Significance of return temperature for BHKW CHP efficiency | Electricity fee <meta name="description" content="Significance of return temperature for the cogeneration unit (BHKW CHP) efficiency: the return temperature is typically 55–70 °C; the difference between VL and RL determines the thermal power — a high return temperature degrades the thermal efficiency"> <link rel="canonical" href="https://stromfee-mauritius.ai/en/glaesern/cogeneration/wizards/ruecklauftemperatur/"> <script type="application/ld+json">{"@context": "https://schema.org", "@type": "Article", "headline": "Significance of return temperature for BHKW CHP efficiency", "mainEntityOfPage": "/glaesern/cogeneration/wizards/ruecklauftemperatur/", "description": "Return temperature typically 55–70 °C; spread between VL and RL determines the heat output — a high return temperature worsens the thermal efficiency and prevents condensation utilization"}</script> <script type="application/ld+json">{"@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{"@type": "Question", "name": "What is a normal return temperature in a BHKW?", "acceptedAnswer": {"@type": "Answer", "text": "Typical values are between 55 and 70 °C, depending on the specific design of the system."}}, {"@type": "Question", "name": "Why is the difference between flow and return important?", "acceptedAnswer": {"@type": "Answer", "text": "The temperature difference (Delta T) is the physical basis for calculating the delivered thermal power."}}, {"@type": "Question", "name": "At what point is the return temperature too high?", "acceptedAnswer": {"@type": "Answer", "text": "A return temperature significantly higher than the setpoint indicates insufficient heat recovery or a flow rate that is too low."}}, {"@type": "Question", "name": "How does the return temperature influence efficiency?", "acceptedAnswer": {"@type": "Answer", "text": "A high return temperature degrades thermal efficiency and complicates the use of condensation heat."}}, {"@type": "Question", "name": "Why must the return temperature remain stable?", "acceptedAnswer": {"@type": "Answer", "text": "Unstable values indicate hydraulic problems or changing load profiles, which hinder the control of the BHKW engine."}}, {"@type": "Question", "name": "What are the consequences of a return temperature that is too low?", "acceptedAnswer": {"@type": "Answer", "text": "A temperature that is too low can indicate a flow rate that is too high, preventing the effective dissipation of thermal energy."}}]}</script> <style>:root{--bg:#fdfcff;--bg-soft:#faf8ff;--surface:#fff;--text:#1d1d1f;--text-2:#515154;--text-3:#86868b;--border:#fed7aa;--border-soft:#efeaf8;--accent:#f97316;--accent-bright:#fdba74;--accent-dim:rgba(234,88,12,.08);--emerald:#ea580c;--font:'Inter',-apple-system,sans-serif;--mono:'JetBrains Mono',monospace;--radius:16px}*{box-sizing:border-box;margin:0;padding:0} 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.wiz-next{background:linear-gradient(135deg,var(--accent),var(--accent-bright));color:#fff;border:0;border-radius:999px;padding:.85rem 1.6rem;font-weight:800;font-size:1rem;cursor:pointer;box-shadow:0 10px 26px rgba(249,115,22,.28);text-decoration:none;display:inline-flex;align-items:center;gap:.5rem} .wiz-next:hover{transform:translateY(-1px)} .benefit{background:linear-gradient(135deg,#fff7f0,#fff);border:1px solid var(--accent-ultra);border-radius:18px;padding:1.3rem 1.4rem;margin:.2rem 0 1.1rem} .benefit h3{margin:0 0 .5rem;font-size:1.2rem;font-weight:800;color:var(--text,#1d1d1f)} .benefit p{margin:0;color:var(--text-2,#515154);line-height:1.6}</style></head><body> <header class="site"><div class="wrap navrow"> <a class="brand" href="/glaesern/">◈ Transparent BHKW</a> <nav class="nlinks"><a href="/glaesern/">All trades</a> <a href="/glaesern/cogeneration/waerme.html">Thermal coupling</a></nav> <a class="navcta" href="#kontakt">System check →</a></div></header> <div class="hero-w"><h1>Return temperature</h1><p>Component assistant · Thermal coupling</p> <div class="livebar"><span class="livedot"></span><b id="lcount2">…</b>Live values from the plant ·<span id="lts2"> verbinde… </span></div></div> <div class="wiz-wrap"> <div id="steps"> <div class="st" data-s="1"><span class="no">1</span> Comprendre </div> <div class="st" data-s="2"><span class="no">2</span>View live</div> <div class="st" data-s="3"><span class="no">3</span>What the AI does</div> <div class="st" data-s="4"><span class="no">4</span>Your benefit</div> </div> <div id="body"></div> </div> <div class="sec"><h2>Diagram — Process & sensors live</h2><p class="lead">The path through the domain, with the actual measurement points of the system.</p><svg viewBox="0 0 920 300" style="width:100%;height:auto;background:#fdfcff;border:1px solid #fed7aa;border-radius:16px"><defs><linearGradient id="bx" x1="0" y1="0" x2="0" y2="1"><stop offset="0" stop-color="#fff"/><stop offset="1" stop-color="#fff7ed"/></linearGradient><marker id="ar" markerWidth="8" markerHeight="8" refX="6" refY="3" orient="auto"><path d="M0,0 L6,3 L0,6 Z" fill="#f97316"/></marker></defs><text x="20" y="30" font-size="14" font-weight="800" fill="#ea580c">Thermal coupling — process diagram</text><text x="20" y="48" font-size="10.5" fill="#86868b">orange = live sensor from the plant · flow from left to right</text><line x1="138" y1="152" x2="204" y2="152" stroke="#f97316" stroke-width="2.5" marker-end="url(#ar)"/><line x1="328" y1="152" x2="395" y2="152" stroke="#f97316" stroke-width="2.5" marker-end="url(#ar)"/><line x1="519" y1="152" x2="586" y2="152" stroke="#f97316" stroke-width="2.5" marker-end="url(#ar)"/><line x1="710" y1="152" x2="776" y2="152" stroke="#f97316" stroke-width="2.5" marker-end="url(#ar)"/><g><rect x="20" y="120" width="118" height="64" rx="12" fill="url(#bx)" stroke="#fdba74" stroke-width="1.5"/><text x="79" y="148" text-anchor="middle" font-size="13" font-weight="700" fill="#1d1d1f"> Kühler </text></g><g><rect x="210" y="120" width="118" height="64" rx="12" fill="url(#bx)" stroke="#fdba74" stroke-width="1.5"/><text x="270" y="148" text-anchor="middle" font-size="13" font-weight="700" fill="#1d1d1f"> Abgas-WRG </text></g><g><rect x="401" y="120" width="118" height="64" rx="12" fill="url(#bx)" stroke="#fdba74" stroke-width="1.5"/><text x="460" y="148" text-anchor="middle" font-size="13" font-weight="700" fill="#1d1d1f"><tspan x="460" dy="-4"></tspan><tspan x="460" dy="14">Plate heat exchanger</tspan></text><text x="460" y="170" text-anchor="middle" font-size="10.5" fill="#86868b"> Übergabe </text></g><g><rect x="592" y="120" width="118" height="64" rx="12" fill="url(#bx)" stroke="#fdba74" stroke-width="1.5"/><text x="650" y="148" text-anchor="middle" font-size="13" font-weight="700" fill="#1d1d1f"> Puffer </text></g><g><rect x="782" y="120" width="118" height="64" rx="12" fill="url(#bx)" stroke="#fdba74" stroke-width="1.5"/><text x="841" y="148" text-anchor="middle" font-size="13" font-weight="700" fill="#1d1d1f"> Wärmenetz </text><text x="841" y="170" text-anchor="middle" font-size="10.5" fill="#86868b">→ Customer</text></g><line x1="460" y1="120" x2="406" y2="88" stroke="#ea580c" stroke-width="1.5" stroke-dasharray="3 2"/><circle cx="460" cy="120" r="3.5" fill="#ea580c"/><g transform="translate(406,58)"><rect x="-52" y="0" width="104" height="30" rx="8" fill="#fff" stroke="#ea580c" stroke-width="1"/><text x="0" y="12" text-anchor="middle" font-size="8.5" fill="#86868b"> Vorlauf </text><text x="0" y="25" text-anchor="middle" font-size="12" font-weight="700" fill="#ea580c" class="svlive" data-k="sbhkw2_rvltemp_anlage" data-u="°C">…</text></g><line x1="460" y1="120" x2="514" y2="88" stroke="#ea580c" stroke-width="1.5" stroke-dasharray="3 2"/><circle cx="460" cy="120" r="3.5" fill="#ea580c"/><g transform="translate(514,58)"><rect x="-52" y="0" width="104" height="30" rx="8" fill="#fff" stroke="#ea580c" stroke-width="1"/><text x="0" y="12" text-anchor="middle" font-size="8.5" fill="#86868b"> Rücklauf </text><text x="0" y="25" text-anchor="middle" font-size="12" font-weight="700" fill="#ea580c" class="svlive" data-k="sbhkw2_rrltemp_anlage" data-u="°C">…</text></g><line x1="650" y1="120" x2="650" y2="88" stroke="#ea580c" stroke-width="1.5" stroke-dasharray="3 2"/><circle cx="650" cy="120" r="3.5" fill="#ea580c"/><g transform="translate(650,58)"><rect x="-52" y="0" width="104" height="30" rx="8" fill="#fff" stroke="#ea580c" stroke-width="1"/><text x="0" y="12" text-anchor="middle" font-size="8.5" fill="#86868b"> Puffer </text><text x="0" y="25" text-anchor="middle" font-size="12" font-weight="700" fill="#ea580c" class="svlive" data-k="rpuffer_t3" data-u="°C">…</text></g></svg></div> <div class="sec"><div class="block"><h3>Thus we connect — read only</h3><p class="step-p">The value comes from<b>Modbus TCP · Plant PLC · M-Bus (meters)</b>of the system —<b>read, not controlled</b>. Everything is<b>in the house</b>calculated, nothing leaves the house. No obligation to disclose operational data.</p></div><div class="block"><h3>Your own LLM for CHP — offline</h3><p class="step-p">Questions in plain language, answered by<b>Your own installation data</b>— local, no cloud. The AI runs internally; the installation remains yours.</p></div><div class="note"><b>Regulatory framework:</b>VDI 4680 (CHP assessment) · AGFW FW 308 (heating network)</div><div class="block"><h3>Associated causal chains</h3><p class="step-p">This component is part of<a href="https://bhkw-anlagen.com/kausalketten.html" style="color:var(--accent)">Installation causal chains</a>— from cause to effect (gas quality → engine → exhaust gas → heat → efficiency). The AI reads the entire chain, not just the individual value.</p></div><div class="block"><h3>Link with the entire installation</h3><p class="step-p">A CHP unit is never alone: electricity, heat and gas are linked, and with PV and battery storage, it becomes a system. The AI calculates the entire installation.</p><div style="display:flex;gap:.6rem;flex-wrap:wrap;margin-top:.6rem"><a href="/glaesern/cogeneration/" style="font-size:.85rem;padding:.4rem .9rem;border:1px solid var(--border);border-radius:999px;text-decoration:none;color:var(--accent)">BESS transparent →</a><a href="/glaesern/hotel/" style="font-size:.85rem;padding:.4rem .9rem;border:1px solid var(--border);border-radius:999px;text-decoration:none;color:var(--accent)">Gläsernes Hotel →</a><a href="/fr/pv-watcher/" style="font-size:.85rem;padding:.4rem .9rem;border:1px solid var(--border);border-radius:999px;text-decoration:none;color:var(--accent)">PV-Watcher →</a></div></div></div><div class="sec faqsec"><h2>Frequently asked questions</h2><details><summary>What is a normal return temperature in a CHP unit?</summary><div class="faq-a">Typical values are between 55 and 70 °C, depending on the specific design of the installation.</div></details><details><summary>Why is the difference between flow and return important?</summary><div class="faq-a">The temperature difference (Delta T) is the physical basis for calculating the delivered thermal power.</div></details><details><summary>From what point is the return temperature too high?</summary><div class="faq-a">A return temperature significantly higher than the setpoint indicates insufficient heat recovery or a flow rate that is too low.</div></details><details><summary>How does the return temperature influence efficiency?</summary><div class="faq-a">A high return temperature degrades thermal efficiency and complicates the use of condensation heat.</div></details><details><summary>Why must the return temperature remain stable?</summary><div class="faq-a">Unstable values indicate hydraulic problems or changing load profiles, which hinders the control of the CHP engine.</div></details><details><summary>What are the consequences of a return temperature that is too low?</summary><div class="faq-a">A temperature that is too low can indicate a flow rate that is too high, preventing the efficient dissipation of thermal energy.</div></details></div> <footer class="site"><div class="wrap"> <div class="fbrand">◈ CHP transparent</div> <p class="fclaim">Connected in read-only mode · local calculation · no cloud. The installation remains with you.</p> <nav class="flinks"><a href="/glaesern/">All trades</a> <a href="/glaesern/cogeneration/waerme.html">Thermal coupling</a> <a href="https://bhkw-anlagen.com/impressum.html">Legal notice</a> <a href="https://bhkw-anlagen.com/datenschutz.html">Data protection</a></nav> <div class="fcopy">© 2026 HR Energiemanagement GmbH · 32257 Bünde · +49 5223 4921030</div> </div></footer> <script> var state={step:1}; function li(t){return '<li>'+t+'</li>';} function nav(s){var b=s>1?'<button class="wiz-back" onclick="go('+(s-1)+')">← Back</button>':'<span></span>'; var n=s<4?'<button class="wiz-next" onclick="go('+(s+1)+')">Next →</button>':'<button class="wiz-next" onclick="go(1)">From the beginning</button>'; return '<div class="wiz-nav">'+b+n+'</div>';} function step1(){return '<div class="step-grid"><img class="step-img" src="../img/step-img.jpg">'+ '<div class="step-grid"><div><p class="step-kicker">Step 3 · What the AI does</p>'+ '<p class="step-p">Return temperature typically 55–70 °C; the difference between flow and return determines the thermal output — a high return temperature reduces thermal efficiency and prevents condensation utilization.</p>'+nav(1);} function step2(){return '<p class="step-kicker">Step 2 · See live</p><h2 class="step-h">The plant — right now</h2><div class="live-head"><span class="livedot"></span><span class="live-status" id="lstatus"> connecting... </span><span class="live-sub">· anonymous reference plant · read-only from the process control system, calculated on-site</span></div><div class="kpis"><div class="kpi" data-k="sbhkw2_rvltemp_anlage"><div class="kl"> Flow </div><div class="kval"><span class="v">…</span><span class="ku">°C</span></div><div class="spark"></div></div><div class="kpi hl" data-k="sbhkw2_rrltemp_anlage"><div class="kl"> Return </div><div class="kval"><span class="v">…</span><span class="ku">°C</span></div><div class="spark"></div></div><div class="kpi" data-k="rpuffer_t3"><div class="kl">Buffer top</div><div class="kval"><span class="v">…</span><span class="ku">°C</span></div><div class="spark"></div></div><div class="kpi" data-k="rpuffer_t6"><div class="kl">Buffer bottom</div><div class="kval"><span class="v">…</span><span class="ku">°C</span></div><div class="spark"></div></div></div><p class="step-p" style="margin-top:1rem">Excerpt from <b id="lcount">…</b> plant measurements. For the detailed <a href="https://bhkw-anlagen.com/erklaervideo/ruecklauftemperatur.html" style="color:var(--accent)">explanation page with video →</a></p>'+nav(2);} function step3(){return '<div class="step-grid"><div><p class="step-kicker">Step 3 · What the AI does</p>'+ '<h2 class="step-h">What the AI reads from these values</h2><ul class="chk">'+li('Deviation from the setpoint temperature (indicator of an <b>excess of heat</b>)')+li('Difference between flow/return to calculate <b>thermal power</b>')+li('Monitoring condensation potential at low return temperatures')+li('Detection of <b>pump malfunctions</b> or narrowing in the circuit')+'</ul></div>'+ '<img class="step-img" src="../img/ki-waerme.jpg" alt="AI monitoring">'+ '<div class="szen-grid"><img class="szen-img" src="../img/szen-waerme.jpg" alt="Scenario" loading="lazy"><div><p class="mon">Monitoring: continuous · Entry/return temperature difference</p>'+ '<p class="step-p"><b>The scenario:</b> the gap narrows, the CHP extracts less heat, overall efficiency and CHP utility are lower.<br>'+ '<b>The AI:</b> detects the shrinking spread early, before the amount of heat drops visibly. <b>It identifies the trend before the limit is reached.</b></p></div></div>'+nav(3);} function step4(){return '<p class="step-kicker">Step 4 · Your benefit</p><h2 class="step-h">Why it matters</h2>'+ '<div class="benefit"><h3>An optimized return temperature maximizes thermal efficiency and prevents unnecessary thermal losses.</h3><p>Maintaining the target range of 55–70 °C ensures process stability. A return temperature that is too high reduces the usability of waste heat for low-temperature applications.</p></div>'+ '<div class="calcbox"><p class="step-p">Heating water flow rate (m³/h) <input id="c0" type="number" step="any" value="40" oninput="r()"> · Flow difference flow/return (K) <input id="c1" type="number" step="any" value="20" oninput="r()"> → <b><span id="o" style="color:var(--accent)">—</span> kW thermal</b></p>'+ '<p class="mon" style="margin-top:.5rem">Calculation: flow rate × difference × 1.16 kWh/(m³·K) (water)</p></div>'+nav(4);} function r(){var v=[];for(var i=0;i<2;i++){var e=document.getElementById('c'+i);v.push(e?parseFloat(e.value)||0:0);}'o');if(o)o.textContent=(Math.round(res*100)/100).toLocaleString('de-DE');}'body').innerHTML=state.step===1?step1():state.step===2?step2():state.step===3?step3():step4();'#steps .st').forEach(function(el){var n=+el.getAttribute('data-s');el.classList.toggle('on',n===state.step);el.classList.toggle('done',n<state.step);});'smooth'});} document.querySelectorAll('#steps .st').forEach(function(el){el.style.cursor='pointer';el.onclick=function(){go(+el.getAttribute('data-s'));};});'https://bhkw-anlagen.com/data/sensor-live.json',HURL='https://bhkw-anlagen.com/data/sensor-history.json',LKEY='sbhkw2_rrltemp_anlage',LIVEDATA=null,HISTDATA=null;function fmtAge(a){return a<90?('vor '+a+' s'):('vor '+Math.round(a/60)+' min');}function fmt(v){return (typeof v==='number')?(Math.round(v*100)/100).toLocaleString('de-DE'):v;}function spark(el,ser){if(!ser||!ser.length)return;var nz=ser.filter(function(x){return x!==0;});if(nz.length<2){el.innerHTML='';return;}var mn=Math.min.apply(0,ser),mx=Math.max.apply(0,ser),rg=(mx-mn)||1;var n=ser.length,w=100,h=26,pts=ser.map(function(y,i){return (i/(n-1)*w).toFixed(1)+','+(h-2-(y-mn)/rg*(h-4)).toFixed(1);}).join(' ');el.innerHTML='<svg viewBox=\'0 0 '+w+' '+h+'\' preserveAspectRatio=\'none\' style=\'width:100%;height:100%\'>'+'<polyline fill=\'none\' stroke=\'#f97316\' stroke-width=\'1.5\' points=\''+pts+'\'/></svg>';}window.__fillLive=function(){var d=LIVEDATA;if(!d)return;var c=d.count||Object.keys(d.sensors||{}).length;var e=document.getElementById('lcount2');if(e)e.textContent=c;var e2=document.getElementById('lcount');if(e2)e2.textContent=c;var st=document.getElementById('lstatus');document.querySelectorAll('.kpi[data-k]').forEach(function(card){var k=card.dataset.k;var s=d.sensors&&d.sensors[k];var vel=card.querySelector('.v');if(s&&vel)vel.textContent=fmt(s.v);if(HISTDATA&&HISTDATA.sensors){spark(card.querySelector('.spark'),HISTDATA.sensors[k]);}});document.querySelectorAll('.svlive[data-k]').forEach(function(el){var k=el.dataset.k;var s=d.sensors&&d.sensors[k];if(s)el.textContent=fmt(s.v)+(el.dataset.u?(' '+el.dataset.u):'');});var s0=d.sensors&&d.sensors[LKEY];if(st)st.textContent=(s0?('Anlage läuft · '+fmtAge(s0.age||0)):'Anlage');var t2=document.getElementById('lts2');if(t2)t2.textContent='aktualisiert '+fmtAge((s0&&s0.age)||0);var lv=document.getElementById('lv');if(lv&&s0){lv.textContent=fmt(s0.v)+(s0.u?(' '+s0.u):'');}var ll=document.getElementById('ll');if(ll&&s0)ll.textContent=s0.l||LKEY;var lt=document.getElementById('lts');if(lt&&s0)lt.textContent='Stand '+(s0.ts||'')+' · '+fmtAge(s0.age||0);};function pullLive(){fetch(LURL,{cache:'no-store'}).then(function(r){return r.json();}).then(function(d){LIVEDATA=d;window.__fillLive();}).catch(function(){var t=document.getElementById('lstatus');if(t)t.textContent='Live nicht erreichbar';});}if(HURL){fetch(HURL,{cache:'no-store'}).then(function(r){return r.json();}).then(function(d){HISTDATA=d;window.__fillLive();}).catch(function(){});}pullLive();setInterval(pullLive,30000); </script></body></html>