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Installer question checklist
Twenty questions, in the order you should ask them. Print this, take it to every quote, and write the answers on it. A good installer will enjoy these questions; that is itself the test.
Heat loss and design
| # | Question | Their answer |
|---|---|---|
| 1 | What is the calculated whole-house heat loss in kW, and can I have the room-by-room calculation? | |
| 2 | What design flow temperature is this quote based on, at the design outdoor temperature? | |
| 3 | Which room is the limiting one, and what did you do about it? | |
| 4 | What SCOP do you expect in this house at that flow temperature — not the datasheet figure? |
Equipment and emitters
| # | Question | Their answer |
|---|---|---|
| 5 | What make, model and output, and why that output rather than the next size down? | |
| 6 | Which radiators are you changing, and which are you leaving? | |
| 7 | Is a buffer tank included, and if so why? (Many systems do not need one.) | |
| 8 | What cylinder size, and what coil surface area? |
Grant and paperwork
| # | Question | Their answer |
|---|---|---|
| 9 | Are you MCS certified, and will you apply for the Boiler Upgrade Scheme voucher on my behalf? | |
| 10 | Does my EPC have outstanding loft or cavity wall insulation recommendations, and how are we handling that? | |
| 11 | Am I eligible for the £9,000 oil/LPG total, and does the install complete before 31 March 2027? | |
| 12 | What happens to my deposit if the voucher application is refused? |
Commissioning and aftercare
| # | Question | Their answer |
|---|---|---|
| 13 | Will you carry out and document a hydraulic balance, and give me the flow rates? | |
| 14 | What weather compensation curve will you set, and will you show me how to adjust it? | |
| 15 | What noise level at the boundary, and have you checked the permitted development limit? | |
| 16 | What is the workmanship warranty, and who honours the manufacturer warranty if you cease trading? |
Price and timing
| # | Question | Their answer |
|---|---|---|
| 17 | Is the price fixed or an estimate, and what specifically could change it? | |
| 18 | What is excluded — scaffolding, electrical upgrade, making good, asbestos? | |
| 19 | Payment schedule: how much before any work starts? | |
| 20 | Start date and duration, in writing. |
The single most diagnostic question is the design flow temperature. An installer who cannot answer it, or who says “it depends”, has not done a heat-loss calculation for your house — which means the SCOP in their quote is a guess.
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Compare at least three installers. Ask each one for the heat-loss calculation and the design flow temperature in writing — that number decides your running cost more than the brand on the box.
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