Mini split drain pan heater??

[thammel]

About ready to take the plunge and buy 2 Mitsubishi mini split heat pumps. I'm seeing ecomfort as a good place to buy and they say you should have a drain pan heater for long term operation below freezing. I don't think my carrier heat pumps have this. Comments on the need? Not cheap!!

My plan is to do the install myself and have an hvac guy do the final evac and leak check. I've got pads poured, outside disconnects installed, condensate drain system in place so a lot is done. I have 2x6 walls so am going to see about running the line sets in the walls. Insulation is in place but no drywall yet. I'll place drywall behind wall unit before hanging that. Going with a 9k btu unit for garage attic (32x12) and 18k but unit for garage (32x28). Already have reznor heater for really cold days.

So....any comments on the need for drain pan heaters?
Tom

 

[EdT]

I'm guessing this is a drain pan under the outside unit that may get condensate in it when operating "backwards" as a heater and you're trying to heat your shop by cooling the outdoors. I guess my first question would be why have a drain pan for an outside unit? the evaporator drain from the AC unit probably just drips outside so why can't the outside unit drip outside? I have two mini splits in my shop building and AFAIK there is not a drain pan heater (or a drain pan for that matter) and they seem to work fine for heating unless it gets really cold. Of course, I have never looked to see if there's any condensate on the outside unit when running it as a heater. I suppose that, depending on the hassle factor, you could try it w/o the heater and install them if there's a problem.

 

[Slowgsr]

Yeah you only need a heater if your unit does heating. I put a 2ton mitsu in, but only does cooling

 

[Milton Shaw]

HE says he is using heat pumps which do generate ice on the outside coil and does need to defrost. Most normal heat pumps when they go in the defrost mode run long enough to melt the ice out of the unit and if there is drainage around the unit no ice buildup occurs other than possible 1/2 inch on the ground. Those mini splits may not generate enough heat during the defrost cycle to keep ice from building up in the base of the unit. If you have been around heat pumps you may have seen the flume of steam that comes out of the units at the end of the defrost cycle when the condenser fan blows out the warm water from the fins.

 

[Jackfre]

Your heat pump will heat to low temps, unlike your carrier. So at say -5* the condensing unit will freeze up and go into defrost mode. That essentially means you are reversing cycle and rejecting heat to the outside unit to melt the ice off. A drain pan heater may be necessary if that condensate doesn't drain out the bottom of the condensing unit. The Hyper-heat mitsu's have the drain pan heater installed from the factory. In MD you probably don't hit the super lows capacities of the Hyper-heat.
This defrost issue is one of the primary reasons you want to wall mount or at least put the condensing unit up on risers. You might actually be able to melt the ice off and have it drain ok, but if it is sitting close to the ground the ice drains out of the unit drops the 1.5" to the pad and then it freezes and that ice builds up to the unit and plugs your drain holes and then the ice builds within the condensing unit and in the worst case makes the very efficient condensing fan a lot shorter. In MD, I don't think I'd bother with it. Just mount the unit off the ground and keep an eye on it. You can always add it later.

 

[thammel]

Yes, you all have it correct; the drain pan heaters are for when the outside unit goes into defrost mode in the winter. My pads already are about 4-6 inches above ground level. I also do plan to elevate the outside units about 6 inches on risers. (Interesting that the mitsubishi risers cost about $71 for a pair (one pair per unit) and you can buy risers from supplyhouse.com for about $2 each!!)

So thanks - I'll do the risers and should be ok!
Tom

 

[fastjohnny]

Your heat pump will heat to low temps, unlike your carrier. So at say -5* the condensing unit will freeze up and go into defrost mode. That essentially means you are reversing cycle and rejecting heat to the outside unit to melt the ice off. A drain pan heater may be necessary if that condensate doesn't drain out the bottom of the condensing unit. The Hyper-heat mitsu's have the drain pan heater installed from the factory. In MD you probably don't hit the super lows capacities of the Hyper-heat.
This defrost issue is one of the primary reasons you want to wall mount or at least put the condensing unit up on risers. You might actually be able to melt the ice off and have it drain ok, but if it is sitting close to the ground the ice drains out of the unit drops the 1.5" to the pad and then it freezes and that ice builds up to the unit and plugs your drain holes and then the ice builds within the condensing unit and in the worst case makes the very efficient condensing fan a lot shorter. In MD, I don't think I'd bother with it. Just mount the unit off the ground and keep an eye on it. You can always add it later.

My hyper heats did not come with drain pan heaters. Mine are mounted on wall, so good drainage. Only had minor ice accumulation needing some heat gun action to thaw, during subzero weather. I opted not to purchase the drain pan heaters initially, and won't unless it becomes more problematic.

 

[Jackfre]

I know the Fujitsu deep heat models do come with the base heaters. I thought the Mitsu's did too. Thanks for the correction

 

[waluyo]

Yeah you only need a heater if your unit does heating. I put a 2ton mitsu in, but only does cooling

whether to 2 tons?