LPHW Unit Heaters

Unit Heaters

Many industrial buildings prefer to run their heating from a piped hot water circuit. Where heat is available in this form then the use of LPHW unit heaters fed on hot water is invariably the most cost-effective method of space heating a room or building. As with electric fan heaters, there are a variety of types and options available and we aim to make choosing the right model as easy as possible. The following guidance is written around the LPHW unit heaters product ranges that we supply namely;

Frico SWS water fed LPHW unit heaters

Frico SWS water fed fan heater. Probably the most cost effective way of turning heated water into heated air

Frico SWH water fed LPHW unit heaters

Frico SWH water fed fan heater. For sophistication of the on board control system, SIRe, there is nothing even close.

Frico SWT water fed fan heater

Frico SWT ceiling hung water fed LPHW unit heater. Heating and destratification but at a price

Kroll LH LPHW unit heater

Kroll LH range of LPHW unit heaters. Competative at the smaller end and with some very large heating capacity at the bigger end of the range

VEAB AW water fed unit heater

VEAB AW. An excellent quality LPHW unit heaters with onboard valve gear.

Cirrus LPHW Unit Heater

Cirrus Unit Heater. The size of the Cirrus range is huge with several casing sizes and internal coil configurations.


Applications for Water LPHW  Unit Heaters

There is no doubt that if you have a good source of heated water on a piped circuit then these unit heaters are a very cost-effective way to discharge the heat in to the areas in which it is needed. Each model has a large range of heat output depending on the flow temperature, return temperature, ambient air temperature, and water flow rate. This means that with the addition of a recirculation air / fresh air mixer cabinet and suitable controls, these ranges are an ideal compliment to heat sources that are bit less controllable than straight oil gas or electricity fired systems. For biomass boilers, solar fed thermal stores and wind turbine heated thermal stores it is useful to have not only a quick and effective means of dumping excess heat, but also a system that can deliver heat from quite low temperatures and be easy to integrate with a secondary heating system when water temperature is too low.

LPHW Unit Heaters – How much Output?

If you are using a water fed LPHW unit heaters to space heat a room, the implication is that you are using available surplus heat and this will be the principle heating for the room. By contrast electric fan heaters are often secondary heating sources. As with any heating requirement the initial stage is to identify the size of the heating requirement. If it is a room you want to heat then this is fairly straight forward; just use our calculator tool.

 

The space heater calculator provides approximate heating requirements for several generic building types, which for most users is accurate enough. For accurate heat loss calculations you would need work it out from scratch using the U values of the various materials that are used to make your room or building. Bare in mind the heat contribution that might be made by other heating in the room, whether it is from a heating system or perhaps from a hot industrial process or machine. If it is a variety of rooms, in other words the heater will be used in several different places, then try to select the largest amount of power that you may need.

Configuration for LPHW Unit heaters

It is seldom the case that a required heat output for a system of water fed unit heaters can be met neatly with a single heater. In most cases there are a number of configurations using a number of models from a range to achieve the overall space heating requirement for an application. Sometimes there is a choice between a number of unit heaters of a large size or a greater number of unit heaters at a smaller size.

Generally the smaller number of larger unit heaters will be more cost-effective in terms of unit heaters cost, control costs and installation cost. But the choice of unit heaters should also take into consideration the shape of the room and air throw of heaters, perhaps using larger unit heaters for larger uniform areas, and using smaller unit heaters for smaller dead areas of the main area.

Uses of Fresh Air in Space heating

Frico SWH SWS LPHW unit heater options

Because the water fed unit heaters usually use a circuit of hot water that is often ‘surplus’ it is quite common that these unit heaters are not merely mounted on wall brackets, in 100% recirculation mode, but mounted on mixer boxes, which themselves are mounted over a vent in the outside wall, enabling heated air to be a mixture of recirculated and fresh air.

With the addition of either manual or motorised dampers, the mixer boxes allow a the flow to through the unit heater to be set at any level from 100% fresh to 100% recirculated and anywhere in between.

Mixer boxes are useful because in addition to being able to take air straight from the room through a grill, the grill can be removed leaving a upstand (spigot) for ducting connection, so that the mixing box can be part of a more complex ducted ventilation system.

The key element to connection to a mixing box where outside air is brought in, is that the heater control system incorporates frost protection functionality, to prevent any chance of water freezing in the coils when the heater coils are not being used for general heating.

As well as mixer box options, there are also filter box options allowing a G3 efficiency filter to be fitted. This fitting is essential if the unit heaters are to be used in dusty environments in order that build up of dust on the coils is prevented.

Mounting And Connection of Water Fed Unit Heaters

The water fed unit heaters that we supply can all be installed for right hand or left hand connections. The heater is merely rotated 180 degrees to switch the connections from one side to the other. The convention is that inlet is the uppermost connection. Connections can be made either with compression fittings or as plain soldered joints.

Water fed unit heater mounting arrangments

Different ways of mounting Frico SWS/SWH range LPHW unit heaters

If filter boxes or mixer boxes are to be used then the heaters would inevitably be wall mounted where the heat distribution is horizontal, however where there is a need to mount from the ceiling, then this can be accommodated using the mount brackets fitted to the back of the heater housing.

This then enables the LPHW unit heater to be mounted to the ceiling from vertical steels and for the water connections can be on either side, or on top for vertical air  distribution. The capability for ceiling mounting is especially important to enable even heat distribution in larger buildings.

While the various water fed unit heaters that we supply are usually used for wall mounting, but with the capability of

Frico SWT water fed unit heater

SWT ceiling mounted water fed unit heater

ceiling mounting where required, there is also a separate product range, SWT, of dedicated ceiling mounted water fed unit heaters, which can be all of, or part of, an array of heating fan coils for larger buildings. The difference with SWT is that the heated air is discharged in a vertical column from the heater. With its ceiling mounting and downwards discharge of warm air it means that these unit heaters also destratify the air as well as heat it so that separate destratification fans are not needed. The SWT is also available with accessories including inlet filter screens, which prolong the coil cleaning service interval, discharge extension collar, which increases the air throw of the unit, and a louver fitting, which distributes air to the sides rather than straight down.

Heat source for Water fed unit Heaters

Whilst many will consider conventional boilers to be the heat source of choice for a hot water circuit, they are not necessarily the most flexible source of heat. Water fed unit heaters are not fussy about what heats the water up and will operate perfectly well from a wide range of water feed temperatures. The SWS and SWH heaters that we supply can work with fed temperature anywhere in the range 60 – 125°C and at pressures up to 10 bar. This means that as well as being ideally suited to conventional large boilers, the units can also use relatively low-grade heat produced by chiller/heat pump/ boiler combinations, where the chiller or heat pump preheats water to say 40-50°C  before the boiler adds top temperature to get it to normal heating circuit flow of say 80°C. The benefit of this type of arrangement is that typically the winter heating costs are lower and that in summer the chiller can be used to cool water for the heating circuit. Even if you have a heat pump or chiller producing 60°C this is hot enough to be used to feed LPHW unit heaters, the only difference being that you will get fewer kilowatts out of it than if the flow temperature was higher. The beauty of LPHW unit heaters is that even for lower temperature flows, they are still a very cost-effective way of discharging heat.

Cooling From A unit Heater?

Often overlooked when choosing whether or not to use mixer boxes as part of the installation, is their usefulness in summer. Industrial buildings particularly those with steel skinned cladding and or heat producing processes can become uncomfortably warm in summer. With mixer boxes behind your fan heaters you can set the box to 100% fresh to draw in relatively cool fresh air to displace warmer air in the building through the various external doors.

If the heaters depend in part on a chiller for the heat generation, then in summer months this can be used as a cold water source so that the ‘heaters’ can be used for cooling the air. Although note that if you do this ensure that you fit a drain to the base pan of the heater and connect it to a drain, so that condensate can be drained off. 

Controls for LPHW unit Heaters

The control of water fed unit heaters make a simple heater into a sophisticated heating system. To consider each of the heater ranges in turn;

Frico SWS water fed LPHW unit heaters

SWS is only designed to operate with, a relatively simple control system.

Airflow Control Thermostatic Water flow control
230v models 5 step control by RE series (exact model dependant on amperage loading)
2 way valve and actuator, with either a T series thermostat or a KRT capillary tube thermostat
415v 3 ph models 2 step control by SWYD1 controller and STDT16 thermal contact motor protection 2 way valve and actuator, with either a T series thermostat or a KRT capillary tube thermostat


Frico SWH water fed unit heater

SWH is a far more sophisticated water fed unit heater, because its control options have a larger variety of functions. The heater unit itself comes equipped with the control option module that you choose.

Control Module  Control functionality Water flow control
SIReB Basic
  • Manual regulation of fan speed and temperature
  • Automatic regulation of fan speed and temperature with integrated thermostat
VOS valve kit on/off comprising;

Part Description
TBVC regulation and adjustment valve
SD230 actuator on/off 230v
AV shutoff valve
BPV10 bypass valve

or a,

VOSP pressure independent valve kit on/off, comprising;

Part Description
TBVCMP independent pressure regulation and adjustment valve
SD230 actuator on/off 230v
AV shutoff valve
BPV10 bypass valve

 

SIReFC Competent
  • Manual regulation of fan speed and temperature
  • Automatic regulation of fan speed and temperature with integrated thermostat
  • Calendar Function
  • Filter sensor
  • BMS control incl. on/off, fan speed, and alarm functions

 

VOS valve kit on/off comprising;

Part Description
TBVC regulation and adjustment valve
SD230 actuator on/off 230v
AV shutoff valve
BPV10 bypass valve

or a,

VOSP pressure independent valve kit on/off, comprising;

Part Description
TBVCMP independent pressure regulation and adjustment valve
SD230 actuator on/off 230v
AV shutoff valve
BPV10 bypass valve
SIReFA Advanced
  • Manual regulation of fan speed and temperature
  • Automatic regulation of fan speed and temperature with integrated thermostat
  • Calendar Function
  • Filter sensor
  • BMS control incl. on/off, fan speed, and alarm functions
  • Eco mode – for energy efficiency control bias
  • Comfort mode – for comfort control bias
  • more advanced BMS controls
  • Maximum limit on return water temperature
  • Stepless heat control

Also there is a variation on the above which is to have a SIReFA WM which also provides automatic control of heating and ventilation using an upstream mixing cabinet

 

 

 

VMO Modulating valve kit, comprising

Part Description
TBVCM regulation and adjustment valve
SDM24 modulating actuator 24v
AV shutoff valve
ST23024 24v transformer for valve actuator

or a,


VMOP
pressure independent valve modulating kit, comprising;

Part Description
TBVCMP independent pressure regulation and adjustment valve
SDM24 modulating actuator 24v
AV shutoff valve
ST23024 24v transformer for valve actuator


Frico SWT water fed unit heater

SWT is only designed to operate with, a relatively simple control system from the following options;

Control Method Unit Control Water flow control
Thermostat onlyThe thermostat starts/stops the fan and also controls the heat supply on/off. The fan is set to run on high speed KRT1900 or T10/TK10 room thermostat TVV20/25, valve + SD20, acutator
2 step airflow controlThe air flow is manually regulated in 2 steps. No heat regulation, maximum water flow through the heating coil. CB20, control panel Nil
2 step airflow control and thermostatThe thermostat starts/stops the fan and also controls the heat supply on/off. The air flow is manually regulated in 2 steps. CB20, control panel
KRT1900 or T10/TK10, room thermostat
TVV20/25, valve + SD20, actuator
5 step airflow controlThe air flow is manually regulated in 5 steps. No heat regulation, maximum water flow through the heating coil. 5 step control by RE series (exact model dependant on amperage loading) Nil
5 step airflow control and thermostatThe thermostat starts/stops the fan and also controls the heat supply on/off. The air flow is manually regulated in 5 steps. 5 step control by RE series (exact model dependant on amperage loading) KRT1900 or T10/TK10 room thermostat TVV20/25, 2-way valve or TRV20/25 3-way valve + SD20, actuator

 
VEAB AW LPHW unit heaters

VEAB AW water fed fan heaters

VEAB AW water fed fan heaters

This range of water fed unit heaters is a little different to the Frico ranges, and they come in 4 sizes, and 3 formats. By way of comparison with the Frico range the nominal outputs for the AW heaters @ 80°C/60°C and 15°C ambient, are 13.9kw, 24.5kw 40.4kw and 61.7kw.

AW-a.  This variant of the AW unit heater comes with a build in valve, actuator and a fan speed controller. This means that with the connection of an external sensor with set point adjustment, that the heater is self regulating by opening and closing the water valve and controlling the airflow. The AW-a with much of its control function built-in therefore has the benefit of a fairly straight forward installation with few cable runs. The AW-a can as an alternative be controlled by external 0…10V control signal.

AW-s.   The AW-s version of the unit heater is the most basic, with only a coil and fan in the box. It is designed to be controlled by external controls (thermostat, 2 or 3 way actuated valve, and or fan speed controller.

AW-af.  This variant of the AW range unit heaters are designed to the used with an upstream mixing plenum and to provide heated fresh air and to provide frost protection. The fan speed is set on installation to suit the application and will run con continuously. The temperature is controlled by a supplied actuated valve.

Although not detailed on our website, we do supply the AW range. Call or email us for details, help and pricing, for your application.

Cirris Range LPHW Unit Heaters (water or steam)

The Cirrus range of LPHW unit heaters are available in 5 different chassis sizes and each chassis size has several further options on the coil arrangement, fan speed and casing style. This makes Cirrus the largest range of water fed fan heaters that we supply.

Cirrus LPHW Unit Heater

Cirrus LPHW Unit Heater

Style H1 is the horizontal discharge unit and has a top mounting bracket which means that the unit will hang from its wall mounting bracket.  The H1 style can be used for hot water or steam up to about 6 bar.

Style V1 simply has a different mounting arrangement on the standard heater allowing it to be hung from a ceiling or roof structure, and having 4 way outlet louvers for maximum dispersion of the outlet air.  The V1 style is suitable for both low and medium temperature hot water (up to 120°C) connection.

Style V2 has an elongated casing that houses the coil and the fan downstream of the coil. The V2 style is suited to larger higher ceiling applications where horizontal discharge units would struggle to achieve even coverage. The V2 style can be used for hot water or steam up to about 6 bar.

The Cirrus range can be fitted with a 1, 2 or 3 row water coil, or a 1 row steam coil.

Although not detailed on our website, we do supply the Cirrus range. Call or email us for details, help and pricing, for your application.

Kroll LH LPHW unit heaters

Kroll LH LPHW unit heater

Kroll LH LPHW unit heater

The LH range of unit heaters from German manufacturer Kroll offers a wide range sizes and are noted for larger sizes with nominal heat outputs upto 118kw. They are competitively priced at the smaller end of the size range (outputs to about 20kw) whilst at the bigger end of the range they offer size and output which is beyond the range of most of the other manufactures.

The larger Kroll unit heaters in this range have two fans and at the output at 90/70°C and

Kroll LH620 LPHW unit heater

Kroll LH620 LPHW unit heater

ambient of -15°C the largest LH range heater produces a thumping 203kw. Other useful features in this range is that there are extensive range of options for filter boxes, louvers, and side outlets. There are also options the heaters being supplied with stainless steel casing as an alternative to the standard powder coating. These unit heaters can also be supplied with explosion proof fan motors, where required.

Tanner LPHW unit heaters

Tanner MDA LPHW fan heater

Tanner MDA LPHW fan heater

The Tanner range of LPHW fan heaters are useful as not only is there a large range that has several 3 phase models as well as single phase models, but there is also a handy range of air movement ancilleries, including louvers, mixing boxes actuated dampers, filters, meshes and grilles. It means that where a solution is sought that is a bit more than just a LPHW fan heater attached to a wall, then there will be an answer to be had within the Tanners MDA range.

Tanner MDA accessories diagram

Tanner MDA accessories diagram

Tanner MDC high pressure LPHW fan heater

Tanner MDC high pressure LPHW fan heater

Also useful within the range are Tanner MDC  unit heaters, which couple a coil with a centrifugal fan rather than a axial fan. This is used where the system fan needs to overcome a bit more system pressure resistance than just the coil and would be used for instace if there was a requirement to connect the heater to ducting to distribute the warm air.


Needless to say, if you need any help on LPHW unit heaters, call us on 01729 824 107.  We probably know the various ranges, “warts an’ all”, better than any other supplier.

 

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