I have a Mammoth model 45 ground water heat pump with a 2", 3,000' horizontal loop. It currently has glycol in it and is in need of some more fluid. I am wondering if I can top it up with methanol instead of glycol, without issues of any kind?

Some suggest to completely flush the glycol out but no one has a reason as to why. What would be the problem in mixing glycol & methanol?

Cheers & thanks for your input.

[email protected]

I recently had this come up and the answer I got from the chemical guru's where we buy our methanol was that if you mix methanol with glycol you get a diesel alternative fuel that is more expensive than plain old deisel.  When I pressed them for potential inter actions/effects they clammed up due to liability issues.  I would test the existing concentration of glycol and use that data as a guideline on what to do.  Methanol has come down, we are currently paying $2.18 a gallon.

Posted By Norm Osback on 30 Jun 2010 12:13 PM
What would be the problem in mixing glycol & methanol?

I'm not aware of any chemical incompatibilities, but how do you propose
to calculate the amount of methanol needed? And even more challenging,
how will you (or any future owner) be able monitor the condition of a
heterogeneous antifreeze mixture? With a hydrometer? ...fuggedaboutit!

Thanks for your replies; Eric, making a diesel fuel alternative would not be a great alternative for my ground loop. I guess the only way to check is to mix some and see what happens.

Fuggedaboutit; I currently have a mixture (according to my hydrometer) of 10-15 degrees F. My understanding is that I need about a 20% Methanol mix, so I would just add that to my line. How do I test it later, good question! What do you use to test the strength of methanol in a system?

Norm

Any alchohol floaty thingy will do.  I got mine from a water furnace dealer that measures both environal and methanol, I doubt it will measure the hybrid.  I have heard that a alchohol tester from a home brewing supply house will also work as long as the scale goes high enough.  I have tried 20%/40 proof beer and the drinkability suffers as the alchohol goes up.

Propylene Glycol is measured with a REFRACTOMETER. Methanol is measured with a HYDROMETER. I don't know how one would impact the measurement of the other. Were I you, I would recharge with glycol to the proper percentage or flush the glycol and start over with the Methanol.

Bergy

P-glycol is heavier than water, methanol is lighter.
For 15°F freeze protection, the specific gravities
should be approximately 1.03 and 0.98, respectively.

A 50-50 mixture would be somewhere in between, with
an s.g. close to 1.00 -- independent of concentration.

Not terribly useful.

How much fluid are you adding? if you simply found your loops at 10 psi and wish to push them to 30, that may only be a few cups of water. no reason to add antifreeze.
Joe

You can test any antifreeze with a freezer and a thermometer.

The idea of putting the mixture in a freezer with a thermometer is a great one!!!  however, most of us do not have freezers that go much below zero deg. F  So we can only test to that level.  Any other suggestions?  What about in a container with some dry ice and check every hour or so?

Using the hydrometer etc is useless, because you have no idea how much of each is in the mixture.  especially true  in large systems

Most manufacturer explicitly warn about mixing them. However, none of them tells you why. So why would you need to test them below 0 degrees F? I don't know any heatpump for geo application with an operating range below 0 degrees.

Posted By the wine wizard on 18 Nov 2010 02:07 PM
The idea of putting the mixture in a freezer with a thermometer is a great one!!!  however, most of us do not have freezers that go much below zero deg. F  So we can only test to that level.  Any other suggestions?  What about in a container with some dry ice and check every hour or so?

Using the hydrometer etc is useless, because you have no idea how much of each is in the mixture.  especially true  in large systems

If you have allready mixed the two, whether it is a small or large system "the pooch is screwed".  Testing for concentration of both in a given system becomes moot.
Eric