Question About Isolation Relay for Mr. Heater Big Maxx

[Natty Bumppo]

Hey guys. New to the forum. I am finishing up a 25x35 barn/garage and am going to mount an 80,000 BTU Mr. Heater Big Maxx this weekend. The owner's manual suggests using an isolation relay if using a thermostat that has a microprocessor. Can anybody help me understand 1) why this is being suggested and 2) a product that will work for this application.

I of course Googled isolation relays and tried to find a product. Seems there are many different types for different applications. Want to be sure I buy the right thing, and then understand what it's doing.

Thanks in advance.

 

[klassenl]

Can you post the specific model number of the unit and a picture of the page in the book that says thus.

 

[Natty Bumppo]

Can you post the specific model number of the unit and a picture of the page in the book that says thus.

Yes, of course. It's model # MHU80. Page 9 of the manual. Thank you.

 

[fitter30]

Look on page 13 top diagram they show a electronic stat and there are no notes about a iso relay. Spark ignition has been for years with no problems with electronic stats. I don't think you will have any problems.

 

[brewchief]

Look on page 13 top diagram they show a electronic stat and there are no notes about a iso relay. Spark ignition has been for years with no problems with electronic stats. I don't think you will have any problems.

Agree with this, isolation relays were commonly used years back when electronic thermostats first came out but I haven't seen anything modern that needed one.

Sent from my SM-G965U using Tapatalk

 

[dogdog]

It's just a 24V coil relay that can handle the load of what ever amp/volt on the other end...

this is the typical setup...

https://support.ecobee.com/hc/en-us...ermostat-installation-with-an-isolation-relay

 

[wanderer]

I have a brand new isolation relay and 24 V transformer sitting here that I bought to try to make a nest thermostat work before I gave up on it. I don’t think I paid a great deal of money for it, maybe $10-$20. If you think you can use it I will ship it to you and you can send me a few bucks on Venmo or whatever to cover the shipping.

 

[Natty Bumppo]

Look on page 13 top diagram they show a electronic stat and there are no notes about a iso relay. Spark ignition has been for years with no problems with electronic stats. I don't think you will have any problems.

Agree with this, isolation relays were commonly used years back when electronic thermostats first came out but I haven't seen anything modern that needed one.

Sent from my SM-G965U using Tapatalk

It's just a 24V coil relay that can handle the load of what ever amp/volt on the other end...

this is the typical setup...

https://support.ecobee.com/hc/en-us...ermostat-installation-with-an-isolation-relay

Thanks for the help and the info gentlemen. Appreciate it.

 

[Natty Bumppo]

I have a brand new isolation relay and 24 V transformer sitting here that I bought to try to make a nest thermostat work before I gave up on it. I don’t think I paid a great deal of money for it, maybe $10-$20. If you think you can use it I will ship it to you and you can send me a few bucks on Venmo or whatever to cover the shipping.

Thanks for that offer. Let me check with a buddy of mine who is an electrician. He was going to check his boxes of parts to see if he had something I could use.

If he doesn't have something I'll certainly take you up on that.

 

[dfiler2]

I installed a Honeywell wifi thermostat to mine about 5 years ago, I had to run a wire to the inside of the unit to pick up the "C" terminal but most of the newer ones I've seen have the "C" terminal already on the outside. It really doesn't make any sense that a relay would be required but if it makes you feel better, go for it.

 

[Natty Bumppo]

I installed a Honeywell wifi thermostat to mine about 5 years ago, I had to run a wire to the inside of the unit to pick up the "C" terminal but most of the newer ones I've seen have the "C" terminal already on the outside. It really doesn't make any sense that a relay would be required but if it makes you feel better, go for it.

Appreciate that. Sounds like maybe a relay isn't necessary. The manual suggests one, so that's why I was looking into it.

 

[dogdog]

Appreciate that. Sounds like maybe a relay isn't necessary. The manual suggests one, so that's why I was looking into it.

dependents on the thermostat you selected and the transformer that thing have... some of those like Echobee and the other one draws a bit more than what the transformer can handle when all valves are operating..... I know that was the reason I went with a separate transformer and isolation relay when I installed it for a friend's heating, his cooling on separate thermostat also echobee, doesn't need it. The other solution for him on the heating was to replace the 40VA with a 70VA or 100VA transformer... I just went with isolation relay.