Tuesday, 18 January 2022

Mitsubishi heat pump back up heat strips

Hi everyone,

A local contractor is installing the following: PUZ-HA24NHA1 outdoor unit, PVA-A24AA7 air handler, MHK1, and an 8k back up heat strip.

Pages 23 and 24 of the service manual explain the activation procedure: https://www.mitsubishitechinfo.ca/si...AA7_201812.pdf

Which is basically use a wired controller (PAR-33MAA or similar) to set mode 11 and 23. The manual also explains the algorithm that is used to activate the strips.

The problem is that my contractor isn't using a wired controller at all to set anything and is suggesting that when using MHK1 setting the mode is not necessary, MHK1 takes care of everything. Unfortunately I cannot find any references to this in the manual and I was wondering if anyone here has experience with installing the strips.

Questions:
1. Is it true that a wired controller is not necessary as part of the set up to active the strips when using MHK1? Any references to the manual/links are appreciated so I can read.
2. When using MHK1, would the air handler still use the same algorithm to turn on the strips, or would the MHK1 decide differently? The service manual has two modes for the strips, one where heater is also used during defrost, and one that heater is only used when temperature isn't rising. Which one would be used by MHK1?
3. I've read elsewhere that MHK1 doesn't indicate at all when the strips are on, how can I tell whether my system is working correctly/efficiently or not? I don't to accidentally be using the strips most of the time.

Thanks!


source https://hvac-talk.com/vbb/threads/2235663-Mitsubishi-heat-pump-back-up-heat-strips?goto=newpost

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