Thanks doitall. Yes, the bypass valve is on the heating side only. Therefore, I will consider, as you suggest, installing a wireless room sat in the lounge although I understand this may need need some wiring adjustments at the boiler or at the programmer to get it to work. Any suggestions where I might find advice on how to replace a wired stat with a wireless one. Also would it be better to buy a combined stat/ programmer and disconnect both the existing room stat and airing cupboard programmer?
TRVs versus Room Thermostat
- Thread starter wbjimmy
- Start date
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You can get advice from the guys on here.
The existing stat must connect in the wiring center with the 3 port valve etc so if you went for an RF stat the receiver should be able to go somewhere handy to that.
Perhaps a pic showing the wires/connections.
Look at the Honeywell DT 92e
The existing stat must connect in the wiring center with the 3 port valve etc so if you went for an RF stat the receiver should be able to go somewhere handy to that.
Perhaps a pic showing the wires/connections.
Look at the Honeywell DT 92e
How about ...
Take the head off the TRV in the hall, and set the stat for a "normal" setting. You need to ensure that the lockshield is set right as you need the hall to be the slowest room to heat. The stat in the hall will generally keep the system running & turn it off when "the house" is warm.
Separately to this, the TRVs in the other rooms will alter their relative temperatures. So when SWMBO wants the lounge warm, turning up the TRV will achieve that without bu**ering everything up.
There is always some interaction - changing TRV settings will alter both the flow/pressure in the system (thus altering the flow through the non-TRV rad), and the change in room temperatures will alter the thermal balance of the house.
I would suggest "just try that" - it's a zero cost option, and I think you'll find it will work. It works for us.
PS - your plumber is a numpty.
Not only does his advice fly in the face of reason, the setup he's told you to use doesn't comply with building regs. Building regs are very clear that there must be an interlock in the system to stop the boiler doing exactly what your plumber has told you to have it doing. It's inefficient in two ways - not only because it means the boiler running all the time, but also because it virtually guarantees that you'll spend a lot of time out of condensing mode (ie running the boiler at a low efficiency).
The regs don't specify that the interlock has to be a room thermostat though. I'm sure there must be other ways to do it ?
One that comes to mind might be a flow sensor in the bypass - when the bypass is flowing (above some minimal rate ?) then shut down the boiler but let the pump keep running. This would effectively use the TRVs as (collectively) a proxy for a "whole house" stat. Once the rooms cool off a bit and the TRVs open a little, the boiler can fire up again.
An alternative might be to sense the flow rate and modulate the boiler flow temperature to suit - a bit like weather comp but using the TRVs to (collectively) sense heat demand.
Take the head off the TRV in the hall, and set the stat for a "normal" setting. You need to ensure that the lockshield is set right as you need the hall to be the slowest room to heat. The stat in the hall will generally keep the system running & turn it off when "the house" is warm.
Separately to this, the TRVs in the other rooms will alter their relative temperatures. So when SWMBO wants the lounge warm, turning up the TRV will achieve that without bu**ering everything up.
There is always some interaction - changing TRV settings will alter both the flow/pressure in the system (thus altering the flow through the non-TRV rad), and the change in room temperatures will alter the thermal balance of the house.
I would suggest "just try that" - it's a zero cost option, and I think you'll find it will work. It works for us.
PS - your plumber is a numpty.
Not only does his advice fly in the face of reason, the setup he's told you to use doesn't comply with building regs. Building regs are very clear that there must be an interlock in the system to stop the boiler doing exactly what your plumber has told you to have it doing. It's inefficient in two ways - not only because it means the boiler running all the time, but also because it virtually guarantees that you'll spend a lot of time out of condensing mode (ie running the boiler at a low efficiency).
The regs don't specify that the interlock has to be a room thermostat though. I'm sure there must be other ways to do it ?
One that comes to mind might be a flow sensor in the bypass - when the bypass is flowing (above some minimal rate ?) then shut down the boiler but let the pump keep running. This would effectively use the TRVs as (collectively) a proxy for a "whole house" stat. Once the rooms cool off a bit and the TRVs open a little, the boiler can fire up again.
An alternative might be to sense the flow rate and modulate the boiler flow temperature to suit - a bit like weather comp but using the TRVs to (collectively) sense heat demand.
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OK I've taken a look at the wiring set up in my existing controls. The room stat ( Drayton Digistat 30002) is situated in the downstairs hall and has a single 4 core wire input - Red,Blue, Yellow and Earth. Upstairs in the airing cupboard is a 7 day HW/CH programmer ( Drayton LP522) connecting to a junction box. I haven't removed the cover of the programmer but the junction box below it contains a maze of coloured wires including live input from a fused box. Two obvious wires lead respectively to the hot water cylinder stat and a three way valve. Instead of rewriting the programmer, would it be possible to simply replace the existing hall stat with a wireless receiver using the existing wiring? What makes me uncertain about doing this is the fact that I understand the Drayton and Honeywell RF receivers have 4 terminals and I only have Red, Blue and Yellow wires feeding the current stat in the hall.
It's a piece of cake to wire the Honeywell DT 92E into what is existing.
Assuming Red is L, Yellow is 3 and Blue is N, you need to confirm.
In the receiver Blue would be N, Red would be L, Yellow would be B, and you link L to A.
Assuming Red is L, Yellow is 3 and Blue is N, you need to confirm.
In the receiver Blue would be N, Red would be L, Yellow would be B, and you link L to A.
Sorry but I really can't understand why you are so determined to spend money and alter the system before trying zero cost/zero disturbance options.
Really, my mother is prone to "isn't it cold" statements while we're perfectly fine, and having a wall stat in the hall, no TRVs on the hall rads, and TRVs everywhere else seems to work fine. It might not be perfect, but it does work - and you do have to adjust the hall rads so the hall doesn't heat up really quickly and turn the system off before the other rooms are warm.
Really, my mother is prone to "isn't it cold" statements while we're perfectly fine, and having a wall stat in the hall, no TRVs on the hall rads, and TRVs everywhere else seems to work fine. It might not be perfect, but it does work - and you do have to adjust the hall rads so the hall doesn't heat up really quickly and turn the system off before the other rooms are warm.
Zero disturbance SimonH2, the receiver can go where the existing room stat is if you like. you then have the perfect solution for around £70.00. Heck you can even take the stat from room to room, set the lounge at 21c and take it to bed with you set at say 17c.
Well that's £70 - which in my book is more than zero. And changing the box on the wall, which again in my book is more than zero work.
If you use a wireless stat, then you're back to square one when SWMBO decides to take it to another room where the rad TRV is turned down lower than she wants and tries to get the room hot with the wireless room stat.
I'm not saying to not do it, just that I find it strange when people insist on spending money and altering (even if only slightly) their systems before they've tried the option that will only take a couple of minutes to set up and will cost nothing at all. OK, it might not work for them, but then they can undo the change in 10s by refitting the TRV head - or it might work for them in which case they've save the £70 on a wireless stat and the 10 minutes to fit the receiver, and the lifetime trying to educate "other half" how to use it properly
Just my opinion, but a stat that can be moved from room to room will be a disaster unless the house is only occupied by rational people who understand how a stat works and how to make it work where there's a TRV. The OP's other half doesn't sound like such a person from the description.
If you use a wireless stat, then you're back to square one when SWMBO decides to take it to another room where the rad TRV is turned down lower than she wants and tries to get the room hot with the wireless room stat.
I'm not saying to not do it, just that I find it strange when people insist on spending money and altering (even if only slightly) their systems before they've tried the option that will only take a couple of minutes to set up and will cost nothing at all. OK, it might not work for them, but then they can undo the change in 10s by refitting the TRV head - or it might work for them in which case they've save the £70 on a wireless stat and the 10 minutes to fit the receiver, and the lifetime trying to educate "other half" how to use it properly
Just my opinion, but a stat that can be moved from room to room will be a disaster unless the house is only occupied by rational people who understand how a stat works and how to make it work where there's a TRV. The OP's other half doesn't sound like such a person from the description.
That's fine for a wired stat, but not for a wireless if the existing programmer is retained.
The relay needs a permanent L and N for power, a separate input to terminal A from the programmer CH ON and a switched live out from terminal B. That's four wires, and I'm sure you would want me to suggest the OP uses the earth wire as a voltage carrying conductor.
Much safer to mount the relay near the wiring centre and run a four core cable to it.
Just buy the cheapest thermostat you can find and fix it to the wall.
Never underestimate the power of the placebo.
Never underestimate the power of the placebo.
If the BDR91 is receiving power from CH ON it is only alive when CH ON has voltage on it, i.e when the timer says it should be on. The control unit and the BDR91 communicate regularly to make sure both are alive. If the BDR91 has been off, it has to go through a "handshaking" exercise with the control unit to make sure they can still communicate every time the programmer turns heating on.
Much safer to have a permanent supply to the relay so this doesn't happen.
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