Froling pump short cycling

[Newfiestang]

I saw that earlier...but with the buffer tank system, I do not see how anything other than #4 is an option.

My system is set to hydraulic system 2 and working fine with buffer tanks.

 

[Smoothride]

Well, I guess then, that is something to try. Thanks.

 

[Newfiestang]

Well, I guess then, that is something to try. Thanks.

Im not so sure thats a good idea unless you know every setting of your system and what its set to. I think when you switch the type of hydraulic system when switched changes a bunch of other settings in the software.

 

[Caiden]

A quick question on storage tank sensor location. Is the top buffer tank sensor located a little way inside of the tank? I'm thinking between the top 5 - 10% of the tank. That's where mine is located and I have no issue. I'm thinking if it's located on the inlet pipe you may have greater heat loss and the temperature in the pipe is dropping a little lower than the buffer tank if there is no flow. Triggering the pump to come on.

I don't have a manual in front of me but if you wanted to increase the differential between turning on and turning off it would probably be referred to as a "hysteresis" value.

chew72, My tanks are about 72" tall and the top tank sensor is at about 58". All my sensors are in 1\2" wells. I purchased the tanks recommended by the supplier. Thanks for the "hysteresis" term. I will look around in the settings to see if I can find that. That is a big problem of mine is understanding what some of the terminology refers to. Thank you for your input.

 

[Caiden]

Caiden, we're looking at installing a Froeling S3 Turbo with two 300 gallon tanks, but we're having some trouble figuring out how much it would cost us installed. Would you, by any chance, be willing to share a breakdown of your costs for the various components and materials, as well as the installation costs billed by your installer? I know that every system is different, but I think I'll be able to extrapolate since I have some sense (a list) of the various controls, valves, fittings, etc. planned. I'm just having a really hard time getting a straight answer, and the current estimate for the fully installed boiler and storage tanks and DHW with pump sensors, controls, fittings, valves, and piping is substantially higher than any estimates I've found online for a P4 installation with two 300 or even larger tanks and DHW and close to double what I've found for comparable systems with an S3 Turbo. I can't quite figure out why the numbers are so much higher except that the labor is a lump sum, and I have no sense of how much actual installation should cost. I would be incredibly grateful for any information!

Mila70, I had a very hard time finding someone to even give me estimates. Heating companies in my area are busy and were not really looking to take on a job of this size. I did finally get 2 estimates. I had the S3 Turbo 50 installed with two 300 gallon tanks (used an existing Boiler mate) and all the recommended controls. I didn't want to cut any corners (which is why I am a little frustrated with my situation now). Both quotes were comparable for equipment. The installer that I chose came highly recommended and is a expert with solid fuels. The cost of just the equipment was about 23K. Piping and fittings and all other necessary equipment with the labor was about another 12K. If I could get to the bottom of the short cycling I would be very happy with the system also. I would say that the 600 gallons of storage would be minimum. I almost went with the 440 gallons and it would have been a stretch to make that work for me. I am heating about 3700 sq. ft. with a fairly tight construction. I hope this helps.

 

[Caiden]

All my sensors are in thermowells in the the tank....or tanks in my case as i have two.

And i have 4 sensors, 2 in each tank. These are located apprx 12" from top and 12" from bottom in each tank.

Yes if the sensors are just strapped on to an uninsulated pipe they will definitely see lower temperatures and not accurately measure the internal tank temperature. The sensors will also see a delay in this configuration.

That is interesting. I have 4 sensors as well and my installer put the all in the same tank. The tanks have 4 ports on the side and they are installed top, mid top, mid bottom and bottom. I wonder what the best is?

 

[Caiden]

Im not so sure thats a good idea unless you know every setting of your system and what its set to. I think when you switch the type of hydraulic system when switched changes a bunch of other settings in the software.

I was able to catch the cycling. I have the pump to 25% minimum. When it is in "off" the pump comes on at 100%. If the temperature in the boiler or the top tank sensor stays the pump will run for 12 seconds then go to 25%. If either of the temps move to turn the pump off it will restart at 100% again.

 

[chew72]

Similar self install, Froling 30kw FHG, Two 500 gallon tanks, Heat exchanger for DHW and 50' of insulated line between buildings plus all the the fittings etc $20-22K

 

[djbutt]

I had the same short cycle time on my Froling. As the boiler cools after a burn the pump would kick on and off every few seconds for a long time. I could hear some water hammer in the pipes when it was happening.

I solved it by installing a time delay relay in the wiring for the pump. The relay will not turn off the power to the pump until it sees a prolonged off signal from the boiler. Every time the boiler tries to cycle the pump off then on again it resets the timer in the relay. The timer is adjustable. I think mine is set to wait 2 minutes. Its been 10 years this way with no issues.

 

[NFH]

I had the same short cycle time on my Froling. As the boiler cools after a burn the pump would kick on and off every few seconds for a long time. I could hear some water hammer in the pipes when it was happening.

I solved it by installing a time delay relay in the wiring for the pump. The relay will not turn off the power to the pump until it sees a prolonged off signal from the boiler. Every time the boiler tries to cycle the pump off then on again it resets the timer in the relay. The timer is adjustable. I think mine is set to wait 2 minutes. Its been 10 years this way with no issues.

Hello,
I have a question for fellow Froling users. I have a Froling S3 Turbo 50 with two 300 gallon storage tanks. I have been running it for about 3 months and love the system. I do have a concern that has been addressed with the supplier. When the boiler is in "Off" mode and the boiler is 4 degrees higher than the top buffer tank temp the circ pump starts. When the tank temp is 3 degrees lower than the boiler the pumps turns off. This temperature fluctuates often boiler up or tank down 1 degree causing the pump to continually cycle on and off sometimes several time per minute. This does not seem to be good for the pump. Shouldn't there be a buffer when the pump cycles on it should remain on for a certain amount of time? Has anyone experienced this issue? If so is there a fix? If not a fix does anyone agree with the supplier that this is "the nature of the beast". Any comments or suggestions would be greatly appreciated. Thanks

Hello Caiden, djbutt, everyone, sorry about raising an old thread but it talks a lot about the issue I have.

We have a Froling T4 wood chip boiler with the H3200 controller. We have it configured to hydraulic mode 4 with four temperature sensors on the buffer tank. The boiler pump is a Wilo with 0 - 10 V linear speed control signal. We also have a motor controlled 3-way valve controlled by the boiler. With the pump speed signal and the valve, the boiler very nicely adjusts the return feed temperature and hot water flow to the buffer tank during the heating cycle.

The boiler runs quite perfectly in heating mode but the pump control misbehaves seriously in standby mode (fire off). The boiler was installed some six years ago and already two boiler circulation pumps have gone broken where I very much suspect the standby mode behaviour.

From the earlier posts I understand a similar issue if not the same concerns specifically hydraulic mode 4 operation. We could change to the simpler two buffer sensor system but I'm afraid we would lose boiler heating power control performance. I've been told the standby mode does not suffer from this pump short cycling but the local support does not seem to be able to figure out how to solve this for hydraulic mode 4, not even with the help from the factory.

Attached a photo of the pump control signal sampled some 20 minutes into standby mode after the heating session. At times the pump is only switched on for less than a second (via the speed signal, power is always on, pump is switched off by the speed signal). This makes no sense already because this pump takes up to 7 seconds to start from speed signal turned on.

We now have actually implemented something similar to what djbutt did to solve the issue (hoping to avoid pump failures in the future). We just cannot control pump power but have to fool the speed signal. We can then avoid switching the pump on an off continuously but this is not a full solution because the boiler tends to keep the 3-way valve closed and only opens it shortly at times. This valve control appears to be similar to explained earlier on the thread, if the boiler temperature exceeds the top buffer tank temperature by about 2 degrees Celsius (some 4 degrees Fahrenheit), the valve starts to open slightly and the pump starts to run (in bursts). However there does not appear to be any hysteresis which makes things even worse.

We have walked through all settings on the manual with our local support and cannot find any parameter really controlling the pump at standby mode. The pump minimum & maximum speed settings do apply for this 0-10V speed controlled pump in heating mode. In standby the max pump speed seems to apply but the pump never enters minimum speed, instead it turns off completely (might use min speed if the buffer tank and the boiler were colder than ever in normal operation). In any case, these settings do not prevent the short cycling even with the speed controlled circulation pump (for which the settings really are for).

I find it very frustrating when Froling advertises this specific hydraulic mode 4 in their brochure, they still do today but do not provide assistance to make it work properly.

Sincerely waiting for comments, NFH

 

[PassionForFire&Water]

I did not read the full write up here, but unless you have a variable speed pump controlled via 0-10V signal from your Froling boiler the speed setting will NOT do anything for you.

It sounds to me that you need to setup a wider differential band.

 

[NFH]

I did not read the full write up here, but unless you have a variable speed pump controlled via 0-10V signal from your Froling boiler the speed setting will NOT do anything for you.

It sounds to me that you need to setup a wider differential band.

Thanks for the response (assuming it was for me).

As above, I have a variable speed pump, controlled via 0-10 V signal from the boiler. The speed settings work fine in heating mode but do not help in idle state.

Indeed a proper hysteresis would be necessary at idle state but there is no single hysteresis parameter available for user to adjust, neither for the installer mode. As far as I know, none of the available parameters can be used to reach some hysteresis for the pump control. Seems this is all fixed in the code or only available at some higher level user mode (I don't know if it exists for Froling).

 

[PassionForFire&Water]

I'm only familiar with Windhager.

Is there a higher level available? SERVIVE level or level for the Froling technician?
You will probably need an access code, or a combination of push buttons to hold at the same time

 

[NFH]

I'm only familiar with Windhager.

Is there a higher level available? SERVIVE level or level for the Froling technician?
You will probably need an access code, or a combination of push buttons to hold at the same time

There is a service level access code for Froling technicians but this is well known for customers too. Nothing there that even the official local Froling support can find. If the factory knew a higher access level, I'd assume they should advice the local support/service personnel but I was told "no response from the factory so far".

I was hoping some of the forum members here would have received some guidance from the factory but it seems not.