What are the merits of gravity feed hot water?

[MEP001]

The Mix-Rite and Dosatrons are interesting alternatives and seem like they should work but again, thats a $1000 science project I don't have time for. To me the gravity feed is still simpler and bulletproof. With the chemical pump set up you still have one or two water inlet solenoids per bay. It also adds two more mutliplexors, one for soap and one for wax, into the mix. If you don't have solenoid for each chemical pump you run the risk of pumping away a bucket of soap or wax if one of the bay solenoids doesn't close.

Yep, all problems that have kept me from trying it. I do know someone who feeds his wax to his pumps that way, and he says it works, but he doesn't care about consistency/accuracy of what he delivers, and he's so cheap he'd rather risk losing a bucket of soap now and then rather than add solenoids so his are just dead-headed.

FWIW with the two washes I retrofitted with the PR-1000A I was really impressed with how well they worked. They were both SMC equipment with a separate tank for each bay, and eliminating that cut down on pump maintenance a huge amount, but the regulators failing and not allowing soap/wax was just too much of a problem.

 

[OurTown]

I eliminated the 80 gallon storage, and re-plumbed the circulator to go back directly to the open tank. I then installed a multiplexer to break the t-stat wire when not in use. Moved the t-stat to the open tank. The multiplexer is activated by the 24 volt hot in any bay. This closes the signal loop to the t-sat, and brings the boiler on if the open tank is not at 115. So at any time I am only keeping the 15 gallons or so hot in the open tank. When no bays are used, the boiler never comes on.

This is a cheap way to lower your gas bill, and sort of create an on-demand heater with your existing boiler.

How long have you had this arrangement? I'm wondering if it could build up carbon in the heat exchanger because it runs short cycles compared to heating an 80 gal tank everytime it runs.

 

[washnvac]

Since 2007 when I bought the place.

 

[2Biz]

I eliminated the 80 gallon storage, and re-plumbed the circulator to go back directly to the open tank. I then installed a multiplexer to break the t-stat wire when not in use. Moved the t-stat to the open tank. The multiplexer is activated by the 24 volt hot in any bay. This closes the signal loop to the t-sat, and brings the boiler on if the open tank is not at 115. So at any time I am only keeping the 15 gallons or so hot in the open tank. When no bays are used, the boiler never comes on.

This is a cheap way to lower your gas bill, and sort of create an on-demand heater with your existing boiler.

This is basically the same way my Mark VII was plumbed. There was a 350K btu Jarco Webn Non-Condensing boiler heating a 10 gallon gravity tank. Needless to say it didn't work when I bought the wash. Even if it did, the efficiency would have been so low it would have been really expensive to operate. Because of the short cycling, it never reached a high enough temperature that allowed it to run in a condensing state. There were no coil fins left on the heat exchanger when I scrapped it out. If you have a non-condensing boiler, I would think this could be an issue?

 

[washnvac]

It is non-condensing. Remember, the unit is not heating at all when no bays are used. Therefore it only heats when a bays are timed up. The heater runs plenty of time to dissipate any condensation. The first two cycles folks normally use are pre-soak and hp soap, both of which use the hot water. When or if this heater fails, I will replace it with a Rinnai.