😭. We now have an air lock on 2 of them but that's a different story. Whenever someone does work on the boiler or radiators it completely knocks out the balance and I have to do it again.

Did they spend time balancing them after the install? If not, it could just be as simple as that. 

barbuda

Boxt are a national company and fit systems to suit the majority of houses.....but not all houses are the same.
The last time I checked, Boxt just ask you basic questions online and then give a quote, without anyone physically calling to make an assessment.
That is fine usually, but if your system is quite old or unusual in any way then Boxt will just fit their standard system and move on to the next job.
There are many reasons why your heating may not work, if your system is over 20 years old then you may have a one pipe system as opposed to the usual 2 pipe system, you may have a really bad airlock but either way a callback would be needed.
Boxt are ok if there are no problems, but if I was spending over £1000, I would like a proper survey first.
I'm sure if you chase Boxt enough they will get back to you, always a plus if you paid by credit card...

FreeBear

barbuda said: Boxt are a national company and fit systems to suit the majority of houses.....but not all houses are the same.

And they also subcontract the installation to the cheapest local Gas Safe plumber they can find. As a result, the plumber just wants to get in, do the job quickly and cheaply. Many of the finer points such as balancing radiators and setting the boiler up properly are then left to the home owner.

The problem the OP describes sounds like a balancing issue rather than a fault with the boiler or pump.

FFHillbilly

if the OP can get any of the radiators working by isolating the others, I'd say there has to be blockage somewhere. system cleaner, followed by a flush would be my suggestion.

Lorian

On fitting a new system boiler on Y plan it's unlikely they replaced the diverter valve and given its making noises too I'd start there. It can be easy enough to free them up if you know what you are doing (the control of the valve is done using 230v mains caution) but if you have a service plan then a call out would be appropriate 

Mr_s

FreeBear said:

barbuda said: Boxt are a national company and fit systems to suit the majority of houses.....but not all houses are the same.

And they also subcontract the installation to the cheapest local Gas Safe plumber they can find. As a result, the plumber just wants to get in, do the job quickly and cheaply. Many of the finer points such as balancing radiators and setting the boiler up properly are then left to the home owner.

The problem the OP describes sounds like a balancing issue rather than a fault with the boiler or pump.

yeh this. They seemed like good lads but they were interested in getting the job done in a single day as opposed to two. I've had a crack at balancing but unfortunately if any of the rads closer to the boiler (upstairs) are on, I can't get a single one downstairs to heat up at all, even if the locksheild valves upstairs are opened the absolute minimum. 

FFHillbilly said:

if the OP can get any of the radiators working by isolating the others, I'd say there has to be blockage somewhere. system cleaner, followed by a flush would be my suggestion.

They have signed off to say they've done a chemical flush but not a power flush. The chemical flush was in with the price. 

Lorian said:

On fitting a new system boiler on Y plan it's unlikely they replaced the diverter valve and given its making noises too I'd start there. It can be easy enough to free them up if you know what you are doing (the control of the valve is done using 230v mains caution) but if you have a service plan then a call out would be appropriate 

They must have. The old valve was in the cupboard with my water tank (was previously gravity fed) that's all gone now and that cupboard is empty. The valve is now internal to the boiler (I think anyway?) 

ThisIsWeird

Yes, the diverter valve (it diverts between CH and instant DHW) is built in to a combi boiler, as is the pump.
(I'm surprised you were able to adjust the pump speed - that's usually controlled by the boiler itself?)
As suspected above, this is most likely a balancing issue. You can heat up any one rad to 'hot' by closing off others?
When they carried out the chemical clean, they most likely opened up all the valves fully so's each rad had a good flow through them. If so, they should have noted how far open each lockshield was.
Mr S, could you check a few rads at random? Pull off the lockshield valve covers and tape a wee paper flag to the spindle, say pointing outwards. Now turn the spindle clockwise until it stops - that's it fully closed. Note down for each rad you check how many turns and part turns this takes.
Please report back, and it might give us a clue.
(Mention which rads, which rooms, where located, and how far/close to the boiler.

FreeBear

ThisIsWeird said: (I'm surprised you were able to adjust the pump speed - that's usually controlled by the boiler itself?)

Modern boilers are complex beasts with lots of menu options. On my boiler, there is a menu option for selecting a pump response curve. Not changed it as the default appears to be working fine.