The Woodwarm Approved F&E Tank
We have been increasingly asked for stainless steel F & E Tanks and now manufacture one suitable for Woodburning and solid fuel installations. It retails at £157.50 + VAT. It comes complete with 25mm urethane insulation for the sides and lid and is pre drilled for 15mm mains inlet, 22mm flow out and 22mm overflow, it would need to have a copper ball valve / float assembly fitted (not supplied).
The purpose of the Feed and Expansion (F&E) tank is to ensure that an open vented circuit never becomes pressurized and to safely collect water from your system that has overheated, in the case of the solid fuel appliance this may be due to many conditions, its worth remembering that unlike a gas, electric or oil you cannot just turn the heat off so precautions need to be taken.
Some typical reasons for the regulations:
- Over firing your stove (sometimes mixing fuels together can give different heat results and when not properly controlled it is possible to over fire your stove) if this heat cannot waste away through natural convection and through the radiator circuit it will make its way up to the F&E tank.
- If you have the type of circuit that requires part of the system to be pumped there is always a danger of power failure, so again the hot water needs to be able to safely collect.
- If you have kept your electric immersion element in your cylinder and the thermostat fails you will need to safely collect the excess water.
- The Woodwarm F&E Tank is constructed in 1.5mm 304 grade stainless steel which will give it an indefinite life span and extremely high heat resistance, it is insulated with 25mm foil backed expanded urethane board and will hold 30 litres.
Dimensions including insulation:- 500mm Long, 362mm Wide, 325mm High.
The F&E tank should be sized and set up to accommodate (without overflowing) at least 5% expansion of the total system contents, ie boiler(s), pipework, radiators and cylinder coil or thermal store etc.
When the system is filled the cold the water level should be set (by bending the ball valve arm) to give around 100mm of water in bottom of the F&E tank, (enough to cover the F&E pipe connection and allow for a possible small drop in water level when the pump is started), so that when the system is heated to it's max temperature (boiling) and the water expands, the resulting water level should be at least a inch or two below the overflow outlet. Also the ball valve inlet should be at least an inch or two above the top of the overflow pipe/max water level to ensure there is no cross contamination between the system water and the incoming cold mains supply. If the F&E tank is too small and constantly overflows and refills with fresh oxygenated water, then this will lead to or increase system corrosion.
A 22mm open vent, with 15mm feed & expansion and 22mm overflow pipe is OK for boilers up to 25 kW, above that will require a 28mm open vent, 22mm feed & expansion and 28mm overflow pipe.
The F&E tank should be well supported and capable of withstanding boiling water, as should all components, ie the ball valve float and overflow pipe must be copper etc.