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[CountryBoyJohn]

A circulating pump isn't necessary if you have even a decent amount of usage.  I have a family of 4, and the two kids only get a bath every few days, and we have no problems with the water cooling between uses.  We have been gone for 3 days and still had enough hot water in the tank that we still had to add cold water in the shower.  Even if the water cools too much, just let the water run for 3 or 4 minutes and you'll be good to go.  Even that minor inconvenience doesn't justify a circulatory pump. 

[Crow]

I'll agree with ^^^^^. Family of 4,20 plate exchanger and on a 30 gallon tank. Have not had a problem at all keeping hot water and don't use extra pump to circulate. Oil shut off to hwh also.

[willieG]

i know you dont need a pump under most condtions but if the plate exchanger is too small perhaps one could be used. 

[Sprinter]

Crow, your using a plate with no circ on the domestic side?  A sidearm requires no circ on the domestic side.  We have much higher usage so a circ is needed to keep up.  I wonder how long of a shower you can get from a 30 gallon and a sidearm ? I know what a 120kbtu plate will do.

[Crow]

 Nope, no circ on the domestic side. Cold water from well through 20 plate and then into 30 gallon water tank. So the tank is just hot water storage. I got this great idea from the fine folks here and so far working flawlessly. Did put a tempering valve on also and it is set at 120* which is still too hot for me but my better half likes it.

[CountryBoyJohn]

Mr. Sprinter, I don't use a circ for my plate either.  I'm set up just like Mr. Crow.  I filled a 400 gallon hot tub with 110 degree water this way.  The water gets hotter the more you use.

[Sprinter]

That makes more sense, I never thought of it installed that way. I guess the sidearm and gravity flow kept me guessing , picturing wrong

[racnruss]

Again,  the plate exchanger will work on its own provided you have a boiler with a lot of water capacity or a very fast recovery boiler.

My Father in law has a Hardy H2.  It only holds like 80 or 100 gallons of water.  So, as you use your domestic hot water, it is cooling the boiler just as fast and it cannot recover fast enough.

He used to have the domestic hot water running through the hot water coil in the H2 and then into the water heater.  Pretty much the same thing as a plate exchanger before the water heater.   The problem was that once you took a couple showers, the boiler itself had cooled down and was trying to recover but it just cant recover fast enough for continuous hot water usage.  Therefore you would run out of hot water just like a normal water heater runs out.

So, we added a circulating pump in his application to circulate water out of the bottom of the water heater, through the hot water coil in H2 and then back into water heater.  Basically doing the same thing as a sidearm but, yes, running a pump instead of adding a sidearm.

[Crow]

racnruss, Great point!  That is very possible to run out if your boiler is on the smaller side regarding water capacity. My P&M only has 90 gallon cap. and have not run out .........yet. I guess my family and I aren't trying hard enough. If/when it cannot keep up I will have to rethink this setup.

[racnruss]

I didn't know that the BL series only held 90 gallons. 

I didn't mention before but my FIL keeps his H2 set pretty low at 140 or 150.  Which he can because of being stainless steel.  You probably have your boiler set much higher than that which probably makes a big difference too.

How much are you heating with your BL? and what climate?

[Crow]

 I have had it running at 190 since I fired it up with 12 degree differential right now. Only heating 1500 sqft plus basement with high hopes to build a shop. I live in Eastern Ontario.

[slimjim]

The B-L series does not require a lot of water stoage because of the massive amount of refractory cement in the base that keeps the fire hot, response time on a call for heat is greatly reduced therefor no need for large water capacity.