New radiators not plumbed in correctly?

helpmee

Hiya,

We live in a townhouse spread over 4 floors. There were originally 13 radiators which all functioned but we replaced two of the smaller ones with large ones, both around 10K BTU.

With all the radiators on, we find that the two larger radiators do not get hot. With all other radiators closed, they get fairly hot but not scolding hot as you'd expect them to be. Of the two pipes connected to each of these two radiators, it's the one without the thermostat/value that gets very hot and the one without the value thermostat that is warm - this sounds a bit backwards to me - I would have expected the pipe with the control to get hot?

We recently upgraded to a larger Valiant boiler so I don't think the problem lies there.

Any replies greatly appreciated.

Thanks!

Billxx

There will be experts out there that add to this but I suspect the system is out of balance.  The hot water is going directly to the return.  There are examples on you tube on how to balance a system.  Apologies if you already know this.

ThisIsWeird

I suspect it's as kissie-Bill says.

There are two aspects to 'balancing', one is to ensure a rad doesn't pinch too much, and the other is that it doesn't receive too little.

You've sorted the first issue by turning off the other rads, but that could still leave the possibility that the new rads are still being starved by their own lockshields. So, if you repeat your test - close off all the other rads as before, but this time open the lockshields (the valves opposite to the TRVs) on the two new rads by a half-turn. No more. (To do this, you'll likely need to pull the caps off to expose the spindle underneath.)

See what happens.

On the 'valves on the wrong end' issue, most (all?) modern TRVs are bi-polar, so it doesn't matter on which end they have been fitted.

Ectophile

With a modern condensing boiler, the radiators shouldn't get scalding hot anyway.  The lower you turn the temperature knob on the boiler, the more efficiently it runs.  That's why you need bigger radiators.

But as others have said, it's likely that the system needs balancing.

ThisIsWeird

That's a good point, although the OP has confirmed that other rads do become 'hot'. So they should expect the new ones to get just as.

Have you also tried bleeding the new rads, Helpmee?

helpmee

Most of the other radiators in the house do get scolding jot.
This problem has been happening for a while. I have tried  bleeding and balancing quite a few times and even had several plumbers try to fix the problem but to no avail.
The fact that I closed all other radiators and these two didn't get very hot suggests it's not a balancing issue no?
I will try again over the weekend and will report back.

ThisIsWeird

helpmee said:

Most of the other radiators in the house do get scolding jot.
This problem has been happening for a while. I have tried  bleeding and balancing quite a few times and even had several plumbers try to fix the problem but to no avail.
The fact that I closed all other radiators and these two didn't get very hot suggests it's not a balancing issue no?
I will try again over the weekend and will report back.

Ok, you bled the rads - good - and turned off other rads - awesome - but have you opened the cool rad's lockshields by a half/full turn yet? (Obviously with their control valves open too?)

FreeBear

ThisIsWeird said: - but have you opened the cool rad's lockshields by a half/full turn yet? (Obviously with their control valves open too?)

May not need to open the lockshields by that much. On some of the radiators here, an eighth to a quarter turn was enough to go from meh to full flow.

ThisIsWeird

FreeBear said:

ThisIsWeird said: - but have you opened the cool rad's lockshields by a half/full turn yet? (Obviously with their control valves open too?)

May not need to open the lockshields by that much. On some of the radiators here, an eighth to a quarter turn was enough to go from meh to full flow.

Yes, but this is initially a fault-finding mission.
If it works, then the OP can revert to tweaks.