3rd Party Boiler

[Potatoman]

Hi, could anybody tell me what controls the temperature of the rooms in the house when  the 3rd party boiler is selected on the heat pump. Thanks.

[sharpener]

I think you need to tell us what make and size of HP you have, what "3rd party boiler" is installed and how, whether you have got rads or UFH or both, and what controls you already have e.g. the manufacturer's own controls and also any additional smart TRVs, room stats etc which are often part of the UFH installation.

[JohnMo]

  On 24/03/2025 at 08:54, Potatoman said:

Hi, could anybody tell me what controls the temperature of the rooms in the house when  the 3rd party boiler is selected on the heat pump. Thanks.

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Way more info needed

[Potatoman]

Hi, the ASHP is an LG 9KW monobloc, all radiator system, the system was left by the installer with Drayton wiser smart radiator valves controlling the heat pump, fixed flow rate, but now all rad valves are set at 23 degrees and weather compensation is operating. The 3rd party boiler is a Worcester 18 /25 oil boiler connected to the ASHP via a cable. As I understand it, when the outside temperature drops below 5 degrees C, which is set via the heat pump controls, the heat pump stops working and sends an electrical signal to the oil boiler to fire up, but when this happens what will control the temperature in the rooms if the heat pump is switched off

[JohnMo]

Heat pump isn't switched off fully the compressor is. All heating control is still heat pump.

 

Your issues are likely to be

 

Heat pump has a run permission from the third part Wiser system. It normally runs WC so I assume the Wiser system always calls for heat?

 

If your WC isn't carried over to the boiler it will just fire away until ALL wiser thermostats are above 23.

 

You need to decide if you are running WC or thermostats!

 

Have a think and report back?

[Nickfromwales]

  On 24/03/2025 at 13:01, Potatoman said:

Hi, the ASHP is an LG 9KW monobloc, all radiator system, the system was left by the installer with Drayton wiser smart radiator valves controlling the heat pump, fixed flow rate, but now all rad valves are set at 23 degrees and weather compensation is operating. The 3rd party boiler is a Worcester 18 /25 oil boiler connected to the ASHP via a cable. As I understand it, when the outside temperature drops below 5 degrees C, which is set via the heat pump controls, the heat pump stops working and sends an electrical signal to the oil boiler to fire up, but when this happens what will control the temperature in the rooms if the heat pump is switched off

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The Drayton kit will still talk to the rad valves, if set up correctly, and you should not see any ‘change’ in heat source.
 

The circumstances that sees the output from the ASHP call to the boiler (aux heater) will see it go to sleep and tell the boiler to fire up, so when the Drayton kit says call for heat is satisfied the output signal (one would assume) will then cease and both devices will go into standby / sleep until the next heating event.

 

The controls will then cascade through beginning with the ASHP, (does OAT = <5°? if yes then fire aux heater) etc, and off to go.

 

Do you have a buffer tank in the install or just heaters > rads? 

[Nickfromwales]

  On 24/03/2025 at 13:10, JohnMo said:

Heat pump isn't switched off fully the compressor is. All heating control is still heat pump.

 

Your issues are likely to be

 

Heat pump has a run permission from the third part Wiser system. It normally runs WC so I assume the Wiser system always calls for heat?

 

If your WC isn't carried over to the boiler it will just fire away until ALL wiser thermostats are above 23.

 

You need to decide if you are running WC or thermostats!

 

Have a think and report back?

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Can’t this have both?
 

I guess it depends on how intelligent the ASHP ctrls are and how it’s all been set up. Very difficult to answer all this here with such limited info tbf! 

[JohnMo]

  On 24/03/2025 at 13:16, Nickfromwales said:

Can’t this have both?

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It can have both, but OP is using thermostats for a heating system run permission to get WC on via ASHP and by default an oil boiler on also. If oil will do similar WC curve great, if not it will just heat whole house to 23+. Which is possibly the reason for the question. Fine if you like a 23 Deg house, but uncomfortable for me.

Edited March 24 by JohnMo

[Nickfromwales]

  On 24/03/2025 at 13:44, JohnMo said:

It can have both, but OP is using thermostats for a heating system run permission to get WC on via ASHP and by default an oil boiler on also. If oil will do similar WC curve great, if not it will just heat whole house to 23+. Which is possibly the reason for the question. Fine if you like a 23 Deg house, but uncomfortable for me.

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One would assume Drayton have thought about this? If the room stats (TRVs in this instance) are set to 21°C the the rooms will get no hotter, regardless of the WC curve, Shirley?

[marshian]

Not quite sure what the question is but my experience with Wiser hubs is that the hub needs to be told what the heating supply is 

 

from memory options are

 

direct electric boiler

gas boiler (with or without opentherm)

oil boiler

ASHP

not sure you can tell the hub you have two heating sources???

 

 

[JohnMo]

  On 24/03/2025 at 14:04, Nickfromwales said:

room stats (TRVs in this instance) are set to 21°C the the rooms will get no hotter, regardless of the WC curve, Shirley?

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OP has ALL set to 23. Isn't the idea of WC you balance energy out with energy in. TRVs are limit stops not permission for boiler or heat pump. TRVs just fine tune balance as required.

 

  On 24/03/2025 at 13:01, Potatoman said:

Drayton wiser smart radiator valves controlling the heat pump, fixed flow rate,

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Need way more information 

[Nickfromwales]

If OP has them set to 23 then isn’t that what they want? If the programming is changing to too high a temp then that’s a programming error. 
 

Those parameters are user definable.

[Potatoman]

Thank you for all the interesting replies, can we talk generically, if you wanted to set up a ASHP e.g. LG and a 3rd party boiler to work as they should do how would you set up the heating controls  so it maintained a temperature of 21 degrees in the house if you had the choice of WC or Wiser controls, and how would everything work together, Thanks

[JamesPa]

  On 24/03/2025 at 15:30, Potatoman said:

Thank you for all the interesting replies, can we talk generically, if you wanted to set up a ASHP e.g. LG and a 3rd party boiler to work as they should do how would you set up the heating controls  so it maintained a temperature of 21 degrees in the house if you had the choice of WC or Wiser controls, and how would everything work together, Thanks

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Doesn't that depend on the design objective eg:

• to run at minimum cost (if so what electricity tarrif)
• because the heat pump alone isnt enough even at the design temperature
• because the heat pump alone isnt enough at some extreme temperature sub design temperature
• to run at minimum carbon emissions
• something else or some combination

 

I cant see how you can design a control strategy until you know what you are trying to achieve and why the system is so complex (presumably one and the same thing - the system is complex because you are trying to achieve something complex)?

 

Also whats the objective of having wiser - is it micro zoning or just dealing with extreme events like solar gain?

Edited March 24 by JamesPa

[Potatoman]

Hi, thank you for your reply, to try and answer your questions, The problem I have got is the installer has left me with wiser controls and has told me that these controls will work when in ASHP mode or 3rd party boiler mode, but they don't, the wiser controls do switch the heat pump off and on but when in 3rd party mode do not switch off the oil boiler, so consequently the house gets too warm. Now I know wiser controls are not the best for ASHP but my problem at the moment is to get the 3rd party boiler working correctly and the reason to have a 3rd party boiler is heat pumps are less efficient at minus temperatures.

[sharpener]

  On 24/03/2025 at 15:30, Potatoman said:

Thank you for all the interesting replies, can we talk generically, if you wanted to set up a ASHP e.g. LG and a 3rd party boiler to work as they should do how would you set up the heating controls  so it maintained a temperature of 21 degrees in the house if you had the choice of WC or Wiser controls, and how would everything work together, Thanks

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Well assuming that the Wiser controls will maintain their setpoints in the individual rooms and will also call for heat if at least one room is below the setpoint it sounds as though you need to add a relay so that the call for heat from the Wiser setup will also enable the boiler (but not otherwise).

 

Then turn down the Wiser settings to 21 or whatever your target room temp is. When on heatpump alone it will still use a flow temp set by the WC so you still get the benefit of it.

 

  On 24/03/2025 at 18:37, Potatoman said:

the reason to have a 3rd party boiler is heat pumps are less efficient at minus temperatures

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I don't think in the UK you will get winter conditions where the boiler will be more cost-effective than the heat pump, so unless the HP is just not big enough I can't see under what circumstances you would want to use the boiler.

[JamesPa]

  On 24/03/2025 at 18:37, Potatoman said:

Hi, thank you for your reply, to try and answer your questions, The problem I have got is the installer has left me with wiser controls and has told me that these controls will work when in ASHP mode or 3rd party boiler mode, but they don't, the wiser controls do switch the heat pump off and on but when in 3rd party mode do not switch off the oil boiler, so consequently the house gets too warm. Now I know wiser controls are not the best for ASHP but my problem at the moment is to get the 3rd party boiler working correctly and the reason to have a 3rd party boiler is heat pumps are less efficient at minus temperatures.

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Assuming lg support the function you could use the wiser controls to set the demand for heat on the heat pump, then set an appropriate bivalent point on the heat pump controller and use that to control the third party boiler.  

 

Obviously I can't tell if that's what your installer did.

 

Whether that is wiser (sorry couldn't resist it) than just optimising the system for the heat pump is another matter.  I have a suspicion that optimising the controls for the heat pump and selecting an electric tariff will work out about the same or cheaper, assuming you have a reasonably sensible heat pump set up.  If there is a difference it's likely to be small and the risk is that by being 'clever' you degrade the heat pump performance and thus end up costing more.

Edited March 24 by JamesPa

[Dillsue]

If you're running weather compensation on the heat pump and it's been set up correctly, why do you need Wiser TRVs connected to the heat pump??  The WC should take care of individual room temps via balanced flow through the rads.

 

Connecting the Wiser system to the boiler will control the house temp when the HP tells the boiler to run. If there's a valid reason for the HP to have a signal from the Wiser system then install a relay, as Sharpener suggested. With a 2 pole relay in place the Wiser system will switch the relay and separate contacts from the relay will separately switch the HP and boiler enable/call for heat signals.

 

What has your installer said about the boiler overheating the house??

[JamesPa]

  On 25/03/2025 at 06:12, Dillsue said:

If you're running weather compensation on the heat pump and it's been set up correctly, why do you need Wiser TRVs connected to the heat pump??  The WC should take care of individual room temps via balanced flow through the rads.

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There seem to be lots of people who still believe that weather compensation is a third class control mechanism specific to heat pumps solely to overcome their limitations, and that micro zoning in both time and space is the  one true and ultimate control system.😒

 

Perhaps the installer is in this deluded camp?

Edited March 25 by JamesPa