Replacing Potterton EP2002 and BG RS2 with Hive Active Heating and Hot Water thermostat

[HarrySvo]

I am looking to replace an old Potterton EP2002 programmer and a BG RS2 thermostat with the Hive Active Heating and Hot Water thermostat. My heating system is a gravity-fed Main HE system boiler.

From what I gather, I need to disconnect the L-5 link, relocate the remaining 5 wire to the L terminal on the Hive backplate, and transfer the N, L, 1, 3, and 4 wires to the new backplate unchanged. Additionally, I should connect the D wire to a connector. Is my understanding correct?

I would greatly appreciate advice on this process, as well as assistance in identifying the L and SL wires from the PS2 thermostat in the junction box located in my airing cupboard. My intention is to remove the PS2 thermostat and install the Hive thermostat in its place.
Thanks in advance.

 

[stem]

From what I gather, I need to disconnect the L-5 link, relocate the remaining 5 wire to the L terminal on the Hive backplate, and transfer the N, L, 1, 3, and 4 wires to the new backplate unchanged. Additionally, I should connect the D wire to a connector. Is my understanding correct?

Yes, that's correct.

Regarding the old room thermostat, the yellow and red live switching wires should be joined together to complete the circuit and the blue neutral isolated. It can be done at the thermostat end with a junction box, [Easiest for DIY] or at its origin, in which case you would have to trace the cable back to identify where it originates from. And as far as I can see there doesn't appear a cable resembling the one to the thermostat entering the wiring centre. So, it may go somewhere else. With a system having only pumped heating it may go to the pump maybe? Unfortunately there are umpteen ways of wiring heating systems up, depending on the connected components, the personal preferences of the installer, if the system has been changed in the past, and the layout of your home. etc.,

The current wiring installation is very poor, with all of the exposed copper at the terminals there is a rick of creating a short circuit, but I'm sure you will fix that during the work.

Also, there shouldn't be exposed coloured wires visible outside of any enclosures, and the cables should be physically secured either with cable clamps, clips, or enclosing them in trunking etc., I've attended several homes where someone had caught the cables with an object and pulled the wires out of the terminals. And when that happens it can be a big job to work out where they've come from.

Finally, if your system does have pumped central heating only with gravity circulation of the hot water, don't forget to set the Hive to gravity mode. I describe it carefully as many householders get confused between 'gravity circulation' of the hot water heating and a storage tank in the loft that keeps the heating system filled with water via gravity, which is something else entirely.

If it is gravity circulation, your installation is slightly unusual as it's rare [but not unknown] to find a gravity hot water system that is fitted with a cylinder thermostat.

 

[HarrySvo]

Yes, that's correct.

Regarding the old room thermostat, the yellow and red live switching wires should be joined together to complete the circuit and the blue neutral isolated. It can be done at the thermostat end with a junction box, [Easiest for DIY] or at its origin, in which case you would have to trace the cable back to identify where it originates from. And as far as I can see there doesn't appear a cable resembling the one to the thermostat entering the wiring centre. So, it may go somewhere else. With a system having only pumped heating it may go to the pump maybe? Unfortunately there are umpteen ways of wiring heating systems up, depending on the connected components, the personal preferences of the installer, if the system has been changed in the past, and the layout of your home. etc.,

Thank you very much for the clarification and for reminding me to set up the gravity mode.

I have successfully installed the Hive system, including the hub, receiver, and thermostat. All the tests outlined in the installation instructions went smoothly. The system is operational, and I can now control it through the app. The receiver displays a blue light, indicating it's in gravity-fed mode.

However, I've noticed an issue. When I set the heating to the desired temperature, both the green heating light and the hot water green light on the receiver illuminate. However, the hot water remains switched off in both the app and at the thermostat. Despite this, the boiler continues to heat the water in the radiators, and my hot water storage tank fills up with hot water within a few hours, while the temperature in the house reached the target one.

If I turn off the heating and then switch on the hot water via the app or thermostat, only the hot water indicator on the receiver becomes active.

I'm concerned that I may have made an error in the wiring. Alternatively, could it be possible that my system isn't gravity-fed as I had assumed? I have a hot water cylinder, a loft tank and have very low pressure at the hot water tap on the first floor (slightly better downstairs). Additionally, there is a central heating pump (Grandfos UPS 15-50x18) and a Drayton mid-position actuator in the airing cupboard.

Regarding the wiring, I followed your advice and connected the red and yellow wires from my old thermostat while isolating the blue neutral. Do I need to locate the other end of these red and yellow wires in a junction box somewhere to either remove them from the box or join them?
And I will definitely sort out the cables in the airing cupboard as you pointed out.

Thank you for your assistance.

 

[stem]

It has a 3-port motorised valve so it is fully pumped not gravity. From the pump the water is directed via the valve to either HW or CH, or both.

My heating system is a gravity-fed Main HE system boiler.

It might be 'gravity fed' but it isn't 'gravity circulation'. So Return the Hive to the fully pumped setting. The gravity setting automatically switches the HW on whenever the CH is on to get Hive working on ancient systems without motorised valves.

Unfortunately Hive incorrectly use the term 'Gravity Fed' in their instructions, so folks think they are referring to the tank in the loft that feeds the heating system. [Feed & Expansion Tank] The term they should use is 'Gravity Circulation'. You are not alone, It confuses many people.

 

[HarrySvo]

Unfortunately Hive incorrectly use the term 'Gravity Fed' in their instructions, so folks think they are referring to the tank in the loft that feeds the heating system. [Feed & Expansion Tank] The term they should use is 'Gravity Circulation'. You are not alone, It confuses many people.

Thanks for explaining this. So back to the default settings and the system works fine now (however I miss the blue light - it was so cute ). Thanks again.

A quick question if you don't mind just for broadening my understanding. "Fully pumped" means that the boiler pumps the heated water both into the hot water circulation and heating system? Or just the hot water? What does my Grandfos pump in the airing cupboard do?

 

[stem]

You have what is known as a Y-Plan system with a three port or mid position motorised valve. There is usually only one pump generally located in the airing cupboard as per your photo.

The very old systems [40 years+] that were installed without motorised valves worked by simply switching the boiler 'on' when hot water only was required. The the water then circulated slowly around the hot water cylinder and boiler using 'gravity circulation' in that warm water is less dense so that it rises and cooler water more dense so it falls. Then when central heating was required the pump was started as well, but the hot water also had to remain on to keep the boiler running. Hence the way that the Hive worked when you selected 'Gravity Fed and Part Pumped Systems'.

 

[HarrySvo]

You have what is known as a Y-Plan system with a three port or mid position motorised valve. There is usually only one pump generally located in the airing cupboard as per your photo.

Thank you, that's much clearer now. Previously, I was under the impression that the hot water and heating operated through separate water circuits. However, it seems I was mistaken, and the same water flows through the boiler to either the radiators or the storage tanks, or both simultaneously. Is my understanding correct?

I appreciate your time in clarifying this for me.

On another note, I have a complaint regarding the Hive system. They only allow for 15-minute intervals when scheduling hot water heating. This means I can only program it for increments of 15, 30 minutes, and so on. With the previous Potterton system, I could set the timer for 20 or 25 minutes (twice a day - morning and evening), which usually provided sufficient hot water for two people in my household to take showers and wash dishes. Occasionally, I would need to boost it. However, with Hive, I find myself having to run my boiler for longer periods, which contradicts their claim of saving money. Their lack of flexibility with these 15-minute steps is quite frustrating. Probably I should leave a feedback on their site.

 

[stem]

Thank you, that's much clearer now. Previously, I was under the impression that the hot water and heating operated through separate water circuits. However, it seems I was mistaken, and the same water flows through the boiler to either the radiators or the storage tanks, or both simultaneously. Is my understanding correct?

Yes, it is now

Provided that by storage tanks you mean hot water cylinder and not the cold water tank/s in the loft, which are only there to keep the system filled with water.

On another note, I have a complaint regarding the Hive system. They only allow for 15-minute intervals when scheduling hot water heating. I find myself having to run my boiler for longer periods, which contradicts their claim of saving money. Their lack of flexibility with these 15-minute steps is quite frustrating. Probably I should leave a feedback on their site.

In reality it shouldn't make any difference. Once the hot water cylinder is up to the correct temperature as selected by you on its thermostat....

.....the thermostat will make the motorised valve close off the hot water anyway and also shut the boiler down (unless central heating is still running) This happens even if the hot water is still set to be 'on' at the Hive. It's important that the hot water is heated up properly to avoid the risk associated with legionella.

But looking at your photo, I don't see any insulation on your hot water cylinder, so this will keep the boiler running to make up the massive heat losses. The idea is the boiler heats the cylinder up, the cylinder thermostat shuts the water heating down when the water is hot and the insulation keeps it hot until you use it. The newer hot water cylinders that come with foam insulation are also very much more efficient at retaining heat than the old tie on cylinder jackets.

Many people leave the hot water 'on' at the programmer all day and leave it to the cylinder thermostat to control it. That way if someone has a bath or shower the boiler will fire up and reheat the hot water again, the rest of the time it will be off.

 

[HarrySvo]

But looking at your photo, I don't see any insulation on your hot water cylinder, so this will keep the boiler running to make up the massive heat losses. The idea is the boiler heats the cylinder up, the cylinder thermostat shuts the water heating down when the water is hot and the insulation keeps it hot until you use it. The newer hot water cylinders that come with foam insulation are also very much more efficient at retaining heat than the old tie on cylinder jackets.

Many people leave the hot water 'on' at the programmer all day and leave it to the cylinder thermostat to control it. That way if someone has a bath or shower the boiler will fire up and reheat the hot water again, the rest of the time it will be off.

Thanks again for the explanation. I will try this approach then and will see how it goes with my gas bills.
There is some insulation (4 soft blankets in red plastic cover which I guess you call "tie on cylinder jackets") which I pushed at one side to make photos.
By the way what is recommended temperature of the hot water in the cylinder?

 

[stem]

Even if they are fitted properly, [There shouldn't be any of the copper cylinder visible through gaps] loose jackets are only about as half as good at retaining heat as the foam insulated cylinders. It's a good idea to insulate the hot pipes too. The more heat you lose the more gas you use. (or oil etc,) In the winter perhaps that's not too much of a problem because any heat that escapes will help heat the house.

In the summer though heat lost is wasted.. A fully heated cylinder if the water isn't used should stay hot for a couple of days, and the airing cupboard should only be very slightly warmer than the room outside.

Legionella bacteria can multiply at temperatures between 20°C and 45°C. So above 50°C is a minimum requirement, but the general recommendation is 60°C to be on the safe side.

Unfortunately regulating the temperature of hot water cylinders is tricky. The mechanical thermostats aren't that accurate and the temperature in the lower third of the cylinder where the thermostat is located is often much cooler than the top where water is drawn off to the taps.

 

[HarrySvo]

Even if they are fitted properly, [There shouldn't be any of the copper cylinder visible through gaps] loose jackets are only about as half as good at retaining heat as the foam insulated cylinders. It's a good idea to insulate the hot pipes too. The more heat you lose the more gas you use. (or oil etc,) In the winter perhaps that's not too much of a problem because any heat that escapes will help heat the house.

Thank you for the tips. I will make sure to insulate my cylinder and pipes properly.

 

[stem]

It's obvious really but I forgot to mention that the boiler's thermostat needs to be set 5 to 10 degrees higher than the hot water cylinder thermostat. Otherwise the cylinder will never get hot enough to switch the cylinder thermostat off.

 

[HarrySvo]

It's obvious really but I forgot to mention that the boiler's thermostat needs to be set 5 to 10 degrees higher than the hot water cylinder thermostat. Otherwise the cylinder will never get hot enough to switch the cylinder thermostat off.

Sorry but I don't get it. The boiler's thermostat is the Hive one and I could not find any temperature setting for hot water neither on the thermostat nor the app.
Here is my diy cylinder insulation by the way.

 

[stem]

Hey, nice job with the insulation.

I could not find any temperature setting for hot water neither on the thermostat nor the app.

That's because Hive doesn't provide that function. Below is the thermostat for your hot water cylinder. Whilst Hive doesn't provide temperature control of the stored hot water, this does. However, Hive will let you set the times that you want the hot water heating to be on/off.

The arrow points to the temperature selected, and when the hot water cylinder reaches this temperature the valve below will close off the flow of water to the hot water cylinder. In your case that it's the pipe on the right I've marked with a red X. When that happens the boiler no longer be heating the hot water cylinder.

Sorry but I don't get it. The boiler's thermostat is the Hive one

The boiler's thermostat is erm.......an integral part of the actual boiler. Something like the one highlighted by the red arrow below maybe? Other versions are available

The boiler thermostat controls the temperature of the water leaving the boiler that is pumped to the hot water cylinder and radiators. The higher the boiler thermostat the hotter the radiators will be to the touch.

If the boiler only produces warm water, it will never heat the hot water cylinder and the system will run continually. So the boiler's thermostat must be set higher than the cylinder thermostat.

There are 3 distinct and separate thermostats that have their own individual functions. In summary:

1. The boiler thermostat controls the temperature of the water leaving the boiler
2. The room thermostat [Hive in your case] controls the temperature of the room
3. The hot water cylinder thermostat control the temperature of the hot water inside the hot water cylinder.

 

[HarrySvo]

The boiler's thermostat is erm.......an integral part of the actual boiler. Something like the one highlighted by the red arrow below maybe? Other versions are available

Ok, now I got it. Thanks.
However my boiler is too simple I guess.
It has only one button - RESET. No dials, no nothing else. It's a Main HE system boiler as I mentioned in my initial message in the thread.
It's kind of a fully automatic?