The two rads still aren't heating quickly. They seemed better when a few rads were on. The flow pipes are both piping hot.
One difference this time is I also turned off the flow side on some of the others last time which I guess would have reduced the the distance the heat had to travel? Its like the heat just can't reach these end rads very well
If the flow pipes are hot on both rads ,the return pipes should be too by now. If they are not there is no flow ,or very little ,through the rads into the return. Are their lockshields fully open ,if they have TRV's remove the actuator heads and ensure the central pin in the body is moving freely.
That being the case, then a new boiler will not solve it. As per Terry Mac you have a circulation issue. Choose from incorrect plumbing, dodgy valves or a physical restriction. A physical restriction could be sludge (probably unlikely), piece of fibreglass entering the system when it was tank fed and stuck on a bend, nail in a pipe (seen this where it heavily restricted flow but did not leak until nail pulled out!), or even an 8mm elbow inside a 15 elbow. Seen all of these over the (many) years
One of the new ones is hot both sides but the rad is only hot on one half. The other is hot on the flow and not return.
I guess these are hard things to diagnose. If I bleed the rads in questions I can pull hot water through quite quickly so it can flow when pushed. All the pipework for these new rads is brand new so I don't see how it can be blocked? Maybe the pump isn't doing its job properly and these are just two far away for it?
I just turned the pump down to 2 from 3 and I think the new rads are getting hotter quicker now... Am I imagining it?
Are you certain it's plumbed in correctly port specifically ?? If it is, that sounds like an issue with that particular rad ,internally. If the flow and return pipework extending from it are both very hot ,that's indicative that water is flowing right out of it . I think you have more than one issue ,and your plumber ain't cutting the mustard if he thinks the boiler needs replacing !!
To be frank a lot of these vertical rads don't heat as quickly as standard panel rads. What's the other rad like ?
Not sure what a bypass is sorry, in an amateur. Hot water seems to be working fine yes. Not got it on at the moment but it was fine this morning.
I am sorry, but you are wrong, and do not understand how heating works. The new pipework may be located after one of the issues mentioned. Openong a valve and getting a flow of hot water is irrelevant to a closed circuit. The pump may be an issue, and it is true that I did not mention it. But my point was that you could fit a massive boiler and see no benefit, as you have a circulation issue. You need a new plumber.
The pump valves could be causing the issue if they’re the old ones. I would be getting them checked/replaced if that hasn’t been done. At the same time would remove the pump head and check if it has debris in it.
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