Preparing Your Heating System For Winter……..

…….Not just preparation for winter

…….Ongoing maintenance regime to ensure the condition of the heating systems

…….Older systems have great potential for operational and efficiency improvements

Typical Heating System Layout

Mixing / Control Group – How They Work

Boiler Circuit

Pumps – “The red ones”

Canned rotor pump…….motor and impeller form one integral unit.

No shaft seal

Bearings lubricated by the liquid

Generally used for smaller capacity systems

Pumps – “Centrifugal Pumps”

Closed coupled pumps……motor and impeller are separate

Pump shaft has mechanical seal

Widely used across the industry

Most common types – Grundfos TP or older LM and Johnson CL

Majority that we now fit are Johnson based on cost and reliability

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

Leaks / signs of leak 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

Noise Pumps should run almost silent….any

noise is sign of a potential issue ( Dead head / air / trapped debris )

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

Water Velocity

SLOW VELOCITY / LOW RESISTANCE HIGH VELOCITY / HIGH RESISTANCE

Pumps…..Fitting invertors for variable speed.

……….Pumps may be bigger than required – designed with “safety margin”, so possibly moving too much water

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

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 10 – 20 minutes depending on system design and type.

To fully assess this, suggest you get specialist. FEC ?

Mixing Valves – The Issues Just because the valve appears to move, it does not mean its working

!

Does valve operate smoothly when moved manually ?

…..if not

Possible debris / sludge / lime scale build up / corrosion

……if this is an issue, this could signify issues throughout the rest of the system

Moving back and forth manually may temporarily clear this, but ultimately only removal and internal inspection is the answer

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

Consider the time and effort that goes into fitting a new seal kit without guaranteed results

Possibly cheaper to fit new valve !

Mixing Valve Actuators Belimo SM24…..discontinued.

Possible replacements SM24a and HT24

New linkage kits are not as good as the old ones where !

Centra VMM 40-24

Linkages quite often the weak point

…….but need to consider why they have failed !

Valves – The Different Types Gate Valves….

Ball Valves…..

Butterfly Valves…..

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 )

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 re-used as seats are also the sealing gasket between the flanges

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

Underfloor Heating and Bench Heating – The Issues……. …….systems with underfloor heating and bench

heating can have massive air issues

Oxygen can permeate through some plastic tubes

( outside to inside )

Low temperatures make it difficult for the air to dissipate

Undulations in the plastic pipes make it difficult to clear air

Joints between steel and plastic pipes notorious for leaks

Use good quality connectors – we generally use brass connectors

Have experienced systems rotting out in under three years when not attended to

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

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

…..combine this with sludge and debris build up, this can result in massive boiler inefficiencies

Efficiencies can be as low as 55 / 65% from the efficiency of a new boiler at 85% - 90%

Systems with buffers can have bigger issues

Bigger water volume = more lime scale = bigger issues !

Sludge and Debris Sludge and debris can slow systems

Sludge and debris can block systems !

Low velocity areas such as trolley loops can block and difficult to flush

…..have had to cut end off pipes to clear with pressure washer !

…..massively dirty job !

Try opening system drains and see what comes out

……if nothing comes out, you’ve got problems !

Water Treatment, Water Softeners, System Filters….

Water treatment should be in all systems…..difficult to appreciate as an investment as cannot be seen, but ultimately will save money in the long run.

…….but you don’t see that saving, as the prevention won’t be appreciated !

Filling systems through water softeners can massively reduce lime scale issues

…….but you don’t see that saving, as the prevention won’t be appreciated !

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.

External Corrosion of Systems Also consider external corrosion !

Overhead irrigation can cover heating pipes with water….

Issue when heating system systems are low temperature, as pipes may not get hot enough to externally dry properly

Especially prolific when pipes are painted, as damp can trap between paint layers

Automatic Fill Sets and Water Top Up 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, ideally with a water meter

New water = New Oxygen and Lime Scale = System Corrosion

Automatic fill sets can also hide system leaks !

Expansion Systems Vital part of any heating system

Compensates for increase in water volume as system heats up

Maintains system pressure

Main sign of failure will be a dramatic increase in pressure, probably seen through blow off through boiler safety valves.

Several different types………..

Diaphragm Expansion System Main problem will be split bag

Where system has several vessels, failure of one may not be totally apparent

Can fail through constant too high water temperatures – must always be fitted to system return

Possible sign of failure would be water coming out of air valve.

Nitrogen Expansion System Old school type system, but

probably the most simplistic

Very little to go wrong ?

Failure can only really be due to leak – difficult to see on nitrogen side !

Compressor Type Expansion System Based on diaphragm type

expansion system

Compressor controls pressure by adding air into bag

Solenoid valve controls pressure by releasing air from bag

Relatively high maintenance, with the potential for issue if not maintained

…potential issues

Split bag

Failed compressor

Failed solenoid valve

Pumped Type Expansion System Another “old school” type system

Potential failure points, but easy to understand

Often “Home made”, but now available commercially as packages

Too much pressure in system, solenoid valve releases water into tank

Too little pressure, pump starts and takes water from tank and puts in back in the system

……Potential failures Pump

Solenoid valve

Buffer Tanks

Be Careful When Draining Systems and Tanks !

Cold Spots and Hot 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 !

Hot Spots – Too much heat in an area

Possible on internal walls

Consider insulating pipes to reduce heat

….Heat Drift Not to be confused with pipework issues !

Glasshouse on a slope ?

Prevailing wind ?

Heat can drift across the glasshouse – side to side / end to end / corner to corner, either by convection ( heat rises ) or by air movement ( leaky glasshouse and prevailing wind )

Hot Spots, Cold Spots or Heat Drift are always generally a sign shown in uneven crop growth in certain areas of the glasshouse.

Air Heaters – Types Generally three different types…..

Priva DF10 ( or similar )

All heat kept in glasshouse and used to produce Co2

Direct fired, need careful positioning, especially in low glasshouses

Air Heaters – Types 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

When positioning, need to consider flue positions, especially when glasshouse fitted with screens

Fitted in glasshouses with overhead spraylines can bring corrosion issues with casings rotting out ( some makes have galvanised housings )

Air Heaters – Types 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

Air Heaters – System Design

Need further advice and assistance ?