Bi-directional TRVs

[grifter]

I know the bi-directional trvs can go on either flow or return pipes but are they reliable and if possible do any of you always just fit on the flow pipe anyway?

 

[Johntheo5]

I've allways installed mine on the return as I feel the sensing heads are measuring a more representative room temperature, mine last ~ 6 to 8 years,

 

[Mottie]

They might be bi-directional but what do they identify as?………

 

[ericmark]

I found on the return, setting the lock shield is harder than on the feed. It could have been the make of the head, I find the speed that the TRV closes means the whole radiator could get hot before the valve had closed, so larger hysteresis on return to on feed.

 

[grifter]

They might be bi-directional but what do they identify as?………

Horizontal and vertical lol

 

[Johntheo5]

Horizontal and vertical lol

I installed 7 out of 8 of mine horizontally, (on the return.). This particular one replaced one which lasted almost 7 years but wasn't a EPH which I now use.

 

[Johntheo5]

I found on the return, setting the lock shield is harder than on the feed. It could have been the make of the head, I find the speed that the TRV closes means the whole radiator could get hot before the valve had closed, so larger hysteresis on return to on feed.

TRVs, or at least the ones I use have a very small hysteresis but are very slow acting, I think tests I did on a new TRV just by moving it from one position to another with a temperature difference of 1.0/2.0C took around 30 minutes to go fully open/shut which I find is a advantage for me.
I have (oil fired boiler) with a digital roomstat that controls a combined dining room & lounge with two non TRVd rads and where we spend 90% of the time, the (non TPI) digital stat gives excellent control of these two rooms to within 0.2/0.3C of SP after a few initial over/under shoots after start up, heating enabled for 16 hrs/day, the boiler, depending on OAT might be switched off (by the stat) for a max of 15/20 mins with a 10 min on time. The remainingTRVd rad rooms seem to hold their room temps reasonably well, when the boiler restarts even after a 15 minute off period, the rads do not get red hot, the just seem to heat up to around their original controlled temperature possibly helped by the fact that, unlike a gas fired boiler, there is no pump overrun on my oil fired boiler?

 

[ericmark]

The problem I had was mother's house, rather a large radiator for size of room, heating turned on, radiator got hot heating turned off, but radiator still heating the room.

The TRV does display both current and target, so that made setting up easier, I slowly closed the lock shield valve, until current never exceeded target, and once set, the radiator only got warm, not stinking hot, and each room was spot on what had been set. This was with a gas modulating boiler, so moving in here, I thought I know how to set up radiators, but no with an oil on/off boiler the TRV does not work as well, it still works, but not like they did with a modulating boiler.

The Energenie TRV head says it has two sensors one for water and one for air, so it can compensate for heat from radiator, the eQ-3 heads say how they detect open windows, and the Wiser say they work out how long to heat the room. Can't remember what Kasa said, but it does seem they are all different. Only the Wiser will actually turn on the boiler.

It would be interesting to compare TRV heads, I think the bases are very similar, but all my TRV heads exercise the bases once a week, and it takes between 3.5 and 5 minutes to fully open, then fully close, then return to the setting. So don't want radiator to heat up too much in that time.

the Kasa and Wiser both give reports, the Wiser one sorry the heating was not being used, however it does show any hysteresis, the Energenie and e-Q3 do not show a graph, and e-Q3 only shows target not current. However, they cost £15 each in 2019 with bluetooth so what do you expect for that price.

What is annoying is having to bin the TRV heads which come with the valve, they are rather useless, marked *123456 what is the good in that?

There can be some debate on if one needs the TRV linked, I don't think they all need to be linked, I have just one linked. Main house three devices can turn on heating, one TRV and two wall thermostats. But last house one thermostat was ample, it does depend on the house design.

 

[Johntheo5]

Are these similar to the Evohome system? which can sometimes use the TRV body (valve), can they control their own individual room temps without reporting back to the base?.
The Evohome I think can't do this as each one reports its temperature and position back every 4 minutes and the controller then decides on the valve position etc, the attachment below shows some understanding of the system.