Questions about connecting an external garage to heat system

[mpilihp]

I have a detached garage with in floor radiant heat piping installed but not hooked up. I dont want to heat it all the time but heat it for a weekend here and there when im working on a project. I was going to use a propane hot water heater and fill the system with glycol since it wouldnt be heated all the time but now I want to consider the possiblity of hooking it up to my house wood boiler system. It really could not handle the load all the time expecially when its sub freezing out but I could fire up the oil beast for that if needed...

Pros to hooking it to the house are:
Simplier, one less heat source to maintain.
No glycol (that would be the plan....)
Would provide a heat dump zone ( currently dont have one so using house heat zone)
No water source in garage so no issue with maintaing pressure in a seperate system in the garage.

Cons from what I can tell:
Wood system could not handle heating house and garage all the time, probably need oil backup for it (but was going to use propane anyhow)
Potential for freezing in underground piping....


So im looking for OTHER CONS to doing this and also suggestions on how to heat it. IE if you think I should just heat it with the propane tank how do I solve the issue of no water source in garage to maintain system pressue.

OR

My concern/question about connecting it to the house system is how do I keep the underground pipe and in floor piping in the garage from freezing.... (IE part of house system and all water filled) I dont mine providing some heat to keep it from freezing but thats it.. (Again only want to heat it on weekends and not all) Can I use a timer of some sort to provide circulation through the system every so many min......

Another thought was to use an indirect hot water tank in the house as a heat source/buffer, have the tank be a zone on the wood boiler system and then put glyco in the tank and zone in the garage and could provide system pressure on the glycol side within the house ?? Then control the system temp via the indirect HW tank temp controller.. and use a thermostat in the garage to control a circulator in the garage to circulate glycol through the tank and the garage infloor pex.... Any thoughts??

Again thanks for your assistance

~ Phil

 

[whippingwater]

You would need a heat exchanger before running to the garage and that system would still need glycol to prevent freezing.

 

[in hot water]

generally we use a small plate HX off the boiler and glycol only the garage loops. Remember that side of the HX will need an expansion tank and relief valve. The HX runs off a zone like the rest of the zones.

I have used an indirect tank as a HX for this purpose, if you can find one cheaper than a HX. You could put the boiler water in the tank side, which offers some buffer capacity, and glycol the coils in the indirect as the garage zone. I've used the Weil McLain indirect "tank in tank" style that way.

hr

 

[mpilihp]

Hi thanks thats what I was thinking with the indirect tank it would provide some buffer capacity and allow the wood boiler to offload excess heat to the buffer tank when its able to and then would be able to provide excess heat to the garage, could set up aqustat so that when ever tank is over X temperater the circ on the garage zone side would run to bleed off the excess heat.

So there isnt anyone out there that has an detached building and running regular water in the loop??

Another question, maintaining pressure on the glycol side, just provide a pressure valve to the house supply water with a gauge on it to maintain the pressure? Should I be putting fittings/drains and such so I can at a later point add glycol?? Whats the process to test and make sure the %of glycol is correct??

~ Phil

 

[Paso]

I have a small shop attached to another building. In that building i heat it with a electric water heater.

You could plumb in the electric water heater in your garage loop and run your house to garage pump 24 / 7 and turn the thermo stat down low ( as I do ) when not using the shop.

That keeps the water heater from running unless it gets too cold which at that point ( freezing ) I don't care if the water heater starts heating.

 

[Peter B.]

mpilihp wrote:

>I have a detached garage with in floor radiant heat piping installed but
>not hooked up.  I dont want to heat it all the time but heat it for a
>weekend here and there when im working on a project.

I'll be interested to know what you end up doing... I'm having a garage built now and plan to install in floor piping, but haven't thought a great deal about how to heat the water as yet. Currently, I heat the house with a wood stove, but might think about a basement boiler at some point in future... and if I did, I might as well heat the garage on a loop.

--

Paso wrote:

>I have a small shop attached to another building. In that building i heat
>it with a electric water heater.

I've been meaning to try to put together a minimal backup heat system for my house using a 20 gallon electric (which, for my domestic hot water costs very little to run), and a baseboard heater (or two) on the first floor.

Have you had good luck with your setup?

--

Thanks...

Peter B.

-----

 

[Paso]

This the 4th Winter ( I think ) maybe 5th time flies when having fun

The first winter I added a second water heater only because we get weeks of minus 40 and I was concerned of it not being adeqete.

I went into the shop the other day with it being closed up for a week and you could hardly breath from the heat. Both water heaters were not heating at that moment.

The shop is 18 x 24 with in floor piping.

I think it is a very good option. Some areas do not allow that type of hook up ( like mine ) But I know it works.

 

[mpilihp]

I have a small shop attached to another building. In that building i heat it with a electric water heater.

You could plumb in the electric water heater in your garage loop and run your house to garage pump 24 / 7 and turn the thermo stat down low ( as I do ) when not using the shop.

That keeps the water heater from running unless it gets too cold which at that point ( freezing ) I don't care if the water heater starts heating.

So is this a CLOSED system not connectd to a water source for maintaining pressure?

So you run the circulatro 24/7 and keep the thermostat on the elect hot water heaters down LOW? how low do they go on the electric hot water heaters??

In your last posting about the shop being closed for a week and being very cold inside, from this im gathering you have just plain water in the system, you run the circulator 24/7 to keep everything from freezing up and the electric tanks are OFF when not wanting to heat is that correct? So just the motion of water through the system keeps it from freezing??

Thanks

 

[mpilihp]

mpilihp wrote:

>I have a detached garage with in floor radiant heat piping installed but
>not hooked up.  I dont want to heat it all the time but heat it for a
>weekend here and there when im working on a project.

I'll be interested to know what you end up doing... I'm having a garage built now and plan to install in floor piping, but haven't thought a great deal about how to heat the water as yet. Currently, I heat the house with a wood stove, but might think about a basement boiler at some point in future... and if I did, I might as well heat the garage on a loop.

-----

Ill keep the forum posted, We switched over to an non gassified wood boiler this year from using a oil boiler and wood stove in the basement as supplemental heat. Using the wood boiler as primary heat now we are using wood at what appears to be the same rate as with the wood stove and no oil and the house is alot warmer (keeping it around 75 now) Wood boiler with the baseboard heat much more effective at getting heat to the living spaces.

~ Phil

 

[Paso]

Yes the system I am talking about is a closed system. ( I have a more than one location going)

The shop being closed for a week and when I opened the door it was super warm inside. ( sorry I wasn't clear )

This particular location the circulator is on a thermostat set very low.

I have two loops not more than 250 ft per loop.

I ran anti freeze the first year but each each fall I charge the system with a garden hose so I'm sure not much anti freeze.

Both water heaters are set to come on anytime the water tempeture drops below setting 130 degrees

 

[mpilihp]

Woops another IMPORTANT question about piping to a detached building.

The garage already has PEX in the concrete floor, layed years ago by a contractor, I dont dare try to drill/penetrate the floor to bring the underground PEX into the garage. Since its going to have glycol in it, can I just bring it up out of the ground and come into the building above the slab through the wall? I could insulate the insulated pex (provide a box shelter at the penetration) Would this be OK other than looks and possibility of damage cause its exposed?

Im looking at using a prefab underground PEX piping someone at work is selling, looks cheap but it is oxygen barrier and is two pex pipes wrapped in what looks like thick felt inside a black corrugated pipe.

~ Phil

 

[rowerwet]

the distance from your house to the garage could be a con depending on what type of pipe you use. you may end up heating the ground as well as your garage with the wrong type. I have 85' of thermopex (12.50 a foot) but don't loose any heat into the ground (manuf. says 1 degree per 100')
Is your OWB pressurized or open? if your house is already open system you won't need expansion tank or HX or glycol.
glycol is only if you don't want any heat in garage unless you are in it, then you need a HX. otherwise just a circulator or zone valve with a thermostat that goes down to 35* would keep garage from freezing for less money. ( antifreeze is $11.50/gal at HD and needs to be changed every 2 years or so, just throwing that money away)
If you do the run to the garage with thermopex or similar you can come up out of the ground and into you garage as long as the outer shell is protected from the sun, just a box will do to keep UV from breaking down the plastic.

 

[mpilihp]

My system is closed pressurized, if I did glycol I would probably use an indirect DHW tank instead of a HX jsut so it would have a heat buffer tank.

Physical distance between the two buildings is about 15ft, piping run because of grade change and where I would want to enter the garage would probably bring the lenght of the run to 60-80 ft guessing on the high side.

One thing I didnt know/think of is having to change the glycol every 2 years? Is that really needed/necessary? I know they recommend changing automobile antifreeze quite often but to be honest if I change it once in the life of a car I own thats pretty good and I usually keep my cars over 5 years at a time.

Also how do you dispose of the waste glycol? Is it hazardous waste?

I think my garage has 4 loops in it at 200 feet each, a quick calc of the needed glyco would be:

Distance for 1 gal in 3/4" pex

1 gal = 231 cu in

231/(pi*r*r)

231/(3.14159265*.375*.375)

231/.44178646640625

522.87 inches or 43.5 ft per gal of glycol

So 4 loops of 200ft plus 100ft of underground = 900/44 = 20.5 gal round up to 22 gal. 50/50 mix?? 11 gal at $12 each is $132 per every two years?? ouch

So with your underground run using thermopex are you running just water in it? Have you ever let it sit unrun/unheated and did it not freeze? How about in the slab how long could it go unheated and not freeze?

My garage is at a higher grade than my basement and I could easily set it up so that when I wasnt heating I could drain the underground pipes but dont know about draining the entire floor slab system.

Would just running a circ pump circulating water through the underground pipes and slab pex keep it from freezing (without providing any heat other than the ambiant temp in the basement where the indirect tank would be??

~ Phil

 

[rowerwet]

Slab heating is slow, there is a lot of mass to heat up before the slab starts giving heat to the air, and after the slab is heated it will hold that heat for quite a while. depending on how often you use the garage it may be better to just put in a water to air HX (like a car radiator with a fan) heating air is much faster and would save you all that aggravation with antifreeze, pumps, thermostats, tanks etc. If you run a business from the garage or make your living in it heating the slab makes sense, otherwise most of the heat will come after you leave the garage. A modine style heater is your best bet, keep the water circulating through it all the time so it won't freeze, and put a switch or thermostat on the fan for when you want heat.
reading around this site I've seen up to 2 days of solid heat to heat the slab under a house, none of which is wasted as you want your house heated all winter.
I almost put antifreeze in my OWB, right before I started filling the system I read the bottle, it did say it should be replaced every two years or so, putting it down a septic system is a bad idea, public sewers are ok, it is not ok to put it directly into streams etc.
I don't worry about the water in my OPB freezing, I leave the circulators running to the HX and my oil furnace keeps the water from freezing, I think it also acts sort of like storage even though it is only 90 gal.
I don't know when you would have to worry about slab pipes freezing, there are thermostats made with probes that monitor the slab temp instead of the air temp for better temp control, otherwise you get larger air temp swings in the space above the slab. someone else will know more about that.

 

[Tony H]

Seems like the idea from "rowerwet" is a good one if you only heat a handful of weekends why waste all the time heating the concrete one of the hanging heaters would work fast and with the grade difference you could even install a shut off and drain so you can empty it easily, just follow the pipe levels for drain line and it should work well. Using the good buried pipe is the way to go and the cost won't be that bad with the short run just build a box around the inlet and it should be fine.
If you decide to go the floor route why not install a propane HW heater and a sidearm to heat the water from the boiler then set the temp low on the HWH and let it circulate all the time to prevent freezing.

 

[mpilihp]

Hi Guys thanks the water to air HX idea, it is a good one, I currently heat the garage when I want it via a 70k btu propane can heater, works ok, needs to be firing constantly basically to keep the garage around 50. The garage is insulated but there are a few 'holes' in the insulation in the ceiling I need to close up.

Reason I wanted the infloor heat is for working on cars (main reason for heating) Im usually on the floor and even though the air is at 50 deg the slab is freezing cold and laying on the floor is hard on the body. Lying on a warm floor is so much better. Also im betting if the floor is heated to 40 deg it will be warmer above as heat rises.

Disposal of the Glycol is the part im having a hard time with, I dont want to start generating hazzardous waste. If I could heat the floor just enough to keep it from freezing (filled with water) all the time and then heat it up for a weekend to do work Id be happy, even if I had to start heating it on say a Wednesday to be ready for Saturday)

This is our first season heating with a wood boiler and when the weather is bitterly cold as its been recently (5 deg) the wood boiler does take time to warm the house up. So not sure if I can even use it to heat the garage, it currently has ghost flows through the heat zones when the wood boiler circ is running and ends up over heating, once I get that resolved Ill know better its ability to provide additional heat.

THanks

~ Phil

 

[mpilihp]

Hi again, Ive been doing some reading about glycol solutions and found in this DOW document that states glycol can last up to 20 years with proper maint. If it lasted 10 years even without much maint Id be happy.

http://www.dow.com/webapps/lit/litorder.asp?filepath=heattrans/pdfs/noreg/180-01332.pdf&pdf=true

They even make a propylene based glycol that is enviromentally safe and provides corrostion inhibitors. DOWFROST. Its expensive. for a 50% mix id need 11 gallons at $105 each....

Thats alot of $ compared to the stuff they sell locally but if its that much better and doesnt need to be changed every two years I think it would be worth it.