Comments on: Will a Heat Pump Work With Your Existing Ducts?

By: Dale

Dale — Sat, 06 Jul 2024 17:25:48 +0000

Hello Allison,
Thanks for the article. I am curious as to the limits of existing ductwork when retrofitted or adapted to low temperature heat sources. I have experience with this using condensing boilers, and now ATW heat pumps.

When the delivery temperature drops, the output of the system drops along with it resulting in longer run times per thermostat cycle. In the hydronics world this is the natural and desired result of lowering the temperature of the delivery medium.
In an ATW heat pump set up the coil is decoupled from a direct connection with the compressor by the hydronic loop and the buffer tank. In such a system, the heat pump is controlled by the temperature in the buffer tank. Thermostat(s) call are to the buffer tank and not directly to the compressor.
I think this decoupling can have positive effects on the operation and performance of the system and compressor and perhaps make is easier to accommodate existing duct work to lower temperature sources, especially heat pumps.
Thanks again,
Dale

By: Allison Bailes

Allison Bailes — Tue, 02 Jul 2024 19:44:53 +0000

In reply to RoyC. Yeah, that wouldn't be good.

By: RoyC

RoyC — Tue, 02 Jul 2024 18:28:01 +0000

Warning: If you go dual-fuel, don’t let the controls operate the furnace and heat pump simultaneously.

By: Tom Coradeschi

Tom Coradeschi — Thu, 27 Jun 2024 01:17:48 +0000

In reply to Phillip Norman. “Easy” if you live in a ranch. Otherwise, not so much.

By: Phillip Norman

Phillip Norman — Wed, 26 Jun 2024 13:35:13 +0000

In reply to Phillip Norman.

My comment is understood only if the reader knows this link that I posted as my “website:”

https://energyconservationhowto.blogspot.com/search/label/HVAC%20Duct%20Design

By: Phillip Norman

Phillip Norman — Wed, 26 Jun 2024 03:40:25 +0000

Blame so much awful ductwork on following of ACCA Manual D Chapter 6. Replacing ductwork is easy and imperative.

By: Andrew Whittaker

Andrew Whittaker — Wed, 26 Jun 2024 02:40:31 +0000

Always had a question about heat pumps. I’m in chilly New England. Most heat pumps that i see draw outside air. Yet our cellars typically are a reservoir of pre-heated air. Why not draw air from them? And pull air into the cellar to pre-heat? Likewise, in summer, cellar air is often cooler, and “redneck AC” pulls this air upward with fans (requires closed windows to augment suction so i don’t use it but a roommate did, quite effectively). Anyway seems a heating/cooling system should use these natural advantages. Am i missing something?

By: James

James — Tue, 25 Jun 2024 21:10:00 +0000

Going thru this now, connected Heat Pump Air Handler to existing 6″ 1974 square ducts. Prior Air Handler had a very loud 6″ squirrel cage fan. New system has 4, 4″ones. I realize i need more ducts to move sir for sure. Unit runs all the time/ variable 3 speed fan but as I now also have a dishwasher, my power use is down over last year for sure. Now just need to reengineer my duct dynasty for more exchange.

By: Allison Bailes

Allison Bailes — Tue, 25 Jun 2024 20:23:42 +0000

In reply to Scott. Scott: Yes, it's a poor assumption, but that's where you can interview the homeowners and find out what their current level of comfort is. If they say things are OK, matching a heat pump with the same air flow should work OK if it also meets the heating load for the house.

By: Allison Bailes

Allison Bailes — Tue, 25 Jun 2024 20:21:18 +0000

In reply to Steve Waclo. Thanks, Steve!