DHW huge temp fluctuations, heat ok, hydronic system -HELP!!

LTrub

Guys, you gave me some stuff to chew about. Now, in MA, I wonder if everyone's swamped with work due to the weather & cold we're finally having! This is not a big rush, but mostly an inconvenience - wife's got flu & fever, though, and I felt bad when she took a hot shower that turned cold within 2 minutes (boiler not calling for heat!) I still think something's keeping it from kicking on when hot water is running and heat's not being called for, maybe clammy's suggestion about lime scale has something to do with it...
Thanks for the fast feedback and help -- and yeah, though I'm handy this job'll be for a pro!
If I go to an indirect DHW I will probably pop for all new high efficiency everything -- unless the efficiency of oil fired equipment hasn't improved much in the last 17 years... I know the gas equipment is now up to some high 90's in efficiency! But gas co wants $500 to run the line to the house from the street, and town only allows it between May and Oct or something like that (avoid digging up streets in winter I guess).
Cheers!

LTrub

DHW huge temp fluctuations, heat ok, hydronic system -HELP!!

Boy I hope someone can help out. We bought this house in August and thought the hot water when showering was kind of messed up, prior owner basically said "oh yeah, if you lowered the mixing valve temp it does that" (we did because it was scalding on occasion), so we raised the mixing valve temp -- GEEZ that hurts! I didn't know it's also called an "anti-scald valve"!

So - if I try to lower the mixing valve (no numbers on it, just play around), I can get it to prevent scalding.

Problem is (and was this way even before lowering mixing valve temp) there are times when the hot water just doesn't get hot at all. I have found that it now (during heating season) seems that we only get the hot water to be good and hot during a cycle when the heat (one of the zone thermostats) is calling for heat. I

f the zone heat is satisfied, I can run the hot water and keep running it, and feel nothing but cold going through the pipe into the Burnham boiler and yet the boiler thermostat temp (gauge on side of boiler) stays high and the burner never kicks on (and the water pipe going from the boiler to the mixing valve is tepid).

Aquastat is Honeywell, not sure of model, but it has hi set to 190, low set to 160, and differential set to 10.

HELP!! Any ideas on what this could be? House (and therefore system) is only about 17 years old, tankless DHW, oil fired becket burner, Barnham boiler and one circulating pump with 3 zone valves.

Thanks in advance for help, short on cash now and very handy (usually) so I hope I can save some $$ and not "shotgun" this, just baffled by it -- doesn't seem to be any kind of flow switch to call for burner to run if DHW is called for, not sure if that's typical.

I think the system was messed up when we bought house and seller swept it under rug -- but odd thing was that during one of our visits to the house before buying there was a heating oil company doing the annual service on the system (no adverse notes on hang tag). Again, sincerely appreciate any help - thanks!

don_185

Get ya

some water saving showerheads or, have a flow regulator install near the coil.

LTrub

Already using low-flow showerheads - something like 1.6 gal per min.
Just seems like the temp swing is too drastic, and I'm baffled by the fact that the DHW can be run until down to 80 at faucette and yet the burner never kicked on...
Any other ideas?

Norm Harvey

Replace your current mixing valve with a thermostatic mixing valve. The thermostatic type will maitain a steady temperature going out by adjusting their guts so to speak.

http://yourhome.honeywell.com/Consumer/Cultures/en-US/Products/Water+Solutions/Water+Control/WaterTemperature/Default.htm



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clammy

things to check

Beside what the others have mentioned how about gettint a pro in besides the tempering valve probally something better then the one you have and have then check your triple aquastat for the low setting shouold maintain boiler water temp with out a call for heat (160) and when calling for heat should limit thew boiler to 180 ,as you have stated that the water is hotter when a zone of heat is calling i would probaly also look at maybe getting your tankless coil clean for it could be coated with lime lowering your coil output at the low maintaning aquastat setting abality to produce enough hot water on the lower temp setting .It could also be that the aquastat bulb is not getting a correct reading because of debrie build up on the aquastat well.For alot of people there tankless coils usually don't give them enough hot water ,a good indirect fired tank will produce more then enough hot water and will also lower your oil comsumpition by not maintaning that 160 boiler temp 24 /7/365 and with a good mixing valve there should not be any fluxation of water temp .peace and good luck clammy

Ragu_5

Good advice from all

Long term prognosis: nobody ever gets enough hot water from a tankless coil. When $ permits, get an indirect fired water heater installed. You will have ample hot water with no temp. fluctuations and you will lower your annual fuel use. Good luck.

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Scott B.

DHW problem

> Guys, you gave me some stuff to chew about. Now,

> in MA, I wonder if everyone's swamped with work

> due to the weather & cold we're finally having!

> This is not a big rush, but mostly an

> inconvenience - wife's got flu & fever, though,

> and I felt bad when she took a hot shower that

> turned cold within 2 minutes (boiler not calling

> for heat!) I still think something's keeping it

> from kicking on when hot water is running and

> heat's not being called for, maybe clammy's

> suggestion about lime scale has something to do

> with it... Thanks for the fast feedback and help

> -- and yeah, though I'm handy this job'll be for

> a pro! If I go to an indirect DHW I will

> probably pop for all new high efficiency

> everything -- unless the efficiency of oil fired

> equipment hasn't improved much in the last 17

> years... I know the gas equipment is now up to

> some high 90's in efficiency! But gas co wants

> $500 to run the line to the house from the

> street, and town only allows it between May and

> Oct or something like that (avoid digging up

> streets in winter I guess). Cheers!



Where in MA are ya? If you are close to me, I'll be happy to stop by and give you a quick opinion, as long as you can wait till I have a slow day.