Heated towel rail cold

[Dave H]

Hi - I have recently installed a heated towel rail to replace a traditional radiator on my single pipe system. The rail is approx 1.5 metres from the old radiator and is tee'd into the hot water storage cylinder. The rail does not get hot ! I have drained the system and bled the rail - just get water venting (ie no air). I also vented the rail with the return valve shut off until it filled with hot water and then opened up the return valve - it got hotter and remained hot with the system set to water only - got a bit cooler when the heating was switched on. This morning when the system started up(water only to start and then water and heating together), the rail remained cold . There is traditional rad also tee'd into the storage cylinder - working fine ! The valves (simple on/off not TRV) are working OK !

Could it be something to do with the level of the pipe run or height of the new rail, or is the new rail competing with the traditional rad also tee'd into the cylinder ?

Any help much appreciated !

Dave H

 

[UKPITA]

I had a similiar problem with a single pipe system radiators would get hot when set to hot water only, however went cool when heating swithed on.... this was due to a airlock.... (Was a right pain to shift)

The system I was working on was a baxi back bolier setup, only way i found to resolve the issue was to remove the thermostat on gas fire and in effect boil the system to allow system to force airlock out through expansion.... (Do not attempt this if you do not know what you are doing, as can do more damage than good!!)

 

[Dave H]

Thanks - I think I have a different problem - all the rads in the house are working OK except the towel rail in the bathroom.

 

[UKPITA]

have you tried closing all the other radiator valves on the other radiators just leaving the towel rail ones open, this will force the water through this radiator, then re bleed and open other valves.... often works

 

[Dave H]

Thanks for the suggestion - yes, I've tried that - rail didn't heat up and just bled water. I also bled the rail until the cold water was replaced with hot (in effect trying to force a flow to the rail) - rail stayed hot while heating system was on but stayed cold when system switched on the following morning.
The pipes feeding the rail are tee'd into the feeds to the hot water cylinder coil - when the system is set to hot water only, the rads upstairs get hot/warm depending on their distance from the cylinder - think this may be why the rail is not getting hot water flowing to it but, having said that, the old rad the rail replaced used to get hot !?

 

[WHPES]

There must be something stopping the water from getting in and not just a balancing issue. If it were balancing the radiator would still warm up to an extent.

Are your valves full bore valves? Could there be an airlock? Could there be any debris inside the radiator? I once found a lump of polystyrene packaging which had got inside a rad.

 

[Dave H]

Valves - not sure if "full bore" but did change the valves yesterday as the original valves seemed to have a very small opening. Also checked that valves and feed pipe into the rasil clear of PTFE/debris etc. Airlock - the rail bleeds water (no air escapes) and did manage to force a flow into the rail (but stayed cold when heating switched on the following day).
The pipes feeding the rail (at the cylinder end) are only warm to the touch (and not as hot as the feeds into the coil) - used to be hot (both flow and to a lesser extent the return).

 

[payney1974]

If your still getting hot water it must be something simple. Have you tryed tryed turning the other rad thats on the primaries off? If theres a gate valve on the return off the cylinder is does that need adjusting? Last but not least, have you tee'd into flow or return twice?

 

[Dave H]

Hi - thanks for the response - tried turning off all rads except the rail - also tried turning off all rads except the rail and the rad in en-suite (both rail and rad in en-suite are set up to be hot when hot water only switched on). I can't see a gate valve on the cylinder return. No - didn't tee into flow or return twice - just extended the existing feeds to the original rad.

My system is single pipe with gravity fed hot water ( ie there are 2 sets of flow and return pipes attached to the boiler - one set is pumped so assume that it feeds rads and the other unpumped (asssume it feeds the cylinder coil). When the sytem is set to hot water only, both sets of pipes get hot (but don't think the pump is operating on this setting) and the upstairs rads get hot/warm depending on how far away from the boiler feeds they are - downstairs rads stay cold. I don't think this is right - thought that only the hot feed to the coil should be operating on the hot water only setting and that the rads should not be getting hot anywhere in the house ?

Is this right and could it be something to do with the rail not getting hot ?

 

[payney1974]

Hi - thanks for the response - tried turning off all rads except the rail - also tried turning off all rads except the rail and the rad in en-suite (both rail and rad in en-suite are set up to be hot when hot water only switched on). I can't see a gate valve on the cylinder return. No - didn't tee into flow or return twice - just extended the existing feeds to the original rad.

My system is single pipe with gravity fed hot water ( ie there are 2 sets of flow and return pipes attached to the boiler - one set is pumped so assume that it feeds rads and the other unpumped (asssume it feeds the cylinder coil). When the sytem is set to hot water only, both sets of pipes get hot (but don't think the pump is operating on this setting) and the upstairs rads get hot/warm depending on how far away from the boiler feeds they are - downstairs rads stay cold. I don't think this is right - thought that only the hot feed to the coil should be operating on the hot water only setting and that the rads should not be getting hot anywhere in the house ?

Is this right and could it be something to do with the rail not getting hot ?

OK there won't be a gate valve on the return if its 28 mm gravity circs (my bad). If the upstairs rads get warm then you probably need an "anti gravity valve on the flow off the 22mm pipes for you ch. I am stumped as to why the new towel rail won't work if you have just extended the tails, if i was you i would just get the boards up and see how the plumber tee'd those tails into the the 28 mm circs
all those years ago .

 

[Dave H]

Thanks - wondered why the feeds were so big (ie 28mm) - guess that proves it's gravity fed ! I can see the tee connections in the airing cupboard -one on the flow to the coil and the other on the return. It's weird - the old rad used to get hot - suggests it's something to do with the rail or the plumbing to it but checked valves and the plumbing is a straight extension - did use a section of UPVC pipe but can't see that is the problem.

 

[payney1974]

so its teed into the 28mm right by the cylinder? does the pipework rise all the way to the towel rail?

 

[Dave H]

The flow does (but not 100% sure as the UPVC section may have a slight fall) - the return has about a 3-4 inch drop on it's way to the rail (in other words a 3-4 inch rise based on the direction of water flow) - in effect the return does not rise all the way from the tee connection to the rail due to this drop (did this to get the pipe under the floor as the return from the original rad was running along the skirting and the flow was under the floor - guess this is the problem !?

 

[oldplumber]

only a thought if changing your levels does not work, drain down your system and refill via a doc on the ground floor to force all the air out via the bleed off screws in the rads and the feed and expn pipe into the feed and expn vessl in the attic. Air locks can be a bugger to move, worth trying,

 

[Dave H]

Thanks - will try if levels are not the problem.

 

[WHPES]

Let us know how you get on.

 

[migoplumber]

just to check, youve said single pipe system.
do you have a one pipe system, ie the flow and return of said towel radiator are fed from the same pipe. if they are your towel rad could be cold locked, but better you define your single pipe system first !

 

[Dave H]

The rads are fed by a sigle pipe system (ie flow and return at bottom of rad) - the towel rail is actually tee'd into the 28mm flow and return to the hot water cylinder coil - the way I have extended the pipes to the towel rail (to keep them under the floor) has built in a rise (3-4 inches) on the return part of the loop so think this is stopping the gravity fed flow ?

 

[Dave H]

Hi - the levels of the return from the rail (which is tee'd into the return on the water cylinder coil circuit) are the problem (the circuit is gravity fed and the return from the rail has a 3-4inch rise built into it).
I am going to make the hot water cylinder circuit pumped with a couple of motorised valves to switch between the water and water/heating settings on the programmer - should also sort the problem of the upstairs rads getting hot when only water slected at the moment.
Thanks a lot for all your suggestions - especially payney1974 (pinpointing the levels problem)and oldplumber,WHPES and UKPITA !