Towel Rail Issue

[callum84]

Hi ,

I have an issue with an en suite towel rail hopefully someone can assist with. Its a combi system, boiler downstairs main living area on first floor. The property is circa 6 years old, serviced every year.

Intermittently the towel rail will not heat up, it gets luke warm like it is trying to. When i turn the TRVs on the other radiators to 0 the en suite one then heats up, usually with some gargling sounds. At other times it goes on no problem via the schedule.

The feed coming through the wall to the lockshield valve (flow) is always hot, it seems from the locksheld valve it then goes cold.

Similarly, if i have the en suite TRV off or at 0 and put the heating on, the rest of the rads heat up and the en suite one goes luke warm with hotter areas at the top, even though the TRV is off. If i then turn the TRV on, the towel rail usually heats up.

The pipework runs from GF to FF loft area then, drops down to the rads / towel rails on the FF.

A plumber has suggested fitting AAVs at the high point on the flow and return on the towel rail pipework however im not sure on this as will mean i continually have to review the boiler pressure and top up when necessary.

From my limited knowledge i assume it will also create weak points in the system that could fail. Ive heard AAVs on heating pipework can be prone to failure or problems.

When the same situation happened circa 3 months ago, the plumber pulled water out of the bleed valve on the towel rail which seemed to have air present in it, this seemed to solve the issue. The towel rail TRV pin at the time he pushed with the back of a spanner and it seemed to 'click' into place which i though was odd as if it had been dislodged some how. The water did look to be quite dirty - for reference the system does have an inhibitor in it.

As the issue can be 'controlled' / effected by the TRV on the towel rail and the other rads Im hoping its not a pipework blockage. Balancing was an area ive been looking into also.

Im not sure whether changing the towel rail valves would be the first option and perhaps a chemical clean of the system.

I am also considering installing a magnetic filter on the system.

If anyone had any comment, suggestions or similar situations it would be greatly appreciated,

BR
CR

 

[ericmark]

Each central heating system is different, however I had problems with my late mothers, and what I found was it had never been commissioned, all the lock shield valves were wide open.

Reading the instructions, it says how to use the differential thermometer to set the lock shield valves. The problem was I could not find my differential thermometer, so I needed another method.

I realised that the time it takes to heat the radiator is important, TRV's are rather slow acting, so if the radiator heats up too quickly, then it will over shoot. So I set about trying to set lock shield without any special tools, the method was starting closest to the boiler, closing the lock shield waiting for pipes to cool, then open 1/4 turn at a time until the feed pipe showed some heat, then move to the next radiator.

It worked, of sorts, but still not as I would like, so I got an electronic TRV head, this showed target and current temperatures on the PC.

Now the setting was easier, after the heating had been running for a couple of hours, if the target was below current closed the lock shield a tad, and vice versa. Ensuring of course the wall thermostat was set high, so all control was from the TRV heads.

I was surprised how well the electronic TRV's worked, rooms once set were within 0.5 degrees of setting, however did find the built-in anti-hysteresis was a bit OTT, in the morning 7 am set to 20°C and 10 am still not quite at 20°C, so would set to 22°C at 7 am and 20°C at 8 am, and this worked A1. It does seem some makes are better than others.

But moved to this house with on/off boiler, rather than the modulating boiler at late mothers house, tried the same method, and is simply did not work, maybe due to micro bore, but found all lock shield valves need to be wide open, I suppect there is a by-pass valve I have not yet found, however it does show it does not work with all homes.

The biggest problem is setting the wall thermostat, again we are told, it should be in a room normally kept cool, that makes sence so as warm weather arives it turns the boiler off before all rooms are at a heat where latter in the day they will be too hot, also should be on the lower floor, again yes heat raises, with no alternative heating, including sun through windows, and with no outside doors, and a room which is used all the time. My house there is no such room, and what it did not say, was a room that cools faster than all other rooms, otherwise as the house cools all other rooms will be too cold before the heating kicks in again.

Without a wall thermostat the boiler would run all summer, so we do need one, but most homes we need some compromise, mothers house we used the hall, and had the hall radiator TRV set about a degree lower than the wall thermostat, since wall thermostat is a bit higher, it worked well, only turning off boiler on warm days.

Best is having TRV heads and wall thermostat linked. As first there was no TRV in the hall, no amount of adjusting the lock shield worked, as open the front door and hall would cool rapid, and if lock shield open enough to reheat hall after door opened then it would then turn off heating in rest of house, biggest single improvement to heating was to add a TRV in the hall.

Out of interest, why asking this in the summer, my boiler has not run for a month?

 

[callum84]

Hi, thanks for your response, asking in the summer so it can be resolved hopefully by the time winter comes and i can have a fully functional healthy system i can rely on.

 

[ericmark]

I now have 9 electronic TRV heads, some rooms are not used every day, and the electronic heads allow me to select which rooms are heated. The idea was to have them linked to the wall thermostat, so if any room was calling for heat, the boiler would run. However, when I finally got the Nest Gen 3 wall thermostat claimed to work with my Energenie MiHome TRV heads, Nest had been taken over by Google, and they had removed support for the heads, so after all the careful planning, my heads still can't call for heat.

In my house the problem is the wall thermostat is in the hall, and the hall simply cools too slowly, one can adjust the lock shield, to adjust the heating speed, but there is no way to adjust cooling speed. I have done nothing to the central heating control, as I have been changing the double glazing, which may change things.

The TRV head is the main thing in the controlling of the central heating, and reports seem to say the Drayton Wiser is the best as it remembers how long it takes to heat the room, so you set the time you want to use the room. I have four TRV's still with mechanical heads, so likely if I get the Wiser system, I will move some TRV heads around and fit wiser ones in the key rooms.

What I can't really understand is why we have a wall thermostat? The idea of a panel to control each TRV seems a much better idea,

which is what the Honeywell EvoHome does. But it is not cheap, and it is easy to spend more on the central heating control, than it will save one.

 

[callum84]

Appreciate the info and sounds like your system is great. Having reviewed my problem, any specific ideas what the issue could be?

 

[Deleted member 267285]

I would look at balancing and air locks before anything else. If it eventually heats up with others off this points more towards balancing. If you don’t want auto air vents maybe consider manual air vents?

 

[callum84]

Thanks for your reply CBW, the AAVs would be located in the loft , in an awkward area, also i was hearing these can be prone to failure and there was differing information on whether should be used on a sealed combi system, having to continually top up the boiler wouldnt be ideal . Its pretty instant the towel rail heats up when 3 or so TRVs in other rooms are switched off, when they are switched back on the towel rail remains hot / working. Appreciate the input thanks

 

[ericmark]

I also think balancing, that's why I said how I went about it.