water temp on boiler with domestic hot water

bauer

Hi All -

I have a well mclain CGt-5 natural gas boiler with domestic hot water on demand. There is a honeywell mixing valve installed on the output of the hot water but despite turning that all the way up, the water coming out at sinks/showers is hot but doesn't get above about 100-105. What should my lower and upper limit be set at on the boiler? It seems the water coming out of the output is hot enough but the honeywell is mixing too much cold in with it? Is that possible?

Any thoughts appreciated!

hot_rod

The tanks need to be about 20F hotter than the mix adjustment to work properly.

What model HW? Some, the ASSE 1070 models are limited to120F max set.

Or it could need a de-liming, clean and rebuild.

bauer

the DHW is a built-in tankless system

hot_rod

what is the temperature setting on the tankless?

bauer

the boiler is set to at 190/210.

hot_rod

so a tankless coil in a boiler it sounds like. Any idea what temperature is coming out of the tankless coil? It too could need a de-scaling.

If you have 140F or hotter on the H port and cold on the C port the valve should mix.

If you have adequate HW supply and turning the knob does not change the mixed temperature I would clean or replace the valve.

bauer

yep, tankless coil. Water coming out of the coil is plenty hot -- well above 140.

Boiler & mixing valve are both new.

hot_rod

what ASSE and model number on the valve, it could be the low temperature model. But it should still reach 120F if cranked all the way.

bauer

it's in a rental property so I will have to check another day --- but I am looking at the manual and see what you are saying... it's the honeywell AM-1. Looks like C-Model has a range of 70-120 and Standard model from 70-145.

I'm definitely not getting 120 out of it --- but if it is the C-model, could I just replace the thermostatic element with the higher temp one?

HVACNUT

Where are you taking temperatures? At the hot out of the mixing valve or at the faucet(s)?
If it's new, it probably wasn't flushed once the water main was turned back on. The AM-1 is a good mixing valve.

hot_rod

I think the C models are intended for point of use, a 1070 listed valve. While it could be used at a coil or tank, point of distribution, outlet temperature is fixed to 120, maybe less? The knob is also lockable, maybe it was locked at that lower 110F setting?

It's always a good idea to have some piping distance between the coil and the H inlet.

It should also have a LF, lead free on the model number to be code compliant these days.

https://forwardthinking.honeywellhome.com/related_links/water/mixing_valve/sell/63_9701.pdf

bauer

thanks for the suggestions - I will double check the model and I can also remove it and try flushing it out.

I was taking temperature both at the mixing valve and at the faucets. Kitchen sink faucet I couldn't get higher than about 105.

hot_rod

In hard water contains, especially with really hot input, they can scale up in a few months time.

Very simple inside a spool that slides up and down, and a copper enclosed wax "pill" heat motor.

Some CLR is good to use to delime them.

Beware there is a spring applying tension to the cartridge when you unscrew the top.

That model is also a low Cv, low flow valve. Usually a 1017 point of distribution valve is a 3 Cv or larger.
If you have noticed some flow restriction, or pressure drop, that could be due to the low flow rating of that model.

For the cost of those valves, I'd be inclined to replace it with a ASSE 1017 point of distribution style, you may solve two problems. The valve you have is intended to be used at a single fixture, point of use.

Regardless of what style or brand, plan on occasional maintenance.