Heating Help

Sorry guys

@ December 10, 2010 10:59 PM in Heating system return duct filling up with water

I missed the sentence stating the return duct was in the attic.

Minnesota Wayne

Walk in cooler with attached freezer

@ December 10, 2010 10:30 PM in Ice build up

This helps a lot.  Box temperature for the walk in freezer will be 38 to 41 degrees.  Code prevents temperatures warmer than 41, and economics tend to limit a colder box.  Produce will be damaged if the air temperature is 34 degrees or colder for a long time.  The freezer at -15 degrees is okay depending upon product.  Ice cream needs a temp in this range to stay solid.  At 0 degrees the ice cream is soft in the cartoon.

The evaporator coil is located inside the cabinet, housing the evaporator fans.  Check for frost ice build up on both sides of the coil,.  The frost on the coils should be even from both sides, top to bottom and left to right.  There should not be any ice coating the coil. 

The freezer fans should run all the time, unless in defrost mode.  This should be 10 to 30 minutes max, depending upon how the system is designed.  If the fans are off, this may be the problem.  Now the question is to determine if the defrost timer clock is stalled/broken, the fans are bad, a bad fuse/breaker for the fan circuit.  If the fans have been off for a time, the suction line will collect frost ice as the evaporator coil is not adding heat to the refrigerant.  Box temperature will rise etc.

Check all the door seals and look for other air infiltration leaks,  Air entering the cooler or freezer will rob you of money.  Check for missing threshold seals on the entry doors, broken or torn door gaskets on each reach in door need to be replaced.  Even a small cut in the magnetic door seal will affect efficiency.  Really look at the bottom of the door and the hinge side as the gasket will roll on the frame, eventually tearing.

The freezer section will have a different refrigerant then the walk in cooler.  R404A is most likely the freezer system.  Is the freezer system the lines with the heavy frost/ice buildup?
One more thing to check would be the sight glass.  If the system has one, it would be located in the liquid line (smaller line) close the the condensing unit outside.  The sight glass allows a person to see the refrigerant flow inside the tubing.  Generally a properly charged system with a TXV valve (located at the inlet to the evaporator coil) will not show any movement of the refrigerant.  As the system has the correct amount of refrigerant.  If there is flash gas or gas bubbles flowing, this may indicate the system is low on charge and part of the problem.  This is the time to call a qualified refrigeration technician.

Thanks, Minnesota Wayne

Most wall furnaces

@ December 9, 2010 8:36 PM in ITT Nesbitt ptact

On most wall furnaces, the blower assembly is easily removed with a couiple of screws and disconnecting the wires or plug. Fan, shroud and wheel or blade as an assembly.

Minnesota Wayne

Is this a freezer?

@ December 9, 2010 8:18 PM in Ice build up

Ice build up on a suction line is normal for a freezer application.  We are not in the AC mode here.  Remember the gas temperature inside the suction line is below the freezing point of water and moisture from the air will collect on the exposed piping and freeze.  Keep your refrigerant guy away from adding/removing charge or changing the txv superheat until other possible causes are eliminated.

How are the evaporator coils?  Are they also iced over?  May be a defrost problem.  Drain pan problem.

Things to help answer your questions. 
Type of unit, walk in, reach in,
Freezer/ refrigerator
temperature inside the box
Temperature the box should be at?
refrigerant type if known
Are all the evaporator fan running? 
Are they running the right direction?

Once external items are eliminated, then items like refrigerant charge, superheat, txv valve operation can be addressed.  Not before.

Thanks, Minnesota Wayne

Has the supply voltage to the contactor been measured while clicking?

@ December 9, 2010 8:03 PM in Clicking contactor on air handler

Measure the supply voltage to the contacter coil.  If the voltage is erratic or less than 20-21 volts the coil will be energized then de-energized  then energized again. 
May need to use a analog meter to see the voltage fluctuation.  Digital meters do some averaging to show a value on the scale.  (Sorry I know others know exactly what is happening internally in the meter).  The point is the digital meter may not show the voltage drop if a relay or electronic control board are controlling this relay. 

If the voltage is erratic, then it is a matter of locating the culprit and making repairs., wiring transformer, supply voltage to the furnace, thermostat wires, thermostat, limit controls, etc.  Could be a bad ground someplace.
Here is a excellent case of following the current path to locate the fault, rather than hop-scotch testing.  Place one meter lead at the transformer neutral.  Start at the transformer 24 volt terminal with the second lead, test each wire/component in the order of the circuit to identify the fault.  Do not overlook anything or assume something is okay.  This is a time where a temporary jumper with alligator clips comes in handy.  The jumper can be used to verify a suspected wire/component.  Remove the jumper after testing.  Do not leave any jumpers across limit controls.

Thanks, Minnesota Wayne

sorry double post

@ December 9, 2010 7:33 PM in Heating system return duct filling up with water

Sounds like a leak from the condensate trap, hoses, heat exchanger etc.

@ December 9, 2010 7:33 PM in Heating system return duct filling up with water

I am going to assume this is a high efficiency gas furnace.  Check for condensate leaks.  Start at the condensate trap and connecting hoses.  The trap plugs up on the outlet and overflows some place else.  Don't forget the pipe/hose from the trap to the building drain.  Many times a piece of garden hose is used and the hose plugs up.  Code states the smallest diameter to use for condensate drain is 3/4 inch. 
If all this checks out then start to look at a failure of the secondary heat exchanger.  A gasket may have let go, the header body cracked or an adaptor to the inducer is cracked, leaking water into the bottom of the furnace/return duct.  A 5 gallon pail is not out of the question for how much condensate a furnace can produce in a 24 hour period.
Take the covers off and start looking.

Regards Minnesota Wayne

CFM

@ November 28, 2010 10:05 AM in Comfortmaker Heating System Short Cycling

Let us know the what temperature rise you measure.  By the model number, it looks like you have a high efficency furnace with a ecm blower motor.  Properly sized duct is very important.  These motors will try to deliver the required air flow at a hugh energy expense if operated at less than design conditions.

cfm delivered by the furnace can be calculated by knowing the temperature rise and the net btu delivered.  Take the net btus from the model number data tag.  Do not use the input.btus ie; 60,000 input 54,000 output.  the 54,000 output is the number to use. you may have to calculate the output if it is not listed specifically.  Output t time efficiency rating of the furnace

CFM = net btu/1.08 x temp rise.  Once actual cfm is determined, then the problem solving begins.  Compare the actual delivered cfm against the design cfm at at a given fan speed will lead in the direction needed to solve the air delivery problem.

keep us posted,
Minnesota Wayne

CFM

@ November 28, 2010 10:05 AM in Comfortmaker Heating System Short Cycling

Let us know the what temperature rise you measure.  By the model number, it looks like you have a high efficency furnace with a ecm blower motor.  Properly sized duct is very important.  These motors will try to deliver the required air flow at a hugh energy expense if operated at less than design conditions.

cfm delivered by the furnace can be calculated by knowing the temperature rise and the net btu delivered.  Take the net btus from the model number data tag.  Do not use the input.btus ie; 60,000 input 54,000 output.  the 54,000 output is the number to use. you may have to calculate the output if it is not listed specifically.  Output t time efficiency rating of the furnace

CFM = net btu/1.08 x temp rise.  Once actual cfm is determined, then the problem solving begins.  Compare the actual delivered cfm against the design cfm at at a given fan speed will lead in the direction needed to solve the air delivery problem.

keep us posted,
Minnesota Wayne

/check temperature rise

@ November 27, 2010 4:03 PM in Comfortmaker Heating System Short Cycling

Some thoughts on your system,.  Check temperature rise across the furnace.  Any probe type thermometer will work.  For a home owner an inexpensive hardware store thermometer will work.  You may have to punch holes in the duct work to insert the thermometer.  Be careful of any refrigerant coils.  This is done by measuring the return air temperature and measuring the supply air temperature.  Subtract the return air temp from the supply temperature.  This is your temperature rise.  Your furnace data tag will state the required temperature rise.IE; 35 to 65 degrees or 50 to 70.  Your target is in the middle. 50 degrees or 60.  use your furnace specs.

Here comes the interesting part.  Once you have measured the temperature rise across the heating section, and compared to the manufacturers specs.  If the temperature rise is above the range stated on the data tag, (which I suspect is the case0  then the question is, is the duct work causing the problem or is the fan speed set wrong. 
You do not state the type of comfort maker you have so I am going to make some assumptions, 90+ percent with a 4 speed indoor blower fan.  If this is the case. then place the high speed motor lead (black) on the heating terminal and use a different fan speed for the air conditioning speed.  If you have a ecm motor then follow the instruction manual to set the fan speed in the heating mode.

That was the easy fix and if it works fine.  I really suspect the supply duct work is undersized for the furnace or like you suspect the return duct is inadequate.  This requires checking cfm at diffusers and return grills.  Testing with toilet tissue is not adequate or a qualified result.  It will tell air movement, what we need to know is how much air at each grill.

All furnaces need the required cubic feet of air flow in a minute (cfm) as designed.  Most sales people and installers under-size both the supply and return ducts to such an extent the furnaces fail prematurely.  A properly sized air delivery system is both effective in delivering the right amount of air to each room and operating quietly

Tempo

@ October 7, 2010 11:03 PM in stink bugs - arrrrggggghhhh (off topic!)

Tempo works for all kinds of crawling critters.  A farm store should have some, maybe some hardware stores. IN Minn it was the ear wigs and now the japanesse beetles and the elm bug.   Mix up a batch and spray on the house, shrubs etc.  Reapply as needed.

Minnesota Wayne

Reuse of the old chimney?????

@ August 22, 2010 7:49 AM in I will have a biler. Should I install tankless water heater?

If the chimney is very old, how solid is the inside?  Has anyone surveyed the integrity of the chimney?  Can the new chimney last the life of the new boiler?  Chimneys do deteriorate and fail.  They need to be inspected on the inside by a qualified person, looking at one from the outside will not tell if the integrity of the flue passage is sound.

Once you know the inside condition of the chimney, this will help in your decision to what type of boiler to purchase.  If the condition of the chimney is such that is has to be replaced, relined etc. that is not cheap. 

All chimneys need to be inspected periodically, more so as they age. 

Minnesota Wayne

The primary winding opens when the secondary is shorted.

@ July 13, 2010 7:55 PM in wiring a new airhandler

They still burn out in my field of work.  Granted they may take a hit and not open the primary the first quick short, but they will burn open. 
The fuse on the secondary lead will protect the transformer if there is a short after the fuse.

Minnesota Wayne

Sounds like the transformer is shorted out.

@ July 11, 2010 6:30 PM in wiring a new airhandler

When line voltage is measured at the transformer power leads and no output voltage, most likely the transformer was shorted out.  Check for 24 volt output to the control board inline fuse if available. 

Ohm out each side of the transformer; the 24 volt side most likely will ohm out fine the 120/240 side will ohm with an infinity reading.  The windings are very fine on the power side of a step down transformer and will burn out easy if the low voltage wiring has been shorted.

Install a 3 or 5 amp fuse in the low voltage side when replacing the transformer to prevent any accidents in the future.

Minnesota Wayne

Sure it is plugged,

@ June 5, 2010 7:28 PM in Can't diagnose 2 1/2 ton residential AC

The condenser is full, no more room for refrigerant, the compressor can only pump what it has available on the suction side. hence the low amp draw, low suction pressure and low high side pressure.  There is NO REFRIGERANT FLOW.  The condenser is so full of refrigerant there is no room for any more causing the internal overload to open.
 
Find the restriction it may only be a partial restriction. 

Minnesota Wayne

Morning David

@ May 30, 2010 8:41 AM in Sizing Room AC

All understandable, you now have ideas to choose from that will best suit your house and lifestyle.

Minnesota Wayne

Sorry readers

@ May 30, 2010 8:37 AM in Superheat

I used a on line chart for my information.  The numbers more represent R-12 rather than R-22.  I should have known better too, in a hurry.

Devan, to answer your question; superheat is additional heat added to the refrigerant vapor once all of the liquid refrigerant has boiled off.  So the measured temperature reading of the suction line will be higher than the measured suction gas pressure converted to temperature using a pressure temperature (pt) chart. subtract the converted temperature from the measured suction line temperature to arrive at the superheat value.

Sub cooling is measured on the liquid line.  Liquid line pressure converted to temperature,  Measured liquid line temperature minus the liquid line converted temperature to arrive at sub-cooling.  Sub-cooling will be the amount of additional heat removed from the liquid refrigerant. 1 degree sub-cooling equal about 2% efficiency.

Sorry for the inaccurate information posted previously;
Minnesota Wayne

use the R-22 charging chart to answer the question

@ May 29, 2010 11:57 AM in Superheat

R-22 At 76.9 psi(g) gauge is equal to 75 degrees F., at 84.1 psig is equal to 80 F.  Your 79 psig is close to the middle of the 2 numbers so lets say 77-78 degrees.

If you measured 58 degrees on the low side or your suction line, then the superheat is 78 - 58 for a difference of 20 degrees. 

What pressure is the 117 for?  High side maybe.

If it is then there may be a problem with the compressors capacity to pump the refrigerant. 

There is an acceptable range, and "it depends" upon the type of system, capillary tube, fixed orifice, or expansion valve.  If you have a true expansion valve ac system then 12-15 degrees of superheat would be in the range, depending upon manufacturer of equipment. A fixed orifice or capillary  tube will have a different value.

Too fully identify the problem, we would need the system pressures, indoor and outdoor temperature, liquid line and suction line temperatures, and compressor amp draw.  State the problem or concern.
Thanks,
Minnesota Wayne

Heat Gain/Loss

@ May 29, 2010 11:41 AM in Sizing Room AC

There is two different calculations, resulting in two different numbers.  One for the heating load, and then the cooling load.  They both take into account the building construction, insulation and window on all exposed walls, including the ceiling and floor or concrete on grade.  In your case it would be the cooling load. 

As far as using the existing furnace and AC,  complete a heat gain/loss for the complete building including the porch.  Check the heat gain numbers (AC) against the capacity of the existing air conditioning system.  If the system is large enough to handle the added load, then install supply and return ducts.  May need to add an additional return duct openings in the room attached to the porch as it may be very hard to have a return duct opening placed in the porch.  I do not know what the basement or crawl space is.  Make sure the supply and return plenums are sized to the full capacity of the furnace.  For what ever reason in Minnesota undersized duct is very common.  Adding a supply or 2 off of the existing undersized ducts never works to expectations. But it is cheap.

Using a minisplit may be in the end a viable alternative.

Minnesota Wayne

Buy to the load

@ May 29, 2010 8:45 AM in Sizing Room AC

Oversizing will cause short run times, uncomfortable conditions and possible issues with mold.  Size to the load & only buy a unit as close as you can to that load.  As Techman said, do a new heat calc, as most likely the windows have been replaced, more insulation in the attic etc., requiring a new heat loss calculation.

The new technology includes the ductless mini-split systems which come in many sizes and configurations.  Some units have the heat pump option which allows the heating load of the area to be covered without running the main furnace.  Just a thought.
 Most of the minisplits have higher seer rating than a wall shaker, operate extremely quiet and qualify for tax credit money. 

do it anyway, geo

@ May 29, 2010 8:30 AM in Tax Credits with Geothermal and Radiant?

I realize you are trying to gain the best bang for your dollar and having the rest of us support your customers installation.  Do the geo with or with out the tax credit.  If there is an audit, what do you have to do? pay back the credit plus a possible fine, so what, your customer still has the most efficient system that we know of today and will have cash in the bank while all of us (the taxpayers) have paid for the system. 

Minnesota Wayne

You are not undercharged!!

@ May 26, 2010 9:56 PM in Can't diagnose 2 1/2 ton residential AC

First off, what kind of training have you had? Not to be critical but just having gauges does not make you a a/c service guy. 

You have described the classic case of a severe restriction.  The problem is where?  Is this a txv system or a fixed orifice or cap tube coil?  When the internal pressure bypass valve opened creating the high pitched squeal and then the overload opened, confirms you created a overcharge situation. 

Other questions; has this system had other problems?, compressor replaced,? poor maintenance?.  Excessive moisture in the system?  How long has the system operated in the restricted state? 

I am going to go out on a limb and suspect this is your first time at the job and the system has operated OK or fair in the past.  You will have to recover all the refrigerant, check the filter dryer, txv, metering orifice, kinked or bent liquid or suction line.  Eliminate the easy ones and then go after the hard ones.  That's all there is, most likely the compressor is OK if the unit has not run for a long time in a vacuum or near vacuum state.  Many of the RUUD units had low pressure switches to protect from loss of charge damage.

Once you have corrected the problem, replace the filter dryer, evacuate the system to 500 microns and weigh in the new charge of refrigerant.  Recheck subcooling or superheat depending on manufacturers specs.

Good Luck,
Minnesota Wayne