AUTOFLAME Mk8 MM Installation And Commissioning Guide

9 Heat Flow
Page 138 Mk8 MM Expansion Features Installation and Set-Up Guide 04.09.2016
9.3 Hot Water Flow Metering
Heat Flow Metering is simply measuring the amount of heat being transferred to the water by a hot
water boiler. If we know the stack losses and the standing losses of the boiler at any moment then
whatever energy is left over must be going into the water.
From the E.G.A. stack losses = 100 – combustion efficiency
Radiation losses are specific to the boiler, 1% radiation losses are typical for a packaged boiler
operating at maximum continuous rating. The loss is constant regardless of boiler output so at 50%
firing rate it would be 2% of the energy input.
The total heat in at any time is given by the heat flow metering so we can calculate the instantaneous
heat going into water. By integrating these values we can get a totalised value.
9.3.1 Hot Water Flow Calculation
Efficiency%  100%

Stackloss
RadiationLosses100
FiringRate

UsefulHeatintoWater  TotalHeat
Efficiency
100
VolumeFlowinlbs/hr
UsefulheatMBTU/Hr
SPHtBTU/lb/°F󰇛FlowTemp–ReturnTemp󰇜


VolumeFlowincuftHr 
VolumeFlowinlbs hr
⁄
DensityofWateratReturnTemperature
Since1cuftHr  0.124676USG.P.M.
VolumeFlowinUSG.P.M. VolumeFlowincuftHr0.124676
Example
A boiler firing at 75% has an input of 20,472,840 BTU/Hr (6MW). The temperature of the flow (MM
Temperature detector) out is 185°F and the temperature of the return T1 is 167°F. The combustion
efficiency is 82% (Mk7), Radiation losses are 1% at maximum continuous rating.
Description Imperial units Metric Units
Firing rate 75% 75%
Input 20.47 MMBTU/HR 6MW
Return Temperature 167°F 75°C
Flow Temperature 185°F 85°C
Sp Ht water 1.0 BTU/lb/°F 4.18KJ/KG/°C
Density Water 60.68lb/cuft @176°F 972 kg M³ @80°C
Combustion Efficiency 82% 82%
Efficiency%  100%

18%
1%100
75%

 80.67%

AUTOFLAME Mk8 MM Specifications

General

Brand	AUTOFLAME
Model	Mk8 MM
Category	Controller
Language	English