Infrared Heaters

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Hello,

Does anyone have any experience modeling ceiling hung infrared heaters
in eQuest?

Thanks,
--
Bill Lafley

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Bill,

Do you have a chart that shows how much renewable energy the unit consumes
and then uses to create heat? What you need to do is create the item in 2
parts. Its renewable component, which might be a solar collector and then
you set up a radiant heater in the room either as baseboard or as your
system in that zone.The thing that I have noticed while modeling is there
are 2 things you are looking at.. products in your building and how they
consume energy, by amount and efficiency. The second is what are you doing
to replace the energy... renewable or are you pulling it from the grid. The
model does not care where it comes from as long as when you use the
renewable it is as efficient as you say it is. I typically use PVWatt
calculator and do manual calculations because someone taught me that. You
can also set up a collector in the utility&economics tab under photovoltaic
modules. This is where you will need the solar information on your
collector.

The weather file needs to be correct because this is where it is pulling
your solar radiation data from watts/meter squared or watts/feet squared.

Hope this helps. (Easier to do by hand)

Thanks,

PETER HILLERMANN

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Bill,

I just read about the infrared heater. If you are using people and equipment
to absorb heat and reradiate it, you have to rely on your schedules to tap
into that calculation.

I am totally guessing because I have never tried to set renewable energy to
a personal and equipment schedule. I'm sure it can be done however when you
look at heat generation from people it can vary from 450 BTU to 2500 BTU so
good luck. I would probably go to ASHRAE and look at the thermal comfort
data for process and heat generation of people and use the same numbers they
have set to those processes. Look at the equipment you are using and see
what it does. Add it all together and subtract from total energy that the
building is consuming.

Man that is complicated, best of luck to you my friend.

Thanks,

PETER HILLERMANN

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Bill/Peter:

I might be missing something, but this is the sort of equipment I think
of when someone says infrared heater:
http://www.spaceray.com/1_infrared-tube-heaters.php

Commonly found in auto garages and open-air outdoor venues.

If you're asking about how to model gas/electric radiant heaters of this
sort in eQuest - I think you've got a definite challenge. You could
play the custom-space-heat-source-scheduling game for hours on end...
but I would first suggest trying a unit heater (gas or electric as
appropriate) with a fan kW/CFM of zero or nearly-zero - see if that
works without errors.

The way this equipment really works is interesting/tricky to us modelers
because it does not need to heat the space air to what we'd normally
call "comfortable" temperatures as the heat can hit your skin and warm
you up without heating the air around you. You might account for this
by modifying the zone heating schedule (the target air temperature) to a
lower figure - though I'm not sure off the top of my head what would be
an appropriate figure - any suggestions?

NICK CATON, E.I.T.

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Nick,

I don't know but check this out http://www.infraredradiant.com/ I was giving
all kinds of solutions just in case.

Thanks,

PETER HILLERMANN

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Im not sure what your talking about as far as renewable energy, but ive always modeled infrared by dropping the zone temp setpoint by ten degrees, setting the fan energy to zero and making the furnace 100% efficient. Some times I lower the heating design temperature as well.

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My 2 cents.

Caveat: I have not actually modeled these (don?t really use them much in Atlanta).

I am assuming you have a separate HVAC unit in addition to these to supply ventilation air (or is it just the infrared heat?). The one?s that I have seen do not really have variable temperature controls they are either on or off.

There are two components to this:

1. Sensible heat gain to the space

2. Radiant heat to occupants (radiant heat to surfaces will eventually end up as heat gain to the space ? correct?)
Of the two ? the first one is a comfort issue and the second is an energy issue. In eQUEST the only reason we care about the comfort issue is that it allows you to turn down the supply air.

My suggestion is that you can model it in two ways:

1. Model it as an internal energy source (you can specify it as gas, electric or hot water). You can specify the input power as well as the Sensible Ratio. The drawback is that you cant control this by thermostat. But if the equipment is an on-off thing this doesn?t matter. The heat gain will be added to the space.

2. This might be the more Accurate way to model this (although its more long winded). The first step is the same ? you model it as an internal source. This is only to run the meter if it?s a gas or hot water run radiator. If its electric you could probably skip this step. The next step is to add a lighting load equivalent to this. eQUEST allows you to separate lighting loads into radiative fractions and sensible fractions. The drawback of course is that you have an additional step to separate out the lighting loads from this (by running the model once without the additional loads in lighting).

Not sure if this will work, but hey ? its free advice ?

Vikram Sami, LEED AP

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Bill,

I might have misunderstood terminology on infrared heater because what people seem to be saying is a radiant heater. We modeled these in a project in Connecticut in 2 ways. If there was only a radiant heater in the zone we used a unit heater, if we were combining it with outside make up air we used a unit ventilator. If you have a package system or some other system within the zone we offset the radiant heat with baseboards.

Sorry if I made things sound too complicated yesterday. I thought you were using some sophisticated radiant heater, but I guess radiant heater and infrared heater are essentially the same thing unless I am confused.

Thanks,

PETER HILLERMANN

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