oil boiler and electric (dual), pressure at 45psi

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Old 10-28-08, 03:46 PM
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oil boiler and electric (dual), pressure at 45psi

electricity is relatively cheap in montreal so we added a 23,ooo watt electric water heater to the boiler 2" pipes of our duplex. what used to be 2 separate pipe circuits (one for the top floor of our duplex, and one for the bottom 2 floors) has been joined with some T connectors. 2 water pumps are now pumping through one 2" pipe at the electric heater. when the tenant upstairs puts up the heat our rads get hot too now. when both pumps are pumping the pressure is at 45psi. with the electic system on. i'm worried that when it gets really cold and the oil boiler is operating all night long the pressure will be 60psi. is this new setup as crazy as i think it is? shouldn't there be two 12,000 watt heaters instead so that the pipe circuits can remain seperate and flow properly? thanks forum
 
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Old 10-28-08, 05:00 PM
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45 PSI is way too high. Don't you have a safety relief valve that opens up at 35 PSI on your setup ? For two floors the pressure should be under 25 PSI when the boiler hits peak temperature.

You don't need two separate boilers of 12 kW each, but you need to zone your system properly for one 23 kW heater.

1) With two circulators, you should wire them so that only the floor that requests heat should turn on its respective circulator pump.

2) Alternatively, with one circulator pump you could install electric zone valves to route the hot water to the floor requesting heat only.

With electricity at 7.5 cent/kwh and fuel oil at $1.00/liter in Quebec, electricity is the way to go.
 
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Old 10-28-08, 08:07 PM
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Jeesh, 7.5 ... don't I wish ! Close to 22 here ...

Another thought is adding flow check valves ... one pump is causing a pressure differential in the other zone, causing flow in both zones.

They may be already zoned ? Do individual t'stats control each circulator ?

Is 23K enough to heat that place ?

I'd definitely look at the pressure also. What is that electric boiler rated for ? ( make / model info would be great ) ...
 
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Old 10-28-08, 10:13 PM
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There are two zones with two thermostats but the electric boiler that was just plumbed into the system has one 2" pipe running through it. To connect the electric boiler to the existing two 2" pipe system, where the pipes operated independently of each other, each with their own pumps, the two 2" pipes were joined into one 2" pipe. Now when the oil boiler kicks in automatically at 10 degrees F, and the electric boiler shuts off, both zones are wanting heat and both pumps are pumping through one 2" pipe running through the inoperative electric boiler. When it was just an oil system there were two pipes with two pumps circulating water in two zones and the pressure was always around 20psi. Now everything goes through one 2" pipe. The maximum recommended pressure for the electric boiler is 28psi. Can this type of installation work?
 
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Old 10-28-08, 10:41 PM
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It sounds as though the smaller electric is installed in parallel with the oil boiler. Which is ok as long as they are piped properly and the controls do what they need to do to switch over ...

Yes it can work I think ... without seeing it, can't be sure though.

But: you've got a heavy duty pressure problem I think.

You've got to get that pressure down! If max on the electric is 28 ... and you've got 45 ? You need to get that checked out STAT! There should be a 30 PSI pressure relief valve on the oil boiler, that should have opened a long time ago and let some pressure off, and I would guess there should be one on the electric also ... if that gauge is accurate and it really is 45 PSI, something is dreadfully wrong ... and needs to be corrected ASAP ...
 
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Old 10-29-08, 11:48 AM
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The boiler is connected in series. The pressure relief valve leaks continuously when the system is on and is now hooked up with a hose to the drain. ====----E----===O=== (two pipes to one pipe to Electric boiler to one pipe to two pipes to Oil boiler to two pipes). The electric boiler is a Thermolec #B23. The contractor has been back three times and has adjusted the schraeder valve and compression tank and there is still no change in pressure. The people upstairs now control our heat as everything goes through one 2" pipe instead of two 2" pipes. Their pump is moving our water as well as their water. Thanks NJ Trooper and reno1962.
 
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Old 10-29-08, 12:09 PM
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I just looked at the Thermolec installation manual and they do permit both series and parallel installations. I prefer the parallel approach; That way the inactive boiler acts like less of a heat sink and steals less heat from the active boiler. Many installers use the series approach since they save $150 from the installation (by not having to install a 1 1/4" zone valve to select between boilers).

http://www.thermolec.com/boilers.htm

All installations described in the Thermolec documentation use one circulator for dual energy systems.

Normally, the circulator pump should not affect system pressure. Only the boiler temperature should affect the system PSI. Is the expansion tank working properly (i.e properly pressurized) ???

It sounds like the installer might have overlooked some details.
 

Last edited by NJT; 10-29-08 at 04:10 PM. Reason: no names please ... PM if you wanna know ...
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Old 10-29-08, 04:15 PM
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The pressure relief valve leaks continuously when the system is on and is now hooked up with a hose to the drain.
Mercy, THAT AIN'T RIGHT!

That's the sure quickest way to destroy them boilers for sure... adding all that oxygen to the sytem and all ... because every time the expansion opens, when the system cools, fresh water is gonna go in to take it's place ... bad for boilers !

No, you've gotta get the installers to make this right ! The pressure should be no different now than it was ...

Not only that, IT'S DANGEROUS!

If I was you, I'd shut it down NOW and make them fix it! Or, get it fixed and submit them the bill.
 
 

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