Short Cycling on Oil- an impossible problem?

SeymourCates · December 2017

@Jamie Hall

Please correct me if I am wrong but are you seriously comparing a functional steam system with a non-functional hot water system and coming to the conclusion that "steam rules"?

That would be the epitome of bias.

Steamhead · December 2017

AJinCT said:
Steamhead, you are factually wrong. The Mitsubishi units have full rated output down to 0F, and reduced capacity to their shutdown point at -13F. Carrier ducted heat pumps have most of their rated capacity down to 0F and below, while the Unico ones drop off hard below 20F, and would likely need backup heat in most applications. If the heat pump can’t meet the load, then it’s smaller than the design load of the house. Not necessarily a bad thing for that particular application, but that has no bearing on whether Mitsubishi heat pumps can heat a house with the backup heat turned off *if their rated capacity is 85-90% of the design load of the house in Connecticut*. I’m assuming a small amount of waste heat from people or appliances in the house, the heat pumps are set to 62F in living spaces and 59F in bedrooms, and our design temp is slightly above or below zero in various places in CT.

They don't heat the place past 55° F at these outdoor temps. You can speculate all you want as to why, but the fact is, they don't heat the place past 55° F at these outdoor temps. If you were there, you would see this, but you're in CT so you can't.

Jamie Hall · December 2017

SeymourCates said:
@Jamie Hall

Please correct me if I am wrong but are you seriously comparing a functional steam system with a non-functional hot water system and coming to the conclusion that "steam rules"?

That would be the epitome of bias.

Nope. I wouldn't do that. It was more a facetious comment. There are many ways to heat a structure; indeed, there are many ways to do almost anything. I have made a rather good (and long -- I'm retired now, by more than a decade) career in engineering by seeking to choose and implement the best solution to the problem at hand, and usually been successful at it. I have no bias as to heating systems; some are better in one situation than others, and worse in some. It all depends on the specific situation.

Steamhead · December 2017

AJinCT said:
The Mitsubishi units have full rated output down to 0F, and reduced capacity to their shutdown point at -13F.

(snip)

If the heat pump can’t meet the load, then it’s smaller than the design load of the house. Not necessarily a bad thing for that particular application, but that has no bearing on whether Mitsubishi heat pumps can heat a house with the backup heat turned off *if their rated capacity is 85-90% of the design load of the house in Connecticut*.

Well, the fact is- for whatever reason- they aren't doing the job.

I'm not going to speculate as to why. Our company did not specify or install these units and does not maintain them. We have no responsibility for them whatsoever, and do not want such responsibility.

But they certainly have an effect on your "heat-pump-űber-alles" narrative, don't they?

SeymourCates · December 2017

You statement is a bit too general. Oil can be utilized and "work properly" provided that one accepts a certain amount of cycling. Any fixed output heating system, even a properly designed NG system, has to cycle on all but the design day (and probably cycles somewhat on that day as well). The simple question is how much cycling is acceptable? Most believe that a system that can run for ten minutes is acceptable from an efficiency standpoint. Then, there are those that believe a two minute cycle on a steam system is perfectly OK for efficiency. So, apparently, it is impossible to get any consensus on the subject.

Furthermore, it is not mandatory to utilize a buffer tank on oil and you'll find that very few actually do it. If there is an acceptable amount of radiation present, one can operate the oil fired system with a 30F differential throughout the heating season and minimize the cycling. Of course, there are those that now must install OAR on an oil fired system believing that they can improve the efficiency by running lower water temperatures. This exacerbates the short cycling thereby killing any benefits they might have attained.

As you noted, high mass radiation is always preferable in such a system.

Steamhead · December 2017

AJinCT said:

Steamhead said:
Well, the fact is- for whatever reason- they aren't doing the job.

I'm not going to speculate as to why. Our company did not specify or install these units and does not maintain them. We have no responsibility for them whatsoever, and do not want such responsibility.

But they certainly have an effect on your "heat-pump-űber-alles" narrative, don't they?
No, your misleading and dishonest anecdote has nothing to do with the viability of heat pumps as a heating technology. I specifically said that many older and/or larger homes would have and need backup heat that is used a few weeks of the year to meet design loads.

By your own logic, if you found an oil fired steam boiler fired at .8GPH, which should output about 95,000 BTU/hr, and it couldn't keep the house warm because the design load of the building is 150,000 BTU/hr, then that would prove that oil fired steam is not a viable way to heat.

It's not rocket science here. What is the design load, how big is the steam system, and how big are the heat pumps? If you're putting in a 100,000 BTU/hr steam boiler, and the heat pumps are 54,000 BTU/hr then the answer should be pretty obvious.

Misleading? Dishonest? Don 't think so.

What have we learned from your postings?

1- You don't like steam heat;

2- You hate oil heat;

3- You love heat pumps;

4- You don't like anyone who disagrees with you.

We've been quite patient here, but there is a limit to that. To call someone misleading or dishonest is against the spirit of this board. There are plenty of people on here who, like myself, simply call things as they see them, without resorting to grade-school name-calling.

If you want to run a board like that, you would be well advised to start your own board and proclaim yourself Moderator. This board only has one Moderator, and it's not you.

Robert_25 · December 2017

I live up on the 45th latitude, and happen to have an oil fired hydronic system, and a heat pump. The heat pump does fine at taking the chill off in November and April, but as soon as it gets cold the comfort level is terrible. Having a breeze through the room that cycles on and off as the unit pauses to defrost itself feels like s*it.

There is no NG in my area to speak of, and lots of old houses. LP is starting to catch on with new construction, but I suspect that is mainly due to a builder price point than cost of operation. For the foreseeable future I suspect heating oil will continue to be the fuel of choice in rural areas and existing homes in the Northeast.

Regarding the question about higher mass oil boilers - they exist, but doesn't the increased standby losses offset the longer cycle time? One of the most efficient oil systems on the market has very little mass - System 2000.

Jamie Hall · December 2017

To Mr. AJ in CT. A few thoughts.

First, on heat pumps. I could design for you a heat pump which would function in Siberia. Would it be the optimum way to heat a structure? No, so I wouldn't do it.

However, a more general comment: you seem to have a tendency characteristic of many younger engineers I have encountered over the last half century plus in practice. You see a solution to something which you love, and apply it regardless of whether it makes sense in the situation at hand or not. Hopefully, with time may come wisdom. It will if you pay attention to how others have approached similar problems. Further, you may come to learn that the latest and shiniest thing out there is not always the best way to do things. Sometimes it is. Sometimes not so much.

HVACNUT · December 2017

I purposely stayed away from this thread because from the beginning, it seemed like @AJinCT was just trying to pick a fight with his holier than thou attitude.
OIL HEAT RULES!!

Erin Holohan Haskell · December 2017

Let's move on. This thread's taking a turn, so I'm closing it.

Short Cycling on Oil- an impossible problem?

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