Control to give HW priority to indirect HW heater

Steve Garson_2

I have a WM GV-5 boiler with 5 zone valves: 4 for radiators and 1 for the indirect HW heater. The Amtrol Boilermater 41 gallon HW heater does not provide enough water to fill a bath tub half-way. I believe this might be because the HW heater does not have a way to prioritize the boiler and shut down the heating zones to heat the water.

Can someone recommend the type of control that I need to get the right hot water output? Or should I have a separate circulator for the HW heater? Or both?

Jamie Hall

What zone control are you using? Some have a built in switch for domestic hot water priority, which you need.

hot_rod

How old is the tank? Those finned copper coils inside tend to lime up over time and performance drops.

EBEBRATT-Ed

Taco zvc406-4 is what you need

Zman

hot_rod said:

How old is the tank? Those finned copper coils inside tend to lime up over time and performance drops.

They don't transfer much when new, the lime plugs them up quickly.

EdTheHeaterMan

What size piping is on the boiler side of the system. I have seen them piped from the boiler to the indirect with 3/4" copper. This is no better than a 40-gallon gas water heater with a 40,000 BTU burner. You need to pipe the boiler side with 1" minimum. Then use 1"copper x 3/4" pipe adaptors at the tank connections to get the full rated capacity.

The next thing to look at is the zone valve. Are you using the old Taco 570 zone valves? They take forever to open. You may be 1/2 way thru the hot water in the tank before they even turn on the boiler. Then there is the boiler pre-purge cycle before the flame starts to heat the boiler water By the time you start to get 180° boiler water to the tank's heat exchanger... you are nearly out of hot water. Then you are playing catch up. Change to a fast acting zone valve

Next thing is to get the priority control like the ZVC 406 mentioned by @EBEBRATT-Ed.

Finally, if that is not enough, you can set the tank temperature higher like 140° or 150° and install a mixing valve on the hot outlet of the tank.

Respectfully Submitted
Mr.Ed

Steve Garson_2

Thanks everyone for the tips. Installing the Taco 5-zone control with priority for the HW heater solved the problem. Since all the wires needed extending, it took almost three hours, but now we fill the bathtub without any problem. Happy wife! Thanks!

bucksnort

EdTheHeaterMan said:

What size piping is on the boiler side of the system. I have seen them piped from the boiler to the indirect with 3/4" copper. This is no better than a 40-gallon gas water heater with a 40,000 BTU burner. You need to pipe the boiler side with 1" minimum. Then use 1"copper x 3/4" pipe adaptors at the tank connections to get the full rated capacity.



Finally, if that is not enough, you can set the tank temperature higher like 140° or 150° and install a mixing valve on the hot outlet of the tank.

Respectfully Submitted
Mr.Ed

Thanks Mr. Ed. I going to install a NOS Bradford White RTV-40 indirect that has 3/4 fittings. The newer models are 1" in/out. I thought i should pipe it all the way in 1" and then neck it down to 3/4".

mattmia2

You could also just put a normally closed relay in series with the heating zones that disconnects the heating zones when it is energized by a DHW call.