Abby Normal wrote
Rod Speed wrote
Abby Normal wrote

When it is sized to the load the problem is it would only shut off for
an hour or two as the house cooled, then it would run steady until
after the sun came up to catch up. No real point in setting back.

That is just plain wrong. The whole point of a set back is that
less is pumped at the setback temp because the losses are lower.
How much lower depends on how well insulated the house is.

The whole point of set back is to lower the temperature for a while.

To reduce the amount of energy consumed to keep it at the higher temp.

This would imply that the house cools down and the
systems stops running during this cool down period.

Correct.

Then it would run less per hour due to the setback indoor
temperature until such a time that it need to start warming
up the house so that it was back up to temperature perhaps
when the occupants awoke or perhaps returned home from work.

Correct.

The problem is shortly after the temperature dropped
to the setback temperature, the heat pump would end
up running steady just to get back up to temperature.

Wrong with the situation being discussed, with
more than one system so it doesnt take a long
time to get it up to the normal temp again.

Typically in the temperate states where air source heat pumps are
used, they are sized with the cooling load in mind and use the heat
strips. One sized for the full heat load will be grossly oversized
for cooling resulting in summer time humidity control problems.

And what was being discussed was having more than one
system and doing that so it doesnt take a long time to get back
to the normal temp and doesnt use the heat strips to do that.

The only way set back works with a
heat pump is if it is grossly oversized.

Wrong again.

No not wrong

Yep, completely wrong.

just unsucessful in educating you.

You cant even keep track of what was actually being discussed.

All that accomplishes is set back without auxiliary heat.
It would short cycle inefficiently except for when it was
trying to recover from a set back.

Not if you one of the systems sized so that doesnt happen.

So you are saying size one for the cooling load, one for the
heating load and one for speedy recovery from set back then?

Three heat pumps now.

Yep, I mentioned 3 for a reason.

Plus all the ductwork and backdraft dampers.

You dont have to duplicate/triplicate all of those.

Let's try to keep this practical and not go to
hypothetical extremes to prove this is possible.

Wasnt doing anything like that.

Noah er I mean Nick is a bad influence on you.

Nothing to do with Nick at all.

In an environment with an ambient dewpoint above 60F there will
be problems with a grossly oversized system in cooling mode.

Again, not if you have more than one system.

Well like I said if you want to install
three heat pumps, knock yourself out.

Two and three was what was being discussed.

Your claim that setback has no value is just plain wrong with THAT situation.