Toshiba A09-01P manual Example, Action

Quick Reference Guide - Page 10

Checking water volume and initial pressure of expansion vessel

The expansion vessel of the Hydro Unit has a capacity of 12 litres. The initial pressure of the expansion vessel is 0.1 MPa (1 bar). The suggested initial water charge is 0.2MPa (2 bar).

The pressure of the safety valve is 0.3 MPa (3 bar).

Verify whether the capacity of the expansion vessel is sufficient using the following expression. If the volume is insufficient, install an appropriate external expansion vessel.

V

<12 L > 12 L

Action

Internal Expansion Vessel Size OK

Internal Expansion Vessel Size too small. Install appropriate external expansion vessel

V:Necessary total vessel capacity (L)

Ɛ:	Water expansion coefficient at average hot water temperature
Vs:	Total water volume in the closed system (Do not include Hot Water Cylinder)
P1:	System pressure at tank setting position (Mpa_abs*).
	(Pipe inner pressure during pump operation before heating device operates = water supply
	pressure)
P2:	Maximum pressure used during operation at tank setting position (MPa_abs*).
	(= safety valve setting pressure)

*The absolute pressure value (abs.) is obtained by adding the atmospheric pressure (0.1 MPa (1 bar)) to the gauge pressure.

Water temperature and expansion coefficient (Ɛ)

Hot water temperature	Expansion rate
(°C)	(Ɛ)
0	0.0002
4	0.0000
5	0.0000
10	0.0003
15	0.0008
20	0.0017
25	0.0029
30	0.0043
35	0.0050
40	0.0078
45	0.0100

Water temperature and expansion coefficient (Ɛ)

Hot water temperature	Expansion rate
(°C)	(Ɛ)
50	0.0121
55	0.0145
60	0.0171
65	0.0198
70	0.0229
75	0.0258
80	0.0292
85	0.0324
90	0.0961
95	0.0967
-	-

Example

Maximum Hot Water temperature: 55°C, initial

water charge: 0.2MPa and system volume: 200 L.

The calculated Vessel capacity (V) is 11.6 L:-

11.6	=	0.0145	x	200
		1	-	(0.2+0.1)
				(0.3+0.1)

In this case V < 12 L therefore the internal expansion vessel is sufficient.

There is no need to install an external expansion vessel.