FAQ
TL;DR: Ground-floor Purmo radiator with Danfoss 013G5164 not heating? Try a flush: set RA‑N to "N" and run ~20 minutes; "set the initial setting … to 'N'" first. Many fixes end in balancing or opening throttled valves. [Elektroda, Zbigniew Rusek, post #16872423]
Why it matters: This FAQ helps flat owners quickly diagnose no‑heat issues tied to RA‑N presets, clogged valves, and basement balancing.
Quick Facts
- Yellow liquid from the vent usually means treated water carrying sludge, not glycol—expect fouling to restrict flow. [Elektroda, kot mirmur, post #16871028]
- RA‑N preset “N” is a full‑flow setting useful for temporary flushing; restore the prior setting after ~20 minutes. [Elektroda, Zbigniew Rusek, post #16872423]
- Small‑passage Danfoss valve bodies can clog; symptoms include top‑hot/bottom‑cold or no flow. [Elektroda, roman 18, post #16872283]
- Ground‑floor no‑heat often traces to throttled supply/return in the basement; opening those restored heat in this case. [Elektroda, Tobiasz22, post #16876122]
- A moving valve pin doesn’t guarantee the valve isn’t stuck seated; tap and free it before deeper work. [Elektroda, E8600, post #16870933]
How do I quickly check if my radiator issue is a clogged valve or system balancing?
Close both radiator valves, open the vent to drain, then open only the supply briefly. If the supply pipe heats fast but the radiator stays cold when the return opens, balancing or basement throttling is likely. If no heat returns on supply, suspect a clogged valve. [Elektroda, Tobiasz22, post #16872557]
What does yellow fluid from the vent mean on a new Purmo radiator?
It usually indicates water mixed with installation sludge, not glycol. Sludge can block the narrow passages in panel radiators and valves, starving flow and heat. A pressure rinse or targeted flush often restores performance. [Elektroda, kot mirmur, post #16871028]
How do I free a stuck Danfoss 013G5164/RA‑N valve?
Remove the thermostatic head, press the valve pin repeatedly, and gently tap the valve body to release the seat. A moving pin can still mean a seated valve, so verify flow afterward. “Just because the pin is moving does not mean the valve is not seated.” [Elektroda, E8600, post #16870933]
What is the RA‑N preset “N” and when should I use it?
RA‑N “N” is the full‑flow preset used for commissioning or flushing. Set to “N” and run for about 20 minutes to wash out silt, then restore the previous preset to avoid over‑flow on the riser. [Elektroda, Zbigniew Rusek, post #16872423]
Could the problem be in the basement, not my apartment?
Yes. Throttled or stuck riser supply/return valves or a regulator can starve ground‑floor radiators. In this thread, heat returned only after the cooperative opened basement valves. If others heat normally, escalate balancing checks. [Elektroda, Tobiasz22, post #16876122]
Why does my riser pipe warm after 5 minutes when the valve is closed, then cool 30 seconds after opening?
That pattern signals pressure imbalance. With the valve closed, the riser warms. Opening the valve lets low‑pressure return dominate, pulling cooler water and dropping supply temperature locally. This supports a balancing or throttling fault. [Elektroda, Tobiasz22, post #16871087]
What’s the first thing to check if only the top of the radiator gets warm?
Verify the return valve is open. A closed return can heat only the top via limited convection, leaving the bottom cold. Open it fully, bleed once, and confirm both valves have flow. [Elektroda, misiekpb, post #16870827]
How can I tell if my Danfoss valve body is clogged?
Typical clues: no heat despite open valves, supply cools quickly when return opens, and other radiators heat normally. Danfoss bodies have small passages that silt can block, especially first season after work. [Elektroda, roman 18, post #16872283]
Could a regulator on the riser be closing my supply when the return is warm?
Yes. Some risers use differential pressure or thermostatic controls linked by a heat pipe. Warm return can drive these to restrict the supply, affecting ground‑floor branches. Inspection and reset in the basement fix it. [Elektroda, E8600, post #16872634]
What is a differential pressure regulator in heating risers?
It maintains stable pressure across the riser to balance flow between flats. If mis‑set or stuck, it can starve the lowest branch. The fix requires access and adjustment at the basement manifold. [Elektroda, E8600, post #16872663]
How‑to: Flush a radiator using the RA‑N and vent in 3 steps
- Close both valves, open the vent to drain until flow stops.
- Open only the supply; let water rush in and out the vent briefly.
- Close vent, set RA‑N to “N” for a short run, then restore the prior preset and reopen return. [Elektroda, Tobiasz22, post #16872557]
Edge case: Why do upper-floor radiators heat while mine stays cold?
A riser valve partially closed “by feel” can equalize supply and return pressures at lower floors, halting flow. Upper floors may still heat, masking the fault. Ask building management to measure and rebalance. [Elektroda, Zbigniew Rusek, post #16874018]
