Can't get Boiler:HotWater to heat water

asked 2015-02-25 07:51:03 -0600

LSurf
487 ●1 ●9

updated 2017-05-17 12:40:56 -0600

__AmirRoth__

4446 ●5 ●17 http://bleedinggreenna...

I have a working model built from some EnergyPlus example files.

In my PlantLoop for heating I have a Storage Tank for preheating, and a WaterHeater:Mixed to provide additional heat. I want to compare this scenario with my baseline scenario, in which I have a Boiler:HotWater for heating.

For this purpose I'm trying to replace the WaterHeater by a Boiler. However, I can't get this to work. I suspect some issue with setpoints, since there is flow through the Boiler, it just doesn't heat. Also, the WaterHeater has a field called Setpoint Temperature Schedule Name, whereas the Boiler doesn't.

I tried fiddling around with the setpoints. Also I've moved the Boiler to the same branch as the Storage Tank, without result.

How can I get my Boiler to heat to 50 °C?

Working with WaterHeater:Mixed

Not working with Boiler:HotWater

Full folder

The problem is with the the second loop in this HVAC system diagram.

HVAC system

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Comments

do you have an operation scheme for the boiler?

Archmage ( 2015-02-25 08:41:29 -0600 )edit

@Archmerage I think I have those correctly set up, but I'm not sure. I have these in my idf-file

LSurf ( 2015-02-25 10:46:35 -0600 )edit

You have PlantEquipmentOperation:HeatingLoad. You may find that PlantEquipmentOperation:ComponentSetpoint is what you need though I've not tested it on your file. See the comments on this answer.

Jamie Bull ( 2015-02-25 10:48:56 -0600 )edit

Awesome Jamie, that did the trick! I guess I'll have to learn more about the Operation scheme's. Can you convert your comment to an answer?

LSurf ( 2015-02-26 02:23:52 -0600 )edit

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answered 2015-02-26 04:03:50 -0600

Jamie Bull

flag of United Kingdom of Great Britain and Northern Ireland

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updated 2015-02-26 04:08:32 -0600

As was also suggested by @Archmage, the problem lies with your operation scheme. Having had a similar problem recently with two water heaters on the same loop, the problem should be solved by adding a PlantEquipmentOperation:ComponentSetpoint object for the loop rather than the PlantEquipmentOperation:HeatingLoad you currently have.

I'm not at all clear on why this is the case. That is, why a PlantEquipmentOperation:HeatingLoad scheme controlling multiple plant items in a PlantEquipmentList doesn't work. There doesn't seem to be anything explaining this in the documentation and I've seem odd behaviour at times so I'd be interested in a more comprehensive answer that gives the reasoning/logic behind it.

For reference, here's the section in the docs about plant and condenser control, though to me it's not clear how to work out the issue from reading it.

Comments

Hi, I am having the reverse problem, when I use PlantEquipmentOperation:ComponentSetpoint on a plant loop with two boilers it doesn't work (ie the boilers don't turn on and I have zero flow) but when I use PlantEquipmentOperation:HeatingLoad it does work. Have you seen this before as well? My problem is I have to use OpenStudio and I can't find an option to change the operation scheme.

Annie Marston ( 2015-05-13 13:00:23 -0600 )edit

I haven't seen this, and don't use OpenStudio. If you're still having problems you might try opening a new question.

Jamie Bull ( 2015-05-21 09:59:26 -0600 )edit

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Can't get Boiler:HotWater to heat water

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