[Equest-users] Boiler temperature for hybrid geothermal heat pump system

[Sharad Kumar via Equest-users]

Hi Siliang,

The Water loop set-point that you have got as may be 70 °F is the water
temperature that is 21.11 °C.

It is obvious to take set-point of the boiler below the Ground source HX as
then it will operate.

The ground source steam temperature may shoot up-to 360-370 °F.

So may be taking steam boiler or steam plus hybrid boiler that is
electricity and keeping the set-point from 180 to 230 °F can be a take.

One can keep the set-point of the ground water heating loop as more than
230 °F to 370 °F may be 360 °F.

Then the functioning will be okay.

Generally the boiler set-point of electrical heater is 180 °F for steam
water to 230 °F which is nearly 82 °C (180 °F ).

*Thanks*,
Sharad.


---------- Forwarded message ----------
From: Siliang Lu via Equest-users <equest-users at lists.onebuilding.org>
To: "equest-users at lists.onebuilding.org" <equest-users at lists.onebuilding.org
>
Cc:
Date: Sat, 6 Aug 2016 16:14:27 -0400
Subject: [Equest-users] Boiler temperature for hybrid geothermal heat pump
system
Hi eQuesters,

 I have a problem regarding hybrid geothermal heat pump system built in  a
heating dominated building. From ASHRAE Handbook, it suggests that boiler
be installed separately from geothermal heat exchanger loop due to high
temperature of boiler.

In addition, one report says that even if there are some cases that boiler
has to be installed into GHX loop, the setpoint shall be 5-10F lower than
GHX setpoint( e.g. 45F). That is because if the boiler is installed in the
GHX loop, it is likely to dump heat back into the ground if boiler setpoint
is higher than GHX setpoint.

 However, heat exchange is related to both temperature and flow rate. With
smaller size of boiler, can we allow to install boiler with higher setpoint
higher than GHX setpoint into the GHX loop? Thanks!

All the best,
Siliang
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