Tempering valve install question

Hi Guys, a question I hope someone can answer. In the pic attached, I circled a valve which WATTS recommends be installed to the cold water feed into the tempering valve. What type of valve should this be? Pressure regulator? Globe? or??

Thanks

I just got a reply from Watts:

Thank you for the inquiry. A globe valve would give you more control as far as flow control but any valve would suffice. You need to be able to cut back on the flow to the cold water feed to compensate for the loss of pressure in the hot water feed from going through the heater. You're attempting to equal the hot & cold feeds to the valve. I hope this helps. Thanks again for the inquiry and for your interest in Watts products.

Sincerely,
Watts Technical Service Team

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Globe valve it is.

You may have some difficulty finding a globe valve. A ball or gate valve is more common and a ball valve will work fine

valve

Regardless of the valve type, you will have an almost impossible job trying to set it to compensate for the pressure differential in the hot water side, because it will constantly change depending on the flow volume through the heater. A good tempering valve controls the cold water flow to maintain the outlet temperature regardless of the cold water pressure.

I could not locate a globe valve locally that would fit the bill, so I ordered one online. Good ol' internet.

I question the whole setup as Watts discusses the 'pressure differential', then recommends a 'flow-control' style valve. Right now, the house that I am working on has the setup as shown in the diagram sans the valve on the cold-water feed side of the tempering valve.

History is that a new boiler was installed 4 years ago to replace the original 196? GM one. Two oil companies later and a complaint of no hot water, they replace the tempering valve with the Watts 70A and leave it set to its max of 160 deg. Another phone call to complain of no hot water and they suggest replacing the control valve in the shower. From what I understand, hot water has always been an issue, but no one is making a big deal.

This is where I come in. I replace the shower control valve as requested and still get no hot water – when I say no hot water, I mean that it is luke-warm at best. I check out the boiler and turn on the hot water to the sink on. I can’t touch the hot water pipe from the heat exchanger into the tempering valve but the ‘tempered’ hot water line is only luke warm. A little research brings up Watts installation instructions for the 70A valve and shows that it was not installed as per their instructions. Incidentally, when I turn the tempering valve down to 120 deg., the ‘tempered’ water turns cold. I have no question about the capacity of the boiler to provide hot water.

I’m going to install the globe valve in the AM and see what happens. If there is still an issue, I’ll keep digging.

As it turned out, the tempering valve was installed backwards. The hot water from the heat exchanger was going to the 'mix' port and the hot water feed to the house was coming out the 'hot' port. At least they got the 'cold' right Makes me wonder how it could be installed wrong when the words are cast right into the side of the valve

I removed it and put it back together the right way and added in the globe valve. I did have to adjust the globe valve to get control over the tempering valve but all is now well, the house has hot water; no more luke-warm showers.