The Grumbach S84 Incubator for Reptile Egg Incubation

I discovered Grumbach incubators from the book Beaded Lizards & Gila Monsters Captive Care & Husbandry which states that “Grumbach incubators are especially well suited for hatching Heloderma eggs”. After some Google searching and browsing through reptile forums I quickly found that the problem with Grumbach, a German manufacturer, is that these machines are not commonly used in the US (especially for reptile egg incubation) and finding information about their incubators and how they are used is scant. The sole distributor here in the States, Lyon USA, seems to have disappeared. The Grumbach website does have English instructions for their incubators so, armed with what little knowledge was available it was off to eBay. As luck would have it I found an older analog Grumbach S84 Compact model for a fair price and picked it up. After downloading the manual from the Grumbach website I sent the next few weeks attempting to get the incubator to where I needed it to be; 82*F with a 90% humidity. But no matter what I tried the coolest stable temperature I could get down to was 89*F. Way too hot for Gila monster eggs! The S84 was made for hatching birds, so I contacted Grumbach directly to see if this unit could be used for reptiles (they have several reptile specific incubators, but again getting one here in the US is a very expensive proposition). They did get back to me and said that the S84 could be used for this, but they did not give me guidance on how to get the temperature to where I needed it. Frustrated, I sold the Grumbach since it was apparent the incubator would not work for my purposes and I did not want to modify or damage this fully functional unit. The hunt for another incubator began.

Then, again on eBay, another S84 popped up but this one was being sold for parts and not working for a deep discount. I figured this unit would be a better fit as I could modify it to fit my needs without having to worry about losing too much money if it didn’t work out. The owner reported that they only tested the incubator on 110v (the Grumbach’s are 220v) so they weren’t sure what worked and what didn’t. This model was digital so, to me, it was worth the risk. The unit arrived and once properly hooked up to my Todd Systems 115v to 220v step-up transformer I was able to get most of the components up and running properly. The exception being the fan. The Heidolph fan was dead and upon contacting Lyon USA found out that Grumbach no longer supplies a replacement and the entire unit (fan, heater, assembly) had to be purchased at a cost of $800! It appears that Heidolph produced these fans specially for Grumbach as I couldn’t find a replacement anywhere. Buying a new unit obviously wipes out any cost savings of purchasing this unit so I started researching other options and found an Ebmpapst 4850 ZW 220v fan, which some Grumbach’s use, to fill the position and it works well! This unit pushes a lower cfm (cubic feet per minute) than most of the others I looked at which is an important factor as we do not need a hurricane to dry the eggs out or draw out the moisture, only for moving the air to provide a consistent temperature.

I want to take a moment to mention again that Grumbach incubators are 220v. Here in the US, our outlets are 110v and a step-up transformer is necessary to properly operate the unit. When I started researching transformers, it quickly became apparent that this was an area to not skimp on. The abundance of lower cost and quality units which are readily available on Amazon and eBay make it seem like they are all the same, but that is far from the case. Perhaps for intermittent use these cheap units would be fine but my incubator will be running continuously for 5-6 months! I read horror stories of how these cheaper units run hot and can catch on fire after a few hours of use, and that you need to double their wattage (if your unit uses 500w, you need a minimum of 1000w or greater transformer) to ensure proper power is supplied. After all these years and planning, the last thing I want is for a cheap component to ruin my eggs, or even worse burn my house down! So, more research ensued and I found a few high-quality transformers; the one I bought from Todd Systems and there was another company ACUPWR, that made equally good equipment.

I set up the incubator well in advance of oviposition to make sure the eggs go straight into a stable environment. I don’t know why, but this second Grumbach was able to achieve the conditions required for incubating Gila monster eggs and it didn’t take long to get everything dialed in. I placed a SensorPush digital thermometer / hygrometer to track my temperature and humidity, as well as some Squamata Concepts S.I.M. egg containers in the incubator and think I am all set. All I need now is the eggs!

I cannot yet comment on how good the Grumbach S84 incubator will be for Gila monster eggs, but feel it should be adequate as it is well insulated and maintains a very steady temperature and humidity while the fan provides a consistent temperature throughout the unit. I must say that it is cool how the digital display can be seen in the dark across the room for obsessive checking:) I’m sure other incubators and DIY units can do the same job, but Grumbach is world renowned and I am fascinated by German engineering (thanks, Leica!). I’ll revise this post after the first year and report how well it does and if I’ll be sticking with it for upcoming hatches.

Update: June 12, 2020

Now that the first successful year of breeding Gila monsters is behind me and the second season is well under way, I wanted to update this post with some additional thoughts on the Grumbach S84 incubator.

The first year, I did not find a good solution for circulating the air and ended up not having a fan at all. Only 5 of 13 eggs hatched (though 4 were bad out of the gate) and I wondered if there may have been a lack of fresh oxygen to sufficiently allow the eggs to grow. This was an area I wanted to improve in 2020 and have found a good solution. I found that 220v fans increased the temperature in the incubator by 8* – 10*F which put the temperature too high for my comfort. Last year, the incubator averaged 78.2*F without the fan, which would put the temps in the mid 80’s and on a hot summer day could wind up in the upper 80’s – certain disaster! Keeping in mind heat from the tank that maintains the humidity also adds a temperature increase, I started off with a 12v computer fan plugged into a 120v converter. Temperature only increased a degree or two, so things were looking promising. I wanted to try a native 120v fan with low wattage and RPM’s to keep the temp low, and found the AC Infinity 8038 axial muffin fan on Amazon which can be purchased with a separate speed controller. My interest was piqued as this fan, of all the AC Infinity 120v fans, only used 4 watts of power and moved 23 cubic feet per minute so it fit the parameters that should work for this application. With a quick order and Prime delivery the fan and controller were at my house in short order and installed for testing. After a few weeks of adjustment between fan speed and humidity control I was able to dial in a steady temperature of 81*F and 90% relative humidity, perfect! Temperature and humidity were constantly monitored (and checked) with my SensorPush system; one sensor in the incubator and one in the egg box. Time will tell if the fan holds up to the high humidity, but the fan seems very well made and I love the external speed controller. With eggs in the incubator now, I am hopeful this new set up will help increase my success in 2020!

I still love this incubator and agree it is an excellent choice for incubating Heloderma eggs. Parts are scarce and expensive, but things are working good for now. One of these days I need to pick up another Grumbach S84 just in case this one fails or I get more pairs of Gila monsters to breed!