mixing valve issues

Discussion in 'Water Heater Forum, Tanks' started by varmint, Mar 27, 2009.

  1. varmint

    varmint builder, designer

    Messages:
    6
    Location:
    northern maryland
    Hi: this is my first post here! I have a Honeywell AM-1 mixing valve (Sparco) installed on my boiler's hot water coil- it's a steam heat boiler, so the coil water gets too hot for comfort or safety, and it's worked fine for 3-4 years. Lately, the hot water pressure seems to pulse up and down, regularly, maybe 3 times in 2 seconds or so- but not all the time. Happens at any hot water supply, while the cold flow stays constant. This is at a fairly low flow rate (we're on a low yield well, so nothing uses more than 1 gal. a minute) and it doesn't cause a problem, just an annoyance. I guess it gives the shower pressure balancing valve some exercise? Before I look for a new element, I thought I'd ask if anyone has any idea about this? Thanks!
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,922
    Location:
    New England
    What do the instructions say, if anything, about deliming the coils in the boiler? The passages could be getting restricted because of mineral deposits.

    Is your storage tank in good shape? Does the pump and overall system pressure fluctuate?
  3. varmint

    varmint builder, designer

    Messages:
    6
    Location:
    northern maryland
    No de-lime or anything else... I have no instructions. Until recently, our water was acidic, so mineral build up was non-existant. The pump pressure and cold water supply are smooth, this problem is only with the hot water, and not all the time! Sometimes, flow is smooth, sometimes pulsing. Always at a modest flow rate... 1/2 gallon a minute or so. Once I switch over to the summer demand heater, I fully expect the problem to disappear, and then I will tear the mixer apart to see what I can clean/fix. There is no storage tank in the system, other than the well pressure tank.
  4. varmint

    varmint builder, designer

    Messages:
    6
    Location:
    northern maryland
    Well, there doesn't seem to be that much interest in this topic, but FWIW, I have decided that the mixing valve is "hunting" because of pressure differences between the hot and cold water supplies- the flow rate thru the coil is reduced, so the cold pressure is greater. As I go to less cold mixing input- hotter output, the pulsing is reduced. I will try acid flushing of the coil, when I shut the boiler down for the summer, but I am not all that hopeful.
Similar Threads: mixing valve
Forum Title Date
Water Heater Forum, Tanks Does Pressure balanced Fixtures make Mixing valves obsolete? Apr 3, 2012
Water Heater Forum, Tanks Honeywell AM-1 Thermostatic Mixing Valves. ( water heater tempering ) Feb 2, 2012
Water Heater Forum, Tanks Power Vent fresh air mixing intake question... Nov 3, 2013
Water Heater Forum, Tanks Water heater size with and without tempering valve Jul 12, 2014
Water Heater Forum, Tanks Water Heater drain valve failure Jun 26, 2014

Share This Page