Open Garage Doors

Einsiedler

They must have been born in a barn or a cave?

Why not just beat the Customer senseless until they agree that closing the O/H door is the actual answer to the question/problem.


EIN

Tom Beaulieu

Heat lost through open overhead garage door

I have an interesting challenge to correct a situation in a system installed several years ago. The situation is the homeowner has a tedency to leave the garage door(s) open for extended periods of time. We discovered this with the use of Hobo Data loggers while trying to "chase a ghost" looking for an intermittant "can't keep the house warm" problem.

We discovered that when the garage door is left open with the outdoor air temp of 10 deg F., the boiler return temperature drops down to as low as 90. The supply temp provided by the boiler is then at 120 degrees which is not enough to satisfy the loads in various parts of the home. In other words the boiler has run out of steam (hot water). There is no boiler protection on this system.

The garage is one of several zones all controlled by thermostats, relays and pumps. 5 zones and pumps are fed by a 4 way mix with outdoor reset. The other five are fed with a primary / secondary / injection pump arrangement. (Don't ask why!! Long story!)

The garage is 1,100 square feet. There are 5 220 ft. loops embedded in the concrete at 12" centers. All loops are connected to one manifold. The manifold is fed by a Taco 008 pump. The design calls for 3.5 GPM @ 8', 140 degree water and 15 degree delta T, 26,250 BTUH, 70 deg. indoor design, -13F outdoor design.

When looking at the performance curve for the 008, I believe the pump will move more like 10 GPM against 8 ft of head. The delta T we are getting accross the garage manifold is 30 degrees. If in fact the water flow is 10 gpm and the delta T is 30 the heat output of the garage floor panel is 150,000 BTU which is everything the boiler has to offer.


Here are the questions:
1) Can the garage floor panel be limited to only provide the 26,250 BTU it was designed for under any circumstances, ie doors open by limiting the flow?

2) Will increasing the resistance in the loops by use of balancing valves increase the head pressure to 14 ft and reduce the flow through the 5 loops to a total of 4 GPM? If so will that limit the output of the panel?

3) Should all garage floor heating systems be isolated by a heat exchanger? Will this limit the drain on the system?

Grumpy

Tom, rather than re-engineer the hydronics, why not install a 5 minute time delay relay on the garage door operator? Of course I'm assuming there is a garage door operator with safety interlocks to prevent false/dangerous closings. Door goes up, travel limit switch shuts off motor and powers the timer relay, times out, makes the circuit to close the door. You might need to put a manual override on it for summer use though. If it is a two impulse closer control, then it gets a bit more difficult.

kevin coppinger_4

If it were only that easy....

why is the door left open so long? A seperate boiler or a talk to that would suggest that if they want to be warm, then try not to heat up the outside.kpc

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J.C.A._3

Can't argue with the last 2 posts.

Dumb is universal. If they can't remember to close the door, let the dice fall where they may.(it ain't your fault...in other words).

Trying to fix a problem caused by stupidity is akin to a puppy chasing his tail. Eventually, they figure that they can't catch it and give up.

The real answer is to bill the stupidity till it subsides. Can you think of anything better? (Sorry..., I've seen the heights of stupidity in the last 2 weeks, and frankly, I'm tired of trying to educate those who are supposedly "educated individuals" . )

I'll quote Frank Zappa, yet again..."Hydrogen is not the most abundent element in the universe. Stupidity FAR outweighs it!". The man knew of which he spoke. Chris

jw

Quick Fix???

Try installing a strap on thermostatic switch on the boilers return set for say 140F? Switch would need to be an open on rise type. Use this to break the power to the circ pump on the garage slab. This way if the house needs heat, it is prioritized over the garage. Simple fix for your simpleton customer.

Might want to make sure you have some glycol in this system, as an open door may cause nasty leaks in the tube!

David_5

How about a door switch

to shut off the garage zone when the door is open. Antifreeze would also be needed. Alarm companies make some nice magnetic switches for this purpose.

David

RELY

what type thermostat

how about a floor temp stat.Check the curve on Taco 007 meets the need perfect!!!!

Phil_6

Really...

if ya spent as much time slapping them upside the head as you did measuring those temps, they'd be warm already ;-)

D lux_2

Smart home

try smarthome.com catalog # 7137 garage door autocloser 79.99 it closes your door when you forget .

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Tom Beaulieu

Responses

The garage is well insulated including thermal breaks at all slab edges. The system is protected with antifreeze. It is designed to maintain an indoor temperature of 70 degrees even though it is typically kept at 50 degrees.

This customer is not leaving his doors open on purpose; in fact I’m sure he is not even aware that it is happening. We discovered that it is the son that is opening the door twice a day to let the dog out. I think once the parents are informed it will be corrected.

I have a responsibility to make a system capable of performing properly no matter what the owners may throw at it. I decided install the door contacts mentioned to disable the garage system pump when the doors are open. Even with that I am concerned that the recovery mode once the doors are closed is going to hamper the systems ability to maintain comfort in the home. I am installing a strap on aqua stat on the boiler return so whenever the return water gets below 140 degrees the garage system pump will be disabled. I think this will cause rapid cycling of that pump at times but it better than the alternative.

This is one of those systems designed by a supply house and installed accordingly. We typically design our own systems. It is we who are ultimately responsible to our customers, the homeowners. All systems designed by us that have garage heat use a heat exchanger to isolate the antifreeze protected garage loops from the main system.

I thank all those that took the time to post their replies. I will certainly return the favor when the situations allow themselves.

Tom

RPA Cert. Hydronic Designer/Installer

Tony_8

A Tekmar 361

has a boiler return sensor to keep it at or above 140F. Seems a slower flow rate thru the floor would have a higher delta T than you already do, compounding the problem.

You may feel responsible for system operation under all conditions, but that is not realistic. I feel this way myself, except not for doors, windows, etc. left open all the time. Want fresh air ? Get an HRV. Trying to accomodate stupidity or laziness will get you treated for ulcers.

hr

A slab

with a belly full of heat will store a lot of BTU's. Generally it can handle intermitent door opening, and recover the temperature, quickly.

Sounds like they need a snowmelt design, not a radiant heat system

Plenty of ways to protect that boiler from return water temperatures, but the unrealistic loads are the problem, not the system, sounds like. Explain this to the users.

hot rod

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John Ruhnke1

Return water sensor

Tom,

What you need is a return water sensor to shut down the garage zone when the return water temps are to low. This will also limit the delta t and limit the maximum amount of btu's delivered to the garage. You can do this with a simple aquastat. Another idea is to install a thermastatic mixing valve on the return and mix bypass water in with return water from the slab. This will acomplish the same result only better. Slowly mixing the water is better then the on off cycle with a aquastat. Tekmar makes some great controls with return water sensors, 363,362 and such. Tekmar is the best way to go but would require extensive rewire and repipe.

JR

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