theromstatic mixing valve for domestic use

[4jaybe4]

Hello,
Any advice would be appreciated. 2 1/2 years ago I recommended a hvac contractor to my painter for an issue with his boiler. i had worked for this contractor in the past, but had left the field at the time. The Painter was not impressed with how the job was handled. At the time they replaced a mixing valve on his boiler that serviced the domestic water. Recently he has started having an issue with it and contacted me.

his system - 16 year old Trianco Heat Maker HW-M2-130
services one radiant heating zone(one mixing valve) and the domestic water use(one mixing valve) which includes one sink, shower and washing machine.

no problems with the space heating

when the hot water tap is turned on in the sink or shower, it runs at normal pressure for 10 -15 secs, then drops to atrickle and returns to full pressure after 10 secs with hot water
he has a contract with the utility company in the area. they responding by saying they would not touch it. A contractor was recommended and declared it to be a bad mixing valve and suggested a whole new system. he contacted me because he felt that the valve should have lasted longer and
he isn't in a position to replace the system
boiler pressure 18psi
boiler water temp 185f
domestic pressure 95psi
domestic temp set for 110f
the mixing valve Apollo 34h10401 125 psi

thank you

[genduct]

Why don't you get the rebuild kit for the valve and have it ready when you open it up for inspection? Also 95 psi domestic water pressure? WOW not supper high but high enough to warrant a pressure reducing valve to make it easier on those faucets and washers?

[4jaybe4]

I don't believe this valve has a replacement kit. I was suprised at the water pressure as well, i felt it might have had some play in why the mixing valve went bad so soon (rated for 125psi) don't know for sure. thanks for the reply

[Vinpadalino]

Hello,
Any advice would be appreciated. 2 1/2 years ago I recommended a hvac contractor to my painter for an issue with his boiler. i had worked for this contractor in the past, but had left the field at the time. The Painter was not impressed with how the job was handled. At the time they replaced a mixing valve on his boiler that serviced the domestic water. Recently he has started having an issue with it and contacted me.

his system - 16 year old Trianco Heat Maker HW-M2-130
services one radiant heating zone(one mixing valve) and the domestic water use(one mixing valve) which includes one sink, shower and washing machine.

no problems with the space heating

when the hot water tap is turned on in the sink or shower, it runs at normal pressure for 10 -15 secs, then drops to atrickle and returns to full pressure after 10 secs with hot water
he has a contract with the utility company in the area. they responding by saying they would not touch it. A contractor was recommended and declared it to be a bad mixing valve and suggested a whole new system. he contacted me because he felt that the valve should have lasted longer and
he isn't in a position to replace the system
boiler pressure 18psi
boiler water temp 185f
domestic pressure 95psi
domestic temp set for 110f
the mixing valve Apollo 34h10401 125 psi

thank you

The coils might be clogged with calcium and need a good acid flush. Check the hardness of the water. Or the mixing valve might be clogged?

[skippedover]

The HeatMaker is a specialty system. Been working on them for many, many, years. Your 'friend' has some real problems but that's not a surprise.

The proper tempering valve on the tankless coil is a Watts 1170A or equipvalent. Just like every other aspect of this industry, there are those who cut corners and those who learn from them and think the cut corner is the correct or only way to do the job. The typical tempering valve installed is a Watts 70A or equivalent and those are two distinctly different valves. The 70A is smaller physically but is designed to regulate temperature at flow rates as low as 3-gallons per minute or greater. Note that a standard low flow shower head is 2.5-GPM!! The 1170A is physically larger but is designed to regulate temperature at flow rates as low as 1/2 GPM! That is significant when it comes to how most hot water gets used in sinks.

The tempering valve also needs to be thermally trapped. That is, the valve needs to be piped so that it is at least 6-inches BELOW the cold water inlet to the tankless. Failure to provide the thermal trap will lead to failure of the thermostat in the valve due to hot water sitting on the thermostat all the time.

Finally, the water temperature at the faucet outlet should never be above 130-degrees. 185 is dangerous and could cause skalding.

Replacing the existing tempering valve witha properly rated tempering valve and properly piping it in should solve the problem.

[4jaybe4]

Skippedover,

I had a feeling it was something along those lines. I am friends with some of the guys at the old place and they told me they put in what they could get a hold of with no research. sad. the one they took out was a brass monster the size of a coffee can.
As for my friend, the biggest issue is the radiant loop under they slab.
no insulation and it is poly butyl. he doesn't feel like tearing up the floor.

Thank you for your advice.