Worcester 27CDi and Honeywell DT92E Thermostat

[EddieCraw]

Hello folks, nice to find a forum with some activity on it!

I've recently wired the DT92e base to my system for wireless control as such:-

Boiler shows Lr Ls Ns - N L Eth for stat connection of which the N and L are supplying the boiler with power.

The Dt92e base shows connections of N L L - A B C

After finding wiring advice on a few sites, I've wired it:-

Boiler - Stat
Ns - N
Ls - L (1st L)
Lr - B (open switch symbl)

Then made connecting links on the stat base from L1 to L2, then L2 to A

Everything seems to be working fine. The wireless stat only fires the boiler when it is in timed mode or on permanently which is good, and if I reduce the stat temp dramatically, the boiler stays off until the room finds the level again then goes through its heating cycles to maintain the new temp. So all looks ok.

(I think the whole point of listing my connections is for reassurance more than anything! ) I'm sure something is slightly wrong....

My main question is the settings.

Am i right in seeing that the boiler should always be set at maximum for the heating, and the rad TRV set to max in the room with stat? If so, is this to reach the stat temp as soon as possible to switch it off quicker?

As a result I'm finding the other radiators glowing hot and the boiler running at 30'C in order to achieve a room temp of 21'C, which is making the house unbearable. (The stat is head height so reading in the right area). Even some TRV's are set to 4 but the rads are blistering hot!!!

If I set my boiler slightly lower, it runs cooler but then takes longer to get to the stats temperature in that room, and the other rads are still glowing.

So what's the general concensus regarding controls?

Turn the boiler down slightly and let it take longer to reach room temp at the stat, or boiler full belt to reach temp quicker, and make sure the TRV's on all radiators are working properly?

I'm going to replace my TRV's on some rads because I think they could be faulty but will check the pins are still moving.

Thanks for your patience reading this lot guys....
Have I wired it right, and what settings do others recommend?

Any advice or opinions welcome.

Cheers, Eddie.

 

[stem]

Hello EddieCraw and welcome to the forum.

You only mention the thermostat, not any time control, so I assume that there is a programmer built into your boiler.

If there is, it's possible that the mains supply you are using for your receiver (LS from the boiler) may not be permanent. It may go off when the boiler's programmer / time switch goes off. If this is the case, then you will need to have a separate live supply for the DT92E.

So you should connect the L & N terminals at the boiler (ST10 terminals) to one of the L terminals and the N terminal accordingly at the DT92E.

Do not link the two L terminals at the DT92E. (They are linked internally inside the DT92E anyway and are only there for convenience, should you need to provide a link between the L and A terminal)

Remove the link between L and A

The A terminal at the DT92E should then be connected to LS (live supply from the boiler) and the B terminal at the DT92E should be connected to the LR (live return to the boiler)

Do not link L2 and A. Here is the diagram from the DT92E manual marked accordingly.

Untitled

• stem
• 18 Feb 2013
• 1

If LS is a permanent live, then you can ignore the above. You are OK as you are.

As the room thermostat turns off the heat to all of the radiators, then its location is critical if it is to work effectively.

1. It should be in a room that does not heat up more quickly than any of the others. Preferably the last room to get warm, so that the TRV's in the other rooms have already started to close off.

2. It should not be in a room subject to other heat sources (fireplace, sunlight, cooking appliances etc.,)

3. Preferably there should not be a TRV fitted to the radiator in the room containing the room thermostat at all, but if one is fitted it should be on MAX. The reason is simple. If the TRV was set to the same temperature, or lower than the room stat in the same room, the TRV would turn off the radiator thus preventing it getting any warmer and so the room stat would never go off, thereby rendering it useless.

4. Regarding the boiler thermostat setting, this depends on many variables; the type of boiler, design and insulation of your home, sizes of radiators etc., Generally condensing boilers are more efficient with a lower return water temperature, so setting the boiler at the lowest setting possible, but yet high enough to get your home warm and comfortable in a reasonable time, is probably the best suggestion. You can adjust this according to the weather so in milder weather run it at a lower temperature than you do when it's freezing outside.

 

[D_Hailsham]

Your wiring is OK, though there is no need to link L1 and L2; they are already linked internally.

Am i right in seeing that the boiler should always be set at maximum for the heating, and the rad TRV set to max in the room with stat? If so, is this to reach the stat temp as soon as possible to switch it off quicker?

TRV is set to max in room with wall stat so it does not prevent wall stat turning boiler off.

In general the boiler stat should be set to max, so the house heats up quicker. The room stat has overall control, so it may turn the boiler off before the boiler has reached the temperature set on the boiler thermostat. This will be particularly true in milder weather.

I'm finding the other radiators glowing hot and the boiler running at 30'C in order to achieve a room temp of 21'C, which is making the house unbearable.

I would have expected the boiler stat to be set to about 75C, not 30C.

Even some TRV's are set to 4 but the rads are blistering hot!!!

The TRVs are probably stuck open. Remove the control head (no water will escape) and try pushing the exposed pin down. It should go down easily and spring up when released.

 

[EddieCraw]

Thanks Stem and D-H for your informative replies. Good stuff and very much appreciated.

Stem, my worcester has a built in timer module with the on/off pins which runs perfectly regardless of the boiler being on or off. Therefore, when the timer switches off, the boiler is off and the wireless stat just calls for heat which is ignored. (Correctly).

On the wiring front, I take it (as D-H says) the wiring is fine, but I still need to remove the links from L1 to L2, and from L2 to A? As that function is inbuilt in the faceplate of the receiver.

But leave it wired :-

Ns - N
Ls - L1
Lr - B

The wiring diagrams from Honeywell show 2 versions which don't quite match the worcester boiler diagrams, but I've followed the first one 'creatively'....

I lowered the boiler to just below the max range and it now runs at 75'F(23'C). It takes a while longer to reach the 21'C in the room with the wall stat but at least it's not straining at the leash to get the house hot immediately!

Having checked my TRV heads, I think only one is working correctly out of 6! That would explain the rads glowing hot in the rest of the house!

The push plate in the heads is slack on most and couldn't push a fart out! Only one is rock solid and clearly reaches/pushes the pin. As for the pins, they all push and release quite easily so not stuck on or off.

My next question is to change the TRV heads....

Looks like I've got pre-war Drayton TRV2's which are like hens teeth!

Are there any equivalents that will match the 30mm thread, as I believe all manufacturers are different and won't interchange. Hopefully one will!
Otherwise it's complete new valves on 6 rads.

Any ideas, and thanks again guys.

 

[ianmcd]

you do realise that even if your TRVs are working correctly that no matter what setting you have them at they will always all be at the same temperature if calling for heat ? the TRV is operated by the temperature of the room and not the radiator so the radiator is either on or off and the temp of the radiator is decided by the boiler thermostat not the TRV when calling for heat

 

[stem]

Stem, my worcester has a built in timer module with the on/off pins which runs perfectly regardless of the boiler being on or off. Therefore, when the timer switches off, the boiler is off and the wireless stat just calls for heat which is ignored. (Correctly).

I know it's working, but my question was, does the power to the DT92E go off when the boiler timeswitch goes off? If it does, then you will need to install a separate permanent live supply and then remove link L2 to A. The manufacturers 'spec sheet' states

"Relay Box Power supply -230 V, 50…60Hz 1VA max. Note –requires permanent mains power supply"

(You can download a copy of the 'spec sheet' here. See the table on page 2 for the info pasted above.)

It may be working OK, but switching it on and off may cause reliability or stability issues, or even loss of memory. For some reason the manufacturer states that it should be permanently powered.

If the DT92E doesn't go off when the boiler time switch does, then all is well and the following apply.

but I still need to remove the links from L1 to L2, .

I doesn't matter. You can leave it if you like, it's not doing any harm, but it's not necessary as they are linked already internally.

and from L2 to A?

If you are not going to run a separate L & N supply, you need to leave that one in place.

 

[D_Hailsham]

On the wiring front, I take it (as D-H says) the wiring is fine, but I still need to remove the links from L1 to L2, and from L2 to A?

It's only the link between L1 and L2 which you can remove. You still need the link between L1, or L2, and A

The Ls terminal on the boiler is live so long as there is power to the boiler's L terminal. Ls and Ns are there to supply power to an external programmer or thermostat.

I don't think you can get spares for TRV2 any more, but send an email to [email protected] ; they are normally very helpful.

 

[EddieCraw]

Thanks again Stem/D-H, will remove the offending L1-L2 link and leave well alone from then. The receiver stays powered after timer goes off, so it must have a perm live feed.

Will try the link for Drayton spares too so cheers D-H.

Ianmcd, as for the TRV temps on each rad, I understand that if my boiler is set to 80'F then it will pump 80'F to each rad. (Until the wall stat reaches set temp then switches off the boiler, then cycles). But surely the TRV will only allow each rad to get hot enough until each TRV reaches temp with the water/gel sensor in the head? Otherwise, whats the point of the markings * - 1-6 on the head?

All my TRV's (except one), are knackered. All set to 2 (to test them, except room with wall stat) but rads still glowing hot. As I said earlier, the push plates are that slack, they clearly aren't pushing the pins into the valves. When they are working/new, the TRV will reduce the amount of hot water getting through and the rads will only just get warm.

Maybe I've not quite understood how they work, I just know mine aren't!

But thanks again for the replies, you've sorted me out and cleared a few things.

Cheers guys.

Eddie.

 

[ianmcd]

No Eddie I thought that was how you thought it worked but it is not,As you say they have markings say 1-6 so lets say setting 2 is 15C the TRv will let the water through to the rad at what ever temp the boiler stat is set at untill the ROOM reaches 15C then the valve will stop the water entering the radiator and the rad will cool untill the room drops in temperature and opens up the valve again, the valve can only open and shut it cant heat up or cool down a rad it is operated by the temp of the room