What does everyone thing about Economizers?

[hcong]

So here is California, any unit over 75,000 btuh and 2500 cfm must have an economizer. I want to know what everyone thinks since you guys actually have dealt with them.

I personally think the theory is good... free cooling, but I had architects, contractors, and tenants tell me to avoid using them because of upfront cost and the fact that people have problems with them breaking too easily.

*dang... think not thing...

[Moonrunner]

Up here, we have people freely dishing out the dough for them since they like the energy savings.

[Six]

Economizers only make sense in certain areas of the US.

Their practicallity is location dependant on that areas climate.

An economizer in Houston is a waste of money. They might actually open just a few times a year.

As far as dependabillity there is nothing to them. Not much to go wrong.

[Dr BLov]

I believe the 2012 Energy code mandates any location above zone 8, units larger than 36,000 btu will have economizers.

[coolwhip]

Great option here in MI. Its also healthier to cool with fresh outside air.

[hvac wiz 79]

I am constantly quoting, repairing & inspecting them. many of the accounts i do use cooling year round so it makes sense

[timebuilder]

Economizers don't have a lot of maintenance issues, but you DO have to add a skillset about understanding and servicing them. In the Philly area, they are money in the bank, because they are like opening a window with a fan in it. When you need cooling in the off season, they save a ton of money on electricity, because the first stage call uses fresh air, and the compressor stays off. If you will often need a second call that brings on a compressor stage, then use a low ambient control to maintain head pressure in addition to the economizer.

[motoguy128]

I'd like to see them more in residential as well. I mean actual high volume economizers, not just little HRV's. The control usually get cost prohibitive it seems and you need pretty large holes punched in a wall too. I know in my home we prefer to kep the windows close because of noise dust and it's a bit of a PITA to modulate a dozen for so windows throughout the day.

[HVAC-matt]

Here in MA where the cooling season is pretty short they save a ton of money. In the off season we set the DA setpoint to 60 and anytime the weather is below 60 the economizer opens and we get free cooling. Same in the summer when its below 55 we get free cooling. We have never had any problems with them either and we have 22 units with economizers.

[Nuclrchiller]

The biggest drawback I've seen with them is they will pull in any outside odors, such as local paper mill, bird crap on roof, etc....

[hcong]

I see the same thing, as long as the climate is right (coastal San Diego = Yes!!!), why would you put a economizer. I guess it is only a minority that don't like them. Sadly, the minority are my customers and I have to listen to their will.

@Dr BLov - really? I should brush up on the new energy code. The code isn't set to release until 2013 here.

@motoguy128 - yeah I agree, and we might see them soon since the code is requiring new construction and some alterations to have fresh air intakes.

[Cooked]

If you're a service tech never stand by a big RTU with an open economizer and smoke a doobie. Especially when it's at a parole office. Many years ago a top tech I knew did just that. Busted! (and fired)

[motoguy128]

Economizer and up and comming fire suppression/sprinkler system requirements should help out residential new construction costs and really kick off an industry that's struggling.


I guess you could make something pretty cheap. You could meet herequirement just using a whole house exhaust fan system with pick0up in the bathrooms, kitchen and bedrooms, then just have a large filter box with a passive inlet on the furnace or airhandler return for make-up air. Same thing as you might do for fresh-air ventilation, except rather than maybe 200-400CFM, it's designed to be more like 600-1000 CFM or roughl 1/2 the total installed system capacity. So the fresh air inlet might be either a 12-16" hood, or if you want a smaller duct, it's a 8-12" mixed flow axial fan.

Uh Oh... now you have me thinking. Its' getting the cost of the controller down that will make the difference. Or just integrating it into something like a Honeywell VP IAQ which alreayd has an outdoor air temp sensro option. So you would just need a new program and use the ventilation terminals.

600CFM at 55F outdoor and 75F indoor gives you about 1 Ton of cooling.

That being said, I know in my home that when I get down to 50F, my house is passively cooling itself adequately on it's own anyway. So it would only be useful on low humidity days when it's 55-65F. So you'd need a more expensive enthalpy controller.