tekmar 157 differential control

[chuck172]

I'm thinking of upgrading my tekmar 156 to the 157 model. I like the variable speed to the storage tank. Is anyone using this control?

 

[sixroses]

I have been using the 157 for a couple of years. I was looking for the "silver bullet",you know the one that will let me burn one time a day and get 2 days worth heat but alas, no such luck yet. The control does a great job of pump speed control but does have a nasty habit of shutting off when return and supply temps are near the top of the curve. I had a second pump hooked to a aquastat that takes over when the tekmar controlled pump shuts off. As far as the variable speed goes seems to work great keeping output at desired delta T.
Steve

 

[chuck172]

stihlwoody, after having experience with the 157, do you feel that charging your storage with the variable speed makes a big difference? I don't understand why your unit shuts off, would you go into more detail?
My tekmar 156 doesn't vary pump speed, just shuts the pump on or off. It did a great job, but the relay is sticking and if Tekmar honors their warranty I was thinking the extra $60.00 put towards the 157 might be worth it.

 

[sixroses]

The 157 shuts down if the delta T differential is one degree or less, this can be a issue on start up or when tank is near 180 and boiler temp is on the way down. I have a GW100 that holds alot of residual heat and if the pump stops, the heat does rise dramatically. The unit has a 5 minute delay programed in that does not let the pump start even if the delta T rises. I have not ran the numbers to figure if full output with a lower delta T or or lower output with a higher delta T puts more btu's into the tank but I tend to believe I am better off with hotter output into the top of the tank is better.I have my second pump set up to run as a overheat pump that is triggered by a aqua-stat and ran off a battery bank and inverter, this also powers on in case of a power outage. Has been working real good for a couple of years.
Steve

 

[chuck172]

If the 157 doesn't work well with gasiiers, maybe I'll stick with the 156. It doesn't throttle the pump, but shuts and restarts it according to the delta t perfectly (as long as the relay doesn't stick!)