- This topic has 4 replies, 4 voices, and was last updated 21 years, 3 months ago by Art_xyz.
18 Aug 2000 at 5:07 pm #273372MasterPlumbersKeymaster
I bought a old steam heat rgister
and a electric hot water pump. Now
I want to ciculate the hot water from the homes hot water tank to the register in the shop. Now how do I stop the pump from circulating hot water into the whole homes cold water system ? email@example.com
18 Aug 2000 at 5:45 pm #287471Harold KestenholzParticipant
Simply put, connect the pump to the hot water outlet with a check valve toward the heater. Connect the heater to the cold water inlet side.
Now, FIGURE OUT HOW TO WATCH THE PUMP AND THE HEATER CONSTANTLY to prevent water flooding the building. The pump must be made of bronze or stainless steel, must be able to withstand city water pressures. If it is cast iron as is probably the heater, oxygen from the water will eat them away in a few months. Rust will be sent throughout your domestic water system. Legionnaire’s disease can appear after letting the water stagnate in the loop over the summer.
One solution: use a separate water heater isolated from the domestic water system – use the existing water heater as is.
OR – install a heating unit where you need the heat.
18 Aug 2000 at 6:47 pm #287472SylvanLMPParticipant
Harold, your right on the money BUT I think a B&G flow control valve would be much better then a check and a PRV installed on the line. (12-15 PSI set pressure)
They possibly could use a separate hot water heater as you suggested to prevent all the great diseases that can grow in these tanks.
They could also use a small boiler OR a heat exchanger for this use.
Having a thermostat connected to the circulator would turn on the circulator only when calling for heat.
I am completely against using a domestic tank used for combination heater as there are NO safety controls only one operation controller on these NON ASME tanks.
Plus like you mentioned about the oxygen in the fresh water destroying everything made of ferrous metals and no means for expansion and contracting POW good BYE unit heater.
There are some very small boilers on the market that would be ideal for one unit (hydronic heater) with all the safety controllers already built in.
18 Aug 2000 at 9:22 pm #287473Harold KestenholzParticipant
Putting a 12 psig pressure reducing valve on the line would bring the pressure in the (non-ASME) tank down. Then the taps and shower would be weak, too. But it is better to be safe than comfortable.
It takes a lot of experience to understand that a licensed plumber is really an engineer trained to prevent sickness and explosions. There is no excuse for saving money by unknowingly misapplying appliances when there is no knowledge why the licenses were required by the legislature.
I’ve seen injuries from low pressure hot water – I am very suspicious about circuits with the possible 125 psig water heater relief valves.
18 Aug 2000 at 10:30 pm #287474Art_xyzParticipant
Some plumbing codes do not allow a domestic water heater to be used for home heating purposes AND RIGHTLY SO.
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