VisionPRO IAQ and HP winter programming...

[badtlc]

I have read about some people successfully using their heat pumps down to 15-20 degrees. I'm hoping my new system will be as successful. Does the VisionPRO learn when the HP can't keep up and turn it off or does it always run the heat pump and just add the AUX heat? Does it only disable the heat pump when the outside temp goes below the HP shutout temp?

Also, does the heat pump control defrosting by itself or is there something in the t-stat that controls it?

Essentially, I want to use my HP as much as possible but I also want my HP disabled if it isn't contributing anything.

[beenthere]

The HP determines when to defrost.

Which heat to use when. Is determined by what has been set up in the installers set up menu.

[speedymonk]

I have found on this site and in my neighborhood, that manufacturers have a default setting of 40 degrees for when the HP switches over to secondary heat source. This is regardless of where you live. I've set mine to switch to secondary/auxilliary heat (gas furnace) when the temp hits 25 degrees. I have a spreadsheet I was given and plugged in all the varaibles of my heat pump and furnace to get a break even point. The gentleman who sent me the program, however, asked me not to share it.

However, request a copy of the install guide of the IAQ. As I was told, don't screw with stuff you don't know. I just adjusted my set points and temps for aux heat. It saved me money and gives me the lowest enery bills in the neighborhood except the the Ukranian fellow who had radiant floor heat plumbed throughout his house and garage. Beat me by $90 on the coldest months last year and I was beating everybody else between $35 and $150.

[badtlc]

I don't have a fossil fuel kit. Shouldn't the VisionPRO select when to lockout the heat pump in that case?

I havent checked to see when the economy break even point occurs between heat pump and my 80% gas furnace. Electricity is so cheap here I'm assuming that temp would be really really low.

[beenthere]

The IAQ is a dual fuel control.

[badtlc]

My economy break even point between my HP and my furnace is -10 F. Is there any danger of not locking out the heat pump down to say 10 degrees F?

[beenthere]

No.

If you don't set a lock out temp.
The stat will switch over to aux when the HP can no longer heat your house. But will use the HP first on every heat call.

I have a lot of DF's set up like that.

You can set it like that first.
Then when you find out what temp the HP has to switch to aux, set up a lock out for that temp, if you don't like the cooler air at those temps.

[VA GENT]

No.

If you don't set a lock out temp.
The stat will switch over to aux when the HP can no longer heat your house. But will use the HP first on every heat call.

I have a lot of DF's set up like that.

You can set it like that first.
Then when you find out what temp the HP has to switch to aux, set up a lock out for that temp, if you don't like the cooler air at those temps.

My installer set up my DF at 40* lockout...with cost of LP gas vs. $0.07 kwh electricity here in Virginia, I plan to reset my call for LP down to at least 30*, maybe lower

beenthere, does the 8303 stat allow you to not set a lockout temperature like the IAQ? Thanks ......

[beenthere]

Yes.

Just set no lock out, and it will use the HP first for every heat call.

[tecman]

My economy break even point between my HP and my furnace is -10 F. Is there any danger of not locking out the heat pump down to say 10 degrees F?

I am not sure what you are trying to say here. Even though the efficiency of your heat pump may look good at -10 deg, the capacity of all heat pumps drops off below 40 deg F. At -10 deg you may be making heat efficiently, but it is likely 10% of the unit's rating or less. That is why another form of heat is required. Not due to efficiency but capacity.

Usually a properly sized heat pump in a modern well insulated house will handle the load by itself down to 20 deg or so.

Paul

[badtlc]

Does the auxiliary heat ever run in conjunction with the heat pump to give it a slight boost? Or, are they always mutually exclusive operations and the aux never runs the same time as the heat pump?

[beenthere]

Dual fuel. The aux only comes on with the HP during defrost.
With electric aux, they run at the same time, when the HP can't handle the load by itself.

[VA GENT]

Dual fuel. The aux only comes on with the HP during defrost.
With electric aux, they run at the same time, when the HP can't handle the load by itself.

And now I wishing that I'd had the LP aux removed when I had my new system installed back in June and instead had the electric strip as aux

[Jopopsy]

Dual fuel. The aux only comes on with the HP during defrost.
With electric aux, they run at the same time, when the HP can't handle the load by itself.

Or, if the set point is reached outside, the aux runs exclusively if oil/gas. Right?

[beenthere]

Correct.

The IAQ does have a droop point that either can run though also.

[badtlc]

2-stage HP IAQ question. How does the IAQ call for Y1 and Y2? Does it call Y2 at the same time as Y1 when it needs both stages or does it only close Y2 or Y1 but never both at the same time?

[skunkiechris]

2-stage HP IAQ question. How does the IAQ call for Y1 and Y2? Does it call Y2 at the same time as Y1 when it needs both stages or does it only close Y2 or Y1 but never both at the same time?

Both at the same time. If you have the manual, on page 23 there is a chart showing what is energized on what type of call. I've attached below...

[badtlc]

Both at the same time. If you have the manual, on page 23 there is a chart showing what is energized on what type of call. I've attached below...

I have the manual but cant find that. Is it in the installer's manual or the user's manual? That is a really useful table. Thanks.