HTP-EFTU Boiler with integrated ECM pump - What is control logic for both BTU output and pump speed?

ekubec

Hi, Folks.

I have learned quite a bit on this forum. And just when I think I understand something, poof! I see the HTP-EFTU (85,000 size) has an integrated ECM pump than can do no more than 9 GPM at 9 ft head. It can be direct piped as it has a bypass valve. It turns down 10:1 so for the 85k = 8,500 BTU. I'm in Denver so it would be derated for altitude another 20%, in my still hypothetical installation.

I understand how independently each of 1.) hot the BTU's would modulate up or down to depending on how much heat was needed to get the water to the target supply temp (out put from boiler) and 2) how the ECM pump would spin faster or slower depending on how much water would need to go through the heat exchanger.

What I don't understand is how the EFTU controls both of these variables with just a temperature set point adjustable parameter (and the 2ndary ones such as outdoor or indoor set back). Is there a delta-t programmable setting in the EFTU?

Let's say my system is perfectly designed (LOL) and the optimal supply temperature is 130 at given conditions. I conceptually understand how the boiler would modulate up BTU's burned to heat the water to 130..... but how would it know that my perfect system needs 5 gpm and not 8 or 1 gpm?

I have read through the installation manual several times, and can't seem to find the words 'delta T' anywhere.

Thanks!

Ironman

I have the same boiler in my house and it’s the one that we install the most.

The internal circulator is a Taco 007e. It’s a simple fixed speed ECM that’s either off or on. The system piping will determine its flow rate. If that is not capable of allowing 8-10 gpm, then p/s piping should be employed.

ekubec

@Ironman thank you. So lets say whole system is a smaller single zone system that max would need about 15,000 BTU. The piping is such that at 2 GPM the head is under 5 ft ( so pretty low head i think). But since it is a small system, at 6 GPM the head goes up to 12 ft. How would this taco pump perform in this system?

specifically when you say:

"

Ironman said:

I have the same boiler in my house and it’s the one that we install the most.

The internal circulator is a Taco 007e. It’s a simple fixed speed ECM that’s either off or on. The system piping will determine its flow rate. If that is not capable of allowing 8-10 gpm, then p/s piping should be employed.

Would smaller system be more likely to require P/S?

Ironman

You’ll have to go to the performance chart for that pump to see how it would perform.

When using p/s, the secondary (system) flow must be equal to, or greater than, the primary (boiler) flow rate.

You probably can pipe it direct if it doesn’t short cycle; if it does, you need a buffer tank.

PC7060

Re the SWT versus outside temperature; you have to set / adjust the ODR curve (really straight line) based on your houses heatloss / BTU requirements. Takes a bit of time but pretty easy to configure from installer menu. The installed will get it close but you will want to adjust to dial in closer.