Right equipment

[Tankmister]

Hi everyone,

I have a Luxaire HL8B048F1 heat pump with electric backup heat. My house is set up for two zones and my zone controller is a Robertshaw 2701-006. I have two Honeywell Visionpro 8000 thermostats.

My auxiliary heat is coming on too soon, sometimes at 4 deg c. I tried installing an outdoor temp sensor and hooking it to my main zone thermostat, but I can only display outside temperature and I am not able to lock out my aux. heat.

In the introduction of the manual to the zone controller says: "Slimzone is compatible with both single stage heating and cooling units and single compressor heat pumps with auxiliary heat".

Is this zone controller compatible with my two stage heat pump? Or is it only allowing the first stage to engage?

Thanks,
Tankmister

[BaldLoonie]

Since it says single compressor (stage) HP with aux heat, that would be no. It is not appropriate for a 2 stage heat pump. I would chat with the installer about why you have this system. Sounds like you have a very expensive 1 stage system, running either always on high or always on low. Ask about upgrading to a Honeywell 322 or 432 panel or a Jackson Z600.

I THINK the 432 can use an outdoor sensor to lock out aux heat in mild weather. But if not, a sensor on each Vision Pro properly set up will.

[Tankmister]

My installer says that the pump controlles the staging, not the zone controller. What else does the zone controller do besides open and close the dampers?

[motoguy128]

Good zone controllers will stage the equipment and can reduce airflow when only a single zone is calling depending on the air handler used and how it's wired. They usually monitor discharge air temperature and have selectable limits that will either stage down the equipment or shut it off if it's is outside the DAT limit.

What really hurts you on design of a zone system is 1) duct sizing for handling the 1st stge of the quipment on a single zone or relying too heavily on the bypass damper, 2) oversizing equipment and short cycling when a single zone of calling.

IMO a good zone system layout with properly sized equipment will not need a bypass damper or at the most least a fairly small one.

[Tankmister]

I'm really frustated with this whole situtation. After spending alot of money on a heating system that isn't preforming like I think it should.

Please tell me if this seems right to you? This morning when I got up the temp in the house was 1 degree below the set point so 5kw of heat came on. After a few minutes all 15kw comes on to bring the heat to the set point. This part makes sense to me. What doesn't make sense to me is that it was only -1.5 deg C outside.

I'm heating about 4600sq ft with a 4 ton unit.

Am I expecting too much from this system or is there something wrong?

Thanks,
Tankmister

[Tankmister]

Also, I emailed Robertshaw and asked them if this zone controller was compatiable with my heat pump and they said yes.

Is there any benefit in upgrading to a Honeywell HZ332?

[BaldLoonie]

Their literature disagrees. From what I read on 2 forms, it is not for a 2 stage heat pump. Single stage and backup only. So your installer has wired the pump for always low or always high. A 322, 432 or Z600 would stage the compressor the way it should. The Z600 can be done by 2 stage thermostat or number of zones calling. Likely the same with the Honeywell panels.

Honeywell stats bring on backup very quickly if you play with the stat. White-Rodgers can have a delay so the stat can see if the heat pump alone can warm things up. If you don't want backup in mild weather, I'd put outdoor sensors on both Vision Pro stats and have the advanced setup changed to stop backup above a preset outdoor temp.

That is a lot of house for 1 system and 4 tons. And at freezing, you are not putting out 48,000 BTUs of heat from that pump.

[Tankmister]

I agree. His reply is pretty generic:
"The panel is compatible with most heat pump systems, make sure you do not use heat pump thermostats."

The "most" is concerning to me.

I tried installing an outside temp sensor, but I can only display the temp. Function 340, option 2 isn't a available. Any ideas?

My feeling is the pump is a little under sized and the ductwork isn't up to snuff. The installer has put quite a few 90's on the runs causing some restrictions. All in all I have high quality equipment with a poor install.

[motoguy128]

With zoning, a little undersized is good.... but low airflow will reduce capacity and make it distribute air less effectively. It might even cause it to short cycle.

4600sqft is qute a bit for a 4 ton unit depending on location and home construction. Then again, if my home was zoned, I'd undersize slightly and go 3 tons on a dual fuel system, but if all electric, I would want 4 tons and oversize slightly for heating capacity. Then again, if all electric, I'd go geothermal.

[BaldLoonie]

Likely those Vision Pros are not set up as heat pump stats for this inappropriate zone panel. Get the right panel, set the stats up as heat pump stats and you'll be able to use the VP to lock out backup in mild weather.

And Robertshaw is right, that panel is compatible with MOST heat pumps. But yours isn't most, it's 2 stage which make up a very small amount of sales.