Flow sensor ??

mike parnell

Is there a type of flow sensor that can be used to make sure the boiler fires up when the hot water is turned on anywhere in the house, having trouble with not having enough hot water unless the house is calling for heat. I have a primary , secondary radiant floor system that works great, learned how to set it up here at heating help .com.. thanks guys for all your help,,



                                          Mike in Hopkinton Ma..

Mark Eatherton

Need a LOT more information...

Like, how are you generating DHW?



How are you generating a CALL for DHW?



How is the DHW generator piped?



Installing a flow switch will lead to short cycling, and we're not talking about a motor cycle for midgets here....



Got pictures and drawings?



ME

mike parnell

Flow sensor ??

Tankless coil in the oil fired boiler,in summer I use a propane fired hot water heater,thats off now....thanks

Mark Eatherton

Got it...

I will defer to the experienced oil men of this site for an answer. Based on my reading tho, I suspect you need to install a dual aquastat to keep the space heating circulator OFF when the boiler temperatures are low, and also to maintain a hot deck condition for the DHW coil.



ME

lchmb

aquastat settings

What is the low, high and differential settings on the boiler aquastat? And is your circulator controlled by the aquastat or a seperate control?

CMadatMe

Define

The gpm kor load? A tankless coil generally has the ability to give 3 to 3.5gpm. What are we running that is giving an issue. Could be that the coil needs a cleaning and a flushing or possilby the coil can't deliver what is needed.



You really need to define what fixtures are running when the issue described happens.

SpeyFitter

How about a HWT?

Sometimes guys will install a tankless coil upstream of an electric Hot water tank (so the hot domestic water coming out of the coil goes into the cold tapping on the tank, the hot tapping on the tank goes to the fixtures). That way the the coil does MOST of the domestic hot water heating with oil/gas and the electric tank just acts as a buffer tank sort of to keep the water that was heated by the coil hot (typically minimal electricity use) and to be there for times of peak demand that may exceed the coil capacity. Probably a cheaper and more reliable set up than some time of control system or flow sensor that you suggest.

mike parnell

HWT

Guys,

 I have a 30 gallon HWT before the tankless for a buffer the cold water goes thru  a pair of flat plate heat exchangers before the tank then to the tankless, I guess the problem may be the primary isnt moving when the hot water is being used,thats why I want to turn on a circulator, also Im guessing the tankless needs to come out to be totally cleaned and flushed....this system has been fine for 8 years now,but now theres a few more people in the house,,,,,,Mike in Hopkinton

Jean-David Beyer

I did that with my old boiler and electric hot water heater.

I had an old GE boiler with a coil. Originally (before I bought it) the house was built using the coil, but the performance was unsatisfactory, or they did not want to run the boiler in the summertime. So they converted to an electric hot water heater. At some point I thought I could save money by running the cold water supply through the coil and through the hot water heater. I did that, using three gate valves, so if the coil leaked or something, I could drop out the coil by turning the knobs. It actually worked quite well. The boiler ran at about 140F, and I do not know what temperature I got out of the coil. It saved money when oil was aroung $0.50/gallon and electricity was about $0.10 per kilowatt-hour. When electricity went to $0.20/KWH it would have saved more, but oil eventually got up to $4/gallon and I never did the numbers. I converted to a gas-fired mod-con with an indirect instead.