FAQ
TL;DR: In one real build, a LEO FB 20V warmed a 55 m³ workshop from 17°C to 24°C in ~5 minutes; “the heater is perfect even at 50°C.” [Elektroda, marcin_marcepan, post #16774825]
Why it matters: If you heat a poorly insulated shop only when you’re there, the right water fan heater and hookup can deliver fast warm‑up without starving the rest of the system.
This FAQ is for DIYers and installers upgrading workshop heat using water fan heaters, small boilers, and buffer ideas in leaky spaces.
Quick Facts
- Heat output depends strongly on supply temperature; size for the room load and desired heat‑up time. [Elektroda, Inkwizycja, post #16742608]
- A 55 m³ workshop can be served by a mini water heater at about 50% duty when targeting ~21°C. [Elektroda, marcin_marcepan, post #16742425]
- Direct feed from the boiler on a dedicated pump and hotter than 60°C supply improves response. [Elektroda, roman 18, post #16743751]
- Reported warm‑up: 17→24°C in ~5 minutes with fan blast noticeable on low speed. [Elektroda, marcin_marcepan, post #16774825]
- With a 25 kW boiler and ~11.5 kW radiators, you may have ~10 kW left for a hall heater. [Elektroda, Magister_123, post #16747743]
How do I quickly heat a poorly insulated workshop without cooling my house radiators?
Feed a water fan heater directly from the boiler on its own pump. Use higher supply temperature for fast response and aim the discharge away from workstations. This setup avoids pulling down the rest of the radiator loop during short, on‑demand sessions. “Give the temperature much higher than 60 degrees.” [Elektroda, roman 18, post #16743751]
Should I add an 80 L double‑coil boiler as a buffer before the heater?
Forum experience suggests skipping the small buffer. A direct connection with adequate supply temperature and fan control delivered very fast warm‑up without starving the system. Small domestic tanks release heat slowly and add complexity for little gain in short, intermittent heating. [Elektroda, guciq, post #16742187]
What is a Volcano VR Mini (or LEO FB 20V) heater?
They are water fan heaters (fan coils) that blow room air across a hot‑water coil. They deliver rapid air temperature rise when supplied with sufficiently hot water and adequate flow. Users reported excellent performance even with 50°C water in a small workshop. [Elektroda, marcin_marcepan, post #16774825]
How much heater power can my 25 kW oil boiler spare for a hall unit?
If your existing radiators absorb about 11.5 kW, you have roughly 13.5 kW remaining, but plan on ~10 kW available in practice. Size the hall heater accordingly or consider staged fans. This headroom figure came from a working calculation in the thread. [Elektroda, Magister_123, post #16747743]
Does supply temperature really change heater output that much?
Yes. Water fan heater capacity depends strongly on supply temperature and flow. Before buying, calculate the room heat demand and the target warm‑up time. “First calculate the power demand…” is sound advice echoed with documentation references. [Elektroda, Inkwizycja, post #16742608]
What if I tried a car heater core—it felt hot nearby but cold a few meters away?
That’s an edge case seen in leaky shops. Small car cores concentrate heat locally; airflow and coil area are limited. Result: hot spot near the unit, cold three meters away, and poor mixing. A purpose‑built water fan heater solves this distribution gap. [Elektroda, marcin_marcepan, post #16742456]
What water temperatures and setpoints worked for fast warm‑up?
One user ran the boiler at 50–60°C, wanted 21°C room temperature, and achieved 17→24°C in ~5 minutes using a LEO FB 20V. Higher supply (>60°C) further improves response if your system and controls allow it. [Elektroda, marcin_marcepan, post #16742470]
How do I reduce fan blast or noise from a water fan heater?
Use the lowest fan speed that meets warm‑up time, then switch off or cycle the fan to maintain. If airflow is still too strong, consider a speed controller rated for your fan motor and reposition the unit. “The only thing that bothers is the fan.” [Elektroda, marcin_marcepan, post #16774825]
Is it better to throttle the heater with a valve or change the fan speed?
Change fan speed first. Throttling flow reduces coil delta‑T and can waste boiler output, while slower airflow keeps coil hot and quieter. If needed, add a balancing valve, but prioritize fan control for comfort and stability. [Elektroda, guciq, post #16742187]
What is an RTL valve?
An RTL (return temperature limiter) is a thermostatic valve that limits the return water temperature, often used on small floor heating loops connected to radiator circuits. It protects against too‑hot floors without mixing stations. [Elektroda, marcin_marcepan, post #16742425]
How should I pipe the heater—any orientation tips?
Connect the heater directly from the boiler, ideally on a separate pump. Some installers prefer reversed coil connections with bottom supply for better air purge on specific units. Ensure proper air venting and service valves. [Elektroda, roman 18, post #16743751]
How many emitters were on the system that still heated the workshop fast?
A reported setup ran nine radiators, a large towel dryer, a small floor loop, and a 300 L domestic exchanger with two coils in series—and the workshop still warmed rapidly. That shows adequate boiler headroom and correct heater choice. [Elektroda, marcin_marcepan, post #16775704]
What’s a simple 3‑step method to size and select a workshop heater?
- Estimate heat demand from temperature rise, volume, and leakage, then set a target warm‑up time.
- Choose a water fan heater whose output at your supply temperature meets that demand.
- Plan a direct, dedicated‑pump circuit and verify boiler headroom. [Elektroda, Inkwizycja, post #16742608]
Can a mini water heater work in a 55 m³, leaky shop used only evenings and weekends?
Yes. A mini water fan heater at ~50% output met the need in a similarly sized, poorly insulated workshop used intermittently. Fast warm‑up and acceptable comfort were reported, with only fan blast noted as a trade‑off. [Elektroda, marcin_marcepan, post #16742425]
How much does it cost to install four water heaters plus a stove for a hall?
One user cited materials around 20,000 PLN but asked how to price labor. Labor varies with pipe runs, pumps, controls, and venting. Use a detailed bill of quantities and bid per heater circuit plus boiler tie‑in to avoid surprises. [Elektroda, Maras_88, post #18237891]
Will a heater starve the rest of my radiators of heat?
Not if you design correctly. A direct, dedicated‑pump feed and sufficient boiler temperature prevented system cooling in the reported case. The rest of the radiators continued operating normally during workshop warm‑up. [Elektroda, marcin_marcepan, post #16774825]
