A Couple of Cold Radiators.

[quelquod]

Winter’s coming, should have tackled this earlier!

The radiators in my utility room and conservatory (relatively recent extension) aren’t getting hot. I’ve no idea if they ever heated properly. A bungalow, all 1 level. The main house is plumbed in microbore but the 2 radiators in question are fed on their own 15mm spur. No idea why. I can’t imagine anything blocking the 15mm stuff that wouldn’t have given trouble with the microbore (?) and the system is water clear with inhibitor. Is it possible to get an airlock in the horizontal spur, never heard of one, or should the pump automatically shift one? I can bleed the 2 radiators but I suppose that only means that EITHER the flow OR return is clear. After an hour or so running there is very slight warmth, no more, in the inlet pipes to the radiators. Turning off most of the other radiators doesn’t improve these two.

Ideas for diagnosis? Fixing is another issue altogether under the parquet! I can get under the main house OK but not the extension.

[richlist]

At the risk of stating the obvious, are you sure that all the valves are fully open? I had a similar problem last year with a bedroom rad' that had a thermostatic valve fitted.....the valve had jammed shut.

[quelquod]

Yes I believe so. The thermostatic valves ‘feel’ all right and it doesn’t seem likely that both have failed and no others in the house. But it’s a possibility, though removing one to check isn’t at the top of the convenience list .

[jfgw]

Yes I believe so. The thermostatic valves ‘feel’ all right and it doesn’t seem likely that both have failed and no others in the house. But it’s a possibility, though removing one to check isn’t at the top of the convenience list .

It is certainly possible for two TRVs to stick and no others. If you take the heads off and can push the pins down a few millimetres and they spring up again, they are almost certainly ok. If you leave the heads off, the valves should be open. Heads can fail.

The pipes are probably not exactly horizontal so an air lock is possible. Try shutting off all of the other radiators (and the hot water if you have a cylinder), and set the pump to its maximum setting.


Julian F. G. W.

[DrFfybes]

What Julian says.
TRVs generally have a locking ring that you unscrew from the valve head then pull it off. Test the pin moves by pushing it down then pliers if it is stuck down.

In our new place 4 valves were stuck shut. I freed them all off and one has stuck again, sadly after I'd drained and refilled with inhibitor.

Paul

[88V8]

Yes I believe so. The thermostatic valves ‘feel’ all right and it doesn’t seem likely that both have failed and no others in the house. But it’s a possibility, though removing one to check isn’t at the top of the convenience list .

Are they a different brand?
If the tail is long enough, to remove a TRV you could shut the lockshield and freeze the inlet?

V8

[Itsallaguess]

The radiators in my utility room and conservatory (relatively recent extension) aren’t getting hot.

I’ve no idea if they ever heated properly. A bungalow, all 1 level.

The main house is plumbed in microbore but the 2 radiators in question are fed on their own 15mm spur. No idea why. I can’t imagine anything blocking the 15mm stuff that wouldn’t have given trouble with the microbore (?) and the system is water clear with inhibitor.

Is it possible to get an airlock in the horizontal spur, never heard of one, or should the pump automatically shift one? I can bleed the 2 radiators but I suppose that only means that EITHER the flow OR return is clear. After an hour or so running there is very slight warmth, no more, in the inlet pipes to the radiators. Turning off most of the other radiators doesn’t improve these two.

Ideas for diagnosis? Fixing is another issue altogether under the parquet! I can get under the main house OK but not the extension.

Hmmm.....I've known of a similar situation where a works colleague had the same symptoms with two radiators in a new extension of theirs, and it turned out that they'd been plumbed in wrongly, and had actually been tapped off the return-leg (cold) of an existing radiator....

I'd be turning off all the other radiators fully, and checking to see if you still even get the 'slightly warm' result in the new ones...

If you only even get the 'slightly warm' result in the new ones where one or more of the old ones are turned on, then this might hint at a similar situation....

Separately, and regarding TRV's perhaps causing these types of issues, I've had experience of TRV's that have needed their exposed pins pulling *up* with a pair of pliers to get them going, so do have a play both ways if you take the TRV heads off the two radiators you're having issues with.

Cheers,

Itsallaguess

[quelquod]

Thanks all.

I’m pretty familiar with TRV operation so when I said they felt all right, I meant that the pins had plenty of spring in them when pushed and when I refit the heads they do come ‘slack’ at about the point you’d expect given the room temperature just now so I’m fairly confident they’re not the problem but I’d rather exhaust other possibilities first to avoid draining the system.

[bungeejumper]

Always ask the stupid questions. Have the radiators been balanced/rebalanced recently?

One of our flat tenants asked her father, a self-described "plumber" (excuse my snorting) to investigate why two of her radiators weren't heating up. He opened up the return valves on every rad in the property, and declared that this would fix the problem. Then the tenant came back onto us like a ton of bricks, complaining that her CH system was even worse now and clearly it couldn't be fixed, and what were we going to do about it?

I imagine the OP knows the procedure for balancing a radiator system, but the question is worth asking. It takes an hour, and it's the first thing I'd check once I was sure that the TRVs weren't sticking. And that all rads had been bled, of course.

BJ

[DrFfybes]

If you turn the TRVs down on all the others to check the new ones, also worth seeing which end gets hot first, and if the TRVs are 'directional'. These days most aren't but it could be an issue.

Paul

[Mike4]

Thanks all.

I’m pretty familiar with TRV operation so when I said they felt all right, I meant that the pins had plenty of spring in them when pushed and when I refit the heads they do come ‘slack’ at about the point you’d expect given the room temperature just now so I’m fairly confident they’re not the problem but I’d rather exhaust other possibilities first to avoid draining the system.

Ok this set of symptoms is typical of an older microbore system where the lockshield valves on the non-working rads have been turned down to almost closed to get the more distant rads working. When nearly closed the gap is TINY and eventually blocks with crud. If your lockshield valves are nearly closed, open them wide to dislodge the crud then return them to the same state as before. This works in about 50% of cases.

Microbore systems are a bundle of trouble once a decade or three old. The pipes are thin and block easily but the blockages are usually at one end or the other, and sometimes disconnecting the ends and poking them out works. Another approach is to get a specialist powerflushing firm in - pflush.co.uk for example. Or they might be pflush.com! Not a recommendation, just one such firm I know of. They have been around doing nothing but powerflushing for about 25 years now so my guess would be they must be reasonably competent to have survived that long.

Edit to correct the spell checker. Huh.

[bungeejumper]

If you turn the TRVs down on all the others to check the new ones, also worth seeing which end gets hot first, and if the TRVs are 'directional'. These days most aren't but it could be an issue.

Deffo a possibility, I'd say. If I read the OP correctly, the rads that aren't working are on a 15mm pipe system that sounds like it's been appended to the microbore system at some time. That in itself would seem to suggest that the balancing task would be more critical than usual.

But yes, rads are sometimes fitted with the flow going the wrong way. Don't ask me how I know, I did it myself once. (Whoops. ). The OP would probably do best to get a notebook and pencil, and fire up the system from cold, and then run around the house noting which rads heated up first, and making sure all the way that the pipes to the TRVs were warmer than the pipes to the lockshield valves. My guess is that the lockshields nearest to the boiler need tightening a bit, and the ones furthest away need opening up, but there's no way of really knowing until this has been done.

I'm also wondering whether the pump is (still) adequate for the system, given that it sounds to have been extended at some time? Bungee Towers's CH system became much less fussy after we swapped the tired old 15/50 pump for a 15/60. A deceptively big difference in flow between the two. Obviously I appreciate that a microbore system's pump will have been more meaty than a normal pump, but you get my meaning?

BJ

[DrFfybes]

Obviously I appreciate that a microbore system's pump will have been more meaty than a normal pump, but you get my meaning?

BJ

D'ya think?

Actually our ancient pump has 3 speeds....
Whiny
Noisy
She can'nae take any more Cap'n

Paul

[Mike4]

Obviously I appreciate that a microbore system's pump will have been more meaty than a normal pump, but you get my meaning?

BJ

D'ya think?

Actually our ancient pump has 3 speeds....
Whiny
Noisy
She can'nae take any more Cap'n

Paul

Whiny + noisy = full of crud, usually.

Take the motor head off and give it a clean!

[DrFfybes]

Obviously I appreciate that a microbore system's pump will have been more meaty than a normal pump, but you get my meaning?

BJ

D'ya think?

Actually our ancient pump has 3 speeds....
Whiny
Noisy
She can'nae take any more Cap'n

Paul

Whiny + noisy = full of crud, usually.

Take the motor head off and give it a clean!

Thanks Mike - I didn't realise you could split them withou getting wet.

It is a Grudfoss Red one (as I suspect 99% of them are) so I'll get the model number and look on t'interweb.

Paul

[Mike4]

Thanks Mike - I didn't realise you could split them withou getting wet.

It is a Grudfoss Red one (as I suspect 99% of them are) so I'll get the model number and look on t'interweb.

Paul

Well it's a Really Good Idea to close the isolating valves each side of it first....

Then just take out the four x M5 set screws holding the motor on, then it *should* just come off complete with impeller. (4mm Allen key IIRC.)

[jfgw]

Thanks Mike - I didn't realise you could split them withou getting wet.

You do get wet if you don't isolate the pump or drain down. You can also get black, and so can the carpet if you are not careful. Plenty of sheets are recommended.

Julian F. G. W.

[bungeejumper]

Well it's a Really Good Idea to close the isolating valves each side of it first....

Thanks for the belly laugh. Of course, closing down the isolating valves is when you get to find out whether the gate valves that haven't been touched for twenty years are still in a co-operative mood.

Mine were, fortunately, but if there's any crud stopping the valve from closing completely then you're going to be the first person to find out. Bucket and sponges at the ready, and open it up a crack at a time.

Or just drain the damn thing down.....

BJ

[quelquod]

So a small amount of negative progress today. I shut off both valves on each radiator then tried bleeding each radiator in turn with each valve open in turn and found that the with the TRVs open the flow from the bleed was pretty strong but with the ‘lockshields’ (really hex heads under a cap) open the flow was quite poor. So my tentative deduction is that there is a restriction of some sort in the 15mm return pipe to the lockshields.

About half of this pipe is reasonably accessible, but the rest is under the parquet extension floor . But I’ve found that the plumber has thoughtfully at least put valves where the 15mm spur joins the main system. I still have difficulty believing that a 15mm pipe has blocked though as the water is so clean???

So I’m wondering about disconnecting this pipe at each end and sticking a compressor on one end?

[Mike4]

Right, mixing up microbore with smallbore in a single heating system as you describe is a monumental bodge unlikely ever to work. You say you don't know if these two rads ever worked but I know - they didn't! What should have been done when adding rads is run a new pair of microbore pipes from each new rad back to the pair of microbore manifolds and connect directly into them. If there are no spare and blanked off connections then new manifolds with more connectors need fitting.

The above is a complete ball ache to do and often massively expensive and disruptive, which means most builders adding new rads to a microbore system will opt for their own custom bodge of some sort when adding an extension. Bodges don't work by definition because if they did, they would not be bodges and would be standard practice. The fact your two new rads are connected in 15mm instead of microbore strongly suggests your builders elected to design themselves a bodge.

Sadly, the fix is to find the microbore manifolds (usually under the airing cupboard floor under the hot water cylinder) and run a pair of microbore pipes from each rad to this location and connect them in correctly. If there was a way to reliably make work whatever the builder elected to do instead, it would have been done in the first place, I suggest. So the fix is to get the builders of the extension back to do the job properly!