Troubleshooting PM
controller / Domestic hot water
Problem
Possible cause
Solution
In general: Does the PM
controller work incorrectly
If the quantity of tap water is normal (temperature unimportant) it
indicates that the PM controller works correctly.
Locate defect in another part
of the installation (see below).
In general:
Are the operating
conditions satisfactory?
The unit requires a primary flow temperature of minimum 60°C
and a differential pressure during operation according to the
information stated in the product sheet for the unit.
Contact district heating
supplier.
PM controller leaking,
Water leaking from Allen
screws at central part of PM
controller
One of the two O-rings is defective (does not influence the PM
control function). If a non-return valve is installed in the DCW inlet
(e.g. in the house service connection or in DCW meter) a safety
valve should be mounted between the non-return valve and the
water heater.
Replace PM controller (use
new sealings).
DHW tap load too low.
The diaphragm of the PM controller is defective.
Replace diaphragm or PM
controller
DHW tap load too low;
Tap temperature too low;
Tap temperature flunctuates;
PM controller wrongly adjusted.
Dirt strainer in primary flow clogged.
Defective non-return valve in thermostatic battery (DHW
tap temperature lower than DHW from unit).
Defective non-return valve in hot-water circulation (circulation
return pipe is getting cold during tapping of hot water).
Lime scale precipitation in plate heat exchanger for DHW
(
t primary too low during DHW tapping).
Dirt in PM controller.
DCW flow too high (big nominal diameter of pipe, high DCW
pressure); in total maximum 16-17 litre per minute
See back of the page.
Clean strainer.
Clean or replace non-return
valve.
Clean or replace non-return
valve.
Replace plate heat exchanger
.
Cleaning, see back of
page
.
DCW reduction can be
added).
Primary return water tempera-
ture too high while on stand-
by; Plate heat exchanger is
cold..
Bypass thermostat is defective or wrongly adjusted.
Replace or adjust by-pass
thermostat correctly
Primary return water tempera-
ture too high while on stand-
by; Plate heat exchanger is
hot.
Dirt (sand, iron splinter or similar) in PM controller. Controller
does not close. Noise from flow can often be heard.
Move handle several times
between red and blue
markings; at the same time
make several hot-water
tappings.
Clean PM controller
.
Primary return temperature
too high during hot water
tapping.
Lime scale precipitation in the plate heat exchanger for DHW
Replace plate heat exchanger
Connecting pieces of the PM
controller do not fit the unit
In particular when replacing PM controller in old units.
Loosen Allen screws; turn half
of the PM controller 180°.
Delivery address:
Stamp / Telephone:
Contact person:
Customer’s address: