Working circuit · S-Plan · Y-Plan · Combi

The heating wiring simulator that behaves like the real thing

Wire an S-Plan, a Y-Plan or a combi, blow the fuse, find the fault. Practise on 23 real call-outs before the next one is yours.

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The demo opens with the launch: leave your email and the link lands in your inbox that day. Laptop or desktop for the simulator; the wiring board on this page works on a phone.

Watch it on YouTube For colleges For employers

Fused spur

Room stat

2-port valve

Boiler

Click a terminal, then another, to draw a wire · Esc cancels

The job

One call-out, start to finish

This is what people pay for: the fault, the meter, the proof. Not a feature list.

10:40
“Heating’s on but there’s no hot water.”
The job sheet, in the customer’s words. Programmer says HW ON, cylinder cold, radiators warm.
10:43
“You put the meter on the cylinder stat.”
Common reads 230 V. The call terminal reads nothing. The cylinder is cold, so it should be calling.
10:46
“Live in, nothing out. You report the fault.”
A failed cylinder thermostat, proven with two readings instead of a guess. Replace it, then prove the repair.
10:52
“Scored. Next job.”
Hints cost points and the right answer earns them. Every call-out is weighted by how often it really happens.

A fully wired S-Plan system in the DrawWarm simulator

The multimeter reading AC voltage at a thermostat terminal

The multimeter on the resistance range testing a component

10:40

“Heating’s on but there’s no hot water.”

The job sheet, in the customer’s words. Programmer says HW ON, cylinder cold, radiators warm.

10:43

“You put the meter on the cylinder stat.”

Common reads 230 V. The call terminal reads nothing. The cylinder is cold, so it should be calling.

10:46

“Live in, nothing out. You report the fault.”

A failed cylinder thermostat, proven with two readings instead of a guess. Replace it, then prove the repair.

10:52

“Scored. Next job.”

Hints cost points and the right answer earns them. Every call-out is weighted by how often it really happens.

Swipe for the next step

components

lessons, every one machine-tested

real call-outs

S-Plan · Y-Plan · Combi

wired and wireless controls

Three modes

Sandbox, Learn, Fault-find

One simulator, three ways in. The demo opens in whichever mode you choose.

The sandbox canvas with heating components placed and ready to wire

Random Fault mode with the multimeter on a live circuit

Any component, any wiring, switch it on.

Build S-Plan and Y-Plan systems from a bare wiring centre, test with the multimeter, and see every terminal go live or stay dead.

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Who it is for

Built for the people who touch the wiring centre

Engineers

Find the fault with the meter, not by swapping parts. Practise on 23 real call-outs before the next one is yours.

See the call-outs

Apprentices

Wire an S-Plan from a bare wiring centre, switch it on, and see exactly why it works.

See the courses

Colleges and employers

Every learner gets their own board. You get a report on who has done what, and how well.

For colleges For employers

The written version

Read the method here. Practise it in there.

Every course, call-out, component and wiring diagram has its own page, generated from the simulator’s own data, so what you read is what the circuit does.

23 call-outs

Fault finding

Every fault in the customer’s words, the method, and what the meter shows.

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7 courses

Courses

45 lessons from mains basics to a full Y-Plan build, each connection checked.

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6 systems

Wiring diagrams

S-Plan, Y-Plan, wireless and combi: every wire, the block numbering, the truth table.

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23 components

Components

Terminals, what each does, how it fails, and the kits each part stands in for.

Browse →

Wondering why nobody taught you this? Why plumbing and heating courses leave out the wiring, and what a one-day course cannot do.

Who built it

A heating engineer, not a software company

Founder video · 40 seconds · to be recorded

“I built DrawWarm because I spent years learning controls the expensive way, on customers’ systems. Now you can make every mistake first on mine.”

Every lesson and every fault is replayed by a test harness before it ships, so what the simulator teaches is what the circuit does.

Myron Lambert · Heating engineer, founder of DrawWarm

The story Watch the channel

Pricing

Two plans. One price list.

The Sandbox is the simulator on its own. The full version adds every course and call-out. Individuals cancel any time; organisations licence seats of either by the year.

Sandbox

£29a month

or £348 a year

One price for everyone, never discounted. Organisations pay the same for each seat.

All 23 components and every system: S-Plan, Y-Plan, combi, wired and wireless
The multimeter: AC volts, resistance, continuity
Save and load your own circuits
Swapper, the whole controls swap guide (the free tier is one swap a month)
The fault trees: every tree, not just the demo
New components as they ship

No courses or lessons
No call-outs or challenges

Join the launch list

Most complete

Full version

£199a month

or £1,990 a year, two months free

Launch offer: £99 a month, half the full price of £199. Launch pricing ends 31 March 2027.

Founding members keep £99 a month for as long as their subscription runs without a break. Cancel, and the launch price ends with it: rejoin later and you pay the price published at that time.

Everything in the Sandbox
All 7 courses: 45 lessons and 5 diagnosis challenges
All 23 call-outs in Random Fault mode
Progress, stars and scores saved to your account
New faults and lessons every month
Email support from the engineer who built it

Reserve the launch price

500 launch places. Card, Apple Pay or Google Pay. Cancel any time; access runs to the end of the paid period. No refunds for changing your mind once access has begun.

Colleges, training centres, employers

Seats of either plan, licensed by the year.

Every person with access uses a seat. A 12-month licence, paid in advance by card or by invoice on 30-day terms, renewing unless you tell us. Add seats at any time in the year. A free pilot comes first.

Plan

Seats, in packs of 10

Every course, lesson and call-out for every seat
Swapper and the fault trees for every seat
Groups, join codes and a tutor report on who has done what, and how well
A manager, admins and tutors, each with the right powers

Want it on your own website, under your own logo? White label, by quote. Two- and three-year terms with the price fixed throughout: ask for a quote.

Full version · 20 seats

£940a seat a year

£18,800 a year for all seats · 5% off the 10-seat price

Launch price until 31 March 2027, kept at renewal while the licence runs without a break. Full price £1,890 a seat a year for this pack.

Seats	Launch, a year	Full price, a year	Off
10	£990	£1,990	—
20	£940	£1,890	5%
30	£890	£1,790	10%
40	£840	£1,690	15%
50	£790	£1,590	20%
60+	by quote

Start a free pilot 60 or more seats, an invoice, or something else? Ask for a quote

A business contract under the business terms: 12 months, paid in advance, no refund once the term starts. Individuals pay monthly or yearly and cancel any time.

The price shown is the price you pay. No VAT is added at checkout. Seats, cancelling, VAT and the other questions.

Questions

Straight answers

I can watch this for free on YouTube. Why pay?

The channel has short videos: about fifteen per cent of what the courses cover, and no wiring you can do yourself. The full version is the working simulator: 45 lessons that check each connection, 23 call-outs with a meter, and your scores saved.

I did a one-day wiring course. Why would I need this?

A day shows you the circuit; it cannot make it stick, and there is no rig to go back to on Tuesday when the fault is in front of you. Gas courses teach gas and plumbing courses teach water, so for most of the trade that day was the only wiring training there was. DrawWarm is the practice after the course: 45 lessons and 23 call-outs you can repeat until the wiring centre is automatic, from £29 a month.

Does it work on my phone?

The site does. The simulator wants a laptop or desktop with a mouse. Send yourself the link from the demo page and open it there.

Does it work on a Chromebook or a locked-down college PC?

Yes. The simulator runs in the browser, so nothing is installed. A normal broadband connection is enough.

Which systems are covered?

S-Plan with 2-port zone valves, wired and wireless. Y-Plan with a 3-port mid-position valve. Combi boilers with a wireless thermostat. Twenty-three components: room thermostats (dial, digital and volt-free), wireless thermostats and receivers, cylinder stats, frost stats, single and dual-channel programmers, zone valves, boilers, the pump, the wiring centre and the multimeter.

What is the difference between the Sandbox and the full version?

The Sandbox is the simulator on its own: every component, every system, the multimeter, save and load your circuits. £29 a month for everyone, always. The full version adds all 7 courses, the 5 diagnosis challenges and the 23 call-outs in Random Fault mode.

Can I cancel?

Yes, from your account, any time. Yes, any time, from your account: nothing more is charged and your access runs to the end of the period you paid for. There are no refunds for changing your mind. When you buy you ask us to start straight away and acknowledge that the 14-day cancellation right no longer applies, as the refund policy explains.

What does it cost?

The Sandbox is £29 a month. The full version is £199 a month, or £1,990 a year. Launch offer: £99 a month, half the full price of £199. Launch pricing ends 31 March 2027. Founding members keep £99 a month for as long as their subscription runs without a break. Cancel, and the launch price ends with it: rejoin later and you pay the price published at that time.

Terminal 10 · switched live

Your first fault is waiting.

The demo opens with the launch: leave your email and the link lands in your inbox that day.

Get the demo link See pricing