I needed a seed germinating heater for my cool night time greenhouse. In trying to find a DIY one on line I came across several coffee maker heater's used to make hot water. This kinda was what I was looking for so I decided to build one of my own. I want to tell you I am very satisfied with this project. For the passed two months I have pushed 130 degree water through 58' of tubing for 24 hours a day. This does add a little heat to the greenhouse but not much. I have not tested mine but it might keep a small greenhouse from freezing. My greenhouse is 6' by 9' and I try to keep my night time temp between 50 and 60 degrees. It takes about two hours to heat the water from a cold start. I have spent less than $60.00 on the entire project. I do not know the cost of running this setup. This setup could also be used for supplying hot water for personal use. Just shorten the return hose. With a thermostat you can set the water to several different settings.
Step 1: Bucket
I used a regular 5 gallon bucket and lid, from Home Depot, to store my pump and return water line. These buckets are inexpensive and can be found in various stores. You might even have one around the house. You will need to cut two holes in the lid. I ran the pump power cord and outflow hose out the same hole. The other hole was for the return water line. I am also using a Deep Fryer thermometer to keep an eye on the temperature of the water.
Step 2: Coffee Maker Heater
The heater is a simple on/off type of coffee maker. Mine was one I had just sitting in a closet. You can buy a new coffee maker from Wal-Mart for under $10.00 or look at a resale shop. I did not remove any wires from the heater. I did leave the switch in so I could turn on/off just the heater. If you leave the switch in line remember to tape around the base to cover the exposed wires. I found out the hard way that this was a missed step. There is a back flow valve, in the hose, that prevents the boiling water from backing up. Your pump will need to be hooked to this side. At one time before I got my pump I was testing the heater out. I found out the heater will heat the water to boiling and shoot it down the exit side. At this time it will draw in water from the cool side. This action make the heater a pump also. I would advise you to not use it in this way. The water coming out the heater is boiling and may lead to burns if you have an accident.
Step 3: Low Flow Pump
I am using a small fountain pump, low flow, to push the water through the heater and hose. I found this pump at Home Depot for under $20.00. I did have a problem, at first, when I was testing without the thermostat. There is a cover, were you hook up the hose, that came off with the very hot water. I just wired it back on and have had no trouble with it coming off. At first I did not have a thermostat to regulate how hot the water would get. In two hours time I was able to raise 68 degree water to over 200 degrees. A little to hot for what I needed.
Step 4: Thermostat
I found an electric hot water thermostat, lower heating coil, at Home Depot for under $9.00. I applied high temp grease, white lithium, to the contact area and taped it to the bucket. I figured this would help make a better contact area. I did not need to cut into the bucket. I took one leg of the heater cord and cut it then I wired it into the thermostat. Then duck taped it to the bucket. There was no need to mount anything inside the bucket. I am not able to set the thermostat to a set temperature. I am able to use it to get to my desired operating temperature and to maintain that temperature. After I took this picture I found out it is upside down. In this setup I am sure you could get 5 gallons of hot water at 180 degrees maybe higher in 2 hours time.
Step 5: Vinyl Hose
As you can see I ran the hose along the top of my shelf. I then placed spacers to hold the seed trays off the hose. This is one continuous hose about 58' in length. Not sure how long you can make it before you lose to much pressure. The hose I used is 3/8" ID and 1/2" OD vinyl. To connect two hose ends together I used 3/8" OD ridged tubing and two small screw clamps. I got most of it from Home Depot or from my shop. The hose is rated for 140 degree hot water. If you are going to be running a hotter water you might get a higher rated hose. The return side just empty's back into the bucket. Because of the warm water and sunlight, on the water tubes, I added some bleach to the water to reduce the growth of algae. I will probably run the temp up around 140 to 150 degrees. I will have to wait until I have some seed trays planted to test the temperature of the soil.
Step 6: Thermometer
The thermometer I used was for a deep fryer. I like for it's long prob. Most any one will do as long as it can be inserted into the water.
Step 7: Materials and Tools
- Bucket with lid
- fountain pump (low flow)
- coffee maker heater and wiring
- hose to fit pump
- small clamps
- small tube for splicing hose
- duct tape
- electrical tape
- lithium grease
- string or wire to fasten hose to shelf
- knife for cutting holes in lid and hose
- wire cutters
- screw driver
- Not sure I have presented everything. This is my first post. If you have any questions please ask. If you have any suggestions please make them. I am a retired shop teacher and like to tinker around the house.