- Jul 20, 2023
- 80
- 122
- Funster No
- 97,489
- MH
- Devon Aztec XL Auto
- Exp
- Limited motorhome and campervan hire previously.
I have been having pump dumps since I got the van last October, however these are due to the hot water being heated, not low temperature.
I can replicate the issue at will. Start with a cold or warmish tank of water, the pump is on at the panel, set the Truma on ECO hot water and wait. The boiler will dump water after about 10-15 minutes, the pump will cut in and the boiler dump again and sometimes keep repeating till it dumps all the water. Hence we cannot leave the water on, unattended. Oh and the water temperature is correct for ECO setting, so not overheating.
So either the
1. Pump pressure is too high
2. Pressure relief valve is too weak
So I purchased a glycerine filled 4 bar pressure gauge suitable for water/ air etc. Added some John Guest 12mm pipe, a JG T piece and inserts. I inserted the gauge immediately after the hot water outlet elbow the one with the clear pipe through the floor.
For anyone not sure this elbow is an Air Inlet and not a pressure relief valve without it you could not empty the boiler due to vacuum.
The automatic frost dump valve (blue knob on top and blue button lower down) is the pressure relief valve, I believe the yellow lever manual version is also. This is set for 2.8 bar max pump pressure and maximum system pressure of 4.5 bar according to data for the dump/safety valve.
So the findings are as follows:-
Everything is as per Devon factory build.
Fiamma Aqua 8 pump factory rated 1.5 bar (21psi) correct for Truma 4E
Pump on and system purged , pressure gauge reads 45psi cold. (2.8 bar is 40.7psi).
So my pump rated at 21psi is setting the system up at 45psi, before the boiler further increases it.
Cost of experiment was about £20 buying everything, took 10 minutes to install.
The Fiamma does not appear to have any cut off adjustment settings
Question
A. Do I fit a new pump, if so, which make. Keep old one as spare.
B. Or fit a pressure control valve plus JG adapters.
C. Have you a better idea?
I can replicate the issue at will. Start with a cold or warmish tank of water, the pump is on at the panel, set the Truma on ECO hot water and wait. The boiler will dump water after about 10-15 minutes, the pump will cut in and the boiler dump again and sometimes keep repeating till it dumps all the water. Hence we cannot leave the water on, unattended. Oh and the water temperature is correct for ECO setting, so not overheating.
So either the
1. Pump pressure is too high
2. Pressure relief valve is too weak
So I purchased a glycerine filled 4 bar pressure gauge suitable for water/ air etc. Added some John Guest 12mm pipe, a JG T piece and inserts. I inserted the gauge immediately after the hot water outlet elbow the one with the clear pipe through the floor.
For anyone not sure this elbow is an Air Inlet and not a pressure relief valve without it you could not empty the boiler due to vacuum.
The automatic frost dump valve (blue knob on top and blue button lower down) is the pressure relief valve, I believe the yellow lever manual version is also. This is set for 2.8 bar max pump pressure and maximum system pressure of 4.5 bar according to data for the dump/safety valve.
So the findings are as follows:-
Everything is as per Devon factory build.
Fiamma Aqua 8 pump factory rated 1.5 bar (21psi) correct for Truma 4E
Pump on and system purged , pressure gauge reads 45psi cold. (2.8 bar is 40.7psi).
So my pump rated at 21psi is setting the system up at 45psi, before the boiler further increases it.
Cost of experiment was about £20 buying everything, took 10 minutes to install.
The Fiamma does not appear to have any cut off adjustment settings
Question
A. Do I fit a new pump, if so, which make. Keep old one as spare.
B. Or fit a pressure control valve plus JG adapters.
C. Have you a better idea?
