Predictika · Heat pump installation designs

An AI sales agent's ground source heat pump design, checked before it goes out

An AI sales agent prepares an installation design for the NIBE S1255 ground source heat pump: the model and the number of units, the collector and brine circuit, the heating pipework, the electrical supply and immersion heater, the accessories and the placement. Before it goes out, the agent sends it to Predictika, which checks it against a declarative model of the installer rules and returns a verdict, every reason and the illustrative price it computed.

Scope: NIBE S1255-6 and S1255-12 ground source heat pump designs (1 x 230 V): collector and brine circuit, heating pipework, electrical supply and immersion heater, accessories, placement and multi-installation, with an illustrative price in pounds. See everything this validator covers

This validator models designs of this kind, not just the scenarios shown below.

  • Collector and brine — a coil of at most 400 m, surface hoses at least 1 m apart, brine protected to -15 C, groundwater only through an intermediate heat exchanger, and the level or expansion vessel that fits the layout.
  • Electrical and heating side — the immersion heater steps for each model, the fuse, the circuit breaker curve, the isolator switch, the external electric heaters and their accessory card, the heating pipe size, flows and supply temperature.
  • Placement, accessories and price — clearances, room height, floor drain and floor load, tundish pipe, the filling kit for up to 8 units, and an illustrative total price in pounds for the heat pumps and accessories.

Any design that touches these rules is in scope — not only the scenarios pictured here. The installer rules follow NIBE's public S1255 installer manual and specification sheet; the 30 m of hose per kW check, the brine volume guide and every price are modeled by Predictika and are not published by NIBE, so the prices on this page are illustrative. Not covered: the S1255-16, 3 x 400 V models, other NIBE heat pumps and installation labor.

The AI sales agentBuilds the heat pump design from the conversation and says it is ready.
Predictika validatorChecks every rule at once and returns the verdict, each finding, and the computed figures.

6 scenarios in 3 groups · each group runs from the agent’s first attempt to the outcome · click one to switch

What the agent proposes

The AI sales agent says

Illustrative agent statement. The validator receives the structured request below.

Proposing agent: AI sales agent (scripted)

Before sending, the agent must call Recorded run

Predictika validator


      

        
        
        
      

      
Waiting for the call.

      
    

  

  
  

    
Where rules-based CPQ gets it wrong
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Our assessment of what a typical rules-based CPQ (product rules, price rules and validation rules, as in Salesforce CPQ) does with the same cases. It is a judgment about effort and reliability, not a claim that nothing can be built.

    
What the validator caughtTypical rules-based CPQPredictika
Limits that depend on the modelOnly with care
The immersion heater steps, the fuse, the pipe size and the flows differ between the S1255-6 and the S1255-12, so each rule has to read the model.		The model and every dependent value are checked together on every call.
Choices that exclude each otherOnly with care
A groundwater source, a cooling accessory, an electric heater and its card each change what else is allowed, so the rules read several choices at once.		All the related choices are checked together on every call.
A fuse that follows the heater powerOnly with workarounds
The needed fuse depends on the model and the immersion heater step, so it must be looked up before it is compared with the fuse in the design.		The needed fuse is computed and compared with the fuse in the design on every call.
A price built from many partsOnly with workarounds
The total adds the heat pumps and every accessory, and the heat pump count changes the filling kit and the sensors needed.		The price is recomputed from the design on every call.
Every problem returned in one answerOnly with workarounds
Rules tend to fire as a step is completed, so a rep often fixes one error and meets the next.		All findings come back together, whatever order the choices arrived in.

  

  

    
What this validator catches: findings from its test cases
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Every rule is checked on every call, in any order the choices arrive; one problem never hides another. Blocking findings stop the design; approval findings need a person to sign off; everything else is computed.

    
1The design has 0 heat pumps; a multi-installation takes 1 to 8.
2The design has 9 heat pumps; a multi-installation takes 1 to 8.
3With 2 heat pumps connected together an external supply sensor (BT25) and return sensor (BT71) are needed.
4An internal immersion heater power of 5,000 W is not an available step for this model (S1,255-6: 0 to 4.5 kW in 0.5 kW steps; S1,255-12: 0 to 7 kW in 1 kW steps).
5An internal immersion heater power of 2,500 W is not an available step for this model (S1,255-6: 0 to 4.5 kW in 0.5 kW steps; S1,255-12: 0 to 7 kW in 1 kW steps).
6The fuse is 25 A; the manual recommends at least 32 A for this model and immersion heater power.
7The fuse is 40 A; the manual recommends at least 63 A for this model and immersion heater power.
8A miniature circuit breaker must have at least triggering characteristic C.
9The heat pump must be installed via an isolator switch.
10The building has an earth-fault breaker; the heat pump should have a separate one.
11A collector coil of 450 m is longer than the 400 m maximum per coil.
12Surface soil collector hoses are 80 cm apart; the distance should be at least 1 m.
13The brine is protected only to -10 C; it must be protected down to -15 C.
14An open groundwater system needs an intermediate frost-protected circuit with an extra heat exchanger.
15The brine pipe is 22 mm; the brine connections are 28 mm copper.
16Indoor brine pipes must be insulated against condensation.
17The level vessel must be the highest point of the brine system; otherwise use an expansion vessel.
18With a cooling accessory or the exhaust air module FLM S45 the brine system needs a pressure expansion vessel in place of the level vessel.
19The chosen external electric heater is 3 x 400 V; this installation is 1 x 230 V (ELK 5 and ELK 8).
20An external electric additional heat ELK needs the accessory card AXC 40.
21The extra shunt group does not cover 100 square metres (ECS 40 up to 80, ECS 41 about 80 to 250).
22The extra shunt group does not cover 300 square metres (ECS 40 up to 80, ECS 41 about 80 to 250).
23The brine filling valve kit does not cover 24 kW (KB 25 up to 12 kW, KB 32 up to 30 kW).
24The brine filling valve kit does not cover 36 kW (KB 25 up to 12 kW, KB 32 up to 30 kW).
25The heating medium pipe is 22 mm; this model connects with 28 mm copper.
26The heating medium flow is 10 cl/s; this model needs at least 16 cl/s at rated output.
27The heating medium flow is 30 cl/s; this model needs at least 38 cl/s at rated output.
28The brine flow is 25 cl/s; this model needs at least 29 cl/s at rated output.
29The brine flow is 50 cl/s; this model needs at least 64 cl/s at rated output.
30The heating supply temperature is 72 C; the maximum is 70 C.
31The compressor supplies up to 65 C; at 72 C the immersion heater would cover the rest.
32The compressor supplies up to 65 C; at 68 C the immersion heater would cover the rest.
33The hot water stop temperature is 55 C; it must be at least 60 C.
34The factory hot water setting is changed and a mixing valve is required.
35The climate system relief valve opens at 500 kPa; the maximum system pressure is 450 kPa.
36The climate system relief valve opens at 300 kPa; 250 kPa is recommended.
37The pipe from the tundish is 22 mm; for this run it must be at least 28 mm.
38A discharge run of 30 m is longer than the 27 m in the sizing table.
39The straight section before the first bend is 200 mm; it must be at least 300 mm.
40The free space in front is 600 mm; the manual asks for 800 mm.
41The free space at the side is 30 mm; about 50 mm is needed so the side panels can be removed.
42A normal installation needs 300 to 400 mm on one side for connection equipment; the design has 100 mm.
43The room height is 1,900 mm; the ceiling height needed is 1,950 mm.
44Water can come from the heat pump; the area needs floor drainage.
45The floor is rated for 300 kg; the filled heat pump weighs 359 kg.
46The floor is rated for 380 kg; the filled heat pump weighs 389 kg.
47The cold water supply is 18 bar; the maximum water supply pressure is 16 bar.
48With thermostats on every radiator or floor loop a bypass valve is needed, or some thermostats must be removed.
49The collector is 150 m of hose; a person should confirm it for 6 kW of heat pumps (this check uses a rule of thumb of 30 m per kW).
50300 litres of brine for 400 m of hose; the manual gives 1 litre per metre as a guide value.
51A large bath is installed; the manual says the system should be supplemented with an extra water heater.
52The heat pump stands against a wall to a sound sensitive room without sound insulation.
53The collector is 200 m of hose; a person should confirm it for 24 kW of heat pumps (this check uses a rule of thumb of 30 m per kW).
54The fuse is 25 A; the manual recommends at least 40 A for this model and immersion heater power.
55The pipe from the tundish is 22 mm; for this run it must be at least 35 mm.

  

  

    
Scenarios and results
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The recorded result of the validator for each scenario on this page: the request the AI agent sent, the verdict, and every finding, in the order they appear above.

    
1. Groundwater, cooling and electric heater: A groundwater S1255-6 with cooling, a level vessel, an ELK 15 heater and a 72 C supply

    
The agent's request. Please quote 1 NIBE S1255-6 heat pump on a groundwater collector of 2 coils of 200 m, with a level vessel and a PCM S40 cooling accessory, a 28 mm heating pipe, a 3,000 W immersion heater on a 32 A fuse with a curve C circuit breaker and an isolator switch, an ELK 15 heater, no filling kit, a 72 C supply and a floor drain. It is ready to send.

    
Verdict: Blocked.

    
    
      
  • Groundwater needs intermediate heat exchanger. An open groundwater system needs an intermediate frost-protected circuit with an extra heat exchanger.
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  • Cooling or ventilation recovery needs expansion vessel. With a cooling accessory or the exhaust air module FLM S45 the brine system needs a pressure expansion vessel in place of the level vessel.
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  • ELK 15 and ELK 213 are 3x400 V. The chosen external electric heater is 3 x 400 V; this installation is 1 x 230 V (ELK 5 and ELK 8).
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  • ELK needs accessory card AXC 40. An external electric additional heat ELK needs the accessory card AXC 40.
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  • Supply temperature above 70. The heating supply temperature is 72 C; the maximum is 70 C.
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  • Supply above 65 relies on immersion heater. The compressor supplies up to 65 C; at 72 C the immersion heater would cover the rest.
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2. Groundwater, cooling and electric heater: The agent resubmits after fixing the errors

    
The agent's request. Please quote 1 NIBE S1255-6 heat pump on a groundwater collector (with an intermediate heat exchanger) of 2 coils of 200 m, with an expansion vessel and a PCM S40 cooling accessory, a 28 mm heating pipe, a 3,000 W immersion heater on a 32 A fuse with a curve C circuit breaker and an isolator switch, an ELK 8 heater with the AXC 40 card, no filling kit, a 55 C supply and a floor drain. It is ready to send.

    
Verdict: Allowed.

    
    
      
  • Design summary. 1 NIBE S1,255 heat pump(s), 6 kW in total, fuse of at least 32 A, illustrative price 8,400 GBP.
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3. Two units, sensors and filling kit: Two S1255-12 heat pumps with a 22 mm heating pipe, no external sensors, short collector coils, a KB 25 filling kit and no floor drain

    
The agent's request. Please quote 2 NIBE S1255-12 heat pumps on a borehole collector of 2 coils of 100 m, with a level vessel and no cooling accessory, a 22 mm heating pipe, a 4,000 W immersion heater on a 40 A fuse with a curve C circuit breaker and an isolator switch, no external electric heater, a KB 25 filling kit, a 45 C supply. It is ready to send.

    
Verdict: Blocked.

    
    
      
  • Multi-installation needs external sensors. With 2 heat pumps connected together an external supply sensor (BT25) and return sensor (BT71) are needed.
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  • Filling valve kit too small. The brine filling valve kit does not cover 24 kW (KB 25 up to 12 kW, KB 32 up to 30 kW).
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  • Heating pipe too small. The heating medium pipe is 22 mm; this model connects with 28 mm copper.
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  • No floor drain. Water can come from the heat pump; the area needs floor drainage.
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  • Collector may be short for the output. The collector is 200 m of hose; a person should confirm it for 24 kW of heat pumps (this check uses a rule of thumb of 30 m per kW).
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4. Two units, sensors and filling kit: The agent resubmits after fixing the errors

    
The agent's request. Please quote 2 NIBE S1255-12 heat pumps on a borehole collector of 6 coils of 130 m, with a level vessel and no cooling accessory, a 28 mm heating pipe, a 4,000 W immersion heater on a 40 A fuse with a curve C circuit breaker and an isolator switch, no external electric heater, a KB 32 filling kit, a 45 C supply, external sensors and a floor drain. It is ready to send.

    
Verdict: Allowed.

    
    
      
  • Design summary. 2 NIBE S1,255 heat pump(s), 24 kW in total, fuse of at least 40 A, illustrative price 15,020 GBP.
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5. Immersion heater and circuit: An S1255-6 with a 5 kW immersion heater, a 25 A fuse, a curve B circuit breaker and no isolator switch

    
The agent's request. Please quote 1 NIBE S1255-6 heat pump on a borehole collector of 2 coils of 200 m, with a level vessel and no cooling accessory, a 28 mm heating pipe, a 5,000 W immersion heater on a 25 A fuse with a curve B circuit breaker, no external electric heater, no filling kit, a 45 C supply and a floor drain. It is ready to send.

    
Verdict: Blocked.

    
    
      
  • Immersion heater power not a step. An internal immersion heater power of 5,000 W is not an available step for this model (S1,255-6: 0 to 4.5 kW in 0.5 kW steps; S1,255-12: 0 to 7 kW in 1 kW steps).
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  • Fuse too small. The fuse is 25 A; the manual recommends at least 40 A for this model and immersion heater power.
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  • Miniature circuit breaker curve B. A miniature circuit breaker must have at least triggering characteristic C.
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  • No isolator switch. The heat pump must be installed via an isolator switch.
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6. Immersion heater and circuit: The agent resubmits after fixing the errors

    
The agent's request. Please quote 1 NIBE S1255-6 heat pump on a borehole collector of 2 coils of 200 m, with a level vessel and no cooling accessory, a 28 mm heating pipe, a 4,000 W immersion heater on a 32 A fuse with a curve C circuit breaker and an isolator switch, no external electric heater, no filling kit, a 45 C supply and a floor drain. It is ready to send.

    
Verdict: Allowed.

    
    
      
  • Design summary. 1 NIBE S1,255 heat pump(s), 6 kW in total, fuse of at least 32 A, illustrative price 5,900 GBP.
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Narration transcript
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The text of the narrated walkthrough, step by step.

    
    
      
  1. Welcome to a demo of Predictika's Validator. An AI sales agent prepares an installation design for the NIBE S1255 ground source heat pump: the model and the number of units, the collector and brine circuit, the heating pipework, and more. Before it goes out, the agent sends it to Predictika, which checks it against a declarative model of the installer rules and returns a verdict, every reason and the illustrative price it computed.
    2. 
      
  2. I will start with the first request by the agent.
    3. 
      
  3. The agent says. Please quote 1 NIBE S1255-6 heat pump on a groundwater collector of 2 coils of 200 m, with a level vessel and a PCM S40 cooling accessory. It is ready to send. The rest of the request is on screen.
    4. 
      
  4. Before it goes out, the agent calls the validator.
    5. 
      
  5. Blocked, with five findings and one approval, all in one answer. An open groundwater system needs an intermediate frost-protected circuit with an extra heat exchanger. With a cooling accessory or the exhaust air module FLM S45 the brine system needs a pressure expansion vessel in place of the level vessel. The chosen external electric heater is 3 x 400 V; this installation is 1 x 230 V (ELK 5 and ELK 8). The other two are on screen.
    6. 
      
  6. The validator returned five blocking findings and one approval in one answer. A check that reads one field at a time would pass most of this; it shows only when the choices in the design are checked against each other.
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  7. What this shows: for a fuse that follows the heater power, a rules-based CPQ can do this only with workarounds.
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  8. Now the agent resubmits.
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  9. The corrected request. It changes the brine vessel to Expansion Vessel, the intermediate heat exchanger to yes, the external electric heater to ELK 8, the AXC 40 card to yes and the supply temperature to 55 C.
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  10. It calls the validator again.
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  11. This time the validator clears it.
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  12. All six earlier findings are cleared.
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  13. Six problems caught in one call, fixed in one pass, and a clean design. That is the value of Predictika's validator: catching mistakes before they reach the build. Now you can try the other scenarios yourself.
    14.