To begin with this looks like a great place to get my question answered. I am a State Certified Plumbing Contractor in Florida and have no experience in electrical circuits. I can do the electrical work in a house with some advice and actually wired most of my current home.

What i need to purchase or build. I am trying to use a tanked hot water heater as the primary "tanked" and a "tankless" electric as a secondary. I have my electric tanked heater on a timer. I want to put a "tankless" one after the tanked one in line with the plumbing. I want a relay or something that keeps the secondary "tankless" off when ever the timer has the primary "tanked" heater engaged. But when the timer has the primary "tanked" turned off, I want the secondary "tankless" to be online; then turn off when timer rengages the primary "tanked". The primary "tanked" draws 27 amps when on but the secondary "tankless" draws 74 amps when fully on and comes on almost at once to full power if all elements engage. This is a 220/240 volt system.

I sure would be grateful if you could direct me to where I could buy one or if someone could email me a circuit. I know someone who could help me make it. Thanks for your time. I would be glad to respond to any plumbing questions you may have by email. I hope I posted this on the right forum thread.

Xelant_Jim

 

Why not use a two (independent) channel central heating controller, that you are probably already familiar with?

These commonly use one channel for the hot water and one channel for the heating.

But you could supply and control each tank heater from its own channel and program the timings according to avoid clashing i.e make sure the one turns off before the other rturns on.

I don't know US suppliers so can't advise here, we have Horstman and Honeywell in UK, which I believe are both US firms.

 

situation. I am just really looking for some type of relay that would just turn the tanless on whenever the tanked is off so that if I decided to turn the tanked on; manually overiding the timer that the tankless would turn off. I was told by friend they make them for backup generators for when the electric goes out like in a hospital or grocery store the generator comes on and then turns off when power is restored. The only problem he says is that they are solid state circuitry and more than I wanted to pay to test what I am trying to do. Thx for your suggestion. Maybe one of those manufacturers you posted will make something similar in a simplier form.

 

Yes you could use a relay system, solid state or mechanical.

However I think you will find building it, testing it and making it failsafe more complicated and expensive than using ready made.

I don't know about Florida building codes but for you to do anything more under European codes would be illegal, judging from your experience description -No offence meant.

Switching 28 amps safely is no mean feat.

 

I just need a diagram for them to build or somewhere to buy a power tranfer switch at a reasonable price. Thanks for your concern but I respect electricity and its power.

 

OK well here's an electricians solution.

In the UK you can obtain mains relays that are directly mountable (plug in no circuit building) into the backplates in mains enclosures.

Here is a link to a suitable UK 30 amp mains version and backplate. You will need to find the equivalent Florida version.

http://www.maplin.co.uk/module.aspx?moduleno=37495.

Basically both the switch contacts and the control coil are mains rated so you simply connect the output from the timer to the relay and switch the mains supply to either tank via the relay. So only one tank is ever connected.

You may need some additional mains suppression for switching this current level, but once again you can buy plug in units.