Heating for Soft Fruit

Transcription

1 Heating for Soft Fruit 19 November 2018 Stonebridge Golf Course Jon Swain

2 Thanks to

3 The wet system

4 Pumps Noise pumps should run almost silent any noise is a sign of a potential issue (dead head/air/trapped debris)

5 Pump speed and water velocity Pumps may be bigger than required designed with safety margin, so possibly moving too much water Modern systems have pumps sized with electrical efficiency in mind older systems often have pumps with quite high electrical requirements as sized when electric was cheap If systems have previously had issues, or when modified for more capacity, bigger pumps may have been fitted which leads to issues with velocity therefore trying to put too much water down too smaller pipe for the volume of water therefore using too much electric

6 Pumps variable speed Fit an invertor to allow pump to be slowed down These can be manually operated and don t necessarily need to be controlled by the environmental computer Saves energy Better system efficiency

7 Pump issues Pump position Generally pump can be positioned horizontally pumping up or down Generally pump can be positioned vertically pumping left or right Shaft must be above the horizontal, otherwise can lead to shaft damage

8 Leaks/sign of leaks Water running from close coupled connection Traces of lime scale running down from close coupled connection Long-term leaks have a good chance of pitting the shaft and therefore pump replacement becomes the probable option. preventative failures If there are traces of lime scale from the close coupled connection, then generally it has been leaking too long for guaranteed repair

9 How to check pump speed Start with cold system. Manually open up to boiler system with temperature in it (not too hot) The period of time it takes for this temperature to come back to the mixing group is the reaction time of the system Should be between minutes depending on system design and type. To fully assess this, suggest you get specialist FEC Energy?

10 Mixing valves the issues Just because the valve appears to move, it does not mean its working Does valve operate smoothly when moved manually? Possible debris / sludge / lime scale build up / corrosion Moving back and forth manually may temporarily clear this, but ultimately only removal and internal inspection is the answer

11 Mixing valves the issues Leak from shaft? Possible strip down and fit new seal kit? Some valves are worth repairing, but If leaking for along time the shaft will be pitted, so repair may not hold for long cheaper to fit new valve

12 Mixing valve actuators Belimo SM24 discontinued Possible replacements SM24a and HT24 Linkages quite often the weak point but need to consider why they have failed New linkage kits are not as good as the old ones were

13 Valves Gate valves Ball valves Butterfly valves

14 Gate valves the issues Normally only one issue..dirt and corrosion Valve won t close Valve won t open Difficulty to operate often results in broken handle Best to not leave fully open or fully closed.always half a turn back from end so that it does not stick (unless actually draining down)

15 Butterfly valves the issues Generally good, and the most popular in modern systems Seats can break down making closing difficult Caused by. Old age Too much heat ( normally boiler flow valve fails) Problem when draining down as systems cannot be fully isolated as damaged seat will pass water Once removed generally cannot be reused as seats are also the sealing gasket between the flanges

16 Air the unseen problem Can cause bad circulation Can stop circulation Effectively reduces the diameter of the pipe where air is trapped Effectively blocks the diameter of the pipe where air fills pipe Effectively reduces the surface area of the pipe, reducing the heat output of the pipe

17 Automatic air vents Don t assume they are working Remove and vent off through valve to make sure its working properly also make sure that all manual vents are free and operate

18 Lime scale the unseen boiler killer Builds up on the heated parts of the boiler Builds up on the boiler tubes, reducing efficiency of heat transfer from fire to water Systems with buffers can have bigger issues Bigger water volume = more lime scale = bigger issues

19 Lime scale combine this with sludge and debris build up, this can result in massive boiler inefficiencies Efficiencies can be as low as 55% - 65% (new boiler 85% - 90%)

20 Sludge and debris Sludge and debris can slow and block systems Low velocity areas such as trolley loops can block and difficult to flush Try opening system drains and see what comes out if nothing comes out, you ve got problems

21 Hot water to air Water to air fan coils Connect to wet heating systems Simple way into piped hot water systems for biomass No fuel lines or combustion issues

22 Air heaters system design Need careful positioning Low fan powers Air distribution issues High number of heaters Lots of heating pipe in glasshouse roof

23 Water treatment Part stream filters can remove a massive amount of sludge and debris Will be appreciated for the first three months of installation, then get forgotten about as the majority of the sludge and debris will have been removed in that first three months Water treatment should be in all systems difficult to appreciate as an investment as cannot be seen ultimately will save money in the long run Filling systems through water softeners can massively reduce lime scale issues

24 External corrosion Issue when heating system systems are low temperature pipes may not get hot enough to externally dry properly Overhead irrigation can cover heating pipes with water Painted pipes damp can trap between paint layers

25 Automatic fill sets Uncontrolled water top up through automatic fill sets can cause massive long term issues Need to monitor the amount of fresh water that is being added, New water = New Oxygen and Lime Scale = System Corrosion Automatic fill sets can also hide system leaks

26 Buffer tanks Be careful when draining systems and tanks

27 Direct fired air heaters Hanging type Priva DF10 ( or similar ) All heat kept in glasshouse and used to produce CO 2 Direct fired, need careful positioning, especially in low glasshouses

28 Cabinet air heaters Upright, Freeblowing Some efficiency lost through chimney Direct fired, need careful positioning, especially in low glasshouse Generally quite tall, so can interfere with screens if not careful Glasshouse fitted with screens Fitting in glasshouses with overhead spraylines can bring corrosion issues

29 Greenhouse cold spots Cold Spots Not enough heat in an area Exposed area / corner / side of glasshouse Install more heating tube Consider insulating glasshouse walls? Possible sign of air lock

30 Greenhouse hot spots Hot Spots Too much heat in an area Possible on internal walls Consider insulating pipes to reduce heat