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Jim Dirkes's profile - activity

2019-04-13 14:35:33 -0500 commented question Meeting Humidity Setpoint with Evaporative Media

I agree that the cooling coils will remove humidity, but that humidity will stabilize at around 40%RH. This is because t

2019-04-08 07:17:34 -0500 commented answer Basic Envelope Change results in opposite EUI results of those expected

It CAN occur just as you describe with a properly created HVAC system. When the building is cooling-dominated and in a m

2019-04-04 07:00:32 -0500 commented answer Is Appendix G becoming irrelevant?

...and Joe Deringer, with whom I'm collaborating on a presentation and who teaches the 90.1 course for ASHRAE, agrees wi

2019-03-20 06:42:17 -0500 answered a question HVAC efficiency changes furnace natural gas consumption

Essentially, this cannot happen ... unless ... the gas heating coil efficiency is different for the higher SEER models O

2019-02-07 05:54:23 -0500 edited answer I need help creating a custom meter using an Output Variable.

Try this: Meter:Custom,RefrigLighting,Electricity,Nameofcasefromobject,NameofvariablefromRDDfile; Output:Meter,RefrigLig

2019-02-07 05:53:28 -0500 edited answer I need help creating a custom meter using an Output Variable.

Try this: Meter:Custom,RefrigLighting,Electricity,Nameofcasefromobject,NameofvariablefromRDDfile; Output:Meter,RefrigLig

2019-02-07 05:51:01 -0500 answered a question I need help creating a custom meter using an Output Variable.

Try this: Meter:Custom,RefrigLighting,Electricity,Nameofcasefromobject,NameofvariablefromRDDfile; Output:Meter,RefrigLig

2019-01-31 14:52:38 -0500 commented answer domestic water heater part load efficiency (E+)

Very Helpful, Matt. I hadn't gone down the thought path far enough to think about instantaneous water heaters, but that

2019-01-29 05:51:13 -0500 answered a question Variable Refrigerant Flow gas-powered auxiliary heat

How about DISabling the VRF completely below 40F AND ENabling a separate gas heater system at the same outdoor air temp?

2019-01-29 05:44:23 -0500 commented answer May you help me to understand following warnings, please?

..and if the project is in South Korea, use an appropriate weather file (instead of Atlanta). That won't affect the fata

2019-01-28 13:45:13 -0500 asked a question domestic water heater part load efficiency (E+)

domestic water heater part load efficiency (E+) I just (inadvertantly) used a part load factor curve for my gas-fired Wa

2019-01-28 11:27:01 -0500 asked a question Hotel rooms with occupancy sensors

Hotel rooms with occupancy sensors Dear UMH people, Occupancy sensors add an interesting wrinkle to modeling a hotel's

2019-01-23 17:37:55 -0500 received badge  Enthusiast
2019-01-14 13:30:11 -0500 commented answer Is Appendix G becoming irrelevant?

... ti seems that creativity is squelched because we're trying to manage only 10% and there is precious little incentive

2019-01-14 13:27:40 -0500 commented answer Is Appendix G becoming irrelevant?

Trying to summarize: 1. We MUST comply with all of the x.4 sections. This covers: * Envelope constructions, min. full

2019-01-14 08:19:58 -0500 commented question Is Appendix G becoming irrelevant?

I am equating "prescriptive" and "mandatory". I'll use "mandatory" going forward. Probably I can simplify my concern by

2019-01-13 17:37:32 -0500 commented question Is Appendix G becoming irrelevant?

If, for example, I can demonstrate better-than-baseline while NOT meeting all the prescriptive requirements, why not?

2019-01-13 17:36:55 -0500 commented question Is Appendix G becoming irrelevant?

That makes sense. It seems, though, that the vast majority of buildings DON"T use > 40% WWR and will most likely just

2019-01-11 10:00:21 -0500 asked a question Is Appendix G becoming irrelevant?

Is Appendix G becoming irrelevant? Dear modeling colleagues, I'm looking down the road a bit and it looks like this: ASH

2018-09-14 01:09:59 -0500 marked best answer Part Load Performance for ASHRAE 90.1

Dear Forum, When modeling for compliance with ASHRAE 90.1, DX and chiller systems must comply with specific requirements for EER / COP and IEER (or IPLV for older versions). That seems to be a "two-edged sword" - you're trying to meet two different criteria, each of which affects the other. For actual / specified equipment you can (in theory) obtain the performance data and create curves which represent the performance. That's somewhat painful, but do-able.

For "baseline" systems, there is no manufacturer data. Hmmmm.... What's a modeler to do?

I have some ideas about how to solve this dilemna, but I'm wondering what others have done. The most obvious solutions are:

  1. Ignore the IEER and hope for the best
  2. Plug in default or example file values and hope for the best
  3. Tinker endlessly with curve coefficients till the result are close to what is needed
  4. Wave a magic wand :)

I'd love to hear what approach you take.

2018-08-13 16:00:24 -0500 commented answer dx coil pyschrometric errors

I see it... For some reason, E+ thinks the air is in outer space and approaching absolute zero temperature. That strikes

2018-08-13 15:54:36 -0500 commented answer dx coil pyschrometric errors

One more thought: How can air density be less than zero? For that matter, how can it even approach zero in atmosphere? I

2018-08-13 15:12:22 -0500 commented answer dx coil pyschrometric errors

Thanks Richard. When I get a minute, I'll suggest it as a new feature

2018-08-13 14:47:56 -0500 commented answer dx coil pyschrometric errors

Clarifying: T/w = "time-weighted" ? If so, all you say makes sense. Thanks! I see a LOT of digital compressors these day

2018-08-13 13:52:56 -0500 asked a question dx coil pyschrometric errors

dx coil pyschrometric errors Dear Forum, Although I have had occasional problems with EnergyPlus giving a fatal error du

2018-08-04 10:03:32 -0500 commented answer VAV rooftop unit + VAV DOAS in the same zone

It's a standard air loop with: * minimum OA controlled to maintain the DOAS OA airflow * EER / IEER adjusted to represen

2018-05-30 03:44:55 -0500 received badge  Nice Question (source)
2018-01-18 12:22:47 -0500 commented answer radiant floor savings vary a lot Atlanta vs Pittsburgh

..and since you are helpfully zeroing in on the likely cause of my discrepancy, I see now that I have differing floor co

2018-01-18 02:48:34 -0500 commented question radiant floor savings vary a lot Atlanta vs Pittsburgh

I am a "newbie" to radiant floors, but that makes perfect sense. The client wanted to evaluate a condition with no floor

2018-01-17 15:51:50 -0500 commented question radiant floor savings vary a lot Atlanta vs Pittsburgh

Simple constant volume heating - no reheat

2018-01-17 15:15:23 -0500 commented question radiant floor savings vary a lot Atlanta vs Pittsburgh

Thanks for the feedback; it's making me think differently about the results! answering some of the questions: I'm onl

2018-01-16 09:36:06 -0500 asked a question radiant floor savings vary a lot Atlanta vs Pittsburgh

radiant floor savings vary a lot Atlanta vs Pittsburgh Dear UMH community, I have modeled two nominally identical buildi

2018-01-02 16:01:09 -0500 commented answer Radiant fractions to surfaces

Thanks, Avi. That's helpful.

2017-12-29 15:20:31 -0500 asked a question Radiant fractions to surfaces

Radiant fractions to surfaces Dear Forum, (Note: also posted this on the E+ Yahoo forum) I am using the ZoneHVAC:HighT

2017-10-19 12:30:43 -0500 commented answer Realistic new construction Baseline

From Eric's very helpful chart, ASHRAE 90.1-2010 applies to a majority of the USA. Does anyone have contrary thoughts (w

2017-10-19 12:14:35 -0500 commented answer Realistic new construction Baseline

Local jurisdiction - understood. I should have explained that the client sells nationally and wants to present a single

2017-10-19 12:00:45 -0500 asked a question Realistic new construction Baseline

Realistic new construction Baseline Dear Forum, A client wants to compare half a dozen commonly used HVAC system approac

2017-09-26 18:59:42 -0500 commented question Internally "conditioned" Cavity Windows (not double skin facade)

What's significantly different about this design than a double facade? It seems the same in principal.

2017-08-29 11:47:41 -0500 commented answer Best output:variable for zone heating / cooling load

Molly, I'm too slow to respond. Sorry! 1) The key which you have provided, I think, is to use the Detailed results for t

2017-08-18 16:06:19 -0500 received badge  Nice Question (source)
2017-08-03 06:57:06 -0500 commented answer VAV rooftop unit + VAV DOAS in the same zone

That's helpful. Thanks! I decided to create a hybrid DOAS + RTU air loop, much as you describe. It's a single zone, both

2017-07-24 07:33:19 -0500 asked a question VAV rooftop unit + VAV DOAS in the same zone

VAV rooftop unit + VAV DOAS in the same zone Dear UMH forum, I'm thinking about the best way to model a supermarket in E

2017-06-06 05:52:51 -0500 asked a question heat recovery wheel bypass logic

heat recovery wheel bypass logic Dear Forum, One of my commissioning projects uses an enthalpy wheel on several AHUs. Th

2017-04-10 08:47:19 -0500 commented answer Auto-extensible object crashes IDF Editor

That helps, Jason. I guess I'll have to stop being lazy until that suggestion gets implemented :)

2017-04-08 10:45:41 -0500 asked a question Auto-extensible object crashes IDF Editor

Dear UMH forum, My IDF has a Controller:MechanicalVentilation object with a lot of Design Specification Zone Air Distribution Object Name zones. I can run the IDF in both v8.6 and v8.7, but the IDF Editor crashes when I attempt to open the IDF, telling me that the :MechanicalVentilation object has too many fields. I can also see in the status window that E+ is auto-extending that object (and the message ".. simulation may be slow..")

Is there a bug here? or something I am missing?

p.s., I'm being lazy because I don't want to edit the IDD; it seems that if the IDF runs, the IDF Editoor should open the file....

2017-04-03 10:26:54 -0500 commented answer EPACT Tax credit energy models

Thanks, Michael

2017-03-22 10:44:37 -0500 commented answer Lighting power density for Multifamily

As usual for you, that's very helpful - Thanks!

2017-03-22 08:02:37 -0500 asked a question Lighting power density for Multifamily

Background: I'm modeling a 7 story multi-family building. The developer wants to design things at a very high level of energy performance, including lighting and plans to provide LED lighting in all rooms. As a result, the occupants won't need to provide their own lighting at all (though I'm sure there will be some). ASHRAE 90.1-2010 specifies maximum lighting power density for multifamily as 0.6 w/sq.ft., which is a fairly stringent requirement. I'm wondering if ASHRAE has assumed a typical lighting design for multifamily, which in my experience includes minimal hard-wired lights, perhaps only in the kitchen, bathrooms and hallway. In that scheme, the overall LPD would be pretty low and occupant-provided lights would become plug loads and unregulated - but would also remain identical for the Baseline and Proposed designs. I want to claim savings for the plug loads if this is the case. (Neither the 90.1 document nor its User Manual address this) Question: For my Proposed scenario (LED lights hard-wired and provided in every space), is it consistent with ASHRAE's assumptions to reduce my plug loads for the Proposed case because we're providing more lighting than is normal for multifamily occupancy?

Full Disclosure: I'm not trying to game the system, but want to be sure I don't leave energy points on the LEED table - so to speak.