Help w/RetroFit Radiant Floor in Old Farmhouse

Pittsjock

Greetings. Lurker, but first time posting. This is a great site!

We live in a 200 year old Colonial (big house/little house) farmhouse in Northern NJ (Zone 6). We typically see below freezing overnight temps for most of the winter with a few blasts of really cold air (single digits to below zero F). We heat with oil and have a fireplace insert in one room which we use mostly for ambiance - although it really warms most of the house up - and for the cold blasts. Not truly necessary but it does help for sure.

About 10 years ago, we decided to replace two old boilers (two zones/big house/little house) with a new one. The house was entirely heated with hot water radiators. The systems put out plenty of heat, but we suffered from the too hot to too cold cycle....We ended up picking Buderus and had the certified plumber install I believe a 205 and Logamatic 2107. Huge difference - our oil consumption decreased by about 40%....and the heat became smooth. Great!

We were starting a renovation at the time on the little house which included proper insulation throughout. I forget R values but we went above code. We decided to install radiant on the renovated side over new wide pine wood floors and tile in the basement. This section of the house is about 1000 sq ft across three floors.

The radiant floor system on the wood was set up as follows. Subfloor (1" T&G hemlock), plywood "snap in" panels with aluminum reflectors (forget brand), then 1" T&G wide pine flooring. The basement floor was repoured....with a moisture barrier, insulation and then slate tiles. Part (144sqft) of the basement includes the boiler room, which retains original slate slab flooring and no insulation on the floor. The system includes on demand hot water with a nice size holding tank (forget size).

Zone 2 (radiant) is FM241 card (I believe) in the Logamatic to an Esbe mixing value, to a Uponor 8 loop manifold. Taco 1/25hp pump on Zone 2...007-F5. There is no room temp thermostat on this zone but the mixing valve does have a sensor on the output side.

The main, uninsulated, original house with cast iron radiators stays as toasty as we like. The new "little house" - renovated side is always cold. The installer has been back a few times, but he is busy and doesn't seem to care that half our house stays about 58F. I am pretty much done with him....and so I find myself here - no real heating experience, but lots of building, mechanical and electrical experience.

1. Zone 2 is moving warm water through the runs. The reference temp on the Logamatic is factory set to 114..Manifold delivery temp yesterday based on 37F outstide was about 95F with a return temp of 80F. The runs were mostly balanced...although they all seem to be pretty much full open. Flow rates are all around .2 gpm. There doesn't seem to be any room to increase the flow rates......

2. I spent an hour waiting on the line yesterday and finally got Buderus tech support and got a hold of Bob. He was fantastic. The call dropped, of course, when we were getting to the good stuff, but we adjusted a couple of things on the controller. We changed the type of building from 2 to 1 - which makes a lot of sense as the system has lagged considerably since we installed the boiler. We also adjusted the heating curve on zone 2....I don't remember what menu exactly...but we changed a setting to 8F (Bob said you could go up to 16F)...then the call dropped when I was looking at the manifold temps and I had no # to get back to him (rookie mistake).

3. The manifold inlet side is now reading 105F...the return is still 80F....seems odd. We may have gotten a degree or two of increase on the room temps...OAT is still 37F. We did this yesterday around 4:30 pm so I figured I would give it a day to see what happens. We have the system set to 58F overnight...stays plenty warm in upstairs bedrooms (Big house)... so the heating system is warming everything up as we speak.

Sorry for the data dump, but I figured more information was better. From my uniformed perspective, it feels like we need to be moving more water through the system..... and given that the only way to increase flow rates on any given run is to shut down other runs...I am guessing we either have a design problem or the circulating pump is undersized?

Thanks, Patrick

yellowdog

rule number 1 for any radiant system is to not set it back at night. especially all the way back to 58°.

Pittsjock

yellowdog said:

rule number 1 for any radiant system is to not set it back at night. especially all the way back to 58°.

Appreciate it...makes sense.

Pittsjock

yellowdog said:

rule number 1 for any radiant system is to not set it back at night. especially all the way back to 58°.

Just checked...there is no setback on Zone 2. The system is set for 58F at night...but Zone 2 says zero setback....

Do we need to be setting the system for the same day and night temps (roughly) and then using setback on Zone 1 to drop the temps on the radiator side so it is nice and cool at night for sleeping?

Ironman

Setback is not a good thing for any hydronic system, especially a radiant floor. You’re not saving anything since all the heat that the structure lost overnight has to be replaced the next morning.

Was a proper design done (which would have included a Manual J heat loss) before the radiant floor was installed? It may be that the radiant floor cannot produce sufficient heat during the coldest weather and needs to be supplemented. Setting it back to 58* would only exasperate the problem.

Pittsjock

Ironman said:

Was a proper design done (which would have included a Manual J heat loss) before the radiant floor was installed? It may be that the radiant floor cannot produce sufficient heat during the coldest weather and needs to be supplemented. Setting it back to 58* would only exasperate the problem.

I had conversations with the contractor generically about heat loss calculations and he assured me that they were done, but he did not share them with me.

I am beginning to understand how setback could tax the system. We have it set back more for comfort than anything else - although I could easily enough manually turn down radiators for better sleeping. We might have to replace a few valves...but ;-)

Ironman

Proper design is the key to getting a radiant floor that performs well. The heat loss calculation is at the heart of it. It also involves calculating the output capacity of the floor, tubing layout and sizing, pump selection, control and piping strategy, equipment selection, etc. Without knowing how much heat the structure requires, or how much the floor can produce, it’s nothing more than a crapshoot.

hot_rod

If you have a lightweight dry radiant like a plate installation, or top produc like Warmboard you could use a small 2-3 setback and be fine. Recovery will be based on the heatload, tube spacing, floor output, etc

Pittsjock

hot_rod said:

If you have a lightweight dry radiant like a plate installation, or top produc like Warmboard you could use a small 2-3 setback and be fine. Recovery will be based on the heatload, tube spacing, floor output, etc

Thanks ....believe they used the Quik Trak panels by Uponor....

After poking around a bunch more, it appears to me that the circulator pump is undersized. Even after balancing the manifold, we are only seeing .2GPM across the circuits. I shut down the 2nd floor circuits...this only increased the flow rates to .35GPM on the downstairs runs. The increase in flow did warm downstairs up to 63F....which feels like progress.

I am going to figure out the head loss and some ballpark heat loss figures and see where we come out.

Ironman

With a properly sized circulator and piping, .5-.7 gpm is the best you’re gonna get with 1/2” loops that are 300’ or less.

Check the Delta T between supply and return. Ideally, 10-12* is what you want on a radiant floor in a dwelling.

hot_rod

If it is the system that uses 5/16” tube, be mindful of the design charts regarding loop length, pressure drop and pump sizing.
The Uponor design guide is a free download It looks like .45 max flow to stay below acceptable velocities. Long loop lengths will need a properly sized pump.

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Uponor-A5060701-Install-Instructions.pdf

Pittsjock

Thanks Ironman. The Delta T is 25F right now....

The install guide is great - ty.

Just got off the phone with Uponor. 6 of the loops are 3/16, 2 are 1/2". The loops are approximately 180' and 250' based on the sq of rooms and use of their Quik Trak system. Uponor uses 250' as the max suggested for this system.

The Uponor tech redid the calculations and came up with the need for ~30ft of head on 4gpm. The current pump is 10 ft head....so massively undersized.

I will order a new circulator pump and report back.

hot_rod

Pittsjock said:

Thanks Ironman. The Delta T is 25F right now....

The install guide is great - ty.

Just got off the phone with Uponor. 6 of the loops are 3/16, 2 are 1/2". The loops are approximately 180' and 250' based on the sq of rooms and use of their Quik Trak system. Uponor uses 250' as the max suggested for this system.

The Uponor tech redid the calculations and came up with the need for ~30ft of head on 4gpm. The current pump is 10 ft head....so massively undersized.

I will order a new circulator pump and report back.

30’ of head seem high.
Looks like a 250’ loop at .45 gpm if 120F water is more like 13’

Unless you are looking for more than .45 gpm per loop?

Pittsjock

hot_rod said:

30’ of head seem high.
Looks like a 250’ loop at .45 gpm if 120F water is more like 13’

Unless you are looking for more than .45 gpm per loop?

If I am reading the Uponor chart correctly..... for .5GPM, 110F water, .118 per foot drop, is 29.5' for a 250' loop? At 120F, I am seeing .44 gpm as 22'?

hot_rod

Is that your design? .44 gpm at 120F, then 22’ is correct

Pittsjock

Greetings Hot Rod and thank you for jumping in here.

The house has pine floors over the 5/16" Quik Trak....I believe the contractor was intending to run at max 110F to avoid problems with the flooring. With that...the chart calls for 29.5' head.

I did find the run calculations too....the longest, per our guesstimate is 252' - the upper limit according to the Uponor rep, but OK.

I just finished installing a Taco 009....per the conversation with the Uponor tech - to give us a little room. I am now able to get at least .44 gpm on all of the runs. The Delta T has already dropped to 16 (from 25F) in about 30 minutes. The manifold water temps are 108F/92F with OAT at 34F. We shall see what happens as things equalize.

I am thinking we may end up needing to adjust the heating curve on the zone but TBD.

As I mentioned, there are two 1/2" runs on the radiant zone - 6 5/16". One of 1/2" is the first run on the manifold. It will squeal if I try and run it below about .55gpm. Is this an issue with the valve itself or telling me something else we should be concerned with?

Also, could I use the return/isolation valve on the manifold on that 1/2" run to restrict and hopefully let me turn the GPM down a bit without squealing?

Pittsjock

Update.

First, thanks Hot Rod for the additional consult! Most appreciated!

I now have the floors up to 73F and the room temps all around 63/64F this morning with OAT of 27. I bumped the Logamatic reference temps up from 113F to 120F and pushed the curve a little - no setback.

I am a little concerned about wood movement on the floors but I guess we shall see.

I am going to raise the reference temp up a little higher -125F and see what happens. I have a few moves with window coverings and a little sealing in a couple of problematic areas so maybe we will get there. We are pretty comfortable as a family at 68F....

One interesting by product is that we are going to have to lower the reference temps on the cast iron radiators...with all this "new" heat in one part of the house, we have lost a persistent draft and the other side (old rads) is now too warm for our tastes.